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: The effectiveness of weight-belts during multiple repetitions of the squat exercise.

Lander JE, Hundley JR, Simonton RL.

Department of Sports Health Science, Life College, Marietta, GA 30060.

The purpose of this study was to examine the effectiveness of weight-belts during multiple repetitions of the parallel back squat exercise. Five subjects were filmed (50 fps) as they performed eight consecutive trials at each of two weight-belt conditions [with belt = WB, without belt = WOB] in random order at their eight-repetition maximum effort. Other parameters examined were ground reaction forces, intra-abdominal pressure (IAP), and mean electromyography (mEMG) for the external oblique (EO), erector spinae (ES), vastus lateralis (VL), and bicep femoris (BF) muscles. All parameters were collected and interfaced to a computer via an A/D converter. WB repetitions were generally performed faster than WOB repetitions, especially by the later repetitions (3.34 vs 3.56 s). WB IAP values were consistently greater (P less than 0.05) than WOB values by 25-40%. IAP increased by approximately 11.5% from the first to the last repetitions. No differences were observed for ES and EO mEMG for belt usage, but values increased by up to 20% across repetitions. Several differences were observed between WB and WOB for the VL and BF mEMG, with WB values being significantly greater. These data suggest that a weight-belt aids in supporting the trunk by increasing IAP, and that any differential effect due to wearing a weight-belt did not occur over eight repetitions.

PMID: 1533266 [PubMed - indexed for MEDLINE]

: Effect of a weightlifting belt on spinal shrinkage.

Bourne ND, Reilly T.

Centre for Sport and Exercise Sciences, School of Health Sciences, Liverpool Polytechnic, UK.

Spinal loading during weightlifting results in a loss of stature which has been attributed to a decrease in height of the intervertebral discs--so-called 'spinal shrinkage'. Belts are often used during the lifting of heavy weights, purportedly to support, stabilize and thereby attenuate the load on the spine. The purpose of this study was to examine the effects of a standard weightlifting belt in attenuating spinal shrinkage. Eight male subjects with a mean age of 24.8 years performed two sequences of circuit weight-training, one without a belt and on a separate occasion with a belt. The circuit training regimen consisted of six common weight-training exercises. These were performed in three sets of ten with a change of exercise after each set of ten repetitions. A stadiometer sensitive to within 0.01 mm was used to record alterations in stature. Measurements of stature were taken before and after completion of the circuit. The absolute visual analogue scale (AVAS) was used to measure the discomfort and pain intensity resulting from each of the two conditions. The circuit weight-training caused stature losses of 3.59mm without the belt and 2.87 mm with the belt (P greater than 0.05). The subjects complained of significantly less discomfort when the belt was worn (P less than 0.05). The degree of shrinkage was significantly correlated (r = 0.752, P less than 0.05) with perceived discomfort but only when the belt was not worn. These results suggest the potential benefits of wearing a weightlifting belt and support the hypothesis that the belt can help in stabilizing the trunk.

PMID: 1810615 [PubMed - indexed for MEDLINE]

3: Med Sci Sports Exerc. 1990 Feb;22(1):117-26.

The effectiveness of weight-belts during the squat exercise.

Lander JE, Simonton RL, Giacobbe JK.

Department of Health and Human Performance, Auburn University, AL 36849-5323.

The purpose of this study was to examine the effectiveness of weight-belts during the performance of the parallel squat exercise. Six subjects were filmed (40 fps) as they performed three trials at each of three belt conditions (NB, none; LB, light; HB, heavy) in random order and three load conditions (70, 80, 90% 1RM (one repetition maximum] in increasing order. The parameters examined were collected and interfaced to a computer via an analog-to-digital (A/D) converter: ground reaction forces, intra-abdominal pressure (IAP), and EMG for the rectus abdominus (RA), external oblique (EO), and erector spinae (ES) muscles. Most differences were observed during the 90% 1RM condition, and only they are presented in this paper. Maximum IAP values were always greater (P less than 0.05) for the weight-belt conditions (LB, 29.2; HB, 29.1 greater th an NB, 26,8 kPa). Similar results were observed for the mean IAP. The integrated EMG (iEMG) activity of the muscles and adjusted mean values for back compressive force and back muscle force followed a similar but opposite pattern, with NB being the greatest. ES mEMG/(L5/S1) values for HB (18.1%) were the least, followed by LB (20.01%) and NB (22.3%). Few differences were observed between belt types. These data suggest that a weight-belt can aid in supporting the trunk by increasing IAP.

Publication Types:

Research Support, Non-U.S. Gov't

PMID: 2304406 [PubMed - indexed for MEDLINE]

4: Med Sci Sports Exerc. 1989 Apr;21(2):186-90.

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Effects of a belt on intra-abdominal pressure during weight lifting.

Harman EA, Rosenstein RM, Frykman PN, Nigro GA.

Exercise Physiology Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760.

Intra-abdominal pressure (IAP) has been widely hypothesized to reduce potentially injurious compressive forces on spinal discs during lifting. To investigate the effects of a standard lifting belt on IAP and lifting mechanics, IAP and vertical ground reaction force (GRF) were monitored by computer using a catheter transducer and force platform while nine subjects aged 28.2 +/- 6.6 yr dead-lifted a barbell both with and without a lifting belt at 90% of maximum. Both IAP and GRF rose sharply from the time force was first exerted on the bar until shortly after it left the floor, after which GRF usually plateaued while IAP either plateaued or declined. IAP rose significantly (P less than 0.05) earlier with than without the belt. When the belt was worn, IAP rose significantly earlier than did GRF. Both with and without the belt, IAP ended its initial surge significantly earlier than did GRF. Variables significantly greater with than without a belt included peak IAP, area under the IAP vs time curve from start of initial IAP surge to lift-off, peak rate of IAP increase after the end of its initial surge, and average IAP from lift-off to life completion. In contrast, average rate of IAP increase during its initial surge was significantly lower with the belt. Correlations are presented which provide additional information about relationships among the variables. Results suggest that the use of a lifting belt increases IAP, which may reduce disc compressive force and improve lifting safety.

Publication Types:

PMID: 2709981 [PubMed - indexed for MEDLINE]

: The effect of back belts on lumbar muscle fatigue.

Ciriello VM, Snook SH.

Liberty Mutual Research Center for Safety and Health, Hopkinton, Massachusetts, USA.

STUDY DESIGN. An experiment was conducted to investigate the effect of wearing a weight lifting belt on the endurance and fatigue characteristics of the extensor muscles of the spine. OBJECTIVE. To evaluate the effectiveness of back belts in preserving the endurance characteristics of the spinal musculature. SUMMARY OF BACKGROUND DATA. Previous studies have investigated the use of back belts in increasing intra-abdominal pressure and thus increasing the stabilization of the spine. Other studies have looked at the association of low back disability and wearing back belts. No study has examined the relationship between wearing back belts and measures of spinal muscle fatigue and endurance. METHODS. Thirteen male industrial workers performed a lifting and lowering task from the floor to a 76.2 cm height at 4.3 min-1 2 days a week for 4 weeks. The load was psychophysically determined and averaged 28.1 kg for a total of 28.9 metric tons moved in 4 hours. Subjects lifted for 1, 2, 3, and 4 hours, respectively, for the first 4 days of the experiment. These were considered training days. During the last 4 days, subjects lifted for 4 hours per day; 2 days with a back belt, and 2 days without a back belt. Maximum isokinetic endurance of the extensors was measured for 50 repetitions (5 sets of 10 repetitions) at the end of 4 hours of lifting. Median frequencies of the electromyographic signal from six locations over the back extensors were measured for 30 seconds at 80% of maximum isometric voluntary contraction after 4 hours of lifting. RESULTS. There were no significant differences in maximum isokinetic endurance, or in the slope of median frequency, between lifting with a back belt and lifting without a back belt. Similarly, a modified Borg scale and a postexperiment survey question were unable to distinguish between wearing a back belt and not wearing a back belt. CONCLUSION. There were no significant differences in maximum isokinetic endurance and electromyographic spectral parameters of the back extensor muscles as a result of wearing a back belt during heavy lifting and lowering tasks.

