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PubMed2004

Isometric strength and dynamic back extensor endurance are unrelated in children ages 6-10 years: a pilot study.

This study assessed the correlation between back extensor isometric force and dynamic endurance in 69 children 6-10 years of age. Subjects were positioned prone with legs and hips supported and restrained on two folded 6-in. mats. 42 subjects (20 girls; 22 boys) performed three 5-sec. isometric back extension efforts against a calibrated dynamometer and peak force values were averaged. An additional 27 subjects (9 girls; 18 boys) also performed a dynamic (0 degrees --> 45 degrees flexion-->0 degrees) back extension test at a frequency of 20 per minute, and the number of repetitions was recorded. Both tests were repeated at a 1-wk. interval. Pearson correlations for the endurance, the isometric force test, and test-retest, and between the functional concentric endurance vs isometric force were .55, .79 (both p<.01), and .03, respectively. These tests have moderate to high reliability but they examine different aspects of back muscle fitness. They should not be used interchangeably to assess back extensor muscle fitness. Further investigation must determine whether different dynamic test frequencies and mat heights yield different results.

Back↗
PubMed1982

Evidence for membrane microheterogeneity in the sarcoplasmic reticulum of fast twitch skeletal muscle.

Sarcoplasmic reticulum (SR) from rabbit back muscles can be readily subfractionated into two morphologically and compositionally different vesicular populations, SRH (heavy) and SRL (light) derived from terminal cisternae and longitudinal SR, respectively. Polyacrylamide gels indicate that SRH contains most of the calsequestrin. Quantitation of freeze-fractured isolated preparations reveals that, while differences in vesicular dimensions are seen in SRH and SRL, the intramembrane particle (Ca2+ ATPase) density is identical. Phospholipid headgroup composition is the same in SRH and SRL, but fatty acyl moieties show significant differences in the ratio of saturated to unsaturated phospholipids in the two fractions. The vesicular dimensions of the purified Ca2+-ATPases, SRHP and SRLP, from the two fractions are identical, but the freeze-fracture particle density is higher in the SRLP fraction. The phospholipid composition remains similar after purification, but the differences in phospholipid fatty acyl composition of the preparations are maintained. SRH and SRHP contain almost twice as much of the unsaturated species as compared to SRL and SRLP. Differences in intramembrane particle density in purified fractions, thermotropic segregation of particles in freeze-fractured purified fractions, as well as differences in turnover of the acyl phosphate, appear to reflect the differences in fatty acyl chain composition of the two SR fractions and provide evidence of microheterogeneity in lipid-protein environment of the SR.

Animals↗
PubMed2005

Intramuscular pressure, tissue oxygenation and EMG fatigue measured during isometric fatigue-inducing contraction of the multifidus muscle.

Simultaneous measurement of intramuscular pressure (IMP), tissue oxygen partial pressure (pO(2)) and EMG fatigue parameters in the multifidus muscle during a fatigue-inducing sustained muscular contraction. The study investigated the following hypotheses: (1) Increases in IMP result in tissue hypoxia; (2) Tissue hypoxia is responsible for loss of function in the musculature. The nutrient supply to muscle during muscle contraction is still not fully understood. It is assumed that muscle contraction causes increased tissue pressure resulting in compromised perfusion and tissue hypoxia. This tissue hypoxia, in turn, leads to muscle fatigue and therefore to loss of function. To the authors' knowledge, no study has addressed IMP, pO(2) and EMG fatigue parameters in the same muscle to gain a deeper sight into muscle perfusion during contraction. As back muscles need to have a constant muscular tension to maintain trunk stability during stance and locomotion, muscle fatigue due to prolonged contraction-induced hypoxia could be an explanation for low back pain. Sixteen healthy subjects performed an isometric muscular contraction exercise at 60% of maximum force until the point of localized muscular fatigue. During this exercise, the individual changes of IMP, pO(2) and the median frequency (MF) of the surface EMG signal of the multifidus muscle were recorded simultaneously. In 12 subjects with a documented increase in intramuscular pressure, only five showed a decrease in tissue oxygen partial pressure, while this parameter remained unchanged in six other subjects and even increased in one. A fall in tissue pO(2) was associated with a drop in MF in only five subjects, while there was no correlation between these parameters in the other 11 subjects. To summarize, an increase in IMP correlated with a decrease in pO(2) and a drop in MF in only five out of 16 subjects. High intramuscular pressure values are not always associated with a hypoxia in muscle tissue. Tissue hypoxia is not automatically associated with a median frequency shift in the EMG signal's power spectrum.

