Percentage Of Maximum Voluntary Contraction Research Articles

Effect of Knee Orthosis Pressure Variation on Muscle Activities during Sit-to-Stand Motion in Patients with Knee Osteoarthritis.

It is yet not known whether the variation in knee orthotics pressure would lead to changes in muscle activity during-sit-to-stand postural transition in patients with knee osteoarthritis (OA). Participants in this analytical study were patients with knee OA. The research design was a cross-sectional study. They were enrolled in the study through a sample of convenience method. The primary outcome measure was surface electromyography for measuring muscle activity while changing knee orthotics pressure during sit-to-stand motion. Data were summarized with mean and standard deviation while Friedman’s test was performed for multiple comparison of variables, at a significance level of p = 0.05. Seven elderly patients with knee osteoarthritis (mean age 71.4 ± 11.8 years) participated in the study. Moderate orthotics (7.3 mmHg) led to a significant increase in the percentage maximum voluntary contraction (MVC) of tibialis anterior compared to that obtained without orthotics. Rectus femoris, vastus medialis, vastus lateralis, and biceps femoris tended to increase the % MVC with an increase in wearing pressure. It was therefore concluded that the muscle activity during sit-to-stand motion could be increased in patients with knee osteoarthritis by wearing flexible orthotics with varying pressure.

Abstract 11194: Reducing Arm Muscle Activation by Using an Ablation Catheter Torque Tool: Electromyographic Analysis and User Perception

Background: Cardiac ablation catheters are small in diameter and require significant finger dexterity and grip strength to maintain stability and maneuver safely. We designed a catheter torque tool to reduce the muscle activation required to manipulate cardiac ablation catheters and improve user perception of task workload. Objective: The purpose of this study was to evaluate muscle usage and user perception when completing a simulated ablation task with and without the use of a novel ablation catheter torque tool. Methods: Participants, comprised of cardiology attendings and fellows, were fitted with surface electromyographic (EMG) sensors on 6 key muscle groups in the left hand and forearm. Maximum voluntary contraction (MVC) was collected for equal comparison among participants. A standard ablation catheter was inserted into a pediatric cardiac ablation simulator and subjects navigated the catheter tip to 6 specific electrophysiologic targets including a 1-minute simulated radiofrequency lesion. EMG activity normalized to percentage of MVC was collected throughout the task. The task was repeated 4 times, twice with and twice without the torque tool, in randomized order. A NASA Task Load Index (TLX) survey was completed by the participant at the conclusion each task. Results: Thirteen participants completed the study. Using Wilcoxon’s test, there was a significant difference (P < 0.01) in mean percent of MVC in 4 of the 6 muscle groups when comparing bare catheter versus catheter with torque tool: abductor pollicis, brachioradialis, flexor carpi ulnaris, and extensor carpi radialis. The total expended energy for the abductor pollicis (P < 0.01) and extensor carpi radialis (P = 0.02) were significantly reduced. Perceived physical demand, effort, and frustration were also significantly reduced when using the torque tool (P < 0.01). Conclusions: Use of our novel catheter torque tool reduced the amount of muscle activation necessary to manipulate an ablation catheter during a simulated ablation task. Users’ perceived physical demand, effort, and frustration were less when the tool was used. This tool may improve catheter stability, increase procedure safety, and reduce operator stress and muscle fatigue when performing catheter ablation procedures.

Differences in Lumbar Multifidus Activity and its Association with Lumbar Range of Motion among patients With Unilateral Chronic Low Back Pain

