Isokinetics and Exercise Science - Volume 10, issue 4

Authors: Schmitz, Randy J. | Arnold, Brent L. | Perrin, David H. | Granata, Kevin P. | Gaesser, Glenn A. | Gansneder, Bruce M.

Article Type: Research Article

Abstract: This study investigated the effects of isotonic and isometric knee extension exercises on strength, power, and surface EMG in male and female populations. Using the knee extensors, ten males and ten females performed a 120 s MVIC and 120 maximal isotonic contractions. Prior to each exercise (t=pre) knee extensor isometric peak torque (strength) and average peak power (power) were tested utilizing three, 3 s MVIC's and three maximal isotonic contractions, respectively. Following each exercise, strength …and power were assessed immediately after (t=:00) and at 2.5 (t=:02.5), 5 (t=:05), 10 (t=:10), and 15 (t=:15) minutes. All strength and power measures were normalized to the respective t=prevalue. Vastus lateralis surface EMG signals were collected during all muscle testing and normalized to the respective t=pre value. Following isometric exercise, both strength and power at t=:00 (68.7%8.7% & 88.0% ± 8.7%) and $t=:02.5$ (82.2% ± 17.8% & 95.2% \pm 5.0%) significantly decreased from t$=$pre (100% ± 0.0%) p<0.05) with greater decreases in strength at each time point (p<0.05). EMG analysis revealed a significant EMG amplitude decrease (p<0.05) att=:00 and t=:02.5 during strength testing with respect to t=pre. Following isotonic exercise, both strength and power at t=:00 (68.0% ± 13.2% & 38.8% ± 10.7%) and $t=:02.5$ (84.5% ± 14.9% & 81.6% ± 14.5%) significantly decreased from t$=$pre (100% ± 0.0%) with a greater power decrease at $t=:00$ (p<0.05). The EMG amplitude of males was significantly less at t=:00 than the respective EMG amplitude for females (p<0.05$) (irrespective of testing condition). We conclude that muscle performance in the fatigued state is dependent upon the type of exercise performed. Show more

Keywords: EMG, power, gender

DOI: 10.3233/IES-2002-0100

Citation: Isokinetics and Exercise Science, vol. 10, no. 4, pp. 167-175, 2002

Authors: Manou, V. | Arseniou, P. | Gerodimos, V. | Kellis, S.

Article Type: Research Article

Abstract: The purpose of this study was to investigate the test-retest reliability of an isokinetic muscle endurance test. The right legs of twelve healthy males were tested on the Cybex Norm isokinetic dynamometer. The protocol consisted of 40 consecutive concentric knee extensions and flexions, performed maximally at an angular velocity of 120°/s. The subjects performed the test twice, five days apart. Total work, endurance ratio, 50% fatigue work, 50% fatigue time and 50% fatigue repetitions were …obtained. A one-way analysis of variance (ANOVA) with repeated measures was used to examine the differences between test and retest values. The reliability coefficient was also established using the ANOVA results. The results indicated that measurements demonstrated high reliability (r>0.819). It could be concluded that the protocol used in the present study can be used to evaluate muscle endurance. Show more

Keywords: test-retest reliability, muscle endurance test, fatigue index, isokinetic

DOI: 10.3233/IES-2002-0101

Citation: Isokinetics and Exercise Science, vol. 10, no. 4, pp. 177-181, 2002

Authors: Tourny-Chollet, Claire | Leroy, David

Article Type: Research Article

Abstract: The purpose of this study was to determine if the two strength ratios calculated from average strength moments could be different between sedentary subjects and soccer players. The hypothesis was that soccer players would present specific strengths and functional strength ratios. The Hecc/Qcon and Hcon/Qecc ratios are functional ratios and form a means of determining strength in the muscular evaluation of the soccer player. Twenty-one amateur national level soccer players and eleven sedentary subjects were tested …for both concentric and eccentric knee extension and flexion strength on the dominant and non-dominant leg with the Kin-Com® isokinetic dynamometer at 3 speeds in concentric contraction (120°·s^{-1} , 60°·s^{-1} and 240°·s^{-1} respectively) and then at 2 speeds eccentrically (120°·s^{-1} and 60°·s^{-1} ). Soccer players present a concentric extensor and flexor strengths significantly higher than that of the sedentary subjects on both the dominant and non-dominant legs. The functional Hecc/Qcon ratio of the soccer players is significantly lower than that of the sedentary subjects at 60°·s^{-1} (0.80 vs. 0.93) and at 120°·s^{-1} (0.88 vs. 1.03) for both legs. In conclusion, the isokinetic evaluation of soccer players and particularly the analysis of the Hecc/Qcon and Hcon/Qecc ratios allow the identification of normative values and can also help to identify potential muscular injuries. Eccentric strengthening exercises can be included in training programs without any risk of altering the specific qualities of the players. The determination of the functional ratios several times during a season could permit the trainer to identify the need for either a collective or individual eccentric strengthening. Show more

Keywords: knee, strength, functional ratios, soccer

DOI: 10.3233/IES-2002-0102

Citation: Isokinetics and Exercise Science, vol. 10, no. 4, pp. 183-192, 2002

Authors: Miller, John P. | Croce, Ronald V.

