Adaptation of a foot plate for use in an isokinetic and isotonic leg press

The use of isokinetic equipment and the leg press exercise have been major components of rehabilitation for the past several years when redeveloping muscular strength. Recently, closed kinetic chain exercises have been shown to be more beneficial and have less adverse affects on the knee when rehabilitating a patient's lower extremity. The purpose of this article is to introduce the leg press foot plate to the rehabilitative community. This foot plate is a versatile piece of equipment that has been adapted for use with various isokinetic, isometric, and isotonic devices in order to do leg press exercises. The device allows for closed kinetic chain strengthening and testing from equipment typically used only for open kinetic chain activities.     

Neuromuscular adaptations to 8-week strength training: isotonic versus isokinetic mode

Previous studies attempted to compare the effectiveness of isokinetic and isotonic training. However, they have provided conflicting results. The purpose of this study was to compare the effects of isotonic versus isokinetic standardized concentric strength training programs of the knee extensors on the neuromuscular system. The standardization of these two training programs was ensured by the equalization of the total external amount of work performed and the mean angular movement velocity. Thirty healthy male students were randomly assigned to the isotonic (IT; n = 11), the isokinetic (IK; n = 11) or the control (C; n = 8) group. Both IT and IK groups trained their dominant lower leg 3 sessions/week for 8 weeks on a dynamometer. The IT group exercised using a preset torque of 40% of the maximal voluntary isometric torque at 70° (0° = leg in horizontal position). The IK group exercised at a velocity ranging between 150° and 180° s^?1. Isotonic, isokinetic and isometric tests were performed on a dynamometer before and after strength training. Surface electromyographic activity of vastus lateralis, vastus medialis, rectus femoris, semitendinosus and biceps femoris muscles was recorded during the tests. Significant strength increases in both dynamic and static conditions were noticed for IT and IK groups without any significant difference between the two trained groups. Agonist muscle activity also increased with training but no change in antagonist muscle co-activity was observed. The two training methods could be proposed by clinicians and athletic coaches to improve concentric muscle strength in dynamic and static conditions.     

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。     

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.     

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.     

Posterior rotator cuff strengthening using theraband(r) in a functional diagonal pattern in collegiate baseball pitchers

The deceleration phase of the pitching mechanism requires forceful eccentric contraction of the posterior rotator cuff. Because traditional isotonic strengthening may not be specific to this eccentric pattern, a more effective and functional means of strengthening the posterior rotator cuff is needed. Twelve collegiate baseball pitchers performed a moderate intensity isotonic dumbbell strengthening routine for 6 weeks. Six of the 12 subjects were randomly assigned to an experimental group and placed on a Theraband(R) Elastic Band strengthening routine in a functional-diagonal pattern to emphasize the eccentric contraction of the posterior rotator cuff, in addition to the isotonic routine. The control group (n = 6) performed only the isotonic exercises. Both groups were evaluated on a KIN-COM(R) isokinetic dynamometer in a functional diagonal pattern. Pretest and posttest average eccentric force production of the posterior rotator cuff was compared at two speeds, 60 and 180 degrees /s. Data were analyzed with an analysis of covariance at the .05 level with significance at 60 degrees /s. Values at 180 degrees /s, however, were not significant. Eccentric force production at 60 degrees /s increased more during training in the experimental group (+19.8%) than in the control group (-1.6%). There was no difference in the two groups at 180 degrees /s; both decreased (8 to 15%). Theraband was effective at 60 degrees /s in functional eccentric strengthening of the posterior rotator cuff in the pitching shoulder.     

Symptomatic and Functional Responses to Concentric-Eccentric Isokinetic Versus Eccentric-Only Isotonic Exercise

Context:

Rehabilitation protocols involving eccentric resistance exercise performed with loading more than 100% concentric 1-repetition maximum are effective in increasing muscle function in both healthy and injured populations. The mode of eccentric exercise (isokinetic versus isotonic) may be an important factor in limiting symptoms of delayed-onset muscle soreness and in improving muscle function after training.

