Isokinetic Strength Training Research Articles

EFFECTS OF TWO DAYS OF ISOKINETIC TRAINING ON STRENGTH AND ELECTROMYOGRAPHIC AMPLITUDE IN THE AGONIST AND ANTAGONIST MUSCLES

The purpose of this study was to examine the effects of 2 days of isokinetic training of the forearm flexors and extensors on strength and electro- myographic (EMG) amplitude for the agonist and antagonist muscles. Seventeen men (mean ± SD age = 21.9 ± 2.8 years) were randomly assigned to 1 of 2 groups: (a) a training group (TRN; n = 8), or (b) a control group (CTL; n = 9). The subjects in the TRN group were tested for maximal isometric and concentric isokinetic (randomly ordered velocities of 60, 180, and 300°·s-1) torque of the dominant forearm flexors and extensors before (pretest) and after (posttest) 2 days of isokinetic strength training. Each training session involved 6 sets of 10 maximal concentric isokinetic muscle actions of the forearm flexors and extensors at a velocity of 180°·s-1. The subjects in the CTL group were also tested for strength but did not perform any training. Surface EMG signals were detected from the biceps brachii and triceps brachii muscles during the strength testing. The results indicated that there were no significant (p > 0.05) pre- to post- test changes in forearm flexion and extension torque or EMG amplitude for the agonist and antagonist muscles. Thus, unlike previous studies of the quadriceps femoris muscles, these findings for the forearm flexors and extensors suggested that 2 days of isokinetic training may not be sufficient to elicit significant increases in strength. These results may have implications for the number of visits that are required for rehabilitation after injury, surgery, or both.

Isokinetic training increases ulnar bending stiffness and bone mineral in young women

Numerous studies have investigated the effects of physical activity on bone health; however, little is known about the effects of isokinetic strength training on bone. While bone mineral density (BMD) is widely used to assess bone health and fracture risk, there are several limitations of this measure that warrant new technology development to measure bone strength. The mechanical response tissue analyzer (MRTA) assesses bone strength by measuring maximal bending stiffness ( EI). We hypothesized that isokinetic strength training of the elbow flexors and extensors would increase ulnar EI, BMD, and bone mineral content (BMC) in young women. Fifty-four women trained the nondominant arm 3 times per week for 20 weeks; 32 trained concentrically (CON) and 22 trained eccentrically (ECC). Subjects were assessed for the following variables pre- and post-training: CON and ECC peak torque of the elbow flexors and extensors with isokinetic dynamometry, ulnar mineral content and density using dual-energy X-ray absorptiometry, and ulnar EI using MRTA. Isokinetic training increased CON (17%) and ECC (17%) peak torque, even when controlling for changes in the untrained arm. Eccentric training increased CON and ECC peak torque while CON training improved CON peak torque only. Isokinetic training increased ulnar EI 28%, which was statistically greater than the untrained arm. Ulnar EI increased 25% with CON training and 32% with ECC training. Both training modes resulted in greater EI gains compared to the untrained limb. Isokinetic training increased ulnar BMC (2.7%) and BMD (2.3%), even when controlling for untrained ulna changes. Both training modalities resulted in BMC and BMD increases; however, only CON training yielded gains when controlling for changes in the untrained limb. In conclusion, isokinetic strength training increases ulnar EI, BMC, and BMD in young women; no statistical differences were noted between CON and ECC training modes.

High eccentric strength training reduces heart rate variability in healthy older men

Background:Evaluation of non-pharmacological therapies that improve autonomic control of the heart rate in older subjects has a clinical significance, because reduced heart rate variability (HRV) can be associated with higher...

