Effects of land vs water jump exercise: Implications for exercise design targeting bone health.

PURPOSE: To quantify ground reaction force (GRF), osteogenic index (OI), muscle activity, and blood lactate levels during continuous jumping performed in water and on land.

METHODS: Thirteen post-menopausal women (59.5 ± 6.8 years) performed two bouts of jumping, on land (LND) and in water at a depth of 1 m (WEX). Each 10-minute, 40-second bout consisted of 2 consecutive sets of squat, lunge, jumping jax, countermovement, and single legged jumps as intervals: 10 seconds maximal effort and 60 seconds recovery at 50% of heart rate reserve (HRR). Pre- and post-exercise lower extremity rate of perceived exertion (RPE) was recorded, and 10-µL earlobe blood samples were collected to assess lactate concentration. During exercise, data were collected for electromyography, GRF, and heart rate. Total GRF (TGRF) and total muscular activity (TMA) during each 10 seconds of jumping were measured. OI for one bout of continued jumps was determined by averaging GRF·ln (number of jumps + 1).

RESULTS: There were no differences between WEX and LND for percent HRR and RPE. TGRF, OI, TMA, and lactate concentration on LND jumps were significantly higher than WEX.

CONCLUSION: At similar cardiorespiratory and RPE levels, the lower impact loading of 10 minutes 40 seconds of interval continuous jumping exercise in 1-m depth was less osteogenic than on land. However, one daily bout of water jumping, 5 days per week resulted in a similar OI as 3 days of jumping on land. WEX might substitute or provide an adjunct to LND exercise to promote bone health.