Isokinetics and Exercise Science - Volume 21, issue 2

Authors: Fukuda, Thiago Yukio | Marcondes, Freddy Beretta | dos Anjos Rabelo, Nayra | de Vasconcelos, Rodrigo Antunes | Junior, Claudio Cazarini

Article Type: Research Article

Abstract: BACKGROUND AND PURPOSE: Neuromuscular electrical stimulation (NMES) is an important tool in clinical practice to improve the recruitment of motor units. Optimal forms of NMES, as well as the optimal frequency to achieve the highest torque with the least possible discomfort are not well established. This study was designed to compare maximum electrically-induced torque (MEIT) in the quadriceps, the maximum intensity tolerated by the subject, and the level of discomfort generated by three types of stimulation. …METHODS: Thirty subjects (mean age of 25.0 ± 3.0 years) participated in the study. Each subject was submitted to three currents: medium frequency (2500 Hz) modulated in low frequency (Russian Current), and two currents of low frequency (50 Hz), i.e. without an intrapulse interval (FES), and another with an intrapulse interval of 100 μs (VMS). The maximum voluntary isometric torque (MVIT) of the quadriceps was measured. The MEIT, the level of discomfort, and the maximum intensity reached were also measured while applying the three types of NMES. The order of the tests was randomized and the torque was normalized in relation to MVIT. RESULTS: The results showed no significant difference between the three types of NMES in relation to the generated torque. However, the subjects were able to tolerate a significantly higher intensity with the medium frequency current, and suffered less discomfort when compared to subjects exposed to low frequency currents. CONCLUSION: Russian Current, FES, and VMS can be used clinically in order to increase the torque of the quadriceps muscle. However, we suggest using the Russian Current in the early stages of a rehabilitation protocol because it showed better tolerance by the participants with less discomfort. Show more

Keywords: Neuromuscular electric stimulation, arthrogenic muscle inhibition, maximal electrically induced torque, isokinetic, quadriceps muscle

DOI: 10.3233/IES-130495

Citation: Isokinetics and Exercise Science, vol. 21, no. 2, pp. 167-173, 2013

Authors: Harrison, Benjamin | Firth, Will | Rogers, Sean | Tipple, Joshua | Marsden, Jon | Freeman, Jennifer A. | Hough, Alan D. | Shum, Gary L.K.

Article Type: Research Article

Abstract: OBJECTIVE: The aim of this study was to investigate how isokinetic lower limb strength and velocity of knee and hip extension correlate to vertical jump performance in university team rugby players. METHODS: Twenty asymptomatic university team rugby players performed a maximal vertical jump test, in which the vertical displacement was measured from maximum standing reach height to maximal height attained from a countermovement jump. A dynamometer assessed the maximal isokinetic strength and velocity of hip and …knee extension in the dominant leg. Peak torque was measured when participants moved at angular velocities of 60 and 120°/s for hip extension, and 120 and 240°/s for knee extension. The highest velocity achieved during isokinetic hip and knee extension up to a maximum level of 360°/s was recorded. RESULTS: Moderately strong correlations were found between knee extension strength and vertical jump height, particularly when testing at faster angular velocities of 240°/s (R=0.609, p=0.002). There was also a significant moderate correlation between maximum knee extension speed and vertical jump height (R=0.540, p=0.007). CONCLUSIONS: The results suggest that focusing on strength/power training of the knee extensors at a high speed may result in improved vertical jump performance. Show more

Keywords: Isokinetics, knee, hip, rugby, biomechanics

DOI: 10.3233/IES-130496

Citation: Isokinetics and Exercise Science, vol. 21, no. 2, pp. 175-180, 2013