A comparison of isokinetic and isotonic predictions of a functional task

Controversy still exists regarding the use of isokinetic and isotonic exercise in rehabilitation. Many authors have compared these two types of training methods on various strength measures and functional activity, but have used open kinetic chain training. The purposes of this investigation were to determine: 1) which form of closed kinetic chain training, isokinetic or isotonic, would produce the greatest increase in one-legged jump reaction force, and 2) which training method most accurately predicts peak force produced during a one-legged jump. Forty-two legs from 21 female volunteer subjects were used. Each subject had her dominant and nondominant extremities identified, and then each extremity was randomly assigned to either isokinetic training, isotonic training, or control. Both training groups trained using a leg press exercise 3 days a week for 5 weeks, while the control extremities did not train. The isokinetic extremities were trained using a velocity spectrum (two sets of 10 repetitions at each speed: 60 degrees , 180 degrees and 240 degrees /sec) and the isotonic extremities trained using the DAPRE technique. Data were analyzed with an analysis of variance (ANOVA). There was no difference between the three groups for change in one-legged jump force. Both isokinetic and isotonic groups increased strength after training, but these changes did not correlate with changes in one-legged jump reaction force. These results suggest that changes in neither isokinetic force nor isotonic weight lifted developed in a nonweight-bearing closed kinetic chain, directly translate into increased force production during a functional activity.     

开链和闭链训练治疗膝关节半月板损伤

背景:开链训练和闭链训练均可应用于膝关节半月板损伤,然而两种方法的机制不一样,临床未见两种训练方法改善膝关节半月板损伤的报道。目的:观察开链训练和闭链训练对青年人膝关节半月板损伤疗效的影响。方法:49例青年人膝关节半月板损伤采用康复保守治疗的患者,随机数字表法将入选患者分为2组,生物反馈开链组(n=25)采用基础治疗联合终末伸膝生物反馈训练,蹬踏闭链组(n=24)采用基础治疗联合单侧下肢蹬踏训练。其中基础治疗包括电针、手法治疗、徒手运动疗法;生物反馈开链训练采用加拿大Thought公司生产的Myotrac infiniti生物反馈仪进行刺激训练;蹬踏闭链训练采用德国GYM80智能力量训练系统蹬踏配件进行训练。1次/d,连续3周。使用膝关节屈、伸、全关节活动度,目测类比评定级法评分、改良Lysholm膝关节评分、日常生活活动能力评分进行疗效评价。研究方案的实施符合四川省骨科医院的相关伦理要求,患者对试验过程完全知情同意。结果与结论:①在关节活动度方面:生物反馈开链组屈、伸、全关节活动度优于治疗前(P<0.05);蹬踏闭链组伸、全关节活动度优于治疗前(P<0.05);生物反馈开链组较蹬踏闭链组改善关节活动度较好,但组间差异无显著性意义(P>0.05);②在疼痛和功能方面:2组治疗后目测类比评定级法评分、改良Lysholm膝关节评分、日常生活活动能力评分优于治疗前(P<0.05);蹬踏闭链组治疗后日常生活活动能力评分好于生物反馈开链组(P<0.05);2组在改善膝关节活动度、疼痛和功能方面均有效果;③结果说明,生物反馈开链组在改善关节活动度方面疗效较好;在控制疼痛的基础上,蹬踏闭链组在改善膝关节功能和日常生活活动能力方面疗效较好。     

Electromyographic evaluation of closed and open kinetic chain knee rehabilitation exercises

