Multidirectional Hop Landings Exceed Osteogenic Thresholds with and with Instruction Withdrawn in Premenopausal Women

Abstract

The purpose of this study was to quantify ground reaction forces across all planes of motion and determine the influence of instruction associated with vertical, forward and lateral hop landings in premenopausal women. Bilateral jump-landings have previously been the focus in this population with forces quantified primarily in the vertical direction. There is a need to understand and quantify the landing forces for different types of exercises to determine their osteogenic potential as a stimulus for bone development across the life stages, in addition to identifying at risk populations. Such exercises could help to build a better skeleton, and maintenance of that would decrease the susceptibility to fractures and osteoporosis in later years. Twenty-one women [Mean (SD): 43.3 (5.9) yr; 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performed a testing session ‘with instruction’ followed by a testing session performed one week later with ‘instruction withdrawn’. The resultant magnitudes (4.02 to 4.93 body weights, BW’s) and rates of strain (237 to 319, body weights per second, BW/s), exceeded previously determined jump-landings thresholds (>3BW’s and >43BW/s, respectively) that have achieved bone gains in this population. Jump-type effects were observed, with larger peak vertical and resultant forces (↑10% to ↑14%; p ≤.001, BW) produced for the vertical hop. Significant differences (p ≤.001) were detected for hop landing ground reaction force’s across all planes of motion (19% to 93%) suggesting that each landing type provides a different type of force distribution as required to optimize bone stimulation. These multidirectional hop-landings represent a unique training stimulus for premenopausal women and exceed osteogenic thresholds thought pre-requisite for bone growth.