Triaxial Modulation of the Acceleration Induced in the Lower Extremity During Whole-Body Vibration Training: A Pilot Study

Abstract

The purpose of the present study was to quantify vibration transmissibility through the lower extremity during exercise on a whole-body vibration (WBV) platform. Six healthy adults completed 20 trials of 30-second static squat exercise at 30 or 40 degrees of knee flexion angle on a WBV platform working at combinations of 5 frequencies (VF: 20, 25, 30, 35, 40 Hz) and 2 amplitudes (VA: low, 1.5 mm or high, 3 mm). Accelerations induced by the platform were recorded simultaneously at the shank and the thigh using triaxial accelerometers positioned at the segmental center of mass. Root-mean-square (RMS) acceleration amplitude and transmission ratios between the platform and the leg segments were calculated and compared between the experimental conditions. An alpha level of 0.05 was set to establish significance. Shank vertical acceleration was greatest at the lower VF (p = 0.028), higher VA (p = 0.028), and deeper squat (p = 0.048). Thigh vertical acceleration was not affected by depth of squat (p = 0.25), but it was greatest at higher VA (p = 0.046) and lower VF (p = 0.028). Medial-lateral shank acceleration was greatest at higher VF and deeper squat (both p = 0.046) and at higher VA (p = 0.028). Medial-lateral thigh acceleration was positively related to both VF (p = 0.046) and VA (p = 0.028) but was not affected by knee angle (p = 0.46). Anterior-posterior shank acceleration was higher at deeper squat (p = 0.046) and at lower VF and higher VA (both p = 0.028). Anterior-posterior thigh acceleration was related positively to the VA (p = 0.028), inversely to the VF (p = 0.028), and not dependent on knee angle (p = 0.75). Identification of specific vibration parameters and posture, which underpin WBV training efficacy, will enable coaches and athletes to design WBV training programs to specifically target shank or thigh muscles for enhanced performance.

Experimental Evidence of the Tonic Vibration Reflex during Whole-Body Vibration of the Loaded and Unloaded Leg

“…Compared to 50Hz, the transmission of Ve acceleration from source to shank was greater with 25Hz where an amplified acceleration response was observed, especially when the leg was loaded. As observed previously [23,31], WBV of 25Hz is more effective at delivering vibration to the musculature of the shank, probably due to more efficient damping of higher-frequency vibration; yet interestingly muscle activation was higher at 50Hz. This may reflect stronger muscular facilitation via supraspinal and spinal (e.g.…”

“…Amplification of vibration acceleration has been shown to occur between 10-40Hz at the ankle [33]; 20Hz WBV also induced greater shank acceleration compared to 40Hz [31]. Such vibration amplification during low frequency WBV, presumably by the structures of the foot and ankle, may favour the use of WBV over tendon vibration for muscular stimulation or for targeted transmission to skeletal structures.…”

Short Duration Small Sided Football and to a Lesser Extent Whole Body Vibration Exercise Induce Acute Changes in Markers of Bone Turnover

“…There has also been interest in the osteogenic potential of whole body vibration (VIB) which provides passive mechanical loading to the skeleton, since the oscillations generated by the vibrating platform impart accelerations to the body [14]. Such training may be more acceptable in individuals either unable or unwilling to perform high impact exercise.…”

The Effect of Whole-body Vibration on Muscle Activity in Active and Inactive Subjects

“…First, the acceleration signal was only measured in the vertical direction. Although the employed platform type (side-alternating) delivers vibrations mainly in the vertical plane [26], tri-axial analysis might be needed to more accurately represent the complexities of vibration transmission in the human body [12]. Second, skin-mounted accelerometers were used, which can allow movements of the soft tissue and skin relative to the bone beneath and may affect the acceleration detected by the accelerometers.…”