The use of closed kinetic chain knee rehabilitation exercises has been advocated in recent years. The primary reason cited for employing closed kinetic chain exercises is that these exercises result in less anteroposterior (A/P) shear force at the knee joint, when compared with traditionally used open kinetic chain exercises. The purpose of this study was to determine the electromyographical (EMG) activity ratio of quadriceps to hamstrings occurring in the following exercises: unilateral one quarter squats, leg extensions (N-K Table), lateral step-ups, and movements on the Fitter (Fitter International, Inc), Stair-master 4000 (Randal Sports/Medical Products, Inc), and slideboard. Ten female student-athletes participated in this study. EMG surface electrodes were applied over the rectus femoris and biceps femoris muscles. The subjects completed three maximum isometric contractions for both muscle groups to obtain baseline EMG data. They then performed repetitions of each exercise. These movements were videotaped simultaneously with a stationary shuttered video camera operating at 30 Hz. A computer program was used to analyze the videotaped performances for knee joint range of motion (ROM). Three trials of data were averaged. Baseline EMG activity was used to determine percentage of maximum EMG activity for each exercise. There were significant differences (p.<01) among the exercises for the following dependent variables: ROM, maximum angle, percent of maximum contraction, time of contraction, and total EMG (EMG area under the curve). This study suggests that the five closed kinetic chain exercises studied result in minimal A/P shear forces at the knee joint.     

Electromyographic Analysis of Single-Leg,Closed Chain Exercises: Implications for Rehabilitation After Anterior Cruciate Ligament Reconstruction

OBJECTIVE: Many knee rehabilitation studies have examined open and closed kinetic chain exercises. However, most studies focus on 2-legged, closed chain exercise. The purpose of our study was to characterize 1-legged, closed chain exercise in young, healthy subjects. SUBJECTS: Eighteen normal subjects (11 men, 7 women; age, 24.6 +/- 1.6 years) performed unsupported, 1-legged squats and step-ups to approximately tibial height. MEASUREMENTS: Knee angle data and surface electromyographic activity from the thigh muscles were recorded. RESULTS: The maximum angle of knee flexion was 111 +/- 23 degrees for squats and 101 +/- 16 degrees for step-ups. The peak quadriceps activation was 201 +/- 66% maximum voluntary isometric contraction, occurring at an angle of 96 +/- 16 degrees for squats. Peak quadriceps activation was 207 +/- 50% maximum voluntary isometric contraction and occurred at 83 +/- 12 degrees for step-ups. CONCLUSIONS: The high and sustained levels of quadriceps activation indicate that 1-legged squats and step-ups would be effective in muscle rehabilitation. As functional, closed chain activities, they may also be protective of anterior cruciate ligament grafts. Because these exercises involve no weights or training equipment, they may prove more cost effective than traditional modes of rehabilitation.     

The specificity of strength training: the effect of posture

There is a paucity of research into the importance of performing strength training exercises in postures specific to the movements they are attempting to facilitate. In addressing this question, 27 previously trained subjects were randomly allocated into heavy weight training and control groups. The weight training group performed 4–6 sets of 6–10 repetitions of the squat and bench press lifts twice a week for 8 weeks. Prior to and after the training period the following tests were conducted: bench press throw at 30% of maximal load, vertical jump, maximal squat and bench press lifts, push-up test performed over a force platform, 40-m sprint, 6-s cycle, and isokinetic tests assessing upper and lower body musculature in varying actions. The results supported the concept that posture is important in training as those exercises conducted in similar postures to the training recorded the greatest improvement in performance. For example, after completion of the training the weight training subjects significantly increased by approximately 12% the maximal load lifted in the bench press exercise and the peak torque in the isokinetic bench press test. However, performance in the isokinetic horizontal arm adduction test was not significantly changed. We speculate that the phenomenon of posture specificity may, at least in part, be caused by the differing postures altering the neural input to the musculature. The results stress the importance of selecting exercises in which the posture closely resembles that of the movements they are attempting to facilitate.     

Upper extremity proprioceptive training

Proprioception following lower extremity injuries is commonly recommended, but there is little information on proprioception training following upper extremity injuries. No studies have evaluated whether proprioception programs for athletes in open kinetic chain activities (throwing, shot putting) should be different than programs for athletes in closed kinetic chain activities (gymnastics, swimming, kayaking, or rowing). In this paper, we provide a rationale for proprioception training for upper extremity injuries in athletes and the importance of analyzing the athlete's sport and activity for specificity of proprioception exercises. We then discuss one popular proprioception exercise, rhythmic stabilization, and propose several additional upper extremity proprioception exercises, along with instructions for the athletic trainer on how to direct the athlete through these exercises.     

