Knee Extension Machine Research Articles

Moderate Velocity Strength Training Increases Peak Muscle Power Quality in Older Women

Previous reports on the effects of strength training (ST) on muscle power did not report how the training affected power per unit of the muscle involvement (muscle power quality, MPQ), or peak movement velocity (PV). The expression of peak power normalized for muscle volume allows better understanding of potential mechanisms for training-induced adaptations. PURPOSE To evaluate the effects of ST on peak muscle power (PP) and PV per unit of muscle at given absolute and relative (same % of 1 RM) resistances in older adults. PURPOSE To evaluate the effects of ST on peak muscle power (PP) and PV per unit of muscle at given absolute and relative (same % of 1 RM) resistances in older adults. METHODS Sixty-two relatively healthy, previously sedentary older adults (23 older men, 65 ± 1 yr and 39 older women, 66 ± 1 yr) were studied before and after a 10 wk unilateral knee extension ST program. To quantify quadriceps muscle volume (MV), computed tomography (CT) imaging of the trained and untrained thighs was performed. Determination of peak knee extensor power was performed on a customized pneumatic resistance knee extension machine. Velocity and power data were filtered using a 10 Hz, low-pass Butterworth filter to remove sensor noise and obtain peak estimates. RESULTS As a result of the ST program, peak power increased significantly in both men and women at the same absolute (APP; P < 0.001) and relative loads (RPP; P < 0.05). Men had significantly greater increases in APP and RPP than women with ST when covarying for baseline differences (both P < 0.001). However, when each subject was tested at the same absolute load and when peak power was normalized for the muscle volume of the trained knee extensors (i.e., absolute MPQ), women increased their MPQ (P < 0.05), but men did not. Both men and women increased their absolute PV (P < 0.001), but decreased their relative PV significantly with ST (P < 0.01). CONCLUSIONS These data indicate that a moderate-velocity ST program increases muscle power quality in women, but not in men, suggesting that in contrast to men, women increase peak power with ST through adaptations other than muscular hypertrophy. Supported by NIH Grants R01 AG-4-2148 and AG-1620501 and NIH training grant T32AG00219.

Moderate Velocity Strength Training Increases Peak Muscle Power Quality in Older Women

Previous reports on the effects of strength training (ST) on muscle power did not report how the training affected power per unit of the muscle involvement (muscle power quality, MPQ), or peak movement velocity (PV). The expression of peak power normalized for muscle volume allows better understanding of potential mechanisms for training-induced adaptations. PURPOSE To evaluate the effects of ST on peak muscle power (PP) and PV per unit of muscle at given absolute and relative (same % of 1 RM) resistances in older adults. PURPOSE To evaluate the effects of ST on peak muscle power (PP) and PV per unit of muscle at given absolute and relative (same % of 1 RM) resistances in older adults. METHODS Sixty-two relatively healthy, previously sedentary older adults (23 older men, 65 ± 1 yr and 39 older women, 66 ± 1 yr) were studied before and after a 10 wk unilateral knee extension ST program. To quantify quadriceps muscle volume (MV), computed tomography (CT) imaging of the trained and untrained thighs was performed. Determination of peak knee extensor power was performed on a customized pneumatic resistance knee extension machine. Velocity and power data were filtered using a 10 Hz, low-pass Butterworth filter to remove sensor noise and obtain peak estimates. RESULTS As a result of the ST program, peak power increased significantly in both men and women at the same absolute (APP; P < 0.001) and relative loads (RPP; P < 0.05). Men had significantly greater increases in APP and RPP than women with ST when covarying for baseline differences (both P < 0.001). However, when each subject was tested at the same absolute load and when peak power was normalized for the muscle volume of the trained knee extensors (i.e., absolute MPQ), women increased their MPQ (P < 0.05), but men did not. Both men and women increased their absolute PV (P < 0.001), but decreased their relative PV significantly with ST (P < 0.01). CONCLUSIONS These data indicate that a moderate-velocity ST program increases muscle power quality in women, but not in men, suggesting that in contrast to men, women increase peak power with ST through adaptations other than muscular hypertrophy. Supported by NIH Grants R01 AG-4-2148 and AG-1620501 and NIH training grant T32AG00219.

Predicting 1-RM isotonic knee extension strength utilizing isokinetic dynamometry

The purpose of this study was twofold: determine which isokinetic determinants correlated best with an isotonic one-repetition maximum (1-RM) and to generate, based on these determinants a formula that will allow clinicians to utilize isokinetic testing to predict an isotonic 1-RM. Fifty female subjects, ranging from 18-35 years of age, participated in this study. Strength measurements using a Cybex II isokinetic dynamometer (peak torque, average peak torque, peak torque:body weight, work per repetition, and total work) and a Cybex isotonic knee extension machine were performed. The subject's height and body weight were recorded. Through linear regression analysis the variables peak torque and body weight were determined to be the best predictors of an isotonic 1-RM. These variables were incorporated in the following formula: Predicted 1-RM = 21.38 + (0.24 × Peak Torque) + (0.18 × Body Weight) which may used utilized by clinicians to predict an isotonic 1-RM.

Nautilus®Training System Versus Traditional Weight Training System

The purpose of this study was to determine the difference in strength of the dominant quadriceps femoris muscle group among subjects utilizing a Nautilus training system, and a traditional weight system. Eighteen college students, 18–23 years of age, volunteered for this study. Subjects were randomly assigned to one of three groups: Group N, Nautilus training system, consisted of six subjects utilizing the Nautilus knee extension machine, performing one set of 15 repetitions to failure, using a 15 RM (repetition maximum) at a count of 5 contract—1 hold—5 release. Group T, traditional, consisted of five subjects utilizing an NK table, performing three sets of 10 repetitions at 10 RM following a count of 1 contract—1 release. Group C, control, consisted of seven subjects who did not undergo any training. The three groups were pre-tested for bilateral quadriceps femoris strength 1 week prior to training, and retested 7 weeks later on the Cybex II Dynamometer. Results of this study, using an ANOVA with F-ratio, demonstrated that the strength gain of the dominant quadriceps femoris muscle is not significantly different between the three groups (p > 0.05). However, group T was significantly stronger than group N and C in average quadriceps strength (p < 0.05). In addition, there was a tendency for group T to demonstrate increased strength gains for all analyses. The authors contend that further investigation must be made to determine whether either method of exercise is superior at increasing quadriceps femoris strength.

An Evaluation of New Knee Extension and Contraction Machine to Knee Contracture.

An Evaluation of New Knee Extension and Contraction Machine to Knee Contracture.

Body composition, aerobic capacity, and density of muscle capillaries in young and old men.

Body composition, aerobic capacity, and density of muscle capillaries in young and old men.