Objective:

To compare functional and symptomatic responses after an eccentric-only (ECC) isotonic exercise protocol and after a combined concentric-eccentric (CON-ECC) isokinetic exercise protocol matched for total exercise volume.

Design:

Observational study.

Setting:

Controlled research laboratory.

Patients or Other Participants:

Twenty-four healthy, untrained, college-aged men (n  =  12) and women (n  =  12).

Intervention(s):

Participants were randomly assigned to the ECC isotonic or CON-ECC isokinetic exercise group and performed a single bout of resistance exercise involving the elbow flexors.

Main Outcome Measure(s):

Measurements of elbow flexion and extension, isometric strength, and muscle point tenderness were obtained before exercise (baseline) and during follow-up sessions (days 2, 4, 7, and 14). Separate 1-way analyses of variance and repeated-measures analyses of variance were used to determine outcome differences. Tukey post hoc testing was performed when indicated.

Results:

At baseline, no differences were present between groups for any measure. The ECC isotonic exercise protocol resulted in a 30% to 36% deficit in muscle strength, a 5% to 7% reduction in elbow flexion, and a 6% to 8% reduction in elbow extension at follow-up days 2 and 4 (P < .01). The CON-ECC isokinetic exercise protocol did not alter muscle strength or range of motion at any time when compared with baseline. Muscle point tenderness increased from baseline on days 2 and 4 in both groups (P < .05) but was not different between groups throughout the recovery period.

Conclusions:

Our results indicated more pronounced functional deficits occurred after a single bout of ECC isotonic exercise than with a CON-ECC isokinetic exercise protocol matched for training volume.     

Effects of combined strength and sprint training on regulation of muscle contraction at the whole-muscle and single-fibre levels in elite master sprinters

Aim: This study aims at examining the effects of progressive strength and sprint training on regulation of muscle contraction at the whole‐muscle and single‐fibre levels in older sprint‐trained athletes. Methods: Eleven men (52–78 years) were randomized to a training (EX, n = 7) or control (CTRL, n = 4) group. EX participated in a 20‐week programme that combined sprint training with heavy and explosive strength exercises, while CTRL maintained their usual run‐based training schedules. Results: EX improved maximal isometric and dynamic leg strength, explosive jump performance and force production in running. Specific tension and maximum shortening velocity of single fibres from the vastus lateralis were not altered in EX or CTRL. Fibre type and myosin heavy chain isoform distributions remained unchanged in the two groups. There was a general increase in fibre areas in EX, but this was significant only in IIa fibres. The 10% increase in squat jump in EX was accompanied by a 9% increase in the integrated EMG (iEMG) of the leg extensors but the 21–40% increases in isometric and dynamic strength were not paralleled by changes in iEMG. Conclusion: Adding strength training stimulus to the training programme improved maximal, explosive and sport‐specific force production in elite master sprinters. These improvements were primarily related to hypertrophic muscular adaptations.     

等速限弧运动对膝关节炎功能影响

目的　探讨股四头肌限弧等速运动角度对膝骨性关节炎患者的疗效。 方法　共78例右膝骨性关节炎患者纳入研究，按随机法赋值从大到小分成3组，每组26例。3组除常规运动训练外，进行不同角度的限弧等速运动训练。训练弧度分别为：A组膝屈90°→10°，B组膝屈60°→10°，C组膝屈30°→10°。每周3 次, 训练 8 周。在治疗前后分别采用疼痛视觉模拟评分法（VAS）评估疼痛改善程度，采用美国特种外科医院（HSS）指数评定膝关节功能情况，同时等速训练仪测定患膝峰力矩（peak torque，PT）、本体感觉误差均值。 结果　3组疼痛、HSS指数、PT较治疗前差异有显著性意义（P <0.05），A组优于B组、C组（P <0.05）；治疗后各组本体感觉较治疗前略有改善，但3组改善程度无统计学差异（P> 0.05）。 结论　不同弧度等速运动可以改善膝关节功能，较大弧度的限弧等速运动获益更明显。     