Effects of Two Days of Isokinetic Training on Strength and Electromyographic Amplitude in the Agonist and Antagonist Muscles

The purpose of this study was to examine the effects of 2 days of isokinetic training of the forearm flexors and extensors on strength and electromyographic (EMG) amplitude for the agonist and antagonist muscles. Seventeen men (mean +/- SD age = 21.9 +/- 2.8 years) were randomly assigned to 1 of 2 groups: (a) a training group (TRN; n = 8), or (b) a control group (CTL; n = 9). The subjects in the TRN group were tested for maximal isometric and concentric isokinetic (randomly ordered velocities of 60, 180, and 300 degrees x s(-1)) torque of the dominant forearm flexors and extensors before (pretest) and after (posttest) 2 days of isokinetic strength training. Each training session involved 6 sets of 10 maximal concentric isokinetic muscle actions of the forearm flexors and extensors at a velocity of 180 degrees x s(-1). The subjects in the CTL group were also tested for strength but did not perform any training. Surface EMG signals were detected from the biceps brachii and triceps brachii muscles during the strength testing. The results indicated that there were no significant (p > 0.05) pre- to post-test changes in forearm flexion and extension torque or EMG amplitude for the agonist and antagonist muscles. Thus, unlike previous studies of the quadriceps femoris muscles, these findings for the forearm flexors and extensors suggested that 2 days of isokinetic training may not be sufficient to elicit significant increases in strength. These results may have implications for the number of visits that are required for rehabilitation after injury, surgery, or both.

Soccer Players' Muscular Imbalances: Restoration with an Isokinetic Strength Training Program

The aim of the study was to investigate the effect of a muscular training program on soccer players' performance which initially appeared imbalanced or bilaterally asymmetrical. During the preparation period, 35 soccer players performed an isokinetic measurement of knee flexors and extensors (60 degrees(-1) and 180 degrees sec.(-1)). 15 of these had muscular imbalances or deficits and followed a specific isokinetic training program for 2 mo., 3 times per week. After the completion of the isokinetic training program, the 35 players underwent the same isokinetic test. Significant differences were noted between the pre- and posttraining measures at both angular velocities in peak torque values, in differences from one limb to the other, and in peak torque ratios for flexors and extensors. Consequently, the application of this specific isokinetic training program can restore imbalances in knee muscle strength efficiently.

Smart Rehabilitation Devices: Part II - Adaptive Motion Control.

This article presents a study of adaptive motion control of smart versatile rehabilitation devices using MR fluids. The device provides both isometric and isokinetic strength training and is reconfigurable for several human joints. Adaptive controls are developed to regulate resistance force based on the prescription of the therapist. Special consideration has been given to the human-machine interaction in the adaptive control that can modify the behavior of the device to account for strength gains or muscle fatigue of the human subject.

Smart Rehabilitation Devices: Part I - Force Tracking Control

Resistance exercise has been widely reported to have positive rehabilitation effects for patients with neuromuscular and orthopaedic conditions. This article presents prototypes of smart variable resistance exercise devices using magneto-rheological fluid dampers. An intelligent supervisory control for regulating the resistive force or torque of the device is developed, and is validated both numerically and experimentally. The device provides both isometric and isokinetic strength training for the human joints including knee, elbow, hip, and ankle.

Adaptive force regulation of muscle strengthening rehabilitation device with magnetorheological fluids

In rehabilitation from neuromuscular trauma or injury, strengthening exercises are often prescribed by physical therapists to recover as much function as possible. Strengthening equipment used in clinical settings range from low-cost devices, such as sandbag weights or elastic bands to large and expensive isotonic and isokinetic devices. The low-cost devices are incapable of measuring strength gains and apply resistance based on the lowest level of torque that is produced by a muscle group. Resistance that varies with joint angle can be achieved with isokinetic devices in which angular velocity is held constant and variable torque is generated when the patient attempts to move faster than the device but are ineffective if a patient cannot generate torque rapidly. In this paper, we report the development of a versatile rehabilitation device that can be used to strengthen different muscle groups based on the torque generating capability of the muscle that changes with joint angle. The device is low cost, is smaller than other commercially available machines, and can be programmed to apply resistance that is unique to a particular patient and that will optimize strengthening. The core of the device, a damper with smart magnetorheological fluids, provides passive exercise force. A digital adaptive control is capable of regulating exercise force precisely following the muscle strengthening profile prescribed by a physical therapist. The device could be programmed with artificial intelligence to dynamically adjust the target force profile to optimize rehabilitation effects. The device provides both isometric and isokinetic strength training and can be developed into a small, low-cost device that may be capable of providing optimal strengthening in the home.

