Level Of Muscular Activity Research Articles

Muscular Activation During Plyometric Exercises in 90° of Glenohumeral Joint Abduction

Background:Plyometric exercises are frequently used to increase posterior rotator cuff and periscapular muscle strength and simulate demands and positional stresses in overhead athletes. The purpose of this study was to provide descriptive data on posterior rotator cuff and scapular muscle activation during upper extremity plyometric exercises in 90° of glenohumeral joint abduction.Hypothesis:Levels of muscular activity in the posterior rotator cuff and scapular stabilizers will be high during plyometric shoulder exercises similar to previously reported electromyographic (EMG) levels of shoulder rehabilitation exercises.Study Design:Descriptive laboratory study.Methods:Twenty healthy subjects were tested using surface EMG during the performance of 2 plyometric shoulder exercises: prone external rotation (PERP) and reverse catch external rotation (RCP) using a handheld medicine ball. Electrode application included the upper and lower trapezius (UT and LT, respectively), serratus anterior (SA), infraspinatus (IN), and the middle and posterior deltoid (MD and PD, respectively) muscles. A 10-second interval of repetitive plyometric exercise (PERP) and 3 repetitions of RCP were sampled. Peak and average normalized EMG data were generated.Results:Normalized peak and average IN activity ranged between 73% and 102% and between 28% and 52% during the plyometric exercises, respectively, with peak and average LT activity measured between 79% and 131% and between 31% and 61%. SA activity ranged between 76% and 86% for peak and between 35% and 37% for average activity. Muscular activity levels in the MD and PD ranged between 49% and 72% and between 12% and 33% for peak and average, respectively.Conclusion:Moderate to high levels of muscular activity were measured in the rotator cuff and scapular stabilizers during these plyometric exercises with the glenohumeral joint abducted 90°.

Objective analysis of surgeons’ ergonomy during laparoendoscopic single-site surgery through the use of surface electromyography and a motion capture data glove

Adding to the ergonomic inconveniences already presented by traditional laparoscopy (LAP), laparoendoscopic single-site (LESS) surgery has been found to entail other more specific problems, including greater reduction in movement freedom, in-line vision with loss of triangulation, and greater proximity of instruments. The objective of this study was to evaluate surgeons' ergonomy during LESS surgery, through the study of muscular activity, wrist angle, and hand movements, and compare it with conventional laparoscopy. The study group was composed by 14 experienced laparoscopic surgeons, all right-handed. Each one performed dissection tasks on a physical simulator through LAP and LESS approaches. For LAP, straight laparoscopic scissors and dissector were used, whilst for LESS articulating tip scissors and dissector were chosen. During both tasks, muscular activity of biceps brachii, triceps brachii, forearm flexors and extensors, and trapezius muscles was registered through surface electromyography. Simultaneously right-hand movements and wrist angles were obtained through a motion capture data glove (CyberGlove(®)), which allowed for the use of a modified RULA test applied to the recorded angles with subsequent establishment of risk levels for the wrist joint. Muscular activity for trapezius (LAP 6.94 ± 4.12 vs. LESS 11.32 ± 4.68; p ≤ 0.05) and forearm extensor muscles (LAP 9.2 ± 2.45 vs. LESS 37.07 ≤ 16.05; p ≤ 0.001) was significantly lower in conventional laparoscopy compared with LESS approach. No statistical significance was obtained between the different sensors, except in 3 of the 11 analyzed CyberGlove(®) sensors. The modified RULA test showed a score of 3 for laparoscopy (unacceptable), whereas for LESS a score of 2 was obtained (acceptable), with statistically significant differences between them (p ≤ 0.05). The LESS approach entails greater level of muscular activity in the trapezius and forearm extensor muscles, but we have found evidences of a better wrist position during LESS compared with traditional laparoscopy.