PMID: 7660236 [PubMed - indexed for MEDLINE]

6: Spine. 1995 Jan 1;20(1):68-73.

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Comment in:

Spine. 1995 Aug 15;20(16):1847.

The effect of lumbar belts on isolated lumbar muscle. Strength and dynamic capacity.

Reyna JR Jr, Leggett SH, Kenney K, Holmes B, Mooney V.

Department of Orthopaedic Surgery, University of New Mexico.

STUDY DESIGN. This study analyzed the effect of lumbar support belts on functional performance. OBJECTIVE. To compare lumbar muscle strength and lifting capacity with and without a lumbar belt. SUMMARY OF BACKGROUND DATA. Industrialized settings have begun to encourage the use of lumbar support belts for their employees. It is believed that the belts may decrease the risk of injury and enhance the functional performance of the individual. METHODS. Twenty-two subjects (average age, 27.5 years) were tested on four separate days to evaluate the effect of a commercially available belt on isolated lumbar isometric strength and functional dynamic lifting capacity. All subjects had no history of low back problems. The order of testing with and without a belt was randomized for both conditions. On the first 2 days, subjects performed a seven-angle isometric lumbar extension strength test, 1 day with and 1 day without a lumbar belt. On the following 2 days, subjects were tested to evaluate functional capacity with and without a lumbar belt. The functional capacity evaluation was performed by progressively lifting weighted canisters from various levels. Heart rates were monitored to ensure that a maximum effort was achieved over the different days. RESULTS. T tests revealed that isometric lumbar strength and functional lifting capacity was not significantly affected by the belt. CONCLUSION. The use of a lumbar belt does not enhance isometric lumbar muscle strength or dynamic lifting capacity.

Publication Types:

PMID: 7709282 [PubMed - indexed for MEDLINE]

: Effectiveness and cost-effectiveness of employer-issued back belts in areas of high risk for back injury.

Mitchell LV, Lawler FH, Bowen D, Mote W, Asundi P, Purswell J.

University of Oklahoma Health Sciences Center, Department of Family Medicine, Oklahoma City 73190.

Back belts have gained popularity under the assumption that their use will reduce low back injuries and thereby decrease the costs. This study sought to examine that hypothesis. A retrospective survey instrument was administered to 1316 workers who perform lifting activities at Tinker Air Force Base, Midwest City, Oklahoma, to identify belt use, lifting requirements, injury, and treatment history. Analysis was also performed on costs applicable to providing the belts, treatment of injury, and lost or limited duty work days. Results show an odds ratio of 1.01 (confidence interval 1.01, 1.02) and P value of .0005 of low back injury with the number and weight of lifts performed in an 8-hour period as well as an odds ratio of 5.56 (confidence interval 3.35, 9.26) with prior history of injury. A protective effect, odds ratio of .65, P value of .019 is noted between lifting and attendance at a back training program. Use of a back belt appears to be marginally effective (odds ratio .60, P value .0508) in reducing injuries when controlling for other related factors. Cost analysis over all diagnoses of low back injury shows less intensive treatment and lower cost per injury for workers injured without a belt versus those injured while wearing a belt. It appears that predictors of low back injury are those expected based on risk assumed (amount of time spent performing lifts, history of injury) and that training programs are effective in prevention of problems. Data suggest that back belts appear to be minimally effective in preventing injury.(ABSTRACT TRUNCATED AT 250 WORDS)

PMID: 8138856 [PubMed - indexed for MEDLINE]

: The effects of lumbosacral support belts and abdominal muscle strength on functional lifting ability in healthy women.

Smith EB, Rasmussen AA, Lechner DE, Gossman MR, Quintana JB, Grubbs BL.

Rehabilitation Services, Kirklin Clinic, Birmingham, Alabama, USA.

STUDY DESIGN: This study focused on lumbosacral support belts, abdominal muscle strength, and lifting ability in healthy women. Subjects underwent manual muscle testing to determine muscle strength and performed lifting procedures to determine lifting capacity. OBJECTIVES: The purpose of this study is threefold: 1) to determine the effectiveness of lumbosacral support belts in improving lifting ability in healthy women, 2) to determine if lumbosacral support belts are more effective for those with weak abdominals than those with strong abdominals, and 3) to determine if the maximum amount of weight varies with abdominal muscle strength. SUMMARY OF BACKGROUND DATA: In a review of published literature, one study has addressed the relationship of lumbosacral support belts and lifting capacity. However, no study has examined the use of lumbosacral support belts and lifting capacity in a female population. METHODS: A convenient sample of 69 healthy women, aged 20 to 40 years, participated in this study. Subjects were categorized into one of three groups based on lower and upper abdominal muscle strength. Each subject then performed two lifting procedures, one with a lumbosacral support belt and one without, to determine two maximum lifts. RESULTS: Women between the ages of 20 and 40 years could lift approximately 1.0 kg more weight from the floor to waist height with the lumbosacral support belt. The maximum weight lifted varied with abdominal strength. Lumbosacral support belts were not more effective for those with weak abdominals than those with strong abdominals. CONCLUSIONS: When applied properly and used in conjunction with proper lifting technique, lumbosacral support belts slightly improved lifting ability in healthy women. The magnitude of the increase, although statistically significant, is not sufficient to advocate the use of lumbosacral support belts to increase lifting capacity.

PMID: 8742213 [PubMed - indexed for MEDLINE]

9: Hum Factors. 1995 Dec;37(4):844-53.

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Effect of lifting belts, foot movement, and lift asymmetry on trunk motions.

Lavender SA, Thomas JS, Chang D, Andersson GB.

Department of Orthopedic Surgery, Rush-Presbyterian-St. Luke's Medical Center, Chicago, IL 60612, USA.

Whether or not lifting belts protect workers from injury is a topic of considerable interest in industry. Not only is the protective effect uncertain, but the biomechanical basis for belt function is unclear. The objective of this study was to determine if lifting belts provide a means for controlling trunk motions during asymmetric material-handling tasks. We recruited 16 nursing personnel as experienced lifters to participate in two lifting sessions. A lifting belt was worn in one session and for a week prior to this session during the subjects' routine work activities. Each session required 42 lifts, distributed across three asymmetry conditions (0, 45, and 90 deg) and temporally spaced 30 s apart. Foot motion was not permitted in half the lifts. Results indicated that during lifting, lateral bending and twisting motions were reduced by both the lifting belt and foot motion; the most pronounced effect was observed at 90 deg of asymmetry. Trunk motions in the sagittal plane during lifting were not affected by the lifting belt. These results appear to support the use of lifting belts in asymmetric lifting conditions, but more research is needed to determine whether the muscles in the torso benefit from the reduced motion or are working harder to overcome this resistance to motion, causing increased internal loads on the spine during asymmetric material-handling tasks.

Publication Types:

PMID: 8851780 [PubMed - indexed for MEDLINE]

: The effect of a back belt on torso motion--survey in an express package delivery company.

Jonai H, Villanueva MB, Sotoyama M, Hisanaga N, Saito S.

National Institute of Industrial Health, Kawasaki, Japan.

