A quasi-experimental study on responses to mechanical loads following different heart rate-based exercise intensities and water depths in postmenopausal women

Abstract

Abstract The present study examined mechanical loads (ML) during a single bout of intermittent water jumps at different intensities and water depths. Nineteen postmenopausal women were non-randomly assigned to shallow-water level (SWL) or deep-water level (DWL) groups and performed four jump modes—countermovement, lunge, leg–arm open, and skipping (SKIP)—at moderate (MI) and high intensity (HI). The integral ML (IML) and average ML (AML) per jump were calculated for each condition. Baseline characteristics were compared between groups using the Mann–Whitney U test. Multi-factor analyses were performed in R, with body height adjusted as a covariate. Results showed that omnibus models revealed no significant depth × intensity interactions. For cumulative loading, a robust main effect of water depth was detected, proving that IML was generally greater in SWL than in DWL under MI. Under HI conditions, depth-modulated contrast magnitudes varied descriptively across modes, with skipping displaying a prominent exploratory post-hoc effect size. Furthermore, a significant main effect of intensity was observed for velocity metrics, wherein AML was consistently higher during MI than HI across all conditions. In conclusion, an intermittent aquatic jumping protocol in SWL at MI offers a generally superior strategy for generating higher cumulative mechanical loading. However, the localized variations in individual post-hoc patterns warrant careful interpretation strictly as exploratory trends potentially influenced by individual body height variations, rather than indicating a true statistical interaction.