Trainability of Muscular Activity Level during Maximal Voluntary Co-Contraction: Comparison between Bodybuilders and Nonathletes

Antagonistic muscle pairs cannot be fully activated simultaneously, even with maximal effort, under conditions of voluntary co-contraction, and their muscular activity levels are always below those during agonist contraction with maximal voluntary effort (MVE). Whether the muscular activity level during the task has trainability remains unclear. The present study examined this issue by comparing the muscular activity level during maximal voluntary co-contraction for highly experienced bodybuilders, who frequently perform voluntary co-contraction in their training programs, with that for untrained individuals (nonathletes). The electromyograms (EMGs) of biceps brachii and triceps brachii muscles during maximal voluntary co-contraction of elbow flexors and extensors were recorded in 11 male bodybuilders and 10 nonathletes, and normalized to the values obtained during the MVE of agonist contraction for each of the corresponding muscles (% EMGMVE). The involuntary coactivation level in antagonist muscle during the MVE of agonist contraction was also calculated. In both muscles, % EMGMVE values during the co-contraction task for bodybuilders were significantly higher (P<0.01) than those for nonathletes (biceps brachii: 66±14% in bodybuilders vs. 46±13% in nonathletes, triceps brachii: 74±16% vs. 57±9%). There was a significant positive correlation between a length of bodybuilding experience and muscular activity level during the co-contraction task (r = 0.653, P = 0.03). Involuntary antagonist coactivation level during MVE of agonist contraction was not different between the two groups. The current result indicates that long-term participation in voluntary co-contraction training progressively enhances muscular activity during maximal voluntary co-contraction.

Effectiveness of powered hospital bed movers for reducing physiological strain and back muscle activation

Battery powered bed movers are becoming increasingly common within the hospital setting. The use of powered bed movers is believed to result in reduced physical efforts required by health care workers, which may be associated with a decreased risk of occupation related injuries. However, little work has been conducted assessing how powered bed movers impact on levels of physiological strain and muscle activation for the user. The muscular efforts associated with moving hospital beds using three different methods; powered StaminaLift Bed Mover (PBM1), powered Gzunda Bed Mover (PBM2) and manual pushing were measured on six male subjects. Fourteen muscles were assessed moving a weighted hospital bed along a standardized route in an Australian hospital environment. Trunk inclination and upper spine acceleration were also quantified. Powered bed movers exhibited significantly lower muscle activation levels than manual pushing for the majority of muscles. When using the PBM1, users adopted a more upright posture which was maintained while performing different tasks (e.g. turning a corner, entering a lift), while trunk inclination varied considerably for manual pushing and the PBM2. The reduction in lower back muscular activation levels may result in lower incidence of lower back injury.

Muscle Activation Levels During Early Postoperative Rehabilitation Exercises in Slap Repaired Patients, a Pilot Study

BackgroundFew studies have examined muscular activation levels during commonly prescribed range of motion (ROM) exercises in a post-surgical superior labral tear anterior to posterior (SLAP) repair patient group. The present cross-sectional study compared shoulder musculature activation levels between postoperative SLAP repair patients with those of a healthy control cohort performing commonly prescribed postoperative shoulder exercises. The maximal ROM (MAX ROM) achieved during exercises was also studied.MethodsTen healthy volunteers and nine postoperative patients (post-SLAP) performed 10 rehabilitative exercises during the recording of electromyogram (EMG) activity from six shoulder muscles. Root mean squared amplitudes normalized to a submaximal reference voluntary contraction (RVC) were analyzed to compare exercises. A two-dimensional video of humeral-trunk angle captured the shoulder ROM for each exercise.ResultsOne significant difference was found between groups; the anterior deltoid mean activity across all exercises was found to be higher in the post-SLAP group 53% RVC [95% confidence interval (CI) = 48% to 57% RVC] compared to the healthy group 46% RVC (95% CI = 42% to 50% RVC) ( p = 0.02). Post-SLAP patients generated the least MAX ROM performing the Pendulum exercise 97°(95% CI = 88° to 107°) and the greatest during Forward Bow 131° (95% CI = 121° to 142°), ( p = 0.002).ConclusionsThe present study identifies the shoulder muscle EMG and MAX ROM obtained during rehabilitation exercise in patients’ after SLAP repair. Knowledge of these parameters will help clinicians match the appropriate exercise to meet the desired objective for the particular rehabilitation goal.