The role of limb torque, muscle action and proprioception during closed kinetic chain rehabilitation of the lower extremity

This paper defines the differences between open and closed kinetic chain exercise and explains the role of limb torque, muscle action, and proprioception during rehabilitation of the lower extremity. Closed kinetic chain rehabilitation is shown to decrease shear forces, increase proprioception, and increase muscle group coordination through examples of progressive exercises. The authors conclude that closed kinetic chain rehabilitation is an economical, efficient, and effective means of rehabilitation, with the ultimate goal of enhancing proprioception, thus gaining lower extremity joint stability.     

A comparison of strength and muscle mass increases during resistance training in young women

Strength gains with resistance training are due to muscle hypertrophy and nervous system adaptations. The contribution of either factor may be related to the complexity of the exercise task used during training. The purpose of this investigation was to measure the degree to which muscle hypertrophy contributes to gains in strength during exercises of varying complexity. Nineteen young women resistance trained twice a week for 20 weeks, performing exercises designed to provide whole-body training. The lean mass of the trunk, legs and arms was measured by dual energy x-ray absorptiometry and compared to strength gains (measured as the 1-repetition maximum) in bench press, leg press and arm curl exercises, pre-, mid- (10 weeks) and post-training. No changes were found in a control group of ten women. For the exercise group, increases in bench press, leg press and arm curl strength were significant from pre- to mid-, and from mid- to post-training (P P?相似文献   

Surface electromyographic amplitude-to-work ratios during isokinetic and isotonic muscle actions

Context: Isokinetic and isotonic resistance training exercises are commonly used to increase strength during musculoskeletal rehabilitation programs. Our study was designed to examine the efficacy of isokinetic and isotonic muscle actions using surface electromyographic (EMG) amplitude-to-work ratios (EMG/WK) and to extend previous findings to include a range of isokinetic velocities and isotonic loads. Objective: To examine work (WK), surface EMG amplitude, and EMG/WK during concentric-only maximal isokinetic muscle actions at 60, 120, 180, 240, and 300 degrees /s and isotonic muscle actions at 10%, 20%, 30%, 40%, and 50% of the maximal voluntary isometric contraction (MVIC) torque during leg extension exercises. Design: A randomized, counterbalanced, cross-sectional, repeated-measures design. Setting: A university-based human muscle physiology research laboratory. Patients or Other Participants: Ten women (mean age = 22.0 +/- 2.6 years) and 10 men (mean age = 20.8 +/- 1.7 years) who were apparently healthy and recreationally active. Intervention(s): Using the dominant leg, each participant performed 5 maximal voluntary concentric isokinetic leg extension exercises at randomly ordered angular velocities of 60, 120, 180, 240, and 300 degrees /s and 5 concentric isotonic leg extension exercises at randomly ordered loads of 10%, 20%, 30%, 40%, and 50% of the isometric MVIC. Main Outcome Measure(s): Work was recorded by a Biodex System 3 dynamometer, and surface EMG was recorded from the superficial quadriceps femoris muscles (vastus lateralis, rectus femoris, and vastus medialis) during the testing and was normalized to the MVIC. The EMG/WK ratios were calculated as the quotient of EMG amplitude (muVrms) and WK (J) during the concentric phase of each exercise. Results: Isotonic EMG/WK remained unchanged ( P > .05) from 10% to 50% MVIC, but isokinetic EMG/WK increased ( P < .05) from 60 to 300 degrees /s. Isotonic EMG/WK was greater ( P < .05) than isokinetic EMG/WK for 50% MVIC versus 60 degrees /s, 40% MVIC versus 120 degrees /s, and 30% MVIC versus 180 degrees /s; however, no differences were noted ( P > .05) between 20% MVIC versus 240 degrees /s or 10% MVIC versus 300 degrees /s. An 18% decrease in active range of motion was seen for the isotonic muscle actions, from 10% to 50% MVIC, and a 3% increase in range of motion for the isokinetic muscle actions from 60 to 300 degrees /s was also observed. Furthermore, the peak angular velocities for the isotonic muscle actions ranged from 272.9 to 483.0 degrees /s for 50% and 10% MVIC, respectively. Conclusions: When considering EMG/WK, peak angular velocity, and range of motion together, our data indicate that maximal isokinetic muscle actions at 240 degrees /s or controlled-velocity isotonic muscle actions at 10%, 20%, or 30% MVIC may maximize the amount of muscle activation per unit of WK done during the early stages of musculoskeletal rehabilitation. These results may be useful to allied health professionals who incorporate open-chain resistance training exercises during the early phases of rehabilitation and researchers who use isotonic or isokinetic modes of resistance exercise to examine muscle function.     