According to the Labor Standard Bureau of Japan, accidental back injuries accounted for about 60% of all occupational injuries and diseases in the last decade. The Ministry of Labor issued guidelines to prevent low back injuries in 1994 to address the problem. The use of back belts is recommended for some special working conditions but details on its proper use were not given. This study was planned to evaluate a newly developed back belt and was done at an express package delivery company where the incidence of low back injury was high. The BackTracker was used to evaluate the effect of the back belt on the range and velocity of torso motion. The results indicated that there were no significant differences in the range of motion (ROM) during flexion/extension, lateral bending, and rotation between with and without the belt. The maximum angular velocity (MAV) of flexion decreased significantly (average decrease: 30 +/- 28.3 degrees/sec) when the back belt was worn. The MAV of extension with belt showed a decreasing tendency though not significant. No notable trends were observed in the MAV, during lateral bending and rotation of the subjects while wearing and not wearing the belt. The results also indicated that the back belt affected differently the torso motion of each subject. This study suggested that this back belt could be useful for tasks with high velocity of flexion/extension and that proper instruction on the use of the back belt is needed for each worker.

PMID: 9127556 [PubMed - indexed for MEDLINE]

: An investigation of respiration while wearing back belts.

Soh TN, Parker PL, Crumpton LL, Mealins C.

Department of Industrial Engineering, Mississippi State University, MS 39762, USA.

The research was conducted to evaluate the frequency of respiration during a repetitive lifting task when abdominal compression occurs from wearing a back belt. Three back belts were evaluated in this study: a nylon back belt, an inflatable back belt and an elastic vest. Analysis of the data revealed that the frequency of respiration increased while wearing the back belts at rest and while performing a repetitive lifting task. A statistically significant increase in the frequency of respiration was found while wearing the nylon back belt during the lifting task.

PMID: 9414356 [PubMed - indexed for MEDLINE]

12: J Spinal Disord. 1998 Feb;11(1):57-64.

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The effect of lifting belt use on multijoint motion and load bearing during repetitive and asymmetric lifting.

Sparto PJ, Parnianpour M, Reinsel TE, Simon S.

Biomedical Engineering Center, Ohio State University, Columbus 43210, USA.

The evaluation of the effect of lifting belts on multijoint coordinated lifting performance has been limited. Thirteen subjects participated in two experiments: (a) fatiguing repetitive sagittal lifting and (b) asymmetric lifting. Both experiments were performed with and without the use of a common flexible lifting belt to determine the effect of belt use on the trunk and lower extremity motion and load sharing. During both tests, the use of the belt was observed to restrict the sagittal trunk range of motion and velocity, while the hip motion and velocity increased. Although one of the risk factors for acquisition of low back pain may be reduced while wearing the belt, the results also demonstrate a need for greater study of the consequences on the risk of injury to the other joints. More laboratory experiments and prospective epidemiological studies are needed before a conclusive recommendation could be made in favor of using the belt as a valid preventive measure.

Publication Types:

PMID: 9493771 [PubMed - indexed for MEDLINE]

13: Spine. 1999 Jun 1;24(11):1124-30.

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The effect of industrial back belts and breathing technique on trunk and pelvic coordination during a lifting task.

McGorry RW, Hsiang SM.

Liberty Mutual Research Center for Safety and Health, Hopkinton, Massachusetts, USA. raymond.mcgorry@libertymutual.com

STUDY DESIGN: Relative phase angle was used to study segmental motion patterns during a lifting and lowering task. OBJECTIVES: To investigate the effect of back belts, breathing technique, and their interaction on lumbar and pelvic motion patterns. SUMMARY OF BACKGROUND DATA: Trunk and pelvic coordination has been investigated in healthy and low back pain populations. Back belts have been shown to alter range of motion and intra-abdominal pressure. Little has been reported about belts and coordination during lifting and lowering. Phase angle has been used for quantifying segmental coordination. METHODS: Six individuals performed lifting/lowering tasks with a 23-kg load under elastic, rigid, and no belt conditions. During a second session, individuals were trained in Valsalva's maneuver and repeated the protocol. Cinematography was used to track trunk and pelvis displacements. RESULTS: Segmental coordination during lowering generally was found to be the inverse of lifting. Significant differences in the relation between lumbar and pelvis phase angles were found during the initial stage of lifting because of the interaction of belt use and breathing. Lumbar range of motion decreased significantly with belt use during lifting and lowering. No significant change in pelvis range of motion was observed. CONCLUSIONS: Back belt use and breathing technique interacted during the initial stage of lifting to significantly alter the lumbar and pelvis phase angles. The change in segmental kinematics was similar to that previously reported for patients with a history of low back pain. Lumbar range of motion significantly decreased with belt use during both lifting and lowering.

Publication Types:

Research Support, Non-U.S. Gov't

PMID: 10361662 [PubMed - indexed for MEDLINE]

: Lifting Belts: A Review.

Rys MJ, Konz SA.

Kansas State University, USA. malrys@ksuvm.ksu.edu

This paper reviews and evaluates the literature related to the effectiveness of protective restraints on abdominal strength, low-back injuries and workers' discomfort. The studies indicate that back belts have potential disadvantages as well as advantages. Belts seem to reduce lifting stress. They may, however, lead to a false sense of security while being worn and may weaken the body, too, so injury occurs when they are not being worn. There also seems to be comfort problems with some belts. More scientific research is needed before any conclusions can be drawn about positive, negative, or long-term effects of lifting belts.

PMID: 10603560 [PubMed - as supplied by publisher]

15: Clin Biomech (Bristol, Avon). 1999 Feb;14(2):79-87.

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Effects of abdominal belts on intra-abdominal pressure, intra-muscular pressure in the erector spinae muscles and myoelectrical activities of trunk muscles.

Miyamoto K, Iinuma N, Maeda M, Wada E, Shimizu K.

Department of Orthopaedic Surgery, Gifu University, School of Medicine, Japan. kei@gix.or.jp

OBJECTIVE: To evaluate the effects of abdominal belts on lifting performance, muscle activation, intra-abdominal pressure and intra-muscular pressure of the erector spinae muscles. DESIGN: Simultaneous measurement of intra-abdominal pressure, intra-muscular pressure of the erector spinae muscles was performed during the Valsalva maneuver and some isometric lift exertions. BACKGROUND: While several hypotheses have been suggested regarding the biomechanics of belts and performance has been found to increase when lifting with belts, very little is known about the modulating effects on trunk stiffness. At present, there is no reason to believe that spine tolerance to loads increases with belts. METHODS: An abdominal belt designed for weightlifting was used. Intra-abdominal pressure, intra-muscular pressure of the erector spinae muscles and myoelectric activities of trunk muscles (erector spinae, rectus abdominis and external oblique) were measured simultaneously during the Valsalva maneuver as well as three types of isometric lifting exertions (arm, leg and torso lift). A paired t-test was used to analyze for statistical differences between the two conditions (without-belt and with-belt) in intra-abdominal pressure, intra-muscular pressure of the erector spinae muscles and in the integrated EMG of the trunk muscles. RESULTS: Intra-muscular pressure of the erector spinae muscles increased significantly by wearing the abdominal belt during Valsalva maneuvers and during maximum isometric lifting exertions, while maximum isometric lifting capacity and peak intra-abdominal pressure were not affected. Integrated EMG of rectus abdominis increased significantly by wearing the abdominal belt during Valsalva maneuvers (after full inspiration) and during isometric leg lifting. CONCLUSIONS: Wearing abdominal belts raises intra-muscular pressure of the erector spinae muscles and appears to stiffen the trunk. Assuming that increased intra-muscular pressure of the erector spinae muscles stabilizes the lumbar spine, wearing abdominal belts may contribute to the stabilization during lifting exertions.