Elite Swimmers With Unilateral Shoulder Pain Demonstrate Altered Pattern of Cervical Muscle Activation During a Functional Upper-Limb Task

Cross-sectional cohort study. To investigate the differences in the level of activation of neck-shoulder muscles between elite swimmers with and without shoulder pain during a functional upper-limb task. Previous studies have reported altered motor control of the neck-shoulder muscles in patients with chronic neck-shoulder pain. Whether the activation of neck-shoulder muscles is altered among elite swimmers who have shoulder pain is unknown. Surface electromyography from the sternocleidomastoid, upper trapezius, and anterior scalene (SCL) muscles was recorded bilaterally in 17 elite swimmers (9 men, 8 women; mean ± SD age, 21 ± 3 years) with unilateral shoulder pain, and 17 age- and sex-matched elite swimmers without pain. Root-mean-square values were calculated and normalized to assess the level of muscular activation 5 seconds before, 120 seconds into, 150 seconds into, and 10 seconds after a functional upper-limb task. The data revealed significant differences between groups for the root-mean-square of both SCL muscles (F = 3.733, P = .016) but not for the sternocleidomastoid and upper trapezius muscles. Swimmers with shoulder pain had higher normalized root-mean-square values in both SCL muscles at 120 seconds (78% on average) and 150 seconds (86% on average) into the task and at 10 seconds after the task (40% on average), as compared with swimmers without shoulder pain (P<.05). The elite swimmers with shoulder pain demonstrated greater activation of the SCL muscles during a functional task and a lower ability to relax the SCL muscles after completion of the task than elite swimmers without shoulder pain. The present findings suggest an altered pattern of cervical muscle activation in elite swimmers with shoulder pain during performance of a functional task.

CIRNE III Abstracts: Congresso Internacional de Reabilitação Neuromusculoesquelética e Esportiva, May 18–21, 2011, Vitória, Brazil

CIRNE III Abstracts: Congresso Internacional de Reabilitação Neuromusculoesquelética e Esportiva, May 18–21, 2011, Vitória, Brazil

Shoulder Muscular Activity During Isometric Three-Point Kneeling Exercise on Stable and Unstable Surfaces

The purpose of this study was to determine if performing isometric 3-point kneeling exercises on a Swiss ball influenced the isometric force output and EMG activities of the shoulder muscles when compared with performing the same exercises on a stable base of support. Twenty healthy adults performed the isometric 3-point kneeling exercises with the hand placed either on a stable surface or on a Swiss ball. Surface EMG was recorded from the posterior deltoid, pectoralis major, biceps brachii, triceps brachii, upper trapezius, and serratus anterior muscles using surface differential electrodes. All EMG data were reported as percentages of the average root mean square (RMS) values obtained in maximum voluntary contractions for each muscle studied. The highest load value was obtained during exercise on a stable surface. A significant increase was observed in the activation of glenohumeral muscles during exercises on a Swiss ball. However, there were no differences in EMG activities of the scapulothoracic muscles. These results suggest that exercises performed on unstable surfaces may provide muscular activity levels similar to those performed on stable surfaces, without the need to apply greater external loads to the musculoskeletal system. Therefore, exercises on unstable surfaces may be useful during the process of tissue regeneration.

