Do Bilateral Vertical Jumps With Reactive Jump Landings Achieve Osteogenic Thresholds With and Without Instruction in Premenopausal Women?
in Journal of Applied BiomechanicsJumps have been investigated as a stimulus for bone development; however, effects of instruction, jump type, and jump-landing techniques need investigation. This study sought to identify whether ground reaction forces (GRFs) for bilateral vertical jumps (countermovement jumps and drop jumps) with reactive jump-landings (ie, jumping immediately after initial jump-landing), with instruction and with instruction withdrawn, achieve magnitudes and rates of strain previously shown to improve bone mass among premenopausal women. Twenty-one women (Mean ± SD: 43.3 ± 5.9 y; 69.4 ± 9.6 kg; 167 ± 5.5 cm; 27.5 ± 8.7% body fat) performed a testing session ‘with instruction’ followed by a testing session performed 1 week later with ‘instruction withdrawn.’ The magnitudes (4.59 to 5.49 body weight [BW]) and rates of strain (263 to 359 BW·s−1) for the jump-landings, performed on an AMTI force plate, exceeded previously determined thresholds (>3 BWs and >43 BW·s−1). Interestingly, significantly larger peak resultant forces, (↑10%; P = .002) and peak rates of force development (↑20%; P < .001) values (in relation to BW and BW·s−1, respectively) were observed for the second jump-landing (postreactive jump). Small increases (ES = 0.22–0.42) in all landing forces were observed in the second jump-landing with ‘instruction withdrawn.’ These jumps represent a unique training stimulus for premenopausal women and achieve osteogenic thresholds thought prerequisite for bone growth.
Clissold and Winwood are with the Dept of Sport and Recreation, School of Applied Science, Toi Ohomai Institute of Technology, Tauranga, New Zealand. Clissold, Winwood, and Cronin are with the Sports Performance Research Institute New Zealand (SPRINZ), AUT University, Auckland, New Zealand. Cronin is also with the School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Perth, Australia. De Souza is with the Dept of Kinesiology, Pennsylvania State University, Pennsylvania, PA.
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