AND BENDING STRENGTH IN YOUNG ADULTS EFFECT OF FOUR WEEKS WHOLE-BODY VIBRATION TRAINING ON BONE MINERAL DENSITY, AND BENDING STRENGTH IN YOUNG ADULTS Jaime Flores, Tatiana Metchkoff, Elbert Chen, Alexandra Auslander, Jose Rocha, and Michael T.C. Liang Department of Kinesiology and Health Promotion, College of Science California State Polytechnic University, Pomona, CA. Introduction R e s u l t s Table 12 Geometric parameters of hip strength analysis by DXA Δ Mean SD p value NARROW NECK CSA 0.0095 0.208 0.836 CSMI** -4.67 2.623 0.001 Z -0.0004 0.147 0.988 CORT 0.015 0.89 BR -0.019 1.297 0.947 INTROTROCHTERIC 2.328 10.939 0.341 CSMI 0.194 2.26 0.697 -0.088 0.26 0.134 0.266 0.648 0.074 FEMORAL SHAFT SA -0.022 0.117 0.383 CSMI* 0.063 0.118 0.03 3.953 18.149 0.33 CORT* 0.046 0.094 0.047 -0.119 0.309 0.093 *P< 0.05; **P< 0.01 Abbreviation: DXA, Dual energy X-ray absorptiometry; Δ mean, mean difference (baseline – post-test); CSA, mineralized bone surface cross-sectional area; CSMI, the cross-sectional moment of inertia; Z, the section modulus; BR, the bucking ratio; Note: CSMI increase means the bone's ability to resist bending force increases Introduction Osteoporosis is a debilitating, age-related bone disease characterized by a net loss of bone mineral density (BMD) and microarchitectural deterioration of bone tissue leading to increased risk of fractures. Research has shown that high-frequency low magnitude whole-body vibration (HFLMBV) training induced favorable results on bone density in human and animal models. Remarkably, the mechanical vibration signals need not be applied for long periods of time to induce osteogenic responses. In human studies, Reyes et al. (2011) reported that high-frequency and low-magnitude vibration stimulus improve BMD and muscular strength in children with disabling ambulatory conditions, especially on the trabecular bone, and concluded that this nondrug, noninvasive WBV intervention is both safe and effective. There is very little data on the use of short-term HFLMBV training on BMD, body composition and bone bending strength in humans. Hypothesis We tested the hypothesis that 4 weeks of HFLMBV training can improve BMD, body composition, and bone bending strength in young adults. Purpose of the Study The purpose of this study was to examine the effects of a 4-week high-frequency low-magnitude whole body vibration training on BMD, body composition, and bone bending strength in young adults. TABLE 1. Bone outcome results obtained by DAX and MRTA Δ Mean SD p value Tibia EI (N.m2) -40 134.9 0.182 BMD arm total -0.002 0.014 0.464 BMD leg total 0.034 0.768 BMD tibia -0.004 0.064 0.774 BMD femoral neck 0.0044 0.017 0.252 BMD total hip* -0.012 0.022 0.021 BMC total hip** -1.725 2.429 0.004 BMD trochanter -0.001 0.025 0.861 BMD Wards -0.007 0.049 0.505 BMD L1-L4 -0.011 0.036 0.166 BMD whole body -0.003 0.018 0.461 *p < 0.05, **p < 0.01 Abbreviation: DXA, dual energy X-ray absorptiometry; Δ Mean, mean difference (baseline - post-test); MRTA, Mechanical response tissue analyzer; EI, bone bending strength; L1-L4, lumbur spine 1-4; BMC, bone mineral content . (Top L) Whole body vibration training; (Top R) whole body DXA scan Summary and Conclusions Materials and Methods Results obtained from between group comparison show that significant changes from baseline to week four in hip BMC (4.56%, p = 0.004), hip BMD (1.2%, p = 0.02) (Table 1), and femoral neck CSMI (p = 0.001), femoral shaft CSMI (6.8%, p = 0.02). (Table 2). No significant change in tibia bending strength was observed in the experimental groups. The above bone parameters change were not observed in the control group. In summary, there were no significant difference between the two experiment groups (G1 versus G2) in BMD, BMC and bone bending strength as the result of the 4-week HFLMBV training suggesting that 1 bout per day and 2 bouts per day whole body vibration training yields similar results on bone parameters. Applying the Hip Strength Analysis software, we observe significant increase in femoral neck CSMI and significant decrease in femoral shaft CSMI and CORT (Table 2). Note that CSMI increases means the bone’s ability to resist bending forces increase. In conclusion, our results indicate that a four-week high-frequency low-magnitude whole body vibration training regimen induced osteogenic adaptation on BMD and BMC at the hip, and in femoral neck bending strength in physically trained young adults. DXA scan of L1-L4 (L) and total hip (R) Subjects. A total of 43 (F=31) physically active women and men, age 20 - 31 years, volunteered to serve as study subjects. Inclusion criteria are: 1) physically active and healthy with a body mass index (BMI) > 18.0 and < 30.0 kg/m2, 2) females with normal menstrual cycle, 3) currently not using any tobacco product, or drink alcohol >2 drinks a day, and 4) must not have participated in WBV training within the past 12 months. A signed informed consent was obtained from each subject before scheduling for baseline study outcome measurements. All subjects completed a pre-test and post-test measurement. Study designs. Subjects were randomly assigned to the following three groups: 1) WBV training, 1 session/day, 20 min each (G1, n=15, F=12), 2) WBV training, 2 sessions/day, 10-min each (G2, n=16, F=12), and 3) no treatment control (CON, n=12, F=7). The High-frequency low-magnitude whole body vibration (HFLMBV) training consisted of one or two sessions/day, 3 days/week for 4 weeks. G1 performed 8 bouts of vibration exercise, once a day; and G2 performed 4 bouts of vibration exercise, twice a day with 1-2 hours resting period between sessions. HFLMBV training session consisted of 2.5 min vibration exercise followed by a 1-min rest after each bout. The CON did not perform WBV training for the entire 4-week study period. WBV training protocol. We used a vertical displacement vibration device (DKN Technology, Alhambra, CA) with a vibration frequency = 40 Hz (e.g., high frequency), and amplitude = 4 g (“g” is Earth’s gravitation force). During the vibration training, subjects in a natural upright standing posture stood on a vibration platform with knees bent at 40o angle, and feet contacting the platform at shoulder width.. Study outcome Measurements. The following study outcome measurements were performed at baseline and at the conclusion of the study. 1. Bone bending strength measurements were obtained using a Mechanical Response Tissue Analyzer (MRTA, NASA Ames Research Center, Moffett Field, CA) which was invented for NASA to assess bone strength in astronauts after space flight missions (Young et al. 1979). The MRTA technology is a noninvasive, non-radioactive and biologically cross-validated with monkey bones for measuring long bone strength that uses the response of a long bone to a low-frequency vibratory stimulus. (Fig. 1 & 2).. 2. Dual-Energy X-ray absorptiometry (DXA) scans with a Hologic Discovery-QDR series densitometer (Bedford, MA, U.S.A) was used for obtaining BMD at the lumbar spine (L1 to L4), femoral neck, lower leg, forearm, and whole body for each subject at California State Polytechnic University Pomona, Musculoskeletal Research Laboratory. 3. Whole body DXA scan to assess whole body fat mass and lean mass of the study subjects. Acknowledgement The authors thanks the study participants for their willingness to serve as the study subjects; without their contributions, this work would not have been possible.