Isokinetics and Exercise Science - Volume 11, issue 2

Authors: Liebermann, Dario G. | Katz, Larry

Article Type: Research Article

Abstract: Purpose: This study assessed the reliability and validity of different methods used to estimate lower-limb muscular power capability based on mechanical variables. For this purpose, vertical jumping was compared with isokinetic knee extensions and with power tests used by practitioners. Methods: Four groups of subjects (N=106) were tested in different conditions. Group-I performed countermovement vertical jumps (CMJ) on a force plate followed by left and right knee extensions on an isokinetic device at 120, 180 …and 240 deg · s^{-1} . Group-II performed CMJ trials followed by 20-m sprints, hand-reach jumps and 1RM leg-press testing. Group-III carried out squat jumps (SJ) in addition to CMJ trials. Finally, Group-IV performed the CMJ test and was retested twice after a short inter-session interval (1–4 days) and after a long one (4.5–5 months). The Pearson correlation was used to assess the validity and reliability of CMJ (p ≤ 0.01, **). Results: Mean peak power during CMJ was correlated with sprint time (r=-0.882^{**} ) and leg-press 1 RM (r=0.797^{**} ), but less with peak hand-reach height (r=0.695; p ≤ 0.05). Isokinetic knee extension power showed also a significant correlation with CMJ power, but its strength depended on the angular velocity (Isok-120 r=0.702^{**} ; Isok-180 r=0.737^{**} ; Isok-240 r=0.599^{**} ). Test-retests showed a strong correlation after a short interval (r=0.915^{**} ) and after a long one (r=0.890^{**} ). Using the SJ technique did not have any effect on reliability (r=0.914^{**} ). Conclusions: CMJ matches other methods used for testing lower-limb power capability. It is highly reliable and it allows a valid assessment of muscular power. Since CMJ is also simple and accurate to perform, it is the recommended method. Show more

DOI: 10.3233/IES-2003-0106

Citation: Isokinetics and Exercise Science, vol. 11, no. 2, pp. 87-94, 2003

Authors: Dauty, Marc | Delbrouck, Claire | Huguet, Dominique | Rousseau, Bertrand | Potiron-Josse, Michèle | Dubois, Charles

Article Type: Research Article

Abstract: The purpose of this study was to define the test-retest reproducibility of concentric and eccentric isokinetic measurements of shoulder rotators. It was carried out at a 26 day ± 4 interval. Fourteen healthy volunteer subjects (7 men and 7 women), aged between 40 and 55 years (47.5 ± 5.6 years), were included. Evaluation was carried out with a Cybex Norm dynamometer and the reliability was calculated according to the intra-class correlation coefficient (ICC 2.1). The protocol …was randomised for the shoulder and for sets of concentric (con) and eccentric (ecc) tests. Concentric sets consisted of 5 movements of internal (IR) and external rotation (ER) at the speed of 60°/sec. then 120°/sec. Eccentric performance was recorded only for the external rotators, to determine the ratio ER_{ecc} / IR_{con} . Results indicated excellent reproducibility for the peak torque (0.91–0.98), total work (0.88–0.96) and average power (0.83–0.94) in concentric muscle action for internal and external rotators and in eccentric muscle action for external rotators at 60 and 120°/sec. On the other hand the strength ratio: ER_{con} / IR_{con} and ER_{ecc} / IR_{con} should be interpreted with caution because of a lower reproducibility (ICC: 0.53–0.83). In conclusion, isokinetic findings relating to concentric and eccentric performance of the internal and external rotators of the shoulder are reproducible under the present protocol. These findings may serve for assessing rotator cuff function at the age where the incidence of rotator cuff overuse becomes a serious problem. Show more

Keywords: shoulder, isokinetic, concentric, eccentric, reproducibility

DOI: 10.3233/IES-2003-0134

Citation: Isokinetics and Exercise Science, vol. 11, no. 2, pp. 95-100, 2003

Authors: Poulis, S. | Rapanakis, P. | Pastra, X. | Poulis, I. | Soames, R.W.

Article Type: Research Article

Abstract: Isokinetic concentric and isometric contractions of the wrist flexors and extensors were recorded from 40 young males using a Cybex II+ isokinetic exercise system using handgrips of 4 cm and 8~cm diameter: the isokinetic recordings were obtained at velocities of movement of 45°/s, 90°/s and 180°/s. For both muscle groups peak torque and work done both decreased with increased velocity of contraction, however average power increased. The wrist flexors generated significantly …(P < 0.01) greater peak torque, work and average power than the extensors, with the extensor/flexor ratio for peak torque being 0.57. No differences were observed between the dominant and non-dominant wrist, or between the size of handgrip used. Show more

DOI: 10.3233/IES-2003-0135

Citation: Isokinetics and Exercise Science, vol. 11, no. 2, pp. 101-108, 2003

Authors: Deighan, M.A. | De Ste Croix, M.B.A. | Armstrong, N.