Incline plyometrics-induced improvement of jumping performance

The aim of this study was to examine the effects of incline plyometrics training on muscle activation and architecture during vertical jumping and maximum strength. Twenty male participants were divided in two training groups which followed after a 4 week training program. The incline plyometrics group (n = 10) trained by performing consecutive jumps on an inclined surface (15°) while the plane plyometrics (PP) group (n = 10) performed the same jumps on a plane surface. Both groups trained four times per week and performed 8 sets of 10 jumps in each session. Subjects performed squat jumps, counter movement jumps and drop jumps (DJ) prior to and immediately after the training period, while the electromyographic activity of the medial gastrocnemius (MGAS) and tibialis anterior muscles and the architecture of MGAS were recorded. Maximal isokinetic and isometric strength of the plantar flexors were performed. Analysis of variance showed that only the IP group improved fast DJ height performance by 17.4 and 14.4% (20 and 40 cm, p < 0.05). This was accompanied by a significantly higher MGAS activity during the propulsion phase (24% from 20 cm and 50% from 40 cm, p < 0.05) of the DJ and a longer working fascicle length (5.08%, p < 0.05) compared with the PP group. There were no significant changes in isokinetic and isometric strength of the plantar flexors after training for both groups. The increase of jumping performance, after incline plyometrics should be taken into consideration by coaches, when they apply hopping exercise to improve explosiveness of the plantar flexors.     

Velocity specificity in early training of the knee extensors after anterior cruciate ligament reconstruction

Resistance-training velocity specificity is known to occur in isotonic training of uninjured subjects and in isokinetic training of injured patients. Whether velocity specificity occurs with isotonic training in injured patients has not been tested, despite the common use of this exercise mode in patients. Thirty-two patients recovering from anterior cruciate ligament reconstruction (ACLR) surgery were tested at approximately 2 and 6 weeks after surgery. The isokinetic injured/uninjured strength ratios of the knee extensors were compared for the test velocities of 60° · s⁻¹ and 210° · s⁻¹, as assessed before and after a 4-week training period. Isotonic training of the knee extensors at 60° · s⁻¹ was applied in formal sessions three times per week. The isokinetic injured/uninjured strength ratios were compared for the two test velocities, and there was no indication that training velocity specificity occurred in these patients. Possible reasons for this finding, which contrasts with previous work, are discussed. Accepted: 12 November 1999     

Resistance training frequency: strength and myosin heavy chain responses to two and three bouts per week

Seventeen subjects performed resistance training of the leg extensor and flexor muscle groups two (2/wk) or three (3/wk) times per week. Changes in the relative myosin heavy chain (MHC) isoform contents (I, IIa and IIx) of the vastus lateralis and isometric, isokinetic and squat-lift one-repetition maximum (1RM) strength were compared between conditions after both a common training period (6?weeks) and number of training sessions (18). After 6?weeks and 18 sessions (9?weeks for the 2/wk group), increments in 1RM strength for the 3/wk and 2/wk groups were similar [effect size (ES) differences?≈0.3, 3/wk?>?2/wk], whereas the 2/wk group presented greater isokinetic (ES differences?=?0.3–1.2) and isometric (ES differences?≈0.7) strength increases than the 3/wk condition. A significant (P?r ²:?0.0–0.5). Thus, isometric and isokinetic strength responses to variations in training frequency differed from 1RM strength responses, and changes in strength were not strongly related to alterations in relative MHC content.     

Effects of resistance exercise combined with vascular occlusion on muscle function in athletes

The effects of resistance exercise combined with vascular occlusion on muscle function were investigated in highly trained athletes. Elite rugby players (n=17) took part in an 8 week study of exercise training of the knee extensor muscles, in which low-intensity [about 50% of one repetition maximum] exercise combined with an occlusion pressure of about 200 mmHg (LIO, n=6), low-intensity exercise without the occlusion (LI, n=6), and no exercise training (untrained control, n=5) were included. The exercise in the LI group was of the same intensity and amount as in the LIO group. The LIO group showed a significantly larger increase in isokinetic knee extension torque than that in the other two groups (P<0.05) at all the velocities studied. On the other hand, no significant difference was seen between LI and the control group. In the LIO group, the cross-sectional area of knee extensors increased significantly (P<0.01), suggesting that the increase in knee extension strength was mainly caused by muscle hypertrophy. The dynamic endurance of knee extensors estimated from the decreases in mechanical work production and peak force after 50 repeated concentric contractions was also improved after LIO, whereas no significant change was observed in the LI and control groups. The results indicated that low-intensity resistance exercise causes, in almost fully trained athletes, increases in muscle size, strength and endurance, when combined with vascular occlusion. Electronic Publication     

