Isokinetics and Exercise Science

The purpose of this study was to demonstrate limb dominance normative strength values (peak torque, relative peak torque, work and relative work) for the plantar and dorsiflexion muscles in professional basketball players, using the Cybex 1200 isokinetic dynamometer. Paired t-tests showed no significant differences between the two limbs, except for peak torque and relative peak torque during plantar flexion at 60 $^{\circ}$ /s( $p<0.05$ ). The ratio plantar/dorsiflexion was also analyzed, with no significant difference between the two limbs. The results of this research study provide very useful information about the level of strength in this particular area, and are useful for prescribing proper rehabilitation programs for injured basketball players.

The aim of our study was to compare the isokinetic concentric(60\ci.s $^{-1}$ , 120\ci.s $^{-1}$ , 240\ci.s $^{-1}$ ) and eccentric(60\ci.s $^{-1}$ , 120\ci.s $^{-1}$ ) strength bilaterally of the knee muscle of soccer players in relationship to their position on the playing field. The hamstrings and quadriceps strength of 21 soccer players were evaluated with a Kin-Com $\textregistered$ (Kinetic Communicator) isokinetic dynamometer. A predominance of the strength moments on the dominant leg compared to the non-dominant leg was not demonstrated, except for the hamstrings in a concentric mode at a 240\ci.s $^{-1}$ speed. Both the concentric and eccentric strengths of the knee flexors and extensors decreased with the increase in angular speed. The relationship between the three positions in the game (forward, midfield, and defender) and the isokinetic strengths measured at different speeds underlined specific differences between each position. These differences were observed at the level of the co-activation of the knee flexors and extensors during the movements specific to the position and between the kicking leg and the stance leg.

The torque characteristics were determined for the ankle dorsiflexors and plantarflexors during concentric and eccentric contractions, at 45 $^{\circ}$ /s with the knee flexed 90 $^{\circ}$ , in 37 young healthy males aged 21 to 24 years. Mean maximum torque during concentric and eccentric contraction was $32.8 \pm 5.5$ Nm and $57.8 \pm 14.3$ Nm(ratio $0.57$ ) for the dorsiflexors, and $86.3 \pm 26.8$ Nm and $86.3 \pm 26.8$ Nm (ratio $0.60$ ) for the plantarflexors. The dorsiflexor/plantarflexor maximum torque ratio was 0.38 and 0.40 for concentric and eccentric contractions. The angle of maximum torque generation was $17.4^{\circ} \pm 13.7^{\circ}$ and $15.7^{\circ} \pm 12.2^{\circ}$ plantarflexion for the dorsiflexors working concentrically and eccentrically respectively. For the plantarflexors the respective angles were $17.0^{\circ} \pm 9.6^{\circ}$ and $23.3^{\circ} \pm 11.4^{\circ}$ plantarflexion: the difference in angle being significant( $p<0.01$ ). The torque characteristics presented in this study provide a standard against which muscle coordination can be determined and the planning of rehabilitation programs set.

In recent years there has been growing concern regarding back pain in schoolchildren. Our research team studied the risk factors in this particular age group including a careful evaluation, still in progress, of trunk performance. The aim of this paper is to present a review of literature and the pertinent questions relating to this field. The issues that will be discussed are:

1. Prevalence and risk factors of low back pain in teenagers: are they related to trunk muscles?

2. Low back pain and school backpacks: some unexpected results relating to a particular trunk muscle performance risk factor