Publication Types:

PMID: 10619094 [PubMed - indexed for MEDLINE]

: Physiological effects of back belt wearing during asymmetric lifting.

Bobick TG, Belard JL, Hsiao H, Wassell JT.

Division of Safety Research, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA. txb4@cdc.gov

This study investigated the effect of wearing a back belt on subjects' heart rate, oxygen consumption, systolic and diastolic blood pressure, and respiratory frequency during asymmetric repetitive lifting. Thirty subjects with materials-handling experience utilized three different belts (ten subjects per belt). Subjects completed six 30-min lifting sessions--three while wearing a belt and three without. Data analyses were conducted on the second, third, and fourth lifting periods. A 9.4 kg box, without handles, was lifted 3 times/min, starting at 10 cm above the floor, ending at 79 cm, with a 60 degree twist to the right. Data analysis indicates that belt-wearing did not have a significant effect on the overall mean values for heart rate, systolic and diastolic blood pressure, and respiratory frequency. Belt-wearing had a significant effect on the overall mean oxygen consumption of the subjects.

PMID: 11703040 [PubMed - indexed for MEDLINE]

: The effects of back belts and load on selected lifting kinematics during a simulated patient transfer.

Willey MS.

Health Science Center, Suite 3, University of Central Arkansas, 201 Donaghey Avenue, Conway, AR 72035-0001, USA. Tel.: +1 501 450 5569; E-mail: marcw@mail.uca.edu

This study used two dimensional biomechanical analysis to examine the effects of back belts and lifting load on selected lifting kinematics during a simulated patient transfer. A human manikin placed in a sitting position was attached to a customized lifting apparatus which controlled the lifting load and direction of the manikin. Eighteen female participants, between the age of 21 and 27, completed six lifts (sit to stand transfers) of the manikin. Three lifts were completed at the 30 lb load condition (no belt, belt 1 and belt 2) and three lifts were completed at the 50 lb load condition (no belt, belt 1 and belt 2). A doubly two way ANOVA found a significant main effect for the belt condition, F(12,6)=10.06, P=0.002. There was no significant effect for load and no interaction existed between belt and load. The results revealed a significant decrease in trunk flexion when participants wore the wider (nine inch) belt during the 30~lb lifts when compared to the no belt trials. No significant differences were found in trunk flexion means with the narrower width (six inch) belt. No significant differences were found in trunk spinal flexion with either belt condition during the 50 lb lifts. There were no significant differences found in either of the belts in the means of lifting time, knee flexion, elbow flexion, forward displacement of the lifter's center of mass, and the lifter's maximum center of mass velocity. The results suggest that wider back belts may be more effective at reducing spinal flexion during patient lifting under moderate load conditions when compared to narrower back belts and to no-belted controls.

PMID: 12441620 [PubMed - as supplied by publisher]

18: Spine J. 2003 Mar-Apr;3(2):93-9.

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Gender influences on spine loads during complex lifting.

Marras WS, Davis KG, Jorgensen M.

Biodynamics Laboratory, Institute for Ergonomics, 1971 Neil Avenue, The Ohio State University, Columbus, OH 43210, USA. marras.1@osu.edu

BACKGROUND CONTEXT: Previous research has documented differences in spine loading between genders when the imposed load is normalized relative to the size of the person. However, under realistic work conditions the magnitude of the load handled is seldom adjusted relative to worker anthropometry. Thus, there is a void in our knowledge in that we do not understand how material handling influences spine loading and potential risk of injury as a function of gender under realistic lifting situations. PURPOSE: To evaluate the differences in spine loading between men and women when exposed to similar workplace demands. STUDY DESIGN: A laboratory study was conducted to investigate the biomechanical responses during realistic free-dynamic lifting tasks when subjects lifted from origins and destinations that were either fixed or set relative to the subject's anthropometry. PATIENT SAMPLE: Twenty men and 20 women asymptomatic for low back pain were recruited to participate in the study. OUTCOME MEASURES: The three-dimensional spine loads were predicted from a well-established electromyography-assisted model. METHODS: Both genders completed a series of symmetric and asymmetric (60-degree clockwise) lifts that originated from two shelf heights ("relative" to knee height and "set" at 35 cm from floor) and terminated at one of two destination heights ("relative" to waist and "set" 102 cm from the floor). Three levels of box weight were investigated (6.8, 13.6 and 22.7 kg). RESULTS: Men had significantly greater compression forces than women (about 640 N). Loading differences between genders were further magnified by several of the workplace factors. The differences between men and women were even greater when lifting either of the heavier loads from the lower fixed shelf (more than 50% greater). CONCLUSIONS: It is apparent that men produce the greater loads on their spines during lifting. However, engineering controls, such as adjustable workplace layout or less weight lifted, may reduce or eliminate gender-specific differences in spine loads. Furthermore, the differences in spine loads appear to be a result of kinematic trade-offs and muscle coactivity differences in combination with unequal body masses between genders. However, when the loads were put into context of the expected tolerances of the spine, women were found to be at increased risk of injury, especially when lifting heavy loads or under asymmetric lifting conditions. Collectively, the results indicate the need to account for differences between the genders when designing the workplace.

Publication Types:

Research Support, U.S. Gov't, Non-P.H.S.

PMID: 14589221 [PubMed - indexed for MEDLINE]

19: J Manipulative Physiol Ther. 2004 Mar-Apr;27(3):186-96.

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Effect of a back belt on reaching postures.

Smith DL, Dainoff MJ, Mark LS, Oates SP, Davis NC.

Center for Ergonomic Research, Department of Psychology, Miami University, Oxford, Ohio, USA. drdean@essenceofwellness.com

OBJECTIVE: The present study investigated the effect of a back belt on reach actions. SUBJECTS: Sixteen undergraduate college students (8 male students, 8 female students) ranging in age from 18 to 22 years. Thirteen subjects were included in the final analysis. SETTING: The Department of Psychology at Miami University, Oxford, Ohio METHODS: Using a well-established set of procedures developed in our laboratory for studying reaching, seated adult participants reached for and retrieved an object placed at various distances from them. Reach distances included values both closer than and farther than each subject's maximum seated reach. The reach task had 2 conditions: picking up and retrieving a small block and skewering and retrieving a small bead with a needle. For each task condition, each subject either wore the belt or did not use a belt. RESULTS: Results indicate that when subjects wore the belt while reaching, they tended to have initial transition points (sitting to nonsitting) closer to their bodies than while not wearing the belt. That is, for a distant object, subjects were more likely to raise their bodies out of the chair rather than perform an extreme seated reach, possibly acting to preserve a greater margin of safety. CONCLUSIONS: The back belt consistently modified reaching postures by limiting extreme ranges of motion during a task that required enhanced stability. Furthermore, the methodology and analysis presented in this article when applied to chiropractic will allow us to begin thoughtful investigation of the effects of chiropractic adjustments on postural transitions and margin of safety.

Publication Types:

Research Support, Non-U.S. Gov't

PMID: 15129201 [PubMed - indexed for MEDLINE]

: Predictive models of safety belt use: a regression analysis of MVOSS data.

Chaudhary NK, Northrup VS.