Knee and hip joint forces – sensitivity to the degrees of freedom classification at the knee

Previous research has demonstrated that the number of degrees of freedom (DOF) modelled at a given joint affects the antagonistic muscle activity predicted by inverse dynamics optimization techniques. This higher level of muscle activity in turn results in greater joint contact forces. For instance, modelling the knee as a 3 DOF joint has been shown to result in higher hip and knee joint forces commensurate with a higher level of muscular activity than when the knee is modelled with 1 DOF. In this study, a previously described musculoskeletal model of the lower limb was used to evaluate the sensitivity of the knee and hip joint contact forces to the DOF at the knee during vertical jumping in both a 1 and a 3 DOF knee model. The 3 DOF knee was found to predict higher tibiofemoral and hip joint contact forces and lower patellofemoral joint contact forces. The magnitude of the difference in hip contact force was at least as significant as that found in previous research exploring the effect of subject-specific hip geometry on hip contact force. This study therefore demonstrates a key sensitivity of knee and hip joint contact force calculations to the DOF at the knee. Finally, it is argued that the results of this study highlight an important physiological question with practical implications for the loading of the structures of the knee; that is, the relative interaction of muscular, ligamentous, and articular structures in creating moment equilibrium at the knee.

1309 踵着床における筋活動の機構的特性(OS14-2バイオエンジニアリング(2)-生物運動・バイオミメティクス・生物流体工学・スポーツバイオメカニクス-)

1309 踵着床における筋活動の機構的特性(OS14-2バイオエンジニアリング(2)-生物運動・バイオミメティクス・生物流体工学・スポーツバイオメカニクス-)

Muscle Activity Analysis in Vertical Jump by Direct Dynamics Simulation with Musculo-Skeletal Model

In this study, the vertical jump is examined as a basic study of jump. And we examine the influence of each muscle of the human body in vertical jump. The human body is modeled as four rigid bodies and analyzed in detail by using the model that includes muscles of the leg. In this research, the mechanism of jump is discussed by using numerical model to which the concept of multibody dynamics and biomechanics is adapted. We performed the experiment of jump and observe the feature behavior of vertical jump. Experimental results show that the angle of each body becomes vertical for ground and the change of the foot angle is small. Then we perform the numerical simulation referring to this experimental data. In order to reduce the amount of calculation, we calculate muscular activity level by correlating it with fewer parameters. We discuss which muscles are necessary for vertical jump. It is found that vasti exerts the biggest power and gluteus maximus has the highest state of normalized muscle activity.

Computer use and adverse health problems – are clinicians concerned?

The use of computers is prevalent throughout many societies today, with people from all age groups, both sexes, and in many careers having regular contact with them either in the home or at the workplace. Existing scientific evidence clearly demonstrates that poor posture, greater muscle activity and musculoskeletal pain, as well as psychological problems such as internet addiction and antisocial personality disorder, are widely found among habitual users of computers. It is important that the negative consequences of current technology on physical and psychological wellbeing are not ignored, and therefore prevention and rehabilitation of these health effects, in computer users, must be urgently considered by clinicians. Pain and discomfort in the upper body, particularly the neck and shoulders, has been found to correlate with habitual computer usage. A further study by Harris and Straker of students who regularly used a laptop computer found reports of discomfort from usage (60%) and also from carrying the laptop (63%). Such musculoskeletal complaints were linked to improper ergonomics and poor posture during computer use. Poor adaptive posture was also seen in children and young adults, with a wide variety of postures employed, although these age groups differed markedly from the postures adapted by adults. Poor posture was also clearly associated with tall people who used the type of small screen normally seen on laptop computers, and commonly sat at inappropriate heights for their leg lengths, suggesting that it would be better to place such devices on a raised platform. Computer users typically report various musculoskeletal complaints. Neck, back and shoulder pain has been found in adolescent computer users. The one year prevalence of neck and shoulder pain, the most commonly reported somatic pain syndrome, is 58 cases per 100 persons. Neck pain and clinical abnormality has also been correlated with greater head rotation and inclination. Similarly, upper torso pain and severe stiffness has been reported by computer users who have high head rotation and keyboard height above elbow level. In addition, low back pain was reported at least once during the working day in female computer users, and the risk factor for low back pain, and pain exacerbation from prolonged sitting during computer use, was calculated as an odds ratio of 1.1–1.5. Back discomfort has been shown, with statistical significance, to be correlated with a downward viewing angle. However, the highest level of muscular activity was found in erect sitting with forward inclination of the body in visual display technology (VDT) workers, and increased stretching of passive structures in the back was caused by poor posture. Existing evidence suggests that the negative effects on muscular activities were due to the fact that different sitting postures during computer use led to different trunk muscle activation. Thoracic upright sitting increased co-activation of global back muscles, whereas lumbar-pelvic upright sitting increased coactivation of local muscle groups. Similarly, neck and shoulder muscles, particularly the descending aspect of the trapezius muscles, were distressed with additional effects on other muscles such as the longissimus capitis. It is likely that an increase in trapezius muscle activity is found when using a standard desk and workplace board (forearm support) compared to a standard desk, although this may be dependent on the elbow flexion angle. The dynamic and sustained contraction of the small muscles of the forearms and hands, and the shoulder, neck and back muscles, during word processor work may be one of the causative factors in neck and shoulder problems. It has been clearly demonstrated that the trapezius muscles engage in static contraction during keyboard work, and that fatigue of the shoulder muscles occurs rapidly during simple shoulder movement even when there is an application of mass on only one arm. Hand/arm symptoms in computer users were found to be mainly caused by poor non-neutral wrist Correspondence to: Pattariya Intolo, Faculty of Health Sciences, Srinakhawirot University, Origkharak, Nakhonnayoik 26120, Thailand. Email: pattariy@swu.ac.th