Knee Extensor Electromyographic Activity-to-Work Ratio is Greater With Isotonic Than Isokinetic Contractions

OBJECTIVE: To determine whether isotonic or isokinetic contractions produced greater electromyographic (EMG) activity per unit of work during isotonic and isokinetic knee-extension exercise. DESIGN AND SETTING: Subjects performed three 3-second maximal voluntary isometric contractions of the dominant knee extensors for EMG normalization. Exercise testing performed on the Biodex System 3 Dynamometer involved 10 isokinetic contractions at 180 degrees.s(-1) and 10 isotonic contractions with the resistance set at 50% of the previously recorded maximal voluntary isometric contraction. SUBJECTS: Recreationally active college students (10 men and 11 women). MEASUREMENTS: Surface EMG signals were collected from the vastus medialis and lateralis muscles and then integrated (IEMG) over the concentric phase of each repetition for both exercises. The IEMG was divided by the total work performed during the concentric phase for each exercise (IEMG/W). RESULTS: We analyzed the IEMG/W data using a 1-between (sex), 2-within (exercise and muscle) repeated-measures analysis of variance. There was a significant main effect for exercise, with the isotonic IEMG/W value being significantly greater than the isokinetic IEMG/W value. Additionally, the IEMG/W relationship did not appear to be affected by sex or individual muscle tested. CONCLUSIONS: Per unit of work performed, the isotonic contractions resulted in greater motor unit recruitment or an increased rate of firing, or both. This finding may have implications for the early phase of rehabilitation, when goals include complete motor unit recruitment of injured or atrophied muscles.     

Muscle fibre types and enzyme activities after training with local leg ischaemia in man

Eight healthy men performed supine one-legged training on a bicycle ergometer 45 min per leg four times per week for 4 week. The ergometer and lower body were inside a pressure chamber, the opening of which was sealed at the level of the crotch. One leg trained with impeded leg blood flow (I-leg), induced by an increased (50 mmHg) chamber pressure, at the highest tolerable intensity. The contralateral leg trained at the same power under normal pressure (N-leg). Before and after training biopsies were taken from the vastus lateralis of both legs and maximal one-legged exercise tests were executed with both legs. Biopsies were repeated when the subjects had been back to their habitual physical activity for 3 months. Training increased exercise time to exhaustion, but more in the I-leg than in the N-leg. After training, the I-leg had higher activity of citrate synthase (CS), a marker of oxidative capacity, and lower activity of the M-subunit of lactate dehydrogenase isoenzymes. It also had a higher percentage of type-I fibres and a lower percentage of IIB fibres, larger areas of all fibre types and a greater number of capillaries per fibre. It is concluded that ischaemic training changes the muscle metabolic profile in a direction facilitating aerobic metabolism. An altered fibre-type composition may contribute, but is not enough prerequisite for the change.     

Alignment control exercise changes lower extremity movement during stop movements in female basketball players

This study was intended to evaluate a short-term intervention designed to improve the lower extremity alignment with neutral position during stop movements of female basketball players when performing a quick-stop jump shot. In this study, 20 healthy female college basketball players (mean age 20.5 years) participated. The authors monitored two groups for 4 weeks: one which trained (n=10) and one which did not train (n=10). The exercise program emphasized the neutral position of lower extremities for dynamic alignment control; the players avoided the valgus position with their knees. Kinematics analysis with a lower extremity angle in the stop action was performed using three digital video cameras and analyzed using software. Following the intervention exercise program, each subject was re-evaluated at two and four weeks to determine changes in movement patterns during the "sink shot" task. Two-way analysis of variance models were used to determine differences at pre-intervention, at mid-term, and post-intervention. After the 2-week intervention, the trained athletes group made basketball shots with greater change of the lower extremity motion pattern during the stop action than did non-trained athletes (p<0.05). However, no significant differences were found between other data of the 2-week and 4-week intervention groups. Results of this study show that two weeks of training can improve the dynamic alignment control of the lower extremities, as measured using the alignment angle of the coronal plane and the torsion angle of horizontal plane during a stop action.     