Preusser Research Group, Inc., Trumbull, Connecticut, USA. NChaudhary@preussergroup.com

A substantial portion of the U.S. population fails to regularly use their safety belts. The explanations for the differential belt use have addressed, for example, socioeconomics, state law, attitudes, and perceived likelihood of being ticketed. The current analyses create predictive models of safety belt use. Using NHTSA's Motor Vehicle Occupant Safety Surveys (Years 1998 and 2000; N = 9577), variables related to belt use were entered into backward stepwise logistic regressions to produce two predictive models (Demographic and Attitudinal) of safety belt use (Always versus Not always). The results indicated that belt use is a complicated issue as there were several interactions between variables. The Demographic predictive model contained main effects for, law types, socioeconomics, population density, a gender-law type interaction, and a three-way interaction between age, marital status, and vehicle type. The Attitudinal model included perceived effectiveness of the belt, fatalistic attitudes, and an interaction between perceived effectiveness of the belt and perceived risk of being ticketed. These models survived a multinomial logistic regression when belt use was parsed into three categories (Always, Part-time, and Infrequent). In addition to variables that affect belt use, the results suggested that the structure of "belt use" as a psychological/behavioral construct is more complicated than once thought. Specifically, a dichotomous breakdown of belt use (Always and Not always) oversimplifies the construct because the predictor factors sometimes affect "part-time" belt users differently than "infrequent" belt users (compared to "full-time" users). Many of the factors included in the models have been previously shown to impact belt use, but the interaction effects--indicating a more complicated relationship between these variables than previously suggested--may contribute to a better understanding of safety belt use.

PMID: 15203949 [PubMed - indexed for MEDLINE]

: An evaluation of a weightlifting belt and back injury prevention training class for airline baggage handlers.

Reddell CR, Congleton JJ, Dale Huchingson R, Montgomery JF.

Texas A&M University, Industrial Engineering Department, College Station, TX 77843, USA.

This study evaluated the efficacy of a commercially available weightlifting belt in relation to reduction of lumbar injury incident rate and severity of injuries over an 8-month period. The study used 642 baggage handlers working for a major airline company as participants. Four treatment groups were randomly selected: a group receiving the belt only, a group receiving a 1 h training class only, a group receiving both a belt and a 1 h training class, and a control group receiving nothing. Two treatment groups were added which contained participants who discontinued use of the belt prior to the end of an 8-month study period. Results indicated that there were no significant differences for total lumbar injury incident rate, restricted workday case injury incident rate, lost workdays and restricted workdays rate, and worker's compensation rates. There was, however, a marginal significant difference for lost workday case injury incident rate. Groups with participants who wore the belt for a while then discontinued its use had a higher lost day case injury incident rate than did either the group receiving training only or the control group. Compliance was an overriding factor as the belt questionnaire response indicated that 58% of participants in the belt groups discontinued use of the belt before the end of 8 months. Comments made on the survey forms indicated that the belt was too hot. Similarly, comments suggested that the belt rubbed, pinched, and bruised ribs. Based on these results, the weightlifting belt used for this study cannot be recommended for use in aid of lifting during daily work activities of baggage handlers. Results indicate that use of the belts may, in fact, increase the risk of injury when not wearing a belt following a period of wearing a belt. As industries are experimenting with the use of belts, it is recommended that great care be taken in any further evaluation and close attention directed towards injuries which occur when not wearing the belt following a period of wearing the belt (ie, off-the-job injuries).

PMID: 15676878 [PubMed]

: Effects of elastic bands on force and power characteristics during the back squat exercise.

Wallace BJ, Winchester JB, McGuigan MR.

Musculoskeletal Research Center, Department of Exercise and Sport Science, University of Wisconsin-La Crosse, La Crosse, Wisconsin 54601, USA.

Athletes commonly use elastic bands as a training method to increase strength and performance. The purpose of this study was to investigate the effect of elastic bands on peak force (PF), peak power (PP), and peak rate of force development (RFD) during the back-squat exercise (BSE). Ten recreationally resistance-trained subjects (4 women, 6 men, mean age 21.3 +/- 1.5 years) were tested for their 1 repetition maximum (1RM) in the BSE (mean 117.6 +/- 48.2 kg) on a Smith machine. Testing was performed on 2 separate days, with 2 sets of 3 repetitions being performed for each condition. Testing was conducted at 60% and 85% of 1RM with and without using elastic bands. In addition, 2 elastic band loading conditions were tested (B1 and B2) at each of the 2 resistances. No bands (NB) represents where all of the resistance was acquired from free-weights. B1 represents where approximately 80% of the resistance was provided by free-weights, and approximately 20% was provided by bands. B2 represents where approximately 65% of the resistance was provided by free-weights, and approximately 35% was provided from bands. The subjects completed the BSE under each condition, whereas PF, PP, and RFD was recorded using a force platform. There was a significant (p < 0.05) increase in PF between NB-85 and B2-85 of 16%. Between B1-85 and B2-85, PF was increased significantly by 5% (p < 0.05). There was a significant (p < 0.05) increase in PP between NB-85 and B2-85 of 24%. No significant differences were observed in RFD during the 85% conditions or for any of the measured variables during the 60% conditions (p < 0.05). The results suggest that the use of elastic bands in conjunction with free weights can significantly increase PF and PP during the BSE over free-weight resistance alone under certain loading conditions. The greatest differences are observed during the higher loading conditions, with the B1-85 condition appearing to be optimal for athletic performance of the ones we tested. The strength training professional could use variable resistance training (VRT) to increase PF and PP more than the traditional BSE can. VRT could also be used to train these 2 performance characteristics together, which might be especially useful in season, when weight-room training volume can sometimes be limited.

PMID: 16686552 [PubMed - indexed for MEDLINE]

23: Ergonomics. 2006 Aug 15;49(10):968-81.

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Quantifying low back peak and cumulative loads in open and senior sheep shearers in New Zealand: examining the effects of a trunk harness.

Gregory DE, Milosavljevic S, Callaghan JP.

Faculty of Applied Health Science, Department of Kinesiology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.

Sheep shearing requires shearers to adopt sustained flexed postures for prolonged periods of time and has been associated with an increased risk of developing low back pain (LBP). However, these postures do not generally result in acute compressive values at L4/L5 exceeding the action limit proposed by the National Institute for Occupational Safety and Health, despite the high prevalence of LBP in this occupation. Therefore, it may not be peak loading that is responsible for LBP in this occupation but instead it may be the effect of cumulative loading over the course of a workday. The primary purpose of this research was to quantify the low back cumulative load exposure in 12 sheep shearers with and without the aid of a commercial trunk harness. Results revealed a significant reduction in the magnitude of cumulative compression with the use of the trunk harness and therefore its use may potentially reduce the risk of injury. The use of the trunk harness also reduced the time spent in axially twisted postures, which have been associated with LBP. However, using the trunk harness also resulted in increased time spent in laterally bent postures, which has been associated with increased risk for pain and injury.

Publication Types:

Research Support, Non-U.S. Gov't

PMID: 16803727 [PubMed - indexed for MEDLINE]

: Trends in strength training--United States, 1998-2004.

Centers for Disease Control and Prevention (CDC).

Strength training is physical activity intended to increase muscle strength and mass. Adults who engage in strength training are less likely to experience loss of muscle mass, functional decline, and fall-related injuries than adults who do not strength train. Studies on strength-training interventions have indicated that inactive older adults who begin regular strength training achieve substantial strength gains within a few months. Because certain health benefits are linked to strength training, a national health objective for 2010 is to increase to 30% the proportion of adults who perform physical activities that enhance and maintain muscular strength and endurance on > or =2 days per week (objective 22-4). This objective is also recommended by the American College of Sports Medicine. CDC analyzed 1998-2004 data from the National Health Interview Survey (NHIS) to determine the annual prevalence of strength training among U.S. adults by age group and race/ethnicity. This report describes the results of that analysis, which demonstrated that although the national prevalence of strength training for U.S. adults increased slightly during 1998-2004, only 21.9% of men and 17.5% of women (age adjusted) in 2004 reported strength training two or more times per week. This is substantially lower than the national 2010 objective of 30% and underscores the need for additional programs to increase strength training among adults.