Article Type: Research Article

Abstract: The aim of this study was to determine the reliability of measures of concentric and eccentric extension and flexion peak moment of the knee and elbow of prepubertal boys. Twenty boys volunteered for the study. Ten performed the knee test and ten performed the elbow test. All subjects were permitted a separate day familiarisation session and were later tested on two separate occasions, exactly 1 week apart, at the same time of day and with the same test …administrators. Peak moment was measured with an adapted Biodex System-3 using continuous concentric-concentric and eccentric-eccentric cycles at 30°/s and 180°/s. The reliability measures were intraclass correlation coefficient (ICC), repeatability coefficient (RC), limits of agreement (LOA) and coefficient of variation (CV). ICCs ranged from 0.55 to 0.97 and CV ranged from 4% to 15%. There was no systematic difference in peak moment between test and retest. The various indices demonstrated moderate to high reliability of peak moment measurements in this age group which compared favourably with the existing literature. The results of the study support the reliability of measures of concentric and eccentric peak moment in studies of children's strength. Show more

DOI: 10.3233/IES-2003-0136

Citation: Isokinetics and Exercise Science, vol. 11, no. 2, pp. 109-115, 2003

Authors: Poulis, S. | Soames, R.W.

Article Type: Research Article

Abstract: Isokinetic range of motion (ISORoM) and peak torque (PT) at the ankle joint were examined in 37 patients, in two different knee positions (extended and flexed at 90°), six months following Lateral Collateral Ligament (LCL) trauma: 2nd and 3rd degree sprains had been sustained by 18 and 19 patients respectively. Patients were immobilized for six weeks in a plaster-of-Paris cast, with 3rd degree sprains undergoing surgical repair prior to immobilization: all patients followed the same physical …therapy regime designed to regain full range of motion by mobilizing the joint, strengthen the muscles and improve proprioception. Significant differences (p < 0.01) in ISORoM were observed between the injured and noninjured ankle for each group, with those with 3rd degree sprains also showing a significant reduction (p < 0.01) in ISORoM compared with 2nd degree sprains. No differences were found in PT generation during concentric and eccentric contractions for both muscle groups. Measurement of the ISORoM and muscular strength, following LCL trauma, appears to be a useful tool in clinical evaluation and treatment planning. Show more

DOI: 10.3233/IES-2003-0137

Citation: Isokinetics and Exercise Science, vol. 11, no. 2, pp. 117-122, 2003

Authors: Williams, C.A. | Hammond, A. | Doust, J.H.

Article Type: Research Article

Abstract: Previous studies of short term power output in young people and adults have used cycle ergometers that cannot control cadence or inertial resistance. An innovative isokinetic ergometer has now been designed and the purpose of this study was to investigate the isokinetic short term power output of twelve 15-year-old adolescent girls and nine 21-year-old female adults. Short term power was measured by a power-cadence test and included the calculation of the optimised peak power (PP_{opt} …) and optimal cadence (C_{opt} ) at PP_{opt} . Each subject completed seven maximal sprints, starting at an initial pedal cadence of 90 rev·min^{-1} which after each subsequent five minute rest period, was increased by 10 rev·min^{-1} . Significant differences in absolute PP_{opt} were found between adolescent (624 ± 985 W) and adult females (740 ± 157 W) respectively (P < 0.05). Significant differences were found in short term power standardised according to leg volume (45.4 ± 10.8 and 25.8 ± 2.1 W·L^{-1} ) between female adolescents and adults but not according to body mass (P > 0.05). The C_{opt} at PP_{opt} for adolescent females (116 ± 6 rev·min^{-1} ) was not significantly different to adult females (118 ± 13 rev·min^{-1} ). These results add to the scarce amount of isokinetic data on females and provide evidence that age differences in power are not due to cadence dependent factors. Show more

Keywords: power-cadence, female, optimised peak power, anthropometric characteristics

DOI: 10.3233/IES-2003-0138

Citation: Isokinetics and Exercise Science, vol. 11, no. 2, pp. 123-131, 2003

Authors: Thevenon, A. | Blanchard-Dauphin, A.

Article Type: Research Article

Abstract: The current study was designed to determine whether alteration of trunk muscles strength caused modification of spinal and lower limb flexibility in healthy subjects. The study was based on the examination of 50 subjects (25 men and 25 women). In women, the extensibility of posterior muscles and ligaments, measured by Schober index or finger to floor distance, was weakly but significantly related to isokinetic strength of flexor muscles of the trunk, and was inversely related to …isokinetic strength of the extensor muscle. In men, no such relation was indicated. Consequently, when measuring the concentric strength of the trunk extensors, particularly in women, trunk flexibility is a factor that needs to be taken account of. Show more

Keywords: Trunk, strength, flexibility, isokinetic

DOI: 10.3233/IES-2003-0139

Citation: Isokinetics and Exercise Science, vol. 11, no. 2, pp. 133-137, 2003