Effects of isokinetic, isotonic and isometric submaximal exercise on heart rate and blood pressure

The purpose of the present study was to compare arterial pressure (AP) and heart rate (HR) responses to submaximal isokinetic, isotonic and isometric exercises currently employed in physical rehabilitation therapy in terms of both magnitude and time-course. To this aim AP and HR were continuously and noninvasively measured in ten healthy subjects performing isokinetic, isotonic and isometric exercises at the same relative intensity. Isokinetic and isotonic exercises consisted of 30 knee extension/flexion repetitions at 40% of maximal effort. Isokinetic speed was set at 180°?·?s^?1. Isometric exercise consisted of a 60-s knee extension at 40% maximal voluntary contraction. The AP showed a rapid and marked increase from the onset of all types of exercise progressing throughout the exercises. Peak systolic (SAP) and diastolic (DAP) arterial pressure were 190.7 (SEM 8.9) and 121.6 (SEM 7.8) mmHg during isokinetic and 197.6 (SEM 11.2) and 128.3 (SEM 7.7) mmHg during isotonic exercise, respectively. During isometric exercise peak SAP and DAP were 168.1 (SEM 6.3) and 102.1 (SEM 3.7) mmHg, respectively [both lower compared to isokinetic and isotonic exercise (P??1, continuing to rise throughout the exercises. The HR response to isometric exercise was significantly less (P?相似文献   

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.     

Effects of low-resistance/high-repetition strength training in hypoxia on muscle structure and gene expression

To test the hypothesis that severe hypoxia during low-resistance/high-repetition strength training promotes muscle hypertrophy, 19 untrained males were assigned randomly to 4 weeks of low-resistance/high-repetition knee extension exercise in either normoxia or in normobaric hypoxia (FiO₂ 0.12) with recovery in normoxia. Before and after the training period, isokinetic strength tests were performed, muscle cross-sectional area (MCSA) measured (magnetic resonance imaging) and muscle biopsies taken. The significant increase in strength endurance capacity observed in both training groups was not matched by changes in MCSA, fibre type distribution or fibre cross-sectional area. RT-PCR revealed considerable inter-individual variations with no significant differences in the mRNA levels of hypoxia markers, glycolytic enzymes and myosin heavy chain isoforms. We found significant correlations, in the hypoxia group only, for those hypoxia marker and glycolytic enzyme mRNAs that have previously been linked to hypoxia-specific muscle adaptations. This is interpreted as a small, otherwise undetectable adaptation to the hypoxia training condition. In terms of strength parameters, there were, however, no indications that low-resistance/high-repetition training in severe hypoxia is superior to equivalent normoxic training.     

Ankle plantar flexion strength in resistance and endurance trained middle-aged adults.

Maximum concentric (CONC) and eccentric (ECC) strength of the ankle plantar flexor muscles were compared between middle-aged adults who regularly participated in resistance exercise training versus those who participated in weight-bearing endurance exercise. A total of 40 men and women with a mean age of 48.9 years (SD = 5.3) were tested for CONC and ECC plantar flexor (PF) strength, using an isokinetic device at 3 velocities: 30, 90 and 180 degrees/s. Mean strength values for the groups of men and women involved in resistance exercise were consistently higher than those involved in the endurance training for the CONC tests, where values ranged from 35% to 46% (avg. 41%, p < .01), but less between-group difference was observed for the ECC loading condition: 4% to 30% (avg. 18%). Thus ECC/CONC ratios, which rose with increasing velocity, were consistently higher for the endurance group vs. resistance-trained. Finally, since concentric PF torque values were found to be quite low for the middle-aged women who did only endurance training, this movement may require preventive strengthening exercises.