Water-based exercises in postmenopausal women: Vertical ground reaction force and oxygen uptake responses

The purpose of the present study was to analyse vertical ground reaction force (Fz) and oxygen uptake (VO₂) responses in six different water-based exercises performed at different cadences by postmenopausal women. Twelve postmenopausal women (57.3 ± 2.6 years, 158.1 ± 6.9 cm, 69.1 ± 10.9 kg) voluntarily took part in the study. Participants completed six sessions corresponding to maximal tests for each water-based exercise. Then, two sessions were performed for the experimental protocols, which comprised the performance of three exercises at three cadences (80, 100 and 120 b min^-1), with Fz and VO₂ measurements. Peak (Fz_peak) and impulse of Fz were determined. In addition, VO₂ percentages relative to maximal VO₂ (VO_2max) values obtained in each maximal test were expressed as %VO_2max. Data were analysed using two-way ANOVA with repeated measures (α = 0.05). As results, significant differences were found in Fz_peak and impulse between the water-based exercises, with similar VO₂ and %VO_2max values between them for each cadence. In addition, with the increasing cadence, Fz_peak (0.20-0.80 BW), VO₂ (5.3-9.4 ml kg^-1 min^-1) and %VO_2max (32.1-57.6%) values increased, while impulse (0.20-0.07 N.s/BW) values were reduced. Therefore, for a same physiological intensity, postmenopausal women experience different Fz loads during