PMID: 16855525 [PubMed - indexed for MEDLINE]

25: Ind Health. 2006 Jul;44(3):493-502.

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Effects of a new industrial lifting belt on back muscular activity, hand force, and body stability during symmetric lifting.

Chen HJ, Lin CJ, Huang CL.

Department of Industrial Engineering, Chung Yuan Christian University, Chung Li 32023, Taiwan.

This work investigated how wearing a new design of back belt affects erector spinae activity, hand force, and body stability. The belt was first tested with static holding tasks and found to significantly decrease the back muscle activity. Actual lifting tasks were further carried out to test the effect of the belt. Ten male subjects performed a symmetric lifting task of low-lying loads (11 and 16 kg) at natural toting velocity, using either a squat or stoop lifting posture, both with and without a belt. The study measured various independent variables using electromyography (EMG), load cells, and motion capture device. The results demonstrated that the belt reduced the load on the erector spinae, as well as the triceps brachii and biceps brachii. The overall mean values of the peak (hand) force did not appear significantly affected while wearing the belt, but the force peaks appeared postponed. The belt did not alter body stability while lifting. From the present findings, the belt effectively changed the force distribution during lifting, at least reducing the muscle load on the back. The belt may be a potentially useful device for symmetric industrial lifting tasks.

Publication Types:

Research Support, Non-U.S. Gov't

PMID: 16922195 [PubMed - indexed for MEDLINE]

: Three-dimensional motion analysis of the lumbar spine during "free squat" weight lift training.

Walsh JC, Quinlan JF, Stapleton R, FitzPatrick DP, McCormack D.

Cappagh National Orthopaedic Hospital, Finglas, Dublin, Republic of Ireland. james.walsh@ireland.com

BACKGROUND: Heavy weight lifting using a squat bar is a commonly used athletic training exercise. Previous in vivo motion studies have concentrated on lifting of everyday objects and not on the vastly increased loads that athletes subject themselves to when performing this exercise. HYPOTHESIS: Athletes significantly alter their lumbar spinal motion when performing squat lifting at heavy weights. STUDY DESIGN: Controlled laboratory study. METHODS: Forty-eight athletes (28 men, 20 women) performed 6 lifts at 40% maximum, 4 lifts at 60% maximum, and 2 lifts at 80% maximum. The Zebris 3D motion analysis system was used to measure lumbar spine motion. Exercise was performed as a "free" squat and repeated with a weight lifting support belt. Data obtained were analyzed using SAS. RESULTS: A significant decrease (P < .05) was seen in flexion in all groups studied when lifting at 40% maximum compared with lifting at 60% and 80% of maximum lift. Flexion from calibrated 0 point ranged from 24.7 degrees (40% group) to 6.8 degrees (80% group). A significant increase (P < .05) was seen in extension when lifting at 40% maximum was compared with lifting at 60% and 80% maximum lift. Extension from calibrated 0 point ranged from -1.5 degrees (40% group) to -20.3 degrees (80% group). No statistically significant difference was found between motion seen when exercise was performed as a free squat or when lifting using a support belt in any of the groups studied. CONCLUSION: Weight lifting using a squat bar causes athletes to significantly hyperextend their lumbar spines at heavier weights. The use of a weight lifting support belt does not significantly alter spinal motion during lifting.

PMID: 17307893 [PubMed - indexed for MEDLINE]

1: Cochrane Database Syst Rev. 2007 Jul 18;(3):CD005958.

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Manual material handling advice and assistive devices for preventing and treating back pain in workers.

Martimo KP, Verbeek J, Karppinen J, Furlan AD, Kuijer PP, Viikari-Juntura E, Takala EP, Jauhiainen M.

Finnish Institute of Occupational Health, Topeliuksenkatu 41 a A, Helsinki, Finland, 00250. kari-pekka.martimo@ttl.fi

BACKGROUND: Training and assistive devices are considered major interventions to prevent back pain among workers exposed to manual material handling (MMH). OBJECTIVES: To determine the effectiveness of MMH advice and training and the provision of assistive devices in preventing and treating back pain. SEARCH STRATEGY: We searched MEDLINE to November 2005, EMBASE to August 2005, and CENTRAL, the Back Group's Trials Register, CINAHL, Nioshtic, CISdoc, Science Citation Index, and PsychLIT to September 2005. SELECTION CRITERIA: We included randomized controlled trials (RCT) and cohort studies with a concurrent control group, aimed at changing human behaviour in MMH and measuring back pain, back pain-related disability or sickness absence. DATA COLLECTION AND ANALYSIS: Two authors independently extracted the data and assessed the methodological quality using the criteria recommended by the Back Review Group for RCTs and MINORS for the cohort studies. One author of an original study supplied additional data for the review.The results and conclusions are based on the primary analysis of RCTs. We conducted a secondary analysis with cohort studies. We compared and contrasted the conclusions from the primary and secondary analyses. MAIN RESULTS: We included six RCTs (17,720 employees) and five cohort studies (772 employees). All studies focused on prevention of back pain. Two RCTs and all cohort studies met the majority of the quality criteria and were labeled high quality.We summarized the strength of the evidence with a qualitative analysis since the lack of data precluded a statistical analysis.There is moderate evidence that MMH advice and training are no more effective at preventing back pain or back pain-related disability than no intervention (four studies) or minor advice (one study). There is limited evidence that MMH advice and training are no more effective than physical exercise or back belt use in preventing back pain (three studies), and that MMH advice plus assistive devices are not more effective than MMH advice alone (one study) or no intervention (one study) in preventing back pain or related disability.The results of the cohort studies were similar to the randomised studies. AUTHORS' CONCLUSIONS: There is limited to moderate evidence that MMH advice and training with or without assistive devices do not prevent back pain, back pain-related disability or reduce sick leave when compared to no intervention or alternative interventions. There is no evidence available for the effectiveness of MMH advice and training or MMH assistive devices for treating back pain.

Publication Types:

PMID: 17636814 [PubMed - indexed for MEDLINE]

: Three-dimensional motion analysis of the lumbar spine during "free squat" weight lift training.

Walsh JC, Quinlan JF, Stapleton R, FitzPatrick DP, McCormack D.

Cappagh National Orthopaedic Hospital, Finglas, Dublin, Republic of Ireland. james.walsh@ireland.com

BACKGROUND: Heavy weight lifting using a squat bar is a commonly used athletic training exercise. Previous in vivo motion studies have concentrated on lifting of everyday objects and not on the vastly increased loads that athletes subject themselves to when performing this exercise. HYPOTHESIS: Athletes significantly alter their lumbar spinal motion when performing squat lifting at heavy weights. STUDY DESIGN: Controlled laboratory study. METHODS: Forty-eight athletes (28 men, 20 women) performed 6 lifts at 40% maximum, 4 lifts at 60% maximum, and 2 lifts at 80% maximum. The Zebris 3D motion analysis system was used to measure lumbar spine motion. Exercise was performed as a "free" squat and repeated with a weight lifting support belt. Data obtained were analyzed using SAS. RESULTS: A significant decrease (P < .05) was seen in flexion in all groups studied when lifting at 40% maximum compared with lifting at 60% and 80% of maximum lift. Flexion from calibrated 0 point ranged from 24.7 degrees (40% group) to 6.8 degrees (80% group). A significant increase (P < .05) was seen in extension when lifting at 40% maximum was compared with lifting at 60% and 80% maximum lift. Extension from calibrated 0 point ranged from -1.5 degrees (40% group) to -20.3 degrees (80% group). No statistically significant difference was found between motion seen when exercise was performed as a free squat or when lifting using a support belt in any of the groups studied. CONCLUSION: Weight lifting using a squat bar causes athletes to significantly hyperextend their lumbar spines at heavier weights. The use of a weight lifting support belt does not significantly alter spinal motion during lifting.