The effect of unilateral and bilateral strength training on the bilateral deficit and lean tissue mass in post-menopausal women

Some have observed maximal strength of simultaneous bilateral homologous limb contraction is less than the sum of strengths of right and left limbs contracting alone; a phenomenon referred to as the bilateral deficit (BLD). There is controversy on whether there is a BLD for all exercises. We assessed whether a BLD occurs across different exercises (leg press, knee extension, and lat pull-down), whether the BLD could be altered with unilateral or bilateral training, and whether unilateral versus bilateral training was more beneficial for increasing lean tissue mass (LTM). Post-menopausal women (~57 years) were randomized to bilateral (n=14) and unilateral (n=12) training, or non-training control (n=24) groups. Bilateral training involved seven exercises performed with bilateral contractions (two sets, 3 days week⁻¹, 26 weeks). Unilateral training involved the same exercises performed with one limb at a time. A BLD was found for leg press and lat pull-down, but not for knee extension. Bilateral training decreased the BLD; whereas unilateral training had minimal effect on the BLD. The unilateral-training group had a greater increase in lower-body LTM compared to the control group (P<0.05); however, there were no differences between unilateral and bilateral training groups. Both training groups had greater increases in LTM of the upper- and whole-body compared to the control group. We conclude that the BLD is apparent for some exercises (i.e., the leg press and lat pull-down) but not others (i.e., knee extension). Bilateral training reduces the BLD; whereas unilateral training has minimal effect on the BLD.     

Exercise Sandals Increase Lower Extremity Electromyographic Activity During Functional Activities

OBJECTIVE: Anecdotal evidence suggests that use of Exercise Sandals results in a number of positive clinical outcomes. However, little research has been conducted to determine their efficacy objectively. Our purposes were to determine the effect of Exercise Sandals on lower leg electromyography (EMG) during activities in the Exercise Sandals and to compare EMG associated with Exercise Sandals with traditional lower extremity rehabilitation exercises. DESIGN AND SETTING: Two within-subjects, repeated-measures designs were used to identify differences in lower extremity EMG: (1) between activities with and without Exercise Sandals and (2) between Exercise Sandals activities and traditional rehabilitation activities. All data were collected in the Sports Medicine Research Laboratory. SUBJECTS: Eighteen subjects involved in rehabilitation using Exercise Sandals for at least 2 weeks within the year before data collection. MEASUREMENTS: Mean EMG amplitudes from the tibialis anterior, peroneus longus, soleus, and lateral gastrocnemius muscles were measured during single-leg stance, side stepping, and "high knees," all performed with and without the Exercise Sandals, as well as single-leg stance on a foam surface and T-band kicks in the sagittal and frontal planes. RESULTS: Exercise Sandals increased lower leg EMG activity, particularly in the ankle invertors and evertors. Also, activities involving the Exercise Sandals resulted in EMG activity similar to or exceeding that associated with traditional ankle-rehabilitation exercises. CONCLUSIONS: These results, coupled with the fact that Exercise Sandals are used in a functional closed kinetic chain manner, suggest that they are an effective means of increasing lower extremity muscle activity.     

The integrated dynamic exercise advancement system technique for progressing functional closed kinetic chain rehabilitation programs

Graded exercise progressions are necessary during the rehabilitation process. We developed the Integrated Dynamic Exercise Advancement System (IDEAS) to fill this void. There appears to be a lack of progression/advancement systems for closed kinetic chain exercises, even though the IDEAS technique for advancing closed chain activities is comprised of two phases: preparing a safe environment and advancing the exercise. Phase one includes a conceptual checklist to assess the safety of the environment. Phase two is a six-step process that challenges each plane of motion by adding speed, workload, external stimuli, and terrain changes. The IDEAS technique is presented to safely prepare an environment and help clinicians to put thought into advancing an exercise program. The IDEAS technique is suggested for use in other arenas such as strength and conditioning.     