A Practical and Feasible Control System for Bifunctional Myoelectric Hand Prostheses

This paper presents an implementation of a practical and low-cost hardware-based control system for multifunctional myoelectric hand prostheses. The model utilizes a mode-switching technique in order to voluntarily control the operation of a dual-mode prosthetic device in two degrees of freedom: grasp/release and pronation/supination. This system was designed specifically to cater to the increasing needs of patients in developing countries, where myoelectric prostheses are scarce and extremely expensive. The design relied entirely on locally-available commercial components and aimed at allowing small prosthetics producers the freedom to utilize and modify the design according to their clients' preferences and requirements. Evaluation tests revealed excellent control and ability to execute basic hand and wrist functions even with short training periods, although results varied with the underlying level of muscular activity.

Lower-extremity musculoskeletal geometry affects the calculation of patellofemoral forces in vertical jumping and weightlifting

The calculation of the patellofemoral joint contact force using three-dimensional (3D) modelling techniques requires a description of the musculoskeletal geometry of the lower limb. In this study, the influence of the complexity of the muscle model was studied by considering two different muscle models, the Delp and Horsman models. Both models were used to calculate the patellofemoral force during standing, vertical jumping, and Olympic-style weightlifting. The patellofemoral forces predicted by the Horsman model were markedly lower than those predicted by the Delp model in all activities and represented more realistic values when compared with previous work. This was found to be a result of a lower level of redundancy in the Delp model, which forced a higher level of muscular activation in order to allow a viable solution. The higher level of complexity in the Horsman model resulted in a greater degree of redundancy and consequently lower activation and patellofemoral forces. The results of this work demonstrate that a well-posed muscle model must have an adequate degree of complexity to create a sufficient independence, variability, and number of moment arms in order to ensure adequate redundancy of the force-sharing problem such that muscle forces are not overstated.

Electromyographical Assessment of Passive, Active Assistive, and Active Shoulder Rehabilitation Exercises

To determine the electromyographical (EMG) activation levels of shoulder musculature during early rehabilitation exercises to regain active range of motion. Descriptive. University clinical research laboratory. Ten asymptomatic volunteers (age, 25 +/- 5 years; height, 171 +/- 7 cm; weight, 78 +/- 15 kg). Fine-wire (supraspinatus and infraspinatus) and surface (anterior deltoid, upper trapezius, lower trapezius, and serratus anterior) electrodes recorded EMG activity from each muscle during 12 therapeutic exercises completed during a single testing session in random order. EMG root mean squared amplitude normalized to a percentage of maximum voluntary contraction (% MVC). Passive exercises generated the lowest mean EMG activity (<10%) for all muscles studied. The standing active shoulder elevation exercises generated the greatest mean EMG activity with an upper boundary of 95% CI (40% MVC). Overall the active-assistive exercises generated a small (<10%) increase in muscle activity compared with the passive exercises for the supraspinatus and infraspinatus muscles, which was not a significant increase (P > .05). This electrophysiological data in normal volunteers suggest that many exercises used during the early phase of rehabilitation to regain active elevation do not exceed 20% MVC. Progression from passive to active-assisted can potentially be performed without significantly increasing muscular activation levels exercises. Upright active exercises demonstrated a consistent and often a statistically significant increase in muscular activities supporting that these exercises should be prescribed later in a rehabilitation program.