Adult↗
PubMed2002

Electromyography and ratings of lumbar muscle fatigue using a four-level staircase protocol.

OBJECTIVE: The purpose of the study was to explore whether a relationship existed between subject's experience and objective measurements of back-muscle fatigue in healthy subjects. This may be used as reference material later. DESIGN: Muscle fatigue in the lower back was measured in healthy subjects using a staircase protocol. BACKGROUND: Muscle fatigue measurement in the lower back is of importance when assessing patients with low-back pain. The subject's experience of muscle fatigue needs to be explored further. METHODS: Twenty healthy subjects with informed consent participated. Borg CR-10 scale responses and electromyography measurements were obtained from low-back muscles of the subjects following a staircase protocol with sustained contractions at 20%, 40%, 60%, and 80% of maximum voluntary contraction. RESULTS: A strong correlation was found between Borg ratings and force (r=0.83) and between slope and force (r= -0.72) but not between Borg ratings and slopes which was at best 0.43 (/r/< or =0.43). CONCLUSIONS: Although subjective ratings and slopes showed a low correlation; increases in force with a concomitant increase in fatigue was reflected both by the subjective ratings and the slope. One cannot use subjective ratings for prediction of the slope for this type of protocol. However, a more complete description of muscle fatigue needs both the slope and the Borg ratings. RELEVANCE: In clinical testing, both subjective and objective measures of muscle fatigue must be considered since they measure different aspects of muscle fatigue. The median frequency slope probably reflects "physical discomfort" but the Borg ratings add a factor of "lack of energy".

Adult↗
PubMed2001

The effects of three different training modalities on the cross-sectional area of the paravertebral muscles.

The purpose of this study was to determine the effect of different training schedules on the cross-sectional area (CSA) of the paravertebral muscles (PA) in chronic low back pain (CLBP) patients. To achieve this goal 59 patients were randomly assigned to three different 10-week rehabilitation programs: stabilization training (group 1, n=19), stabilization training combined with dynamic resistance training (group 2, n=20) and stabilization training combined with dynamic-static resistance training (group 3, n=20). The CSA of the PA was derived from standard computerized tomography (CT) images at three different levels. The CSA of the PA was found to increase statistically in group 2 (upper end-plate of L4) and group 3 (upper end-plate of L3 and lower end-plate of L4). In contrast, no statistical differences over time were found in group 1. Since stabilization exercises have no effect on the CSA of the PA, intensive lumbar resistance training seems to be necessary to restore the size of the PA in CLBP patients with atrophied back muscles. No systematic difference in hypertrophy between dynamic and dynamic-static strengthening training modes was found.

Adult↗
PubMed2004

A possible methodological flaw in comparing dominant and nondominant sided lumbar spine muscle responses without simultaneously considering hand dominance.