Similar hormonal responses to concentric and eccentric muscle actions using relative loading

Conventional resistance exercise is performed using sequential concentric (CON) and eccentric (ECC) contractions, utilizing the same muscle load. Thus, relative to maximal CON and ECC resistance, the ECC contraction is loaded to a lesser degree. We have recently shown that at the same absolute load, CON contractions are associated with greater growth hormone (GH) but similar total testosterone (TT) and free testosterone (FT) responses compared with ECC contractions and attributed the larger GH response to greater relative CON loading. In the present study, we have examined the same endocrine parameters to six different upper and lower body exercises using relative loading rather than absolute loading, hypothesizing that GH responses would be similar for CON and ECC actions, but TT and FT responses would be greater after ECC contractions. Seven young men with recreational weight training experience completed an ECC and CON muscle contraction trial on two different occasions in a counterbalanced fashion. The exercises consisted of four sets of 10 repetitions of lat pull-down, leg press, bench press, leg extension, military press, and leg curl exercises at 65% of an ECC or CON 1–RM with 90 s between sets and exercises. CON and ECC actions were performed at the same speed. ECC 1-RMs were considered to be 120% of the CON 1-RM for the same exercise. Blood samples were collected before, immediately after, and 15 min after the exercise. GH significantly increased across both trials but was not different between the two trials. Total testosterone was not significantly altered in response to either trial; however, free testosterone concentrations increased in response to both ECC and CON trials. Data suggest that CON and ECC muscle contractions produce similar GH, T, and free testosterone responses with the same relative loading.     

Effects of 20-day bed rest with and without strength training on postural sway during quiet standing

Aim: To examine the effect of unweighting as a possible contributory factor to a reduced calf muscle volume on postural sway during quiet standing, changes in postural sway following bed rest with or without strength training were investigated. Methods: Twelve young men participated in a 20‐day bed‐rest study. Subjects were divided into a non‐training group (BR‐Con) and a strength training group (BR‐Tr). For the BR‐Tr group, training was comprised of dynamic calf‐raise and leg‐press exercises to maintain the muscle volume of the plantar flexors. Before and after bed rest, subjects maintained quiet standing in a barefoot position on a force platform with their eyes open or closed. During the quiet stance, foot centre‐of‐pressure (CoP) and the mean velocity of CoP was calculated. Muscle volume of the plantar flexors was computed using axial magnetic resonance images of the leg. Results: After the bed‐rest period, the muscle volume decreased in the BR‐Con group but not in the BR‐Tr group. The mean velocity of CoP as an assessment of postural sway, however, increased in both groups. These results indicate that the strength training during bed rest cannot counteract the increase in postural sway. Conclusion: We concluded that postural sway increases following 20 days of bed rest despite maintenance of the muscle volume of plantar flexors as the main working muscles for the human postural standing.     

A new method for measuring power output in a single leg extension: feasibility,reliability and validity

Summary A method is described for measuring the explosive power of the leg in extension which has been found safe and acceptable for all age groups and levels of physical capability. The extension movement takes 0.25–0.40 s in a push through 0.165 m against a flat pedal. At the end of the push the leg is fully extended. The movement is made seated so that the forces are contained between the buttocks and the foot. The seat position is adjusted for leg length and the push is transmitted by a lever and chain to spin a flywheel. The gearing is such that resistance to the movement remains nearly constant throughout the extension. The final angular velocity of the flywheel is measured by an optoswitch and used to calculated the average leg extensor power (LEP) in the push. The reliability of the power measurement was evaluated in 46 subjects ranging in age from 20 to 86 years; they included medical students and geriatric day patients. They were tested on two occasions separated by a week. The maximal values on the first occasion (best of at least five trials) ranged from 30 to 300 W (mean ± 1 SD = 154 ± 88 W). There was no significant difference on re-test and the coefficient of variation was 9.4%. In a subgroup of 9 non-naive subjects who were measured by an experienced observer it was 6.3%. As expected, power was lower in women than in men and declined sharply with age. The sex difference was less when the values were expressed as power per body mass; a sharp age-related decline remained. The results from the LEP rig were compared with results obtained in the same subjects on the same occasion from similar pushes against an isokinetic dynamometer and two-legged jumps on a force plate. There was a highly significant correlation in both cases, Spearman's rank correlation (rho) = 0.73,P < 0.001,n = 16 subjects (age 27 ± 7.5 years) and rho = 0.86,P < 0.001,n = 13 subjects (age 39 ± 10.4 years) respectively.     