Differences in loading of the temporomandibular joint during opening and closing of the jaw

Kinematics of the human masticatory system during opening and closing of the jaw have been reported widely. Evidence has been provided that the opening and closing movement of the jaw differ from one another. However, different approaches of movement registration yield divergent expectations with regard to a difference in loading of the temporomandibular joint between these movements. Because of these diverging expectations, it was hypothesized that joint loading is equal during opening and closing. This hypothesis was tested by predicting loading of the temporomandibular joint during an unloaded opening and closing movement of the jaw by means of a three-dimensional biomechanical model of the human masticatory system. Model predictions showed that the joint reaction forces were markedly higher during opening than during closing. The predicted opening trace of the centre of the mandibular condyle was located cranially of the closing trace, with a maximum difference between the traces of 0.45 mm. The hypothesis, postulating similarity of joint loading during unloaded opening and closing of the jaw, therefore, was rejected. Sensitivity analysis showed that the reported differences were not affected in a qualitative sense by muscular activation levels, the thickness of the cartilaginous layers within the temporomandibular joint or the gross morphology of the model. Our predictions indicate that the TMJ is loaded more heavily during unloaded jaw opening than during unloaded jaw closing.

Reduced scapular muscle control and impaired shoulder joint position sense in subjects with chronic shoulder stiffness

The purpose of the present study was to determine (1) if joint position sense (JPS) in subjects with shoulder stiffness (SS) differs from that in controls; (2) if, when JPS is reduced in SS, it is related to scapular muscular activities in the mid/end ranges of motion; and (3) if a person’s function is associated with his or her level of JPS. Eighteen subjects with unilateral SS and 18 controls were included. Each subject performed abduction by self-selecting an end/mid range position. The electromagnetic motion-capturing system collected kinematic data while surface electromyography collected muscle activities (upper trapezius, lower trapezius, and serratus anterior muscles). Subjects were asked to move the upper limb to the target position (end/mid range) accurately without visual guidance. Reduced JPS was observed in subjects with SS (2.7 degrees in mid range, p < 0.05). The JPS was enhanced by an increased scapula muscular activation level in the end range of motion ( R = −0.61 for SS and −0.41 for controls) and by coordination among muscles’ activation in the mid-range of motion ( R = −0.87 for SS and R = −0.53 for controls). Impaired JPS was also related to self-reported functional status ( R = −0.56) in subjects with SS. Shoulder JPS in subjects with chronic SS is impaired in comparison with controls. In the mid-range motion, the coordination of scapula muscular activation is related to shoulder JPS. Impaired JPS is also function-related in subjects with SS. These findings suggest that the coordination among scapula muscles’ activation were important to consider in the rehabilitation of patients with chronic SS.

Pelvic Stabilization and Semisitting Position Increase the Specificity of Back Exercises