STUDY DESIGN: Different factorial designs analyzing the same data were compared for consistent interpretation. OBJECTIVE: To assess hand dominance as an explanatory factor when comparing dominant and nondominant side back muscle response time delay and fatigability. SUMMARY OF BACKGROUND DATA: A number of studies have evaluated lumbar spinal muscle responses to sudden load and fatigue. Although the dominant side of the back is usually determined by considering hand dominance, few studies explicitly consider hand dominance as part of the explanatory model and assume that right- and left-handed patients are not unique cohorts. METHODS.: The erector spinae and multifidi lumbar muscle groups in patients with chronic low back pain (CLBP) were investigated. For the response time to a sudden load, the biceps brachii muscle was compared with erector spinae and multifidi muscles to understand any compensatory upper extremity movement patterns. For fatigue, the erector spinae and multifidi muscle median frequency (MF) and its slope (MFS) were measured during a 1-minute isometric back extension maneuver. RESULTS: Altogether, 46 patients with CLBP were studied. Right- and left-handed subjects did not differ in reported disability based on the Oswestry Disability Index, (F1, 44 = 2.11, P < 0.153). The dominant and nondominant side response times were significantly different for left-handed patients but not for right-handed patients. The nondominant side back muscles, located on the contralateral side of the dominant hand, were faster for the right-hand dominant patients and slower for the left-hand dominant patients. In the muscles on the nondominant side of the back, the left-hand dominant patients demonstrated significantly more fatigue than right-hand dominant patients. However, in the muscles on the dominant side of the back, neither set of patients demonstrated fatigability. CONCLUSIONS: When examining differential lumbar muscle responses, failing to consider hand dominance explicitly in conjunction with the side assessed resulted in confounding effects. The results of the study indicated a delayed back muscle response time on the nondominant side. This delayed response time raises the possibility that unbalanced muscle activity could prompt a decreased, uncoordinated, asymmetric bracing effect, thereby increasing the risk of lumbar segment buckling. Further studies are needed to investigate the characteristics of the back muscles on the same side of the dominant hand and the factors mediating neuromuscular differences in patients with CLBP. Understanding the effects of hand dominance on fatigue in certain back muscles should lead to better treatments thereby improving neuromuscular control in patients with CLBP.

Adult↗
PubMed2006

Muscle activity onset in the lumbar multifidus muscle recorded simultaneously by ultrasound imaging and intramuscular electromyography.

BACKGROUND: Delayed anticipatory muscle activity response in deep abdominal and back muscles has been observed in patients with low back pain, indicative of a pathological condition. Muscle activity onset is traditionally recorded by intramuscular electromyography, but there is a need for a non-invasive and less cumbersome recording method in large clinical studies. An experimental study was carried out to explore whether high-frame rate m-mode ultrasound could measure anticipatory muscle responses ("onset") in the lumbar multifidus muscle reliably and comparably accurate to intramuscular electromyography. METHODS: Muscle activity onset was recorded by ultrasound m-mode and intramuscular electromyography. Ultrasound m-mode with a temporal resolution of 500 s(-1) (frames per second) was used to record rapid movements caused by muscle deformations in multifidus. In ultrasound m-mode, the frequency of each echo signal from 0.15 mm incremental depth levels is analysed. The frequency of these signals is proportional to the velocity of the interrogated tissue. The mean amplitude of the high-pass filtered echo signals within a pre-set depth range was plotted against time, and used to indicate onset. The results were compared to muscle activity onset in the multifidus recorded simultaneously by intramuscular electromyography. FINDINGS: High inter-rater agreement was found for visual determination of onset within both methods. The smallest detectable difference was 21 and 24 ms for electromyography and the ultrasound methods, respectively. The ultrasound m-mode method recorded muscle activity onset in the deep multifidus on average 16 ms (SD 21) later than intramuscular electromyography. For single trials, large variation and thus unacceptable method agreement was found. INTERPRETATION: Ultrasound m-mode imaging at high time resolution can detect onset of muscle activity comparably accurate to intramuscular electromyography, but with a small systematic delay that should be corrected for in onset determination by m-mode ultrasound. Regardless of recording method, onset estimates should be based on averaged values of repeated trials. Further studies are needed to explore the applicability of the ultrasound method in clinical settings.

Adult↗
PubMed1993

Muscle strength in osteoporotic versus normal women.

Strong back muscles contribute to good posture and skeletal support. Osteoporosis, being a metabolic bone disease, should not affect muscle strength. In this study we were interested in comparing the back extensor strength (BES) of osteoporotic and normal women. Fifty-five women ages 40-85 years who had a documented diagnosis of osteoporosis and were referred for initiation of proper exercise programs were included in our study after meeting the inclusion criteria. They all had evaluation of their posture, back and upper extremity strength, and physical activity score through our Rehabilitation of Osteoporosis Program--Exercise (ROPE). In addition, to avoid the interference of pain on application of maximal effort, we did not include subjects with acute back pain or those who experienced back pain with maximal effort during the testing trial. BES for osteoporotic women ranged from 16 to 65 lb (mean +/- SD, 36.5 +/- 15.5) for ages 40-59 years, 9 to 55 lb (mean +/- SD, 29.9 +/- 10.6) for ages 60-69 years, 6 to 52 lb (mean +/- SD, 24.3 +/- 10.2) for ages 70-79 years, and 17 to 27 lb (mean +/- SD, 21.2 +/- 4.2) for ages 80 years or older. Comparison of these data with the BES of 25 normal women, with statistical adjustment for age, demonstrated that the osteoporotic women had significantly lower BES than the normal women. A longitudinal study of a larger group of women would be of great interest for clarifying whether the weakness of back extensors precedes and, indeed, contributes to compression fractures of the spine.

