Isokinetics and Exercise Science - Volume 6, issue 3

Authors: Gajdosik, Richard L.

Article Type: Research Article

Abstract: This study examined the influence of age on calf muscle length and passive stiffness variables at different stretch velocities. Ten younger aged men (31 [SD 6] years), nine middle aged men (48 [SD 6] years), and nine older aged men (70 [SD 6] years) were tested using a KIN-COM 500R dynamometer. The right calf muscles were stretched from relaxed plantar flexion to maximal passive dorsiflexion at four randomly ordered velocities of 5°·s−1 , 30°·s−1 , 60°·s−1 and 120°·s−1 with negligible surface EMG activity (< 0.05 m V) in the calf muscles at all velocities. The maximal passive dorsiflexion …angle, maximal passive torque, initial passive angle (defined at 20% of the maximal passive torque), angular change, and passive stiffness ratios (Δ torque/ Δ angle) through the defined range of motion (ROM) and through the last 10° of ROM were analyzed with ANOVA procedures. The maximal passive dorsiflexion angle decreased as age increased (P<0.05). The maximal passive torque increased as the velocity of stretch increased (P<0.001) and velocity of stretch interacted significantly with the age groups (P<0.01); the older men had less maximal passive torque at 60°·s−1 and 120°·s−1 (P<0.05). The passive stiffness ratios through the defined ROM showed a significant effect of stretch velocity (P<0.01). Within the last 10° of dorsiflexion ROM the ratios showed a significant effect of group (P<0.05), stretch velocity (P<0.001), and interaction (P<0.001). For the younger and middle aged men the passive stiffness increased as the stretch velocity increased, but for the older men the passive stiffness decreased as the stretch velocity increased, perhaps influenced by muscle atrophy, changes in muscle fiber type and changes in the amount of adipose tissue. The results indicated that decreased calf muscle length was associated with decreased maximal passive torque and decreased passive stiffness for older men beyond 60 years of age. Show more

Keywords: Aged, Calf Muscles, Men, Passive Stiffness

DOI: 10.3233/IES-1997-6301

Citation: Isokinetics and Exercise Science, vol. 6, no. 3, pp. 163-174, 1997

Authors: DeStaso, Joel | Kaminski, Thomas W. | Perrin, David H.

Article Type: Research Article

Abstract: The purpose of this study was to determine how isokinetic eccentric and concentric peak torque/body weight ratios and time to peak torque values relate to drop vertical jump heights in 30 healthy subjects (12 men and 18 women, age =22.7±2.2 yr, ht =169.6±8.9 em, wt =67.2±11.9 kg). Drop vertical jumps were performed from a box 50 cm high. Subjects were tested isokinetically on each leg for the motions of knee extension and ankle plantar flexion. Eccentric and concentric peak torque (PT)/body weight ratios along with time (s) to eccentric and concentric peak torque were extracted from the Kin Com II …computer. A stepwise multiple regression analysis was conducted to determine the relationship between the eight predictor variables and drop vertical jump height. Knee extension concentric PT/body weight ratio was the most significant predictor of drop vertical jump height, accounting for 23% of the variance. This finding suggests that the stretch-shortening cycle can be simulated using isokinetic strength measurements and that drop vertical jump height can be attributed in part to concentric knee extension strength. Show more

Keywords: Eccentric, Concentric, Peak torque, Time to peak torque, Plyometric

DOI: 10.3233/IES-1997-6302

Citation: Isokinetics and Exercise Science, vol. 6, no. 3, pp. 175-179, 1997

Authors: Kroll, Penny G. | Muhlhauser, Ronald W. | Parsons, N. Cole | Taylor, Christopher D.

Article Type: Research Article

Abstract: This study examined the effect of a 20% increase in straight leg raise (SLR) on concentric isokinetic measures of work in subjects with tight hamstrings. Subjects were deemed eligible if passive SLR of the dominate limb was <70° and if subjects had no documented problems with the tested limb. Thirty-two volunteer subjects were randomly assigned to experimental and control groups (n=16 each) and baseline measures were completed. Experimental group subjects then participated in supervised stretching and a home program with SLR re-assessment prior to each supervised session. Within 24 hours of an experimental subject reaching the 20% targeted increase in …SLR range, that subject and a control subject were re-tested. The results showed no significant change in work production despite a 20% increase in SLR. This study suggests that a modest increase in SLR does not adversely affect the strength of tight hamstring muscles. Clinical implications are that an increase in flexibility of a tight muscle may not adversely effect a subject's ability to maximize muscular potential. Show more

Keywords: Increase hamstring flexibility, SLR, Peak torque, Work, Effects

DOI: 10.3233/IES-1997-6303

Citation: Isokinetics and Exercise Science, vol. 6, no. 3, pp. 181-185, 1997

Authors: Potter, Helen M. | Strauss, Geoffrey R.

Article Type: Research Article

Abstract: Isokinetic trunk muscle strength of 36 postpartum women was evaluated using the Kin-Com dynamometer at 24 and 25 weeks following vaginal delivery of a healthy infant. Test-retest reproducibility of a standardised isokinetic testing protocol was evaluated in concentric and eccentric muscle actions through a 50° range of motion at velocities of 20 deg/s and 40 deg/s for the trunk flexors and extensors. Moderate agreement was found for inter-test reproducibility (ICCs from 0.67 to 0.85; CVs from 8.8% to 15.9%). Intratest reproducibility was high (ICCs from 0.90 to 0.95). The ratio of trunk extensor to flexor strength was similar in …both concentric and eccentric action at both velocities (p>0.05). The ratio of strength at the two velocities was similar for both muscle groups in both actions (p>0.05). Eccentric strength was significantly higher than concentric strength. Eccentric strength did not vary with velocity while concentric strength displayed an inverse relationship with velocity (p<0.05). Show more

Keywords: Trunk muscle strength, Postpartum, Abdominals, Isokinetics

DOI: 10.3233/IES-1997-6304

Citation: Isokinetics and Exercise Science, vol. 6, no. 3, pp. 187-196, 1997