Aim: To determine the significant difference in lumbar multifidus activity within the patient with unilateral chronic low back pain and its association with lumbar range of motion. Study design: Analytical cross-sectional study Study setting and duration: Former institute of Dow University of Health Sciences, Karachi, Pakistan (Institute of Physical Medicine and Rehabilitation) which has become Sindh Institute of Physical Medicine and Rehabilitation and study duration was March 2020 to December 2020. Methodology: About 128 patients with unilateral chronic low back pain were assessed for the lumbar multifidus activity based on the percentage of maximum voluntary contraction through surface electromyography. Lumbar flexion and extension range of motion was measured through Modified-Modified Schober’s test. All the data were analyzed through the Statistical Package of Social Sciences 21. Nonparametric tests were employed. The level of significance was 0.05. Results: The lumbar multifidus activity was significantly increased (p<0.001) on the painful side than the non-painful side. However, there was a significant negative correlation (rh=- 0.551, -0.703; p<0.001) of only painful side lumbar multifidus activity with flexion and extension range of motion. Conclusion: Activity of painful side lumbar multifidus increases in unilateral chronic low back pain. Furthermore, it increases with a decrease in lumbar flexion and extension range of motion. Keywords: Correlation Study, disability, Low Backaches, non-specific low back pain, Surface Electromyography

Comparison of Muscle Activation between Traditional, Diamond and Knuckle Push Up Among Trained Men

This study was conducted to compare the muscle activation during traditional, diamond and knuckle push up among trained men. Thirty men that had at least one year experience in fitness training involved as participants in this study. Participants were required to perform all the three kinds of push up in a randomised order to avoid bias effects in exercise order. Electromyography method was used to obtain the pectoralis major, triceps brachii and anterior deltoid muscle activation. Muscle activation was reported as percentages of maximal voluntary contraction. One way repeated measure analysis of variances (ANOVA) was conducted to compare the muscle activation between the three push up protocols. Results showed that the muscle activation of pectoralis major and anterior deltoid were highest during traditional push up while being the lowest during diamond push up. However, the muscle activation of triceps brachii was highest during diamond push up and lowest during traditional push up. As the conclusion, we can see that the position and distance of hands on the floor will give effects on the muscle activation. As the implication of this study, coaches, athletes and individuals can manipulate techniques while performing a movement to obtain more muscle activation to specific muscle of interest during a movement.

Psychophysiological responses to manual lifting of unknown loads.

BackgroundThe handling of unknown weights, which is common in daily routines either at work or during leisure time, is suspected to be highly associated with the incidence of low back pain (LBP).ObjectivesTo investigate the effects of knowledge and magnitude of a load (to be lifted) on brain responses, autonomic nervous activity, and trapezius and erector spinae muscle activity.MethodsA randomized, within-subjects experiment involving manual lifting was conducted, wherein 10 participants lifted three different weights (1.1, 5, and 15 kg) under two conditions: either having or not having prior knowledge of the weight to be lifted.ResultsThe results revealed that the lifting of unknown weights caused increased average heart rate and percentage of maximum voluntary contraction (%MVC) but decreased average inter-beat interval, very-low-frequency power, low-frequency power, and low-frequency/high-frequency ratio. Regardless of the weight magnitude, lifting of unknown weights was associated with smaller theta activities in the power spectrum density (PSD) of the central region, smaller alpha activities in the PSD of the frontal region, and smaller beta activities in the PSDs of both the frontal and central regions. Moreover, smaller alpha and beta activities in the PSD of the parietal region were associated only with lifting of unknown lightweights.ConclusionsUncertainty regarding the weight to be lifted could be considered as a stress-adding variable that may increase the required physical demand to be sustained during manual lifting tasks. The findings of this study stress the importance of eliminating uncertainty associated with handling unknown weights, such as in the cases of handling patients and dispatching luggage. This can be achieved through preliminary self-sensing of the load to be lifted, or the cautious disclosure of the actual weight of manually lifted objects, for example, through clear labeling and/or a coding system.

Forearm muscles fatigue induced by repetitive braking on a motorcycle is best discriminated by specific kinetic parameters.