PMID: 17307893 [PubMed - indexed for MEDLINE]

: Effect of a stiff lifting belt on spine compression during lifting.

Kingma I, Faber GS, Suwarganda EK, Bruijnen TB, Peters RJ, van Dieën JH.

Institute of Fundamental and Clinical Human Movement Sciences, Faculty of Human Movement Sciences, Vrije Universiteit, Amsterdam, Netherlands. I_KINGMA@FBW.VU.NL

STUDY DESIGN: An in vivo study on weightlifters. OBJECTIVES: To determine if and how a stiff back belt affects spinal compression forces in weightlifting. SUMMARY OF BACKGROUND DATA: In weightlifting, a back belt has been reported to enhance intraabdominal pressure (IAP) and to reduce back muscle EMG and spinal compression forces. METHODS: Nine experienced weightlifters lifted barbells up to 75% body weight while inhaling and wearing a belt, inhaling and not wearing a belt, and exhaling and wearing a belt. IAP, trunk muscle EMG, ground reaction forces, and kinematics were measured. An EMG-assisted trunk model, including IAP effects, was used to calculate spinal compression and shear forces and to reveal the contribution of back muscles, abdominal muscles, and IAP to moment generation. RESULTS: The belt reduced compression forces by about 10%, but only when inhaling before lifting. The moment generated by IAP increased when wearing a belt and inhaling, but this moment was small and the increase was largely negated by the flexing moment generated by abdominal muscles. CONCLUSIONS: Wearing a tight and stiff back belt while inhaling before lifting reduces spine loading. This is caused by a moment generated by the belt rather than by the IAP.

PMID: 17047531 [PubMed - indexed for MEDLINE]

4: Clin Auton Res. 2005 Apr;15(2):83-91.

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Cerebral autoregulation is temporarily disturbed in the early recovery phase after dynamic resistance exercise.

Koch A, Ivers M, Gehrt A, Schnoor P, Rump A, Rieckert H.

Dept. III, German Naval Medical Institute, Kopperpahler Allee 120, 24119, Kiel-Kronshagen, Germany. koch@email.uni-kiel.de

AIM: To determine cerebral blood-flow velocity (CBFV) and parameters of dynamic cerebral autoregulation (CA) during and after exhausting resistance exercise. METHODS: Strength endurance (23 repetitions) and maximal strength training (8 repetitions) in 16 female and 16 male athletes on a leg curler (m. quadriceps training; approx. 2 s contraction) in the upright position. Registration of ECG, blood pressure by Finapres, CBFV by transcranial Doppler (TCD), and breathing by a Zak breathing-belt. Additional repetitive ergospirometry (O2-uptake, CO2-elimination, ventilation) and blood gas analyses were performed in a subgroup of seven athletes. From BP and CBFV cerebrovascular resistance (CVR), pulsatility index (PI) as well as LF-power, gain and phase-angle (frequency analysis) were derived. RESULTS: All athletes showed significant (p<0.01) 15 % to 30 % increases in CBFV during both training sets without signs of flow depression due to Valsalva maneuvers. In the early recovery, when blood pressure rapidly decreased, CBFV amplitude significantly (p<0.01) increased for 60-80 seconds with mean flow (Vm) at the exercise level, while CVR and PI showed conflicting results, similar to a presyncopal reaction. Ergospirometry and blood gas analyses revealed no evidence of major changes in pCO2, but phase angle was reduced (p<0.001) after exercise, together with an LF power increase (p<0.001). CONCLUSION: An unexpected increase in CBFV amplitude and in Vm occurs directly after dynamic resistance exercise without increased pCO2, which is comparable to a maximum leg press with hypercapnia. CVR and PI results as well as data from frequency analysis show similarities to presyncopal reactions, on the one hand, and point towards a temporarily disturbed cerebral autoregulation, on the other.

Publication Types:

Clinical Trial

PMID: 15834764 [PubMed - indexed for MEDLINE]

: An electromyographic analysis of sumo and conventional style deadlifts.

Escamilla RF, Francisco AC, Kayes AV, Speer KP, Moorman CT 3rd.

Michael W. Krzyzewski Human Performance Laboratory, Division of Orthopaedic Surgery, Duke University Medical Center, P.O. Box 3435, Durham, NC 27710, USA. rescamil@duke.edu

PURPOSE: Strength athletes often employ the deadlift in their training or rehabilitation regimens. The purpose of this study was to compare muscle activity between sumo and conventional style deadlifts, and between belt and no-belt conditions. METHODS: Six cameras collected 60-Hz video data and 960-Hz electromyographic data from 13 collegiate football players who performed sumo and conventional deadlifts with and without a lifting belt, employing a 12-RM intensity. Variables measured were knee angles and EMG measurements from 16 muscles. Muscle activity were averaged and compared within three 30-degree knee angle intervals from 90 to 0 degrees during the ascent, and three 30-degree knee angle intervals from 0 to 90 degrees during the descent. RESULTS: Overall EMG activity from the vastus medialis, vastus lateralis, and tibialis anterior were significantly greater in the sumo deadlift, whereas overall EMG activity from the medial gastrocnemius was significantly greater in the conventional deadlift. Compared with the no-belt condition, the belt condition produced significantly greater rectus abdominis activity and significantly less external oblique activity. For most muscles, EMG activity was significantly greater in the knee extending intervals compared with the corresponding knee flexing intervals. Quadriceps, tibialis anterior, hip adductor, gluteus maximus, L3 and T12 paraspinal, and middle trapezius activity were significantly greater in higher knee flexion intervals compared with lower knee flexion intervals, whereas hamstrings, gastrocnemius, and upper trapezius activity were greater in lower knee flexion intervals compared with higher knee flexion intervals. CONCLUSIONS: Athletes may choose to employ either the sumo or conventional deadlift style, depending on which muscles are considered most important according to their training protocols. Moderate to high co-contractions from the quadriceps, hamstrings, and gastrocnemius imply that the deadlift may be an effective closed kinetic chain exercise for strength athletes to employ during knee rehabilitation.

PMID: 11932579 [PubMed - indexed for MEDLINE]

6: Spine. 2002 Feb 1;27(3):282-90.

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Effect of belt pressure and breath held on trunk electromyography.

Lee YH, Kang SM.