3. Normative isokinetic trunk performance parameters in schoolchildren

4. Correlation of sporting activities with back pain and isokinetic trunk strength

5. Preliminary results associating isokinetic trunk strength and back pain

6. Pertinent new questions

The purpose of this research was to compare isometric values(0 $^{\circ}$ s $^{-1}$ ) with isokinetic values generated at slow speeds(12 $^{\circ}$ s $^{-1}$ , 30 $^{\circ}$ s $^{-1}$ and 60 $^{\circ}$ s $^{-1}$ ) based on measurement of 40 college males. A one-way ANOVA indicated a significant difference with respect to speeds ( $F_{3,148} = 13.10$ , $p<0.01$ ). A post hoc analysis showed that all speeds were significantly different from each other. The greatest average maximal hamstring strength values were produced with isometric(0 $^{\circ}$ s $^{-1}$ ) contractions and the least average maximal hamstring strength at 60 $^{\circ}$ s $^{-1}$ . It is suggested that if a true absolute maximal hamstring strength test is desired for the hamstring musculature one should use a speed of 0 $^{\circ}$ s $^{-1}$ . Regression analysis indicated that a speed of 12 $^{\circ}$ s $^{-1}$ produced the best regression equation. It is suggested that, the term peak strength rather than maximum strength should be used for speeds greater than 0 $^{\circ}$ s $^{-1}$ .

The purpose of this study was to determine the effects of magnets on concentric and eccentric isokinetic peak and average force production of the dominant knee extensor musculature. All subjects were randomly assessed via isokinetic dynamometry (KinCom 500H, Chattecx Corp.) for concentric and eccentric peak and average force production of the quadriceps in the conditions of magnet, placebo magnet, and control (no magnet). Subjects were assessed at test velocities of 60 and $120$ $^{\circ}$ /s. Twenty-one subjects (age $= 24.2 + 5.1$ yrs, $ht = 174.6 + 8.2$ cm, $wt = 73 + 6.9$ kg) voluntarily participated in the study. Subjects were excluded if they reported a history of knee surgery or sustained a knee injury within the past six months. Two three-way MANOVA's (velocity $\times$ mode $\times$ treatment) were used to determine differences between variables. MANOVA revealed significant differences between test velocities( $p<0.001$ ) and mode of contraction $p<0.05$ ) for peak force production and significant differences between test velocities( $p<0.05$ ) and mode of contraction( $p<0.001$ ) for average force production. MANOVA revealed a significant difference between testing conditions for average force production( $p<0.05$ ). However, Tukey's post-hoc analysis found no significant difference between conditions. Based on the results of this study, application of a magnetic pad to the quadriceps muscles does not appear to increase acute force production. Further research is needed to critically evaluate other purported effects of magnetotherapy.

Maximum concentric and eccentric isokinetic plantar flexion peak torque values were evaluated in a closed kinetic chain in eight volunteers from a high-level junior soccer team, with a median age of 17 (range 16--18) years. An isokinetic dynamometer was used and the reproducibility of a previously unevaluated position of the subject was assessed. The test-retest interval was 48 hours. The reproducibility of the test was high, with Intraclass Correlation Coefficients (ICC) of 0.87--0.97 for right- and left-sided concentric and eccentric recordings. The mean peak torque generation was significantly higher in eccentric muscle action compared with concentric; 324 (SD 107) vs 177 (SD 55) Nm. We conclude that one valuable method for measurements of plantar flexion torque in the ankle joint could be in the closed kinetic chain position.

The objective of this study was to analyze the performance of knee muscles in the affected and nonaffected sides of ACL patients as well as with healthy asymptomatic subjects. Fifty-four males, 27 with asymptomatic knees and 27 patients with tear in ACL were included in the study. Subjects performed concentric knee extension and flexion efforts at 60\ci/s and 180\ci/s on a Biodex isokinetic dynamometer. Isokinetic peak torque, angle to peak moment of quadriceps (Q) and hamstring (H), and hamstrings/quadriceps ratio (HQR) were measured. There was a significant decline in the mean strength of Q at 60\ci/s for the involved side compared with either the uninvolved side or with that of the healthy subjects, but not in H. There was also a significant decrease in mean Q strength at 180\ci/s of the involved side of ACL patients compared with the healthy young males. There was a significant difference in mean angle to peak moment of Q at 180\ci/s in the healthy group compared with the involved side of the patients and a significant difference for the same parameter in H at 60\ci/s in the involved compared with the healthy group and uninvolved sides of the ACL patients. There was no significant difference in hamstrings/quadriceps ratio between the groups. It was concluded that the effect of ACL tear on H strength is significantly less than that on the Q one year post-injury. Angle to peak moment offers original and practical information for the determination of individual performance in post ACL injury patients.