A prototype rehabilitation device with variable resistance and joint motion control

Resistance exercise has been widely reported to have positive rehabilitation effects for patients with neuromuscular and orthopaedic conditions. This paper presents the design of a versatile rehabilitation device in the form of a rotating joint arm mounted on the adjustable seat that provides passive resistance during strength training for muscles. The resistance is supplied by a magnetorheological damper. Intelligent controls are developed to produce resistance force based on the prescription of the therapist. The device provides both isometric and isokinetic strength training and is reconfigurable for several human joints. Special consideration has been given to the human–machine interaction in the adaptive control algorithms that can modify the behavior of the device to account for strength gains or muscle fatigue.

Rehabilitation device with variable resistance and intelligent control

Resistance exercise has been widely reported to have positive rehabilitation effects for patients with neuromuscular and orthopaedic conditions. This paper presents an optimal design of magneto-rheological fluid dampers for variable resistance exercise device in the form of a knee brace. An intelligent supervisory control for regulating the resistive force or torque of the knee brace has also been studied. The device provides both isometric and isokinetic strength training for the knee.

Influence of Oral Contraceptives on Bone Adaptations to Isokinetic Strength Training in Young Women

Influence of Oral Contraceptives on Bone Adaptations to Isokinetic Strength Training in Young Women

Influence of Oral Contraceptives on Bone Adaptations to Isokinetic Strength Training in Young Women

0756 PURPOSE: To assess the independent and synergistic effects of oral contraceptive (OC) use on bone mineral density (BMD) and bone mechanical stiffness (EI) in college-aged females after unilateral isokinetic resistance training. METHODS: Forty six females (age 20 ± 1.4 yr, height 163.8 ± 6.2cm, weight 58.9 ± 8.6kg, %fat 27.9 ± 4.8) were categorized as OC users (OC, N = 22) or not (NOC, N = 24) and participated in 32 weeks (3 d/wk) of unilateral arm and leg training, angular velocity 60°/s, using isokinetic dynamometers. BMD and EIMRTA were assessed using dual-energy x-ray absorptiometry (DXA) and mechanical response tissue analysis (MRTA), respectively. RESULTS: Leg and arm muscular strength increased by 16% and 15%, respectively (P < 0.001), beyond the pre- to post-training changes observed in the control limbs. Muscular strength gains were not associated with any consistent changes in either leg or arm EIMRTA, nor did groups using or not using OC respond differently. Both BMD of the tibia for the control leg and for the total body increased by small but significant amounts (1.4% and 0.4%, respectively; P <0.05) in the NOC group. The OC group showed no increase in these two measures, suggesting a potential suppressive effect of OC on bone mass accumulation in these skeletally immature females. However, BMD increased in the ulna bilaterally (P <0.01) and in the total hip of the trained leg only (P <0.05), regardless of OC use. CONCLUSION: These results suggest that oral contraceptives may limit attainment of total body peak bone mass in young adult females. Variable effects on appendicular bone were inconsistent in both control and regions of interest for assessing isokinetic training. Further studies are needed to determine the interactive effects of OC use and isokinetic resistance training on measures of bone strength. Supporting agency: United States Army Medical Research and Materiel Command, Grant #DAMD17-00-1-0114

Effects of isokinetic strength training on walking in persons with stroke: A double-blind controlled pilot study