Tibial displacement and rotation during seated knee extension and wall squatting: A comparative study of tibiofemoral kinematics between chronic unilateral anterior cruciate ligament deficient and healthy knees

BackgroundFollowing anterior cruciate ligament (ACL) rupture, the knee becomes unstable with alterations in joint kinematics including anterior tibial displacement (ATD), and internal tibial rotation. Therapeutic exercises that promote faulty kinematics should be discouraged, especially early post-reconstruction, to avoid graft stretching and possibly longer-term osteoarthritis. Our study aimed to compare ATD and tibial rotation during two commonly prescribed exercises, namely: open kinetic chain (OKC) seated extension and closed kinetic chain (CKC) single leg wall squatting in ACL-deficient and healthy knees.MethodsEight ACL-deficient patients and eight healthy subjects matched for age, gender and sports history were assessed using Qualisys 3D-Motion Analysis System to track 17 infrared markers while performing a seated knee extension with 3 kg weight and a unilateral wall squat. We developed a model to measure joint kinematics through 70° of knee flexion and extension. ANOVA and paired t-tests compared relative ATD and tibial rotation between exercises and groups at 10° increments of flexion and extension.ResultsWe found increased ATD in the wall squat compared to the seated extension (p = 0.049). There was no difference in ATD between the healthy and ACL-deficient knees but overall the tibia was significantly more internally rotated (p = 0.003) in ACL-deficient knees, irrespective of the exercise, possibly interfering with the screw-home mechanism.ConclusionsCKC exercises, in particular wall squats, are not necessarily safer for patients with ACL-deficiency and possibly ACL-reconstruction; although generalization should only be made with appropriate caution. Clinicians require a detailed knowledge of the effect of exercise on knee joint kinematics.     

Influence of muscle strength to weight ratio on functional task performance

Existing models of muscle deconditioning such as bed rest are expensive and time-consuming. We propose a new model utilizing a weighted suit to manipulate muscle strength, power, or endurance relative to body weight. The aims of the study were to determine as to which muscle measures best predict functional task performance and to determine muscle performance thresholds below which task performance is impaired. Twenty subjects performed seven occupational astronaut tasks (supine and upright seat egress and walk, rise from fall, hatch opening, ladder climb, object carry, and construction board activity), while wearing a suit weighted with 0–120 % of body weight. Models of the relationship between muscle function/body weight and task completion time were developed using fractional polynomial regression and verified with pre- and post-flight astronaut performance data. Spline regression was used to identify muscle function thresholds for each task. Upright seat egress and walk was the most difficult task according to the spline regression analysis thresholds. Thresholds normalized to body weight were 17.8 N/kg for leg press isometric force, 17.6 W/kg for leg press power, 78.8 J/kg for leg press work, 5.9 N/kg isometric knee extension and 1.9 Nm/kg isokinetic knee extension torque. Leg press maximal isometric force/body weight was the most reliable measure for modeling performance of ambulatory tasks. Laboratory-based manipulation of relative strength has promise as an analog for spaceflight-induced loss of muscle function. Muscle performance values normalized to body weight can be used to predict occupational task performance and to establish relevant strength thresholds.     

Electromyographic behaviour of the gastrocnemius muscle during knee extension and flexion performed on the leg press.

