Transmissibilidade vibratória em mulheres de meia idade submetidas à exercício de vibração de corpo inteiro: estudo em três posições corporais

Abstract

Whole body vibration exercises (WBVE) show beneficial clinical effects in several populations due to the transmission of mechanical vibrations generated on a vibrating platform (VP), for the individual who is in contact with it. The most used posture is standing with a knee semi-flexion, however, disabling clinical conditions may require adaptations. The purpose of this study was to evaluate the vertical transmissibility of mechanical vibration in the knees, lumbar spine, sternum and head, of women over 40 years old, in three different positions: standing with knee-flexion (squatting position, SQ), sitting on a chair with the feet resting on the platform and 45º ankle angle (SIT) or perpendicular to VP (PLAT). Methodology: Thirty volunteers were submitted to WBVE with vibration frequency of 7.5 Hz, amplitude of 2.5 mm, with corresponding intensity of 0.12 g, exposed for 10 seconds and 20 seconds resting, in each position. Four monoaxial accelerometers were used in the measurement. The acceleration measure expressed by the root mean square (RMS) was estimated for each signal, and the transmissibility RMS (TRMS) calculated using simple ratio TRMS (%) = (RMSBody / RMSVP) x100, (RMSBody = RMS of the body accelerometer and RMSVP = from VP). Several safety-related responses (pain, vertigo, fear, tingling and discomfort) were assessed using their own instruments. Results: Thirty women, with an average age of 56 years, were selected voluntarily. Most white (56%), non-smokers (96%) and sedentary (56%), 73.3% were overweight (overweight or obese). WBVE was perceived as a low effort / fatigue exercise (96.7%) and 40% did not report any insecurity or discomfort. There was loss of TRMS throughout the body, as indicated by other studies. Resonance phenomena was observed in the knee segment, both in the SQ and PLAT positions. Comparing the maximal acceleration integrals among all conditions (body regions and postures), the legs had about 9 times higher magnitudes compared with the hip and this magnitudes of acceleration about 3 times higher compared with the head. The sternum was the point of lowest vibration in all postures. Considering head acceleration transmissibility, PLAT represented the safest posture. Conclusions: Based on results, a therapeutic protocol was developed. Posture chosen as most appropriate to perform seated WBVE was SIT posture, recorded less head vibration, smaller transmissibility or resonance knees and less fear or vertigo.