Adult↗
PubMed2000

Sudden and unexpected loading generates high forces on the lumbar spine.

STUDY DESIGN: A cross-sectional study of spinal loading in healthy volunteers. OBJECTIVES: To measure the bending and compressive forces acting on the lumbar spine, in a range of postures, when unknown loads are delivered unexpectedly to the hands. SUMMARY OF BACKGROUND DATA: Epidemiologic studies suggest that sudden and unexpected loading events often lead to back injuries. Such incidents have been shown to increase back muscle activity, but their effects on the compressive force and bending moment acting on the spine have not been fully quantified. Furthermore, previous investigations have focused on the upright posture only. METHODS: In this study, 12 volunteers each stood on a force plate while weights of 0, 2, 4, and 6 kg (for men, 40% less for women) were delivered into their hands in one of three ways: 1) by the volunteer holding an empty box with handles, into which an unknown weight was dropped; 2) by the same way as in 1, but with volunteer wearing a blindfold and earphones to eliminate sensory cues; or 3) by the volunteer sliding a box of unknown weight off a smooth table. Experiments were carried out with participants standing in upright, partially flexed, and moderately flexed postures. Spinal compression resulting from muscular activity was quantified using electromyographic signals recorded from the back and abdominal muscles. The axial inertial force acting up the long axis of the spine was calculated from the vertical ground reaction force. The bending moment acting on the osteoligamentous spine was quantified by comparing measurements of lumbar curvature with the bending stiffness properties of cadaveric lumbar spines. RESULTS: The contribution from abdominal muscle contraction to overall spinal compression was small (average, 8%), as was the axial inertial force (average, 2.5%), and both were highest in the upright posture. Peak bending moments were higher in flexed postures, but did not increase much at the moment of load delivery in any posture. Peak spinal compressive forces were increased by 30% to 70% when loads were suddenly and unexpectedly dropped into the box, and by 20% to 30% when they were slid off the table, as compared with loads simply held statically in the same posture (P < 0.001). The removal of audiovisual cues had little effect. CONCLUSIONS: Sudden and alarming events associated with manual handling cause a reflex overreaction of the back muscles, which substantially increases spine compressive loading. Manual handling regulations should aim to prevent such events and limit the weight of objects to be lifted.

Abdominal Muscles↗
PubMed2006

Electromyographic activity of trunk and hip muscles during stabilization exercises in four-point kneeling in healthy volunteers.

Stabilization exercises are intended to optimize function of the muscles that are believed to govern trunk stability. Debate exists whether certain muscles are more important than others in optimally performing these exercises. Thirty healthy volunteers were asked to perform three frequently prescribed stabilization exercises in four-point kneeling. The electromyographic activity of different trunk and hip muscles was evaluated. Average amplitudes obtained during the exercises were normalized to the amplitude in maximal voluntary contraction (% MVIC). During all three exercises, the highest relative muscle activity levels (> 20% MVIC) were consistently found in the ipsilateral lumbar multifidus and gluteus maximus. During both the single leg extension (exercise 1) and the leg and arm extension exercise (exercise 2) the contralateral internal oblique and ipsilateral external oblique reached high levels (> 20%MVIC). During exercise 2 there were also high relative activity levels of the ipsilateral lumbar part and the contralateral thoracic part of the iliocostalis lumborum and the contralateral lumbar multifidus. During the leg and arm extension exercise with contralateral hip flexion (exercise 3) there were high relative muscle activity levels of all back muscles, except for the latissimus dorsi muscle. The lowest relative muscle activity levels (< 10% MVIC) were found in the rectus abdominis and the ipsilateral internal oblique during all exercises, and in the contralateral gluteus maximus during exercises 1 and 2. The results of this study show that in exercises in four-point kneeling performed by healthy subjects, hip and trunk muscles seem to work together in a harmonious way. This shows that when relative activity of muscles is measured, both "global and local" muscles function together in order to stabilize the spine.