Department of Industrial Management, National Taiwan University of Science and Technology, Taipei, Taiwan, ROC. yhlee@im.ntust.edu.tw

STUDY DESIGN: This study examined the effect of a belt on ventilation and trunk muscle activities during repetitive lifting tasks with a control of breathing type and belt pressure. OBJECTIVES: To evaluate the effect of the lifting belt on the trunk muscle electromyography (EMG) and to parse out potential interaction between ventilatory changes and lifting belts. SUMMARY OF BACKGROUND DATA: Although both tensed thorax and compressed abdomen are considered to assist transferring the force from torso to pelvis in lifting, there has not been any consideration of the interaction between the two chambers in most published analyses. METHODS: Eleven male study participants participated in the study. They performed five minutes of paced repetitive squat lifts at frequencies of one or three lifts per minute, with loads of 10 or 25 kg. Belt pressure was set at 0 (no belt), 10, and 20 mm Hg. Study participants lifted with inspire-hold and expire-hold for a period of 5 minutes. Lift ventilation data and trunk muscle normalized electromyography (NEMG) (including rectus abdominis, external oblique, latissimus dorsi, and erector spinae) for the final lift were collected for analysis. RESULTS: The results indicate that the ventilation demand for lifting was not different with or without use of a belt. The prelifting erector spinae NEMG was 8-11% maximum voluntary contraction (MVC) lower and the latissimus dorsi NEMG was 15-21% MVC lower than that without belt. This is also the case in the lifting phase. The rectus abdominis NEMG was increased by 4% MVC and the external oblique NEMG was increased by 3-5% MVC while lifting with a belt. CONCLUSIONS: These data do not lead to a statistical effect of lifting belt pressure on ventilatory behavior. It appears that the use of a belt in lifting significantly decreased the back muscular activation yet increased the abdominal muscular activation. Thus, claims of benefits derived from the use of a belt in lifting remain controversial. The simultaneous controls of the air volume held and pressure of the belt during the moment-controlled lifting tasks allowed this presentation of belt effects on trunk muscle NEMG unique from that in most of the literature.

Publication Types:

PMID: 11805693 [PubMed - indexed for MEDLINE]

1: Clin Biomech (Bristol, Avon). 2006 Aug;21(7):668-75. Epub 2006 May 6.

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Wrapping of trunk thoracic extensor muscles influences muscle forces and spinal loads in lifting tasks.

Arjmand N, Shirazi-Adl A, Bazrgari B.

Division of Applied Mechanics, Department of Mechanical Engineering, Ecole Polytechnique, P.O. Box 6079, Station centre-ville, Montréal, Que., Canada H3C 3A7.

BACKGROUND: An improved assessment of risk of spinal injury during lifting activities depends on an accurate estimation of trunk muscle forces, spinal loads and stability margin which in turn requires, amongst others, an accurate description of trunk muscle geometries. The lines of action of erector spinae muscles are often assumed to be linear despite the curved paths of these muscles in forward flexion postures. METHODS: A novel approach was introduced that allowed for the proper simulation of curved paths for global extensor muscles in our Kinematics-driven finite element model. The lever arms of global muscles at different levels were restrained either to remain the same or decrease only by 10% relative to their respective values in upright posture. Based on our earlier measurements, static lifting tasks at two trunk flexions (40 degrees and 65 degrees ) and three lumbar postures (free style, lordotic and kyphotic) with 180 N in hands were analyzed. FINDINGS: Muscle forces and spinal compression at all levels substantially decreased as the global extensor muscles took curved paths. In contrast, the shear force at lower levels increased. Allowing for a 10% reduction in these lever arms during flexion increased muscle forces and compression forces at all levels. Despite smaller muscle forces, wrapping of global muscles slightly improved the spinal stability. INTERPRETATION: Consideration of global extensor muscles with curved paths and realistic lever arms is important in biomechanical analysis of lifting tasks. Reduction in the erector spinae lever arms during flexion tasks could vary depending on the lumbar posture. Results advocate small flattening of the lumbar curvature in isometric lifts yielding smaller compression and shear forces at the critical L5-S1 level.

Publication Types:

PMID: 16678948 [PubMed - indexed for MEDLINE]

2: Eur Spine J. 1999;8(5):388-95.

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Comment in:

Spine. 2002 Aug 15;27(16):1754.

Lumbar spine stability can be augmented with an abdominal belt and/or increased intra-abdominal pressure.

Cholewicki J, Juluru K, Radebold A, Panjabi MM, McGill SM.

Biomechanics Laboratory, Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, P.O. Box 208071, New Haven, CT 06520-8071, USA. cholewicki@biomed.med.yale.edu

The increased intra-abdominal pressure (IAP) commonly observed when the spine is loaded during physical activities is hypothesized to increase lumbar spine stability.The mechanical stability of the lumbar spine is an important consideration in low back injury prevention and rehabilitation strategies. This study examined the effects of raised IAP and an abdominal belt on lumbar spine stability. Two hypotheses were tested: (1) An increase in IAP leads to increased lumbar spine stability, (2) Wearing an abdominal belt increases spine stability. Ten volunteers were placed in a semi-seated position in a jig that restricted hip motion leaving the upper torso free to move in any direction. The determination of lumbar spine stability was accomplished by measuring the instantaneous trunk stiffness in response to a sudden load release. The quick release method was applied in isometric trunk flexion, extension, and lateral bending. Activity of 12 major trunk muscles was monitored with electromyography and the IAP was measured with an intra-gastric pressure transducer. A two-factor repeated measures design was used (P < 0.05), in which the spine stability was evaluated under combinations of the following two factors: belt or no belt and three levels of IAP (0, 40, and 80% of maximum). The belt and raised IAP increased trunk stiffness in all directions, but the results in extension lacked statistical significance. In flexion, trunk stiffness increased by 21% and 42% due to 40% and 80% IAP levels respectively; in lateral bending, trunk stiffness increased by 16% and 30%. The belt added between 9% and 57% to the trunk stiffness depending on the IAP level and the direction of exertion. In all three directions, the EMG activity of all 12 trunk muscles increased significantly due to the elevated IAP. The belt had no effect on the activity of any of the muscles with the exception of the thoracic erector spinae in extension and the lumbar erector spinae in flexion, whose activities decreased. The results indicate that both wearing an abdominal belt and raised IAP can each independently, or in combination, increase lumbar spine stability. However, the benefits of the belt must be interpreted with caution in the context of the decreased activation of a few trunk extensor muscles.

Publication Types:

PMID: 10552322 [PubMed - indexed for MEDLINE]

: Analysis of squat and stoop dynamic liftings: muscle forces and internal spinal loads.

Bazrgari B, Shirazi-Adl A, Arjmand N.

Department of Mechanical Engineering, Ecole Polytechnique, Montreal, QC, Canada.

Despite the well-recognized role of lifting in back injuries, the relative biomechanical merits of squat versus stoop lifting remain controversial. In vivo kinematics measurements and model studies are combined to estimate trunk muscle forces and internal spinal loads under dynamic squat and stoop lifts with and without load in hands. Measurements were performed on healthy subjects to collect segmental rotations during lifts needed as input data in subsequent model studies. The model accounted for nonlinear properties of the ligamentous spine, wrapping of thoracic extensor muscles to take curved paths in flexion and trunk dynamic characteristics (inertia and damping) while subject to measured kinematics and gravity/external loads. A dynamic kinematics-driven approach was employed accounting for the spinal synergy by simultaneous consideration of passive structures and muscle forces under given posture and loads. Results satisfied kinematics and dynamic equilibrium conditions at all levels and directions. Net moments, muscle forces at different levels, passive (muscle or ligamentous) forces and internal compression/shear forces were larger in stoop lifts than in squat ones. These were due to significantly larger thorax, lumbar and pelvis rotations in stoop lifts. For the relatively slow lifting tasks performed in this study with the lowering and lifting phases each lasting approximately 2 s, the effect of inertia and damping was not, in general, important. Moreover, posterior shift in the position of the external load in stoop lift reaching the same lever arm with respect to the S1 as that in squat lift did not influence the conclusion of this study on the merits of squat lifts over stoop ones. Results, for the tasks considered, advocate squat lifting over stoop lifting as the technique of choice in reducing net moments, muscle forces and internal spinal loads (i.e., moment, compression and shear force).

PMID: 17103232 [PubMed - indexed for MEDLINE]