ONE LEG WHOLE-BODY VIBRATION EFFECTS ON MUSCULAR STRENGTH AND BALANCE ABILITY: TRAINED VS UNTRAINED LEG.

Introduction Whilst exposure to vibration is traditionally regarded as perilous, recent research has focussed on potential benefits. Acute physiological responses to muscle vibration and to whole body vibration exercise are reviewed, as well as the training effects upon the musculature, bone mineral density and posture. Indeed, whole-body vibration training has recently received a lot of attention with reported enhancements of strength and power qualities in athletes. Unilateral strength training produces an increase in strength of the contralateral homologous muscle group. This process of strength transfer, known as cross education, is generally attributed to neural adaptations. It has been suggested that unilateral strength training of the free limb may assist in maintaining the functional capacity of an immobilised limb via cross education of strength. The aims of this study were to assess the effects of an 5-week periodized training program with whole-body vibration on cross education. Methods Nine healthy males (24±3,35 years; 1,76±0,04 m; 72,22±6,59 kg; 23,25±1,53 kg/m2) performed 10 training sessions on whole-body vibrations platform (Nemes; Ergotest, Rome, Italy). They were exposed to a vibration load in monopodalic half squat position at the muscles resonance frequency. Quadriceps femoris circumferences, vastus lateralis and medialis EMGs, isometric maximal voluntary contraction (MVC), vertical jump (CMJb) and balance tests were performed before and after the conditioning program on trained limb and untrained contralateral. All data were analyzed with ICC (95% CI), Wilcoxon's and Student's t-test for paired data on SPSS v.15 software, and P<0,05 was chosen as the significant rate. Results and Discussion Quadriceps femoris circumferences significantly increased after the conditioning program on trained limb and untrained contralateral (p<0,001). Mean and best values in vastus lateralis EMGs significantly increased in trained limb (p <0,05) but not in the contralateral untrained. Vastus medialis, however, did not significantly increase. All subjects significantly improved in MVC and CMJb both on trained leg (p<0,05) and untrained contralateral (p<0,05) while balance test showed significant improvements only in bipodalic (p<0,05) and monopodalic trained limb executions. Conclusions Like other studies that have analyzed whole body vibration exercises, this survey indicates that a specific vibrations protocol can improve strength and power qualities both in training limb and untrained contralateral. This data support the theory of cross-education gains in the lower limbs following unilateral strength training. Therefore, more studies are needed to analyze the performances on whole-body vibrations platform and the effectiveness of cross strength training.