Adult↗
PubMed1990

Histopathological changes in paravertebral muscles by chronic discopathies.

Samples of paravertebral muscles were obtained from the lesion sites of forty patients operated on for recurrent lumboischiadic syndrome of discogenic etiology. None of the specimens was physiological. All of them were pathologically altered in various grades of involvement. The histopathological changes were highly varied. The findings included muscle fibre atrophy of a nonspecific type, neurogenic atrophy of typical fascicular distribution. Apart from atrophic fibres there were hypertrophic ones either at the same time or in connection with another histopathological process. Changes of myopathic nature were also present with rounded up muscle fibres and shift of nuclei from the subsarcolemnic spaces into the centre of the muscle fibre, multiplication of the connective tissue and vicarious growth of adipose tissue. The visible neuromuscular spindles contained thickened connective tissue capsules and atrophied intrafusal fibres. The present authors' conclusion of their interpretation of these histopathological changes is that they are not produced by one but by a whole set of factors. What results is a cyclic nature of the changes, when it is hard to decide whether we are facing a primary cause or its sequela. The regular company of discopathies are repeated microtraumas during recurrent paravertebral contractures and spinal blocks. A not negligible part can be played also by primary muscle diseases affecting, among others, back muscles, e.g. progressive muscular dystrophy of Duchenne's and Becker's type, various myopathies, nonspecific myositis and paravertebral polymyositis, and other rheumatological involvement. These muscular diseases with disturbed proprioception causing unphysiological posture and loading the spine can share in the origin degenerative processes on intervertebral disks.

Adult↗
PubMedDate not supplied

[Effect of short-term thermal loads on tissue respiration of skeletal muscles and internal organs of chickens during hypokinesia].

The effect of high temperature (35 degrees C) on the gas exchange and tissue respiration of skeletal muscles and viscera of 47 chickens weighing 1100-1700 g was investigated on hypokinesia days 1, 20, 40 and 60. After 2 hour thermal exposure the rate of oxidative processes decreased, particularly on day 40. Oxygen consumption by femur, chest, neck and heart muscles decreased and that by back muscles did not change on hypokinesia days 30 and 60. Carbon dioxide production by various muscles was lower on day 20 and unchanged on day 60. The respiration quotient of the skeletal muscles and viscera increased on hypokinesia days 1 and 60. It can therefore be concluded that thermal exposure combined with hypokinesia produces not only quantitative but also qualitative metabolic changes.

Animals↗
PubMed1984

Studies on steroid receptors in human and rabbit skeletal muscle - clues to the understanding of the mechanism of action of anabolic steroids.

The mechanism of action of steroid hormones in target tissues include the binding of the steroid molecule to specific receptors in the cytoplasm. Steroid receptors may therefore be regarded as mediators of hormone action. The presence of such receptors in tissues reflects their hormone-sensitivity and the receptor levels are indicative of the relative potential for a direct hormonal action on the tissue in question. Using 3H-labeled synthetic ligands and a charcoal adsorption assay, the presence of specific androgen, glucocorticoid and estrogen (in rabbits only) receptors was demonstrated in human and rabbit skeletal muscle cytosol. These tissues can therefore be regarded as targets for these steroids. Scatchard analysis was then used to quantitate the receptors in muscle in different conditions. In back muscle of scoliotic patients, the concentrations of androgen and glucocorticoid receptors were similar on the convex and concave sides, except the concentration of glucocorticoid receptors (per g of wet weight), which was higher on the convex side. The tissue concentration (per g of wet weight) of glucocorticoid and estrogen receptors (but not of androgen receptor) was higher in rabbit soleus (slow-twitch) muscle than in the gastrocnemius/plantaris (fast-twitch) muscle complex. When the concentrations were related to the number of nuclei (i.e. expressed per mg of DNA), however, only the estrogen receptor concentration differed between the muscles (higher in soleus). Muscle atrophy in rabbit gastrocnemius muscle was induced by tenotomy or denervation and led to similar changes with an increase with time in androgen and glucocorticoid receptor levels (expressed per g of wet weight or per mg of protein) and a concomitant loss of muscle weight and protein. The total muscle content of receptors or the receptor concentration expressed per mg of DNA were also increased, but to a lesser extent. Synthetic anabolic-androgenic steroids can act directly on skeletal muscle in view of their capacity to bind to the androgen receptor as shown in the present study. Relative binding affinities of anabolic-androgenic steroids to the androgen receptor were similar in rabbit and rat skeletal muscle and in rat prostate. The protein/DNA ratio in the muscle samples was used as an estimation of the size of the "functional DNA-unit". The results indicate that slow-twitch fibers have smaller "DNA units", but also that muscle atrophy causes a decrease of the size of the "DNA unit".(ABSTRACT TRUNCATED AT 400 WORDS)