The gastrocnemius was analysed in 10 male volunteers during knee flexion and extension with the foot in normal, plantar flexion and dorsal flexion positions. Hewlett-Packard surface electrodes, an electromyographic signal amplifier, a computer equipped with an A/D conversion plaque (Model CAD 10/26), a software specially designed to record and analyse the signals, a horizontal leg press, and electrogoniometers were used. The gastrocnemius muscle showed strong potentials at the end of knee extension and beginning of knee flexion. The muscle presented a similar activity both in the upper and lower platforms. As to bilateral action, the right gastrocnemius presented stronger potentials on the upper platforms, whereas the potentials were bilaterally similar on the lower platforms. As for foot position, the gastrocnemius presented strong potentials when the foot was in plantar flexion. The remaining positions had no effect on the work of the muscle.     

Human soleus muscle protein synthesis following resistance exercise

AIM: It is generally believed the calf muscles in humans are relatively unresponsive to resistance training when compared with other muscles of the body. The purpose of this investigation was to determine the muscle protein synthesis response of the soleus muscle following a standard high intensity bout of resistance exercise. METHODS: Eight recreationally active males (27 +/- 4 years) completed three unilateral calf muscle exercises: standing calf press/heel raise, bent-knee calf press/heel raise, and seated calf press/heel raise. Each exercise consisted of four sets of 15 repetitions (approximately 15 repetition maximum, RM, or approximately 70% 1RM). Fractional rate of muscle protein synthesis (FSR) was determined with a primed constant infusion of [2H5]phenylalanine coupled with muscle biopsies immediately and 3 h following the exercise in both the exercise and non-exercise (resting control) leg. RESULTS: FSR was elevated (P < 0.05) in the exercise (0.069 +/- 0.010) vs. the control (0.051 +/- 0.012) leg. Muscle glycogen concentration was lower (P < 0.05) in the exercise compared with the control leg (Decrease from control; immediate post-exercise: 54 +/- 5; 3 h post-exercise: 36 +/- 4 mmol kg(-1) wet wt.). This relatively high amount of glycogen use is comparable with previous studies of resistance exercise of the thigh (i.e. vastus lateralis; approximately 41-49 mmol kg(-1) wet wt.). However, the exercise-induced increase in FSR that has been consistently reported for the vastus lateralis (approximately 0.045-0.060% h(-1)) is on average approximately 200% higher than reported here for the soleus (0.019 +/- 0.003% h(-1)). CONCLUSIONS: These results suggest the relatively poor response of soleus muscle protein synthesis to an acute bout of resistance exercise may be the basis for the relative inability of the calf muscles to respond to resistance training programs.     

Comparison in eccentric exercise-induced muscle damage among four limb muscles

This study tested the hypothesis that changes in indirect markers of muscle damage following maximal eccentric exercise would be smaller for the knee extensors (KE) and flexors (KF) compared with the elbow flexors (EF) and extensors (EE). A total of 17 sedentary men performed five sets of six maximal isokinetic (90°?s^?1) eccentric contractions of EF (range of motion, ROM: 90°?C0°, 0?=?full extension), EE (55°?C145°), KF (90°?C0°), and KE (30°?C120°) using a different limb with a 4?C5-week interval in a counterbalanced order. Changes in maximal isometric and concentric isokinetic strength, optimum angle, limb circumference, ROM, plasma creatine kinase activity and myoglobin concentration, muscle soreness, and echo-intensity of B-mode ultrasound images before and for 5?days following exercise were compared amongst the four exercises using two-way repeated-measures ANOVA. All variables changed significantly following EF, EE, and KF exercises, but KE exercise did not change the optimum angle, limb circumference, and echo-intensity. Compared with KF and KE, EF and EE showed significantly greater changes in all variables, without significant differences between EF and EE. Changes in all variables were significantly greater for KF than KE. For the same subjects, the magnitude of change in the dependent variables following exercise varied among the exercises. These results suggest that the two arm muscles are equally more susceptible to muscle damage than leg muscles, but KF is more susceptible to muscle damage than KE. The difference in the susceptibility to muscle damage seems to be associated with the use of muscles in daily activities.