Isokinetics and Exercise Science - Volume 7, issue 4

Authors: Gajdosik, Richard L.

Article Type: Research Article

Abstract: The purpose of this study was to examine the contribution of the passive resistive torque to the total peak concentric isokinetic torque of the calf muscle-tendon unit. Thirty healthy, active women (age: 32 [SD 8] years) were tested using a KIN-COM 500H force dynamometer. The right calf muscle-tendon unit was first stretched passively at 5 dg from relaxed plantar flexion to the maximal angle of available dorsiflexion to measure the passive resistive torque. Subjects then performed …maximal concentric plantar flexion from the maximal dorsiflexion angle at randomized test velocities of 30, 60, 120 and 180 dg. The passive resistive torque was subtracted from the total concentric peak torque to determine the active concentric peak torque. The angular delay from the onset of movement to the angle of total peak and active peak torques, and the percent contribution of the passive resistive torque to the total peak torque were calculated. One-way ANOVA procedures showed that the total and active peak torques decreased, and their respective angular delays increased, with increasing test velocities (P < 0.001). The active peak torque was less than the total peak torque (P < 0.001), and the angular delay for the active peak torque was greater than for the total peak torque among all test velocities (P < 0.001). The percent contribution of the passive resistive torque to the total peak torque ranged from 10.5% but this did not differ among the four concentric test velocities. The passive resistive torque contributed significantly to the total peak concentric torque and shifted the angular delay toward the onset of movement. The passive resistive torque contribution was essentially constant among the four test velocities, probably influenced by the decrease in concentric peak torques and the increase in the angular delay that resulted from the increasing test velocities. Show more

Keywords: calf muscles, passive resistive torque, muscle function, peak torque

DOI: 10.3233/IES-1998-0029

Citation: Isokinetics and Exercise Science, vol. 7, no. 4, pp. 135-143, 1998

Authors: Gulick, Dawn T. | Chiappa, Jeffrey J. | Crowley, Kevin R. | Schade, Mark E. | Wescott, Scott R.

Article Type: Research Article

Abstract: 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 x Peak Torque) + (0.18 x Body Weight) which may used utilized by clinicians to predict an isotonic 1-RM. Show more

Keywords: repetition maximum, isotonic, isokinetic

DOI: 10.3233/IES-1998-0030

Citation: Isokinetics and Exercise Science, vol. 7, no. 4, pp. 145-149, 1998

Authors: Weiss, Lawrence W. | Relyea, George E. | Ashley, Candi D. | Propst, Robert C.

Article Type: Research Article

Abstract: If independent variables collectively account for each person's ability to vertically jump, then appropriate manipulations of any or all of these factors would be expected to improve jumping performance.Furthermore, if training may elicit the desired manipulations, then the identification of specific weaknesses would enable clinicians and scientists to individualize interventions so as to maximize the effects. In the present exploratory investigation, equations were developed predicting depth vertical jumping (DVJ) distance, a technique …roughly simulating the myriad of scenarios in which a rapidly decelerated linear movement precedes vertical jumping.To accomplish this, body composition and 32 variables generated during the performance of concentric-only velocity-spectrum squats were obtained using 52 men and 50 women. At each of four different squatting velocities four force and four power variables met conservative reliability standards for selection as potential predictors of jumping performance. Two explanatory regression equations generated via a forward stepwise approach yielded R-values of 0.89 and 0.90 and SEE ranging from 0.059 to 0.060 meters (2.32 to 2.36 inches). Relative peak power (peak-power-to-body-weight ratio) during squatting exercises performed at 1.43 meters.sec-1 as well as at each individual's optimal velocity for power production were significant predictors of DVJ distance.The predicted distance was also significantly attenuated if subjects were female. Based upon the variables assessed in this investigation, it appears that for young adults, the higher the relative peak squatting power at moderately fast velocities the greater the DVJ performance, and being female negatively impacts this type of jumping. Show more

DOI: 10.3233/IES-1998-0031

Citation: Isokinetics and Exercise Science, vol. 7, no. 4, pp. 151-159, 1998

Authors: Hartsell, H.D.

Article Type: Research Article

Abstract: Body position and stabilization is a controversial issue for shoulder rotational testing in the scapular plane. The purposes were to determine the effects of body position on the external/internal rotation (ER/IR) ratios and how closely they approximated previously reported ratios. Twenty-two healthy, informed subjects participated in test-retest isokinetic sessions involving two body positions (seated, standing), two rotational joint motions (external,internal), three velocities (60,120,180 dgs) and two contraction types (concentric, eccentric). Intraclass correlation …coefficients ranged from 0.89--0.93. A three-way ANOVA with repeated measures, used to analyze the data for contraction type separately, showed significant effects (p < 0.000) for body position regardless of body position. Concentrically, significant effects were observed for gender (p<0.018), velocity (p < 0.000) and body position x velocity x gender (p < 0.003). It was concluded that use of the standing position with adequate stabilization is viable and perhaps more applicable to activities of daily living. Secondly, the `acceptable' ER/IR ratios (0.6--0.7) previously defined should be extended to 0.5--0.7 to allow for varying joint and body positioning. Show more

Keywords: scapular plane, external/internal rotation, concentric/eccentric, ratios

DOI: 10.3233/IES-1998-0032

Citation: Isokinetics and Exercise Science, vol. 7, no. 4, pp. 161-170, 1998