engleski

The effects of unilateral strength training on contralateral balance performance

Introduction Unilateral strength training primarily has ipsilateral effects, whereas its secondary effects are termed as contralateral strength training effects. Studies have shown positive dependence between the lower limb strength and balance in elderly people (Pijnappels i sur., 2008). It is well known that combining strength and balance training has positive effects on balance in young adults (Thorpe and Ebersole, 2008). Until the present day no analyses have been carried out as to prove whether the unilateral strength training affects the improvement in the contralateral balance in young women. Methods Physically active young women participated in a 4- week (3 times a week) progressive training performed on an isokinetic device. The participants were separated into two groups: experimental–trained (15) and control–not trained group (15). The EXP group carried out the con-con ankle and knee joint training on the isokinetic device known as Biodex System 3 at a relatively high speed (ankle-60, knee-180). The single leg balance of both trained and non-trained leg was tested on the Biodex Balance System. Statistical significance of the difference between the initial and final measuring values was assessed by using the two-way repeated measure ANOVA. Results The results have shown that the difference between the initial and final measures of the single-leg balance of a trained (F1, 28 = 8, 43 ; p=0, 007 ; ŋ=0, 231) and non-trained (F1, 28 = 9, 25 ; p=0, 005 ; ŋ=0, 248) leg in the EXP and CON group is statistically significant. In the experimental group the single-leg balance of the trained (non- dominant) leg was improved by 25.04%, whereas the non-trained (dominant) leg improved its balance by 18.8%. The control group did not demonstrate any change in balance performance. Discussion Given the fact that leg extensors and flexors have to be able to produce force very quickly (Izquierdo i sur., 1999) as to preserve and establish balance, it has been assumed that the strength training at relatively fast contraction rate would significantly affect the balance improvement. This research confirmed the above said. Unilateral isokinetic concentric-concentric strength training of extensors and flexors of the lower leg and foot in physically active women does not only result in ipsilateral, but also in contralateral change in balance. These findings open up many possibilities for application of the unilateral strength training not only in sport, but also in different rehabilitation processes. Izquierdo M, Aguado X, Gonzalez R, López JL, Häkkinen K. (1999). Eur J Appl Physiol Occup Physiol. Feb ; 79(3), 260-267. Pijnappels Mirjam, Reeves Neil D, Maganaris Constantinos N, van Dieën Jaap H. (2008). J Electromyogr Kinesiol, 18(2), 188-96. Thorpe, J.L. & Ebersole, K. (2008). J Strength Cond Res, 22(5), 1429-1433.

Isokinetics; unilateral strength training; contralateral balance

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