Objectives: The goal most often stated by persons with stroke is improved walking function. The purpose of this study was to determine the effects of isokinetic strength training on walking performance, muscle strength, and health-related quality of life in survivors of chronic stroke. Methods: Twenty participants (age, 61.2 ± 8.4 years) with chronic stroke were randomized into 2 groups. The experimental group undertook maximal concentric isokinetic strength training, whereas the control group received passive range of motion of the paretic lower extremity 3 times a week for 6 weeks. The Kin-Com Isokinetic Dynamometer (Chattanooga Group Inc., TN) was used for both the strengthening and passive range of motion exercises. The Mann-Whitney U test was used to compare the changes in scores (postintervention minus baseline) between the control and experimental groups for a composite lower extremity strength score, walking speed (level-walking and stair-walking) and health-related quality of life measure (36-Item Short Form Health Survey [SF-36]). Results: Both the experimental and control groups increased their strength and walking speed postintervention; however, there were no differences in the changes in walking speed between the groups. There was a trend (P =.06) toward greater strength improvement in the experimental group compared with the control group. No changes in SF-36 scores were found in either group. Conclusions: Intervention aimed at increasing strength did not result in improvements in walking. The results of this study stress the importance of controlled clinical trials in determining the effect of specific treatment approaches. Strength training in conjunction with other task-related training may be indicated. Copyright © 2001 by National Stroke Association

The Effect of Concentric Isokinetic Strength Training of the Quadriceps Femoris on Electromyography and Muscle Strength in the Trained and Untrained Limb

The purpose of the present investigation was to examine the effects of unilateral concentric isokinetic leg extension training on peak torque (PT) and electromyographic (EMG) responses in the trained and untrained limbs. Twenty adult men were randomly assigned to a training (TRN, n = 11) or control (CTL, n = 9) group. The TRN group performed 6 sets of 10 leg extensions 3 days per week for 12 weeks at a velocity of 90°s−1. All subjects were tested every 4 weeks for PT and EMG responses of both legs at a velocity of 90°s−1. The 3-way mixed factorial analysis of variance (ANOVA) indicated a significant (p < 0.05) increase in PT over the 12 weeks in both the trained and untrained limb for the TRN group but no significant change in PT in either limb for the CTL group. The results of the 3-way ANOVA for the EMG data indicated no significant change in EMG amplitude in the trained or untrained limb for the TRN or CTL group. The increase in PT in the absence of a change in EMG may result from hypertrophic factors and/or changes in the other muscles or muscle groups involved in leg xtension.

The Effect of Concentric Isokinetic Strength Training of the Quadriceps Femoris on Electromyography and Muscle Strength in the Trained and Untrained Limb

The purpose of the present investigation was to examine the effects of unilateral concentric isokinetic leg extension training on peak torque (PT) and electromyographic (EMG) responses in the trained and untrained limbs. Twenty adult men were randomly assigned to a training (TRN, n = 11) or control (CTL, n = 9) group. The TRN group performed 6 sets of 10 leg extensions 3 days per week for 12 weeks at a velocity of 90 degrees.s(-1). All subjects were tested every 4 weeks for PT and EMG responses of both legs at a velocity of 90 degrees.s(-1). The 3-way mixed factorial analysis of variance (ANOVA) indicated a significant (p < 0.05) increase in PT over the 12 weeks in both the trained and untrained limb for the TRN group but no significant change in PT in either limb for the CTL group. The results of the 3-way ANOVA for the EMG data indicated no significant change in EMG amplitude in the trained or untrained limb for the TRN or CTL group. The increase in PT in the absence of a change in EMG may result from hypertrophic factors and/or changes in the other muscles or muscle groups involved in leg extension.

Effects of isokinetic strength training on concentric and eccentric torque development in the ankle dorsiflexors of older adults.