Maneuvering a motorcycle in racing conditions or for prolonged time is sufficiently demanding that on many occasions forearm muscles reach a state of functional failure when riders cannot properly brake or operate the throttle. This study intends to discriminate which ones of the several dynamometric parameters used in the literature to characterize the Force-time (F-t) curve during voluntary contractions are more sensitive to neuromuscular fatigue in simulated motorcycle-riding conditions. Thirty-three adults performed an intermittent fatiguing protocol (IFP) that simulated the brake-pulling and throttle-twisting actions, by using a hydraulic system equipped with a pressure sensor. Sixty pressure-time (P-t) curve parameters, including the rate of pressure development (RPD) and area under the curve were measured to characterize the time course of the braking maximal voluntary contraction (MVC). Two types of variables were used to analyze the P-t curve: 1) Times interval (from 0 to 30-50-100-500-1000 and 2000 ms); 2) Percentages of MVC (10-30-60-90%MVC). Overall significant (p ≤ 0.05) fatigue-related declines were observed only at time intervals longer than 100 ms and contraction intensities higher than 30%MVC. Strong and significant linear declines (p < 0.001) were observed at 500 ms and 1 s for normalized pressures, as well as for the ratio RPD60%MVC/MVC (p < 0.003) throughout the IFP. Our results suggest considering RPD at time windows of 0–500 ms and 0–1 s, and contraction intensities comprised between 30% and 60% of MVC, as more suitable criteria to study fatigue-related decrements in performance rather than the classical MVC force.

Comparative Analysis of the Electromyography Activity of Core Muscles During Balance Pad- and Sling-assisted Exercises

Background: Unstable surface-based core training can significantly enhance core strength, but no studies have compared the effects of balance pad- and sling-assisted exercises. Objects: To study the effects of unstable surface-based balance pad- and sling-assisted core strength exercises on muscle activity. Methods: Twenty male students aged 20-25 years participated in this study. The effects of three types of core strength exercises, performed with a sling or balance pad, on the activities of three muscles, i.e., the right musculus obliquus externus abdominis (EO), right erector spinae (ES), and right gluteus maximus (GM), were examined. Results: 1) In the glute bridge exercise, the percentage of maximum voluntary contraction of the EO, ES, and GM were significantly different between the balance pad- and sling-assisted exercises. The relative contribution of the ES and GM activities to all muscle activity were not significantly different between the two training types, whereas that for EO showed a significant difference. 2) There was no significant difference in the percentage value of maximum voluntary contraction (%MVC) among the EO, ES, and GM during the “leg-lifting with flat support”exercise, and there were no significant difference in the relative contributions between the two training types. 3) In the “side bridge leg separation exercise”, the %MVC of the ES, EO, and GM were significantly different between the two training types. Conclusion: Sling training for core muscles was generally better than balance pad assist training. The majority of physiotherapy patients require core training. Our results could guide physiotherapists in the choice of targeted exercises for these patients.

Sonomechanomyography (SMMG): Mapping of Skeletal Muscle Motion Onset during Contraction Using Ultrafast Ultrasound Imaging and Multiple Motion Sensors.

Background: Available methods for studying muscle dynamics, including electromyography (EMG), mechanomyography (MMG) and M-mode ultrasound, have limitations in terms of spatial resolution. Methods: This study developed a novel method/protocol of two-dimensional mapping of muscle motion onset using ultrafast ultrasound imaging, i.e., sono-mechano-myo-graphy (SMMG). The developed method was compared with the EMG, MMG and force outputs of tibialis anterior (TA) muscle during ankle dorsiflexion at different percentages of maximum voluntary contraction (MVC) force in healthy young adults. Results: Significant differences between all pairwise comparisons of onsets were identified, except between SMMG and MMG. The EMG onset significantly led SMMG, MMG and force onsets by 40.0 ± 1.7 ms (p < 0.001), 43.1 ± 5.2 ms (p < 0.005) and 73.0 ± 4.5 ms (p < 0.001), respectively. Muscle motion also started earlier at the middle aponeurosis than skin surface and deeper regions when viewed longitudinally (p < 0.001). No significant effect of force level on onset delay was found. Conclusions: This study introduced and evaluated a new method/protocol, SMMG, for studying muscle dynamics and demonstrated its feasibility for muscle contraction onset research. This novel technology can potentially provide new insights for future studies of neuromuscular diseases, such as multiple sclerosis and muscular dystrophy.

Effect of Increased Lumbar Lordosis on Lumbar Multifidus and Longissimus Thoracis Activation During Quadruped Exercise in Patients With Chronic Low Back Pain: An EMG Study.

The objective was to investigate the electromyographic activity of the lumbar multifidus (MF) muscle and longissimus thoracis muscle, along with their activity ratio (MF longissimus thoracis ratio), during quadruped stabilization exercise performed with neutral posture and with increased lumbar lordosis in patients with chronic low back pain (CLBP). A total of 23 patients with CLBP (12 females and 11 males) were recruited based on inclusion and exclusion criterion. Each patient performed 4 exercises in random order, with surface electromyography electrodes and an electrogoniometer attached. A cross-sectional study design was used to measure the amplitude of muscle activation (as a percentage of maximum voluntary contraction) in each patient across the 2 muscles (MF and longissimus thoracis) during quadruped stabilization exercise with neutral posture and with increased lumbar lordosis. A 2-way analysis of variance was conducted, which demonstrated a statistically significant increase in the recruitment of MF with increased lumbar lordosis in patients with CLBP during quadruped exercise. An increase of 9.7% and 16.9% maximum voluntary contraction in MF electromyographic activity was observed in lumbar lordosis posture during the quadruped leg raise and quadruped leg-arm raise exercise, respectively (P < .01), when compared to the neutral posture. The increased recruitment of MF with lumbar lordosis in the quadruped position has strong implications in the assessment and management of patients with CLBP.

Comparison of musculoskeletal load using two devices for manual height adjustment of the hospital bed

Objectives. Patient manual handling in bed causes lower back pain (LBP) among Thai nurses. This study aims to develop an extension device for manual height adjustment of the hospital bed, and to evaluate its efficiency in preventing LBP among Thai nurses. Methods. Eleven participants were enrolled for electromyography measurement in eight right muscles. Subsequently, 56 volunteer nurses were recruited by convenience sampling for observational risk assessment by rapid entire body assessment (REBA) and satisfaction evaluation. The characteristics of the participants, percentage of maximum voluntary contraction (%MVC) of each muscle, REBA scores and satisfaction in using the device were analyzed by descriptive statistics, multivariate analysis of variance, paired t test and Wilcoxon signed-rank test, respectively. Results. %MVC values of the six muscles, i.e., biceps brachii, deltoideus, trapezius, latissimus dorsi, erector spinae and hamstring, were found to have a 4–18% decrease. The REBA scores decreased for both left and right when using the extension device, and all participants were more satisfied with the extension device than the hand crank of the hospital bed. Conclusions. The use of the extension device for manual height adjustment of the hospital bed developed from this study helps to prevent LBP among healthcare workers across settings.

Core Muscle Activity During Physical Fitness Exercises: A Systematic Review.

The aim of this study was to systematically review the current literature on the electromyographic (EMG) activity of six core muscles (the rectus abdominis, the internal and external oblique, the transversus abdominis, the lumbar multifidus, and the erector spinae) during core physical fitness exercises in healthy adults. A systematic review of the literature was conducted on the Cochrane, EBSCO, PubMed, Scopus, and Web of Science electronic databases for studies from January 2012 to March 2020. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were used. The inclusion criteria were as follows: (a) the full text available in English; (b) a cross-sectional or longitudinal (experimental or cohorts) study design; (c) the reporting of electromyographic activity as a percentage of maximum voluntary contraction (% MVIC), millivolts or microvolts; (d) an analysis of the rectus abdominis (RA), transversus abdominis (TA), lumbar multifidus (MUL), erector spinae (ES), and the internal (IO) or external oblique (EO); (e) an analysis of physical fitness exercises for core training; and (f) healthy adult participants. The main findings indicate that the greatest activity of the RA, EO, and ES muscles was found in free-weight exercises. The greatest IO activity was observed in core stability exercises, while traditional exercises showed the greatest MUL activation. However, a lack of research regarding TA activation during core physical fitness exercises was revealed, in addition to a lack of consistency between the studies when applying methods to measure EMG activity.

