Whole-body vibration during passive standing in individuals with spinal cord injury: effects of plate choice, frequency, amplitude, and subject's posture on vibration propagation.

BACKGROUND: To date, few pharmacologic or rehabilitation interventions for sublesional osteoporosis (SLOP) or low bone mass of the hip and knee regions after spinal cord injury (SCI) have produced significant or sustained increases in lower extremity bone mineral density. Whole body vibration (WBV) is a potential intervention for the prevention and/or treatment of SLOP.

OBJECTIVE: To identify the optimal WBV conditions (ie, plate, frequency, amplitude, and subject posture) among men with chronic SCI during passive standing and facilitate the implementation and future evaluation of the efficacy of WBV and passive standing for prevention and treatment of SLOP in men with SCI.

DESIGN: This phase 0 device development study assessed the lower extremity propagation characteristics of WBV in men with and without SCI by using a variety of a priori specified plates, frequencies, amplitudes, and postures that facilitate lower extremity vibration absorption while minimizing vibration propagation to the head.

SETTING: A tertiary SCI rehabilitation center in Toronto, Canada.

PARTICIPANTS: Healthy men with chronic paraplegia (n = 5) and those without SCI (n = 7), ages 20-50 years, weight 68-113 kg, and height 168-188 cm.

INTERVENTIONS: An EasyStand standing frame (Altimate Medical Inc, Morton, MN) was fitted onto 2 commercially available vibration platforms: WAVE (WAVE Manufacturing Inc, Windsor, Ontario, Canada) and Juvent (Juvent Medical Inc, Somerset, NJ). Accelerometers were attached to the participants' forehead, hip, knee, and ankle to measure vibration propagation. Vibration parameters evaluated were posture (knee angles of 140°, 160°, and 180° [180° for Juvent only]), vibration frequency (25 Hz, 35 Hz, and 45 Hz), and vibration amplitude (0.6 mm and 1.2 mm [WAVE only]). The subjects were exposed to all combinations of posture, frequencies, and amplitudes during the experiments (total parameter combinations: 12 WAVE and 9 Juvent).

MAIN OUTCOME MEASUREMENTS: Peak-to-peak vibration and transmissibility of vibration were recorded and computed for each accelerometer at the tested locations.

RESULTS: Variations in frequency generated the most noticeable changes in propagation characteristics, followed by variations in knee angle and amplitude.

CONCLUSIONS: WBV therapy delivered with use of the WAVE platform with a knee angle of 140°, plate frequency of 45 Hz, and amplitude of 1.2 mm met our a priori criteria for the "optimal WBV condition." Future studies should evaluate the therapeutic efficacy of the WAVE platform by using these parameters to maintain or augment bone mass among persons with SCI and SLOP.