This study quantifies concentric and eccentric dorsiflexor muscle torque at various movement velocities and determines the neuromuscular effects from short-term practice of repeated maximal voluntary contractions using an isokinetic resisted exercise program in older adults. Twenty-eight subjects (76.3+/-4.6 years) trained concentric and eccentric dorsiflexion 3 days per week for 2 weeks at 30 degrees, 90 degrees, and 180 degrees/s through 40 degrees of dorsiflexion range of motion. Peak torque, rate of torque development, surface electromyography, and strength curves at each velocity were compared before and after training. Increases were found for concentric (27%) and eccentric (20%) dorsiflexor peak torque and concentric rate of torque production (20%-53%) across all movement velocities (p < .01). Training also significantly increased dorsiflexor concentric (64%) and eccentric (55%) surface electromyography; taken together, this is evidence of apparent adaptation of neural factors in older adults with short-term training. These findings support that eccentric and concentric strength training enhances the control and production of ankle muscle dorsiflexor torque in older adults, with implications for improving functional mobility of the ankle joint.

The effects of concentric isokinetic strength training of the quadriceps femoris on mechanomyography and muscle strength

The effects of concentric isokinetic strength training of the quadriceps femoris on mechanomyography and muscle strength

Isokinetic strength training of the hemiparetic knee: Effects on function and spasticity

Purpose: To determine whether isokinetic training can improve the strength of the hemiparetic knee musculature, functional mobility, and physical activity and to evaluate its effect on spasticity in long-term stroke survivors. Design: Nonrandomized self-controlled trial. Subjects: A volunteer sample of 15 community-dwelling stroke survivors of at least 6 months. Intervention: A 6-week (3 days/week, 40 minutes/day) program consisting of warm-up, stretches, reciprocal knee extension and flexion isokinetic strengthening, and cool-down for the paretic limb. Main Outcome Measures: Peak isokinetic hamstring and quadriceps torque, quadriceps spasticity, gait velocity, timed Up and Go, timed stair climb, and the Human Activity Profile (HAP) scores were recorded at baseline, after training, and 4 weeks after training cessation (follow-up). Results: Paretic muscle strength improved after training ( p < .05) while tone remained consistent ( p > .87). Gait velocity increased after training ( p < .05) and at follow-up ( p < .05). Changes in stair climbing and timed Up and Go were not significant ( p > .37; p > .91), although subjects perceived gains in their physical abilities at follow-up ( p < .01). Conclusions: Gains in strength and gait velocity without concomitant increases in muscle tone are possible after a shortterm strengthening program for stroke survivors. The psychological benefit associated with physical activity is significant.

Effects of rest interval on isokinetic strength and functional performance after short-term high intensity training.

OBJECTIVES: The ability to maximally generate active muscle tension during resistance training has been established to be a primary determinant for strength development. The influence of intrasession rest intervals may...

THE EFFECTS OF SHOULDER ISOKINETIC STRENGTH TRAINING ON SPEED AND PROPULSIVE FORCES IN FRONT CRAWL SWIMMING 713

The purpose of this study was to investigate the effects of shoulder isokinetic strength training on 50 M sprint time (50ST), propulsive force of arm stroke (ASP) and whole stroke (WSP) in front crawl swimming. Twenty-eight swimmers (8 male and 20 female, Age=18.3 ± 1.3 yrs, Ht. = 165.0± 8.8 cm, Wt.=57.8 ± 9.0 Kg) were matched and then randomly assigned to a isokinetic strength training group (IST, n=14) or control group(n=14). Both groups had the same swimming training program, except that the IST group added shoulder internal/external rotation isokinetic strength training using the MERAC dynamometer. All subjects trained six times per week for five weeks. Statistical analysis indicated that there were significant(p<0.05) changes in the IST group: dominant arm internal rotation strength at speed of 180 deg/s (from 26.3 ± 9.1 ft-lb to 33.8 ± 9.2 ft-lb), 50ST (from 37.1 ± 4.8 sec to 33.4 ± 4.0 sec), ASP (from 2.2 ± 1.7 Kg.M/sec to 2.5 ± 1.9 Kg.M/sec) and WSP (from 3.4± 2.4 Kg.M/sec to 3.6 ± 2.4 Kg.m/sec). No significant(p>0.05) changes were found in the control group. It is concluded that 5 weeks of swimming training combined with isokinetic strength training could significantly improve swimmers' propulsive forces and swimming speed.