To examine the effect of pelvic stabilization and two lower-limb configurations on the EMG activity of back and hip extensor muscles during a dynamic back extension exercise on a machine and to compare them between sexes. Twenty-two healthy volunteers (11 men and 11 women) performed five trunk flexion-extension cycles at 40% of their maximal voluntary contraction (MVC) in a machine designed for back exercise. Two different positions were used: 1) seated position (seat horizontal, knees at 90 degrees ) and 2) semisitting position (seat slightly tilted forward at 15 degrees , knees at 45 degrees of flexion). In each position, three pelvic stabilization conditions were tested: 1) unrestrained (control condition), 2) partially restrained (posteriorly), and 3) totally restrained (posteriorly and anteriorly). EMG signals were recorded bilaterally with 12 pairs of electrodes placed on back muscles as well as on the gluteus maximus and biceps femoris. The muscular activation level, that is, the percentage of EMG amplitude relative to the maximal EMG obtained from MVC, was used to asses the relative contribution of each muscle group across exercises. In both sexes, two main results were found: 1) pelvic stabilization (partially and totally restrained) significantly (P < 0.05) increased the activity of all back muscles (average of 12%) and 2) semisitting position significantly decreased (range = 8-27%) the activity of two hip extensors compared with the seated position. Sex differences were also observed relative to the activity of some back muscles as well as the biceps femoris. Combining pelvic stabilization and semisitting position in back exercise machines might be a useful way to localize the effects of endurance training at the back muscles and this in both the sexes.

走運動および自転車運動における最大酸素摂取量の差を決定する要因&lt;br&gt;～ MRI 画像からみた筋活動レベルに着目して ～

The purpose of this study was to determine the difference in the attainment rate of maximal oxygen uptake in cycling and running (%cycVO2max). Seven healthy male subjects (22.9±1.3 yrs, 171.9±4.7 cm, 61.0±5.2 kg) participated in a maximal incremental exercise test for running and cycling. During the exercise testing, oxygen uptake, carbon dioxide output, respiratory exchange rate, minute ventilation, tidal volume, respiratory rate, and heart rate were measured. Attainment rates of each physiological measurement for cycling and running were shown as %cycVO2max, %cycVCO2max, %cycRERmax, %cycVEmax, %cycVt, %cycRR and %cycHRmax. Transverse relaxation time (T2)-weighted spin echo images were acquired before and after the exercise periods. Exercise-induced T2 values of each muscle and muscle-group are indices of muscular activity level, so the difference between the T2 value of cycling and running in each muscle or muscle group was shown as ΔT2%. VO2max in cycling was 92.2% of VO2max in running. Significant correlations were observed between %cycVO2max and %cycVCO2max, %cycVO2max and %cycRR. Furthermore, significant correlations were recognized between %cycVO2max and ΔT2% of the m. quadriceps femoris, %cycVCO2max and ΔT2% of the m. quadriceps femoris, %cycVCO2max and the m. triceps surae, as well. These results show that the higher muscular activity level of the thigh in cycling increases the uptake of oxygen in the muscle. The T2 value shows that the uptake or redistribution of fluid within muscle is driven by the accumulation of lactate and inorganic phosphate. Therefore, the T2 value of maximal incremental exercise would reflect the anaerobic capacity of the muscle. Judging from the significant correlations between %cycVO2max and %cycVCO2max or %cycRR, the anaerobic capacity of each subject would also affect the difference between the maximal oxygen uptake of cycling and running.

Effect of pelvic stabilization and hip position on trunk extensor activity during back extension exercises on a roman chair

To assess the effect of pelvic stabilization and hip position on the electromyographic activity of trunk extensors during Roman chair exercise. A secondary objective was to compare genders. Repeated measures. Eleven men and 11 women volunteers. Five trunk flexion-extension cycles for 3 Roman chair conditions: (i) pelvis unrestrained; (ii) pelvis restrained; and (iii) hip at 40 degrees flexion. Electromyographic signals were recorded on the back muscles, as well as on the gluteus maximus and biceps femoris. The percentage of electromyographic amplitude relative to the maximal activity was used to assess the level of muscular activation of each muscle group across the exercises. For both genders, the Roman chair conditions did not influence the activity of the back and gluteus muscles. The hip-at-40 degrees-flexion condition significantly reduced the activity of the biceps femoris (average of 4-18%) relative to the other 2 conditions. Gender differences were observed on the activity of the biceps femoris in all Roman chair conditions. The hip-at-40 degrees-flexion condition would allow the Roman chair exercise to train the targeted back muscles more specifically by overloading them over a longer duration in order to induce physiological changes.