Ergonomics assessment of passive upper-limb exoskeletons in an automotive assembly plant

Over the years, the industry’s interest in using external support devices, such as exoskeletons, is increasing. They are introduced as a new technique for improving the conditions of workers and for reducing the risk of musculoskeletal injuries. An investigation of muscle activity, Jonsson’s (Jonsson, 1982) ergonomic acceptance ranges, and shoulder range of motion was conducted with a sample of 12 workers using an upper extremity exoskeleton in an automotive assembly line. The operators performed continuous cycles of dynamic overhead work consisting of the assembly of the car body at the underside of the car making use of pneumatic screwdrivers. The EMGs (anterior part of deltoid, trapezius, latissimus dorsi and erector spinae) were measured for the muscle activity analysis on the one hand, and for the ergonomics study on the other hand. The latter consisted of an approach based on Jonsson’s work, that establishes acceptance thresholds of cumulative percentage of maximum voluntary contraction of muscle activity (%MVC) in a work cycle. The joint angles motion capture was carried out by measuring the angles of the neck, back, and arms joints. All measurements were performed during experimental sessions with and without an exoskeleton. The key findings show reductions of 34% and 18% of the deltoid and the trapezius muscular activities, respectively, which in turn could lead to a reduction of discomfort and fatigue. The erector spinae and latissimus dorsi muscles were not significantly affected by exoskeleton. The values of muscular activity were also represented over Jonsson’s acceptance areas. Referring to the posture, some differences were found in the range of movement of back, neck, and arms owing to the use of the exoskeleton; however, the differences were smaller than 5% in all cases.

Abdominal muscle activation: An EMG study of the Sahrmann five-level core stability test.

Background:Sahrmann five-level core stability test protocol has been used to evaluate the ability of the core muscles to stabilize the spine. However, validation studies on the Sahrmann protocol are limited.Objective:The purpose of this study was to compare the different levels of Sahrmann five-level core stability (levels 1–5) on the muscle activity of rectus abdominis (RA), external oblique (EO), and transverse abdominis/internal oblique (TrA/IO).Methods:Twenty-two asymptomatic male participants aged 21.3.59 years were recruited. Participants were instructed to perform maximum voluntary contraction (MVC) and five levels of Sahrmann five-level core stability test guided with a pressure biofeedback unit (PBU). The surface electromyography (EMG) data of each muscle during five levels of Sahrmann five-level core stability test were normalized as a percentage of MVC.Results:Results showed significant differences in the normalized EMGs of RA [(4) = 64.80, .001], EO [(4) = 58.11, .001], and TrA/IO [(4) = 56.00, .001] between the five levels of Sahrmann five-level core stability test. Post-hoc analysis revealed Sahrmann levels 5 and 3 have significantly higher abdominal EMG signals than levels 4, 2, and 1 (.001).Conclusion:In conclusion, the Sahrmann five-level core stability test differs according to the level of Sahrmann tests. Significantly higher abdominal muscle activities were observed during levels 3 and 5. Therefore, the classification exchange in levels 3 and 4 of the Sahrmann five-level core stability test should be reconsidered in the future.

Reliable measurement of incisal bite force for understanding the control of masticatory muscles

ObjectiveIn the present study, we aimed at evaluating the steadiness of incisal bite force during isometric contractions of masticatory muscles. DesignTwo separate experiments were carried out in 11 healthy young women. A first experiment was performed to test the reliability of our protocol for measurement of incisal bite force steadiness. The second experiment aimed to evaluate the steadiness of incisal bite force at four submaximal (i.e., percentage of maximum voluntary contraction, MVC) levels (5 %MVC, 10 %MVC, 15 %MVC, and 20 %MVC), along with the bilateral myoelectric activity of two masticatory muscles (temporalis and masseter). ResultsThe results from the first experiment showed that our protocol is substantially reliable (intraclass correlation coefficient, ICC > 0.80) for estimating force variability and moderate reliable (0.60 < ICC < 0.80) for estimating spectral properties of force signals. In the second experiment, we found that force standard deviation (SD) increased proportionally to the power of mean force, and coefficient of variation (CoV) was higher at low-intensity contractions and maintained at an approximately constant level for high-intensity contractions. The force-EMG relationships were linear for both muscles at the contraction intensities evaluated in the study (5 %MVC to 20 %MVC), and the median frequency did not change with contraction intensity. ConclusionTherefore, we presented a reliable method to estimate the incisal bite force, along with additional data on force control and myoelectric activity of jaw elevator muscles during isometric steady contractions.

Barbell back squat: how do resistance bands affect muscle activation and knee kinematics?

ObjectivesThis study aimed to determine whether looped resistance bands affect knee kinematics and lower body muscle activation during the barbell back squat.MethodsTwenty-six healthy participants (13 female, 13 male) calculated their...

전완의 등척성 수축시 상대적인 중력토크를 고려한 근지구력시간 추정의 회귀모델

Despite of muscle group and posture variability, regression model to estimate endurance time have mainly developed by using the percentage of maximum voluntary contraction (%MVC). This paper presented two regression models by using the relative load intensity %MVC and the relative gravitational torque ratio %GTR (gravitational torque ratio) as a prediction variable for the biceps brachii muscle, and compared these models with the existing models. Sixty volunteers (30 females, 30 males) participated in this study, and performed isometric contraction exercises at 6 relative load intensities from 30% to 80% of MVC increasing by 10%, respectively, until their exhaustion to determine endurance times. Two regression models were induced from two relations between the measured endurance times and %MVC and between those and %GTR, and compared with the existing models by their correlation, determinant coefficients (r2) and mean square errors (MSE). The results demonstrated that the presented models were valid to estimate muscle endurance time by using %GTR of the biceps brachii muscle.

Impact of Hydration Status on Electromyography and Ratings of Perceived Exertion During the Vertical Jump

Background: The vertical jumping task is commonly used to assess lower-body power output in athletic populations, in addition to being commonly used to during investigations of hydration and anaerobic performance. Changes in neuromuscular function during a hypohydrated state have been proposed as a potential mechanism to decreases in anaerobic performance. Objectives: The primary purpose of this investigation was to examine the impact of hydration state on electromyography during the vertical jumping task. Methods: Twenty recreationally trained males were tested in three hydration conditions (hypohydrated, euhydrated, and control). Testing included maximal voluntary contractions of the vastus lateralis, vastus medialis, semitendinosus and medial gastrocnemius. Participants performed three maximal countermovement and squat jumps respectively for a total of six jumps in each condition. Both mean muscle activity and percentage of maximal voluntary contraction were calculated across the propulsive phase of each jump. Additionally, measures of RPE and the use of a mood rating scale were used as subjective measures. Results: No differences were seen in mean muscle activity and percentage of MVC in either of the jumping conditions (p &gt; 0.05). Significant differences were seen with higher ratings of perceived exertion as well as lower levels of mood ratings after the hypohydrated condition (p = 0.02 and p = 0.048 respectively). Conclusions: Decrements seen in vertical jump performance during a hypohydrated state appear to be caused from changes other than neuromuscular function and muscle activity. Differences in subjective measures may provide insight into changes in motivational levels and potentially impacting performance.

Ultrasound imaging of dorsal neck muscles with speckle tracking analyses \u2013 the relationship between muscle deformation and force

The development of methods of non-invasive measurement of neck muscle function remains a priority in the clinical sciences. In this study, dorsal neck muscle deformation vs time curves (deformation area) were evaluated against incremental force, recorded from non-invasive real-time ultrasound measurement. The results revealed subject-specific moderate to strong linear or non-linear relationships between deformation and force. Test-retest variability showed strong reliability for all five neck muscles summed together and fair to good reliability for the five muscles evaluated separately. Multivariate statistics were used to analyse the interactions between the dorsal neck muscles during different percentages of maximal voluntary contraction (MVC). Low force (10–20% MVC) was related to muscle shortening; higher force (40–80% MVC) showed combination of shortening and elongation deformation in the muscle interactions. The muscle interactions during isometric MVC test were subject-specific, with different combinations and deformations of the five neck muscles. Force ≥40% MVC were associated with a forward movement of the cervical spine that affected the ultrasound measurement of the dorsal neck muscles. Ultrasound with speckle-tracking analyses may be best used to detect low levels (<40% MVC) of neck muscle activity.

Muscular Activation Differences during Daily Activities in a Unilateral Trans-Femoral Amputee

Lower-limb amputees often exhibit an increased atrophy of remaining skeletal musculature as compared to the non-amputated side. This difference in lean mass may present variations in the contribution of physical effort between the affected and unaffected musculature. While most literature has focused mainly on microprocessor-controlled prosthetics, few investigations have examined mechanical (i.e., un-powered) prosthetics during daily activity tasks. PURPOSE: The purpose was to examine the electromyographical activity of the lower limb musculature of the amputated versus non-amputated side in a unilateral trans-femoral amputee. METHODS: The participant (n=1, age=26) performed four activities of daily living (i.e., sit-to-stand, 10-meter walk, and stair ascent and descent without support) with an above-knee mechanical prosthetic. The participant completed each task three times with 1-minute rest in between each trial. EMG was recorded, on both sides of the body, at the following sites and compared to a percentage of maximal voluntary contraction (%MVC): gluteus maximus (GM), gluteus medius (GMed), rectus femoris (RF), and biceps femoris (BF). Ratios (affected:unaffected) and percent differences between the affect and unaffected sides of the body were calculated. RESULTS: Results demonstrated large mean muscular activation differences of 34% for RF and 20% for GMed throughout overall movement patterns. Small mean activation differences were seen within the GM (2%) and BF (1%). The largest observed imbalance ratios for the sit-to-stand trials were in the RF (1:18) and GM (4:1). For the 10-meter walk, the largest differences were seen in the GM (3:1) and GMed (4.5:1). During the stair ascent without support, only the RF and GMed showed large imbalances between limbs (i.e., 1:3.5 and 3:1, respectively). Lastly, for the stair descent, the GM (4:1) and GMed (2:1) demonstrated a large imbalance; while BF and RF exhibited small differences. CONCLUSIONS: Results indicate that performing daily tasks for amputees may provide large imbalances in muscular effort between limbs. While some imbalances (increased motor unit recruitment) favored the unaffected limb, the affected limb did display increased recruitment in the gluteal musculature during walking, stair climbing, and sit-to-stand tasks.

A Study on Trunk Muscle Activation of 2 Deep Water Running Styles (High-Knee and Cross-Country Style) and Land Walking.

Deep water running (DWR) is an aquatic aerobic exercise which involves running in water without the feet touching the bottom of the pool, and it may involve different activation of trunk muscles compared with running or walking on land. This form of exercise is gradually being adopted as a form of therapeutic exercise for people with low back pain. It is proposed that different types of running or walking in water may be a more comfortable form of training for the trunk and abdominal muscles compared with exercising on dry land. This study aimed to examine the trunk muscle activation in DWR in 2 different styles-high knee style and cross-country style, and these were compared with walking on land. Eleven healthy individuals (2 females and 9 males, mean age = 24 [4.6]) were recruited for this study. Surface electromyography was used to examine the activities of the right transversus abdominis, rectus abdominis, lumbar multifidus, and lumbar erector spinae muscles in 5 conditions: static standing on land and in water, running in deep water with high knee and cross-country styles, and finally walking on a treadmill. The percentage of maximal voluntary contraction of the transversus abdominis was significantly higher for both running styles in DWR, compared with that of static standing in water. Comparing directly the 2 styles, muscle activity was higher with a high knee action compared to without. The activation of transversus abdominis during high-knee DWR was comparable with that during treadmill walking and this may have clinical implications. The results of this study confirmed that running in deep water with a high knee action activated trunk muscles differently compared with standing or walking on land.