Androgens↗
PubMed2005

Electromyographic functional analysis of the lumbar spinal muscles with low back pain.

The lumbar paraspinal muscles were examined by surface electromyography (EMG) in 22 patients with low back pain and 22 healthy volunteers. Surface electrodes were placed bilaterally on the lumbar multifidus and longissimus muscles at the level of the spinous process of the third lumbar vertebra. Kinesiologic EMG was recorded, in standing resting position, during the following trunk motions: trunk forward flexion and extension, lateral bending and axial rotation. No muscular activity was observed in the full trunk flexion position in the control group. In contrast, continuous muscle activity was observed in the low back pain group. On axial rotation, an intermuscular time lag was observed at the beginning of the motion in the control group. In the low back pain group, there was no such time lag. Paraspinal muscle activities restricted lumbar range of motion, and protect from injury for movement. This suggests their role as stabilizers.

Adult↗
PubMed1988

Involvement of the 60 kDa phosphoprotein in the regulation of Ca2+ release from sarcoplasmic reticulum of normal and malignant hyperthermia susceptible pig muscles.

Junctional sarcoplasmic reticulum (SR) vesicles isolated from back muscles of normal and malignant hyperthermia susceptible (MHS) pigs were phosphorylated by addition of MgATP in the presence of 5 mM Ca2+ and 1 microM calmodulin (CaM). The major site of phosphorylation was a 60 kDa protein both in normal and MHS SR. The maximal amount of phosphorylation in MHS SR (5 pmol P/mg SR) was significantly lower than that in the normal SR (12 pmol P/mg SR). The phosphorylated 60 kDa protein was spontaneously dephosphorylated both in normal and MHS SR. Ca2+ release from the passively loaded SR was induced by a Ca2+-jump, and monitored by stopped-flow fluorometry using chlorotetracycline. In the absence of preincubation with MgATP, no significant difference was found in any of the kinetic parameters of Ca2+ release between normal and MHS SR. Upon addition of 20 microM MgATP to the passively loaded SR to phosphorylate the 60 kDa protein, the initial rate of Ca2+ release in normal SR significantly decreased from 659 +/- 102 to 361 +/- 105 nmol Ca2+/mg SR per s, whereas in MHS SR the rate decreased from 749 +/- 124 to 652 +/- 179 nmol Ca2+/mg SR per s. Addition of 20 microM adenosine 5'-[beta, gamma-imido]triphosphate (p[NH]ppA) did not significantly alter the initial rate of Ca2+ release both in normal and MHS SR. These results suggest that the previously reported higher Ca2+ release rate in MHS SR (Kim et al. (1984) Biochim. Biophys. Acta 775, 320-327) is at least partly due to the reduced extent of the Ca2+/CaM-dependent phosphorylation of the 60 kDa protein. Two-dimensional gel electrophoresis study showed that amount of a protein with Mr = 55,000 was significantly lower in MHS SR than in normal SR suggesting that the abnormally lower amount of 55 kDa protein would cause the lower amount of phosphorylation of the 60 kDa protein in MHS SR.

Animals↗
PubMed1990

The effectiveness of weight-belts during the squat exercise.

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.

Abdomen↗