Article Type: Research Article

Abstract: The purpose of this study was twofold: 1) compare the effect of movement velocity and movement pattern on the electromyographic activity (EMG) of the quadriceps as measured by the Root Mean Square of the electromyogram (rmsEMG) and the Median Frequency of the electromyogram (mfEMG) during isokinetic testing and 2) compare the effect of movement pattern on the torque production of the quadriceps during isokinetic testing. Fourteen healthy adult females with no known knee pathologies and familiarity …with isokinetic testing performed six continuous isokinetic movements at 100^{0}&middot;s^{-1} , 200^{0}&middot;s^{-1} , 300^{0}&middot;s^{-1} and 400^{0}&middot;s^{-1} . Movements were performed in a reciprocal pattern, (maximal knee extension followed by maximal knee flexion), and a non-reciprocal pattern (maximal extension followed by relaxation of the hamstrings). Statistical analyses revealed there was a difference in the rmsEMG for the quadriceps on the effect of velocity (F=3.2, P<0.05) with post hoc analysis revealing significant differences in the rmsEMG between 100 and 300^{0}&middot;s^{-1} (F= 5.6, P<0.05), and between 100 and 400^{0}&middot;s^{-1} (F = 6.7, P<0.01) with the highest rmsEMG being seen during the slowest velocities. For the mfEMG there were significant differences when comparing the velocity of movement F= 7.8, P<0.001), specifically when comparing the slowest velocity 100^{0}&middot;s^{-1} with 200^{0}&middot;s}^{-1} (F = 4.9, P<0.05), 300^{0}&middot;s}^{-1} (F= 8.8, P<0.005) and 400^{0}&middot;s}^{-1} (F = 22.7, P<0.001) with the highest mfEMG observed at the lower velocities. No difference was noted either in EMG or torque between the reciprocal and non-reciprocal movements. The results of this study suggests that during isokinetic testing the EMG activity of the quadriceps is altered as velocity changes with regard to the rmsEMG and mfEMG. Specifically as velocity increases overall muscle activity decreases as measured by the rmsEMG. In addition as velocity increases there is a shifting toward recruitment of slower velocity muscle fibers as measured by the mfEMG. These results also suggest that movement pattern (reciprocal vs. non reciprocal) does not effect the EMG for quadriceps activity during isokinetic knee extension. Show more

Keywords: EMG, root mean square, median frequency, quadriceps

DOI: 10.3233/IES-2002-0103

Citation: Isokinetics and Exercise Science, vol. 10, no. 4, pp. 193-198, 2002

Authors: Heitkamp, Hans-Christian | Mayer, Frank | Fleck, Mark | Horstmann, Thomas

Article Type: Research Article

Abstract: In a previous study, balance training yielded a gain in strength in middle-aged men and women [6]. However, whether such training can yield positive results in highly conditioned athletes has not been addressed. A group of 10 male and 10 female judokas volunteered for a 6-week balance training on rolling boards, pegtops, soft mats and large rubber balls 3 times per week. Pre- and post training of two-legged balance was measured on a stabilometer, one-legged standing …time on a narrow rim and bilateral isokinetic strength at 60°/s concentric and eccentric modes, 120°/s concentric mode and isometrically for the knee extensors and flexors. Except for concentric movement at 60°/s in women, significant improvements in strength were indicated. It is therefore concluded that balance training may be useful for both male and female judokas for increasing strength and balance. Show more

Keywords: judo, balance, knee extensors, knee flexors

DOI: 10.3233/IES-2002-0104

Citation: Isokinetics and Exercise Science, vol. 10, no. 4, pp. 199-202, 2002

Authors: Dervisevic, Edvin | Bilban, Marjan | Valencic, Vojko

Article Type: Research Article

Abstract: The objective of this study was to examine the influence of isokinetic training and low-frequency electrostimulation in three groups of male athletes (N=20, each group). Three different training methods have been compared: isokinetic training (IT) alone, training with low-frequency electrostimulation (LEFS), and the combination of the two methods. Maximal muscle power was measured before and at the end of the training programs, using a REV 9000 isokinetic dynamometer. The findings indicate that …all training methods result in significant increase in muscle strength. However, the largest training effect was due to the combination of IT and LFES. Show more

DOI: 10.3233/IES-2002-0105

Citation: Isokinetics and Exercise Science, vol. 10, no. 4, pp. 203-209, 2002

Authors: Tsaklis, P. | Abatzides, G.

Article Type: Research Article

Abstract: The purpose of this paper is to present a rehabilitation program following ACL reconstruction. This program consists of isotonic as well as isokinetic muscle strengthening components. Forty-five post-ACL surgery patients took part in this study. They were all male athletes participating in different events. Patients were divided randomly into 3 groups of 15 corresponding to 3 distinct rehabilitation programs which continued for 3 months after surgery. During the first month the groups followed the same …paradigm. For the next two months, group A continued the practice by using only isotonic strengthening exercises, group B used exclusively isokinetic strengthening exercises and group C performed a combined program of isokinetic and isotonic exercises. The three groups appear to have improved until the 3rd post operative month, with highly significant pre-post differences in the various measured parameters. However, group C patients achieved the highest outcome scores and therefore our recommendation calls for a mixed isokinetic-isotonic program. Show more

DOI: 10.3233/IES-2002-0107

Citation: Isokinetics and Exercise Science, vol. 10, no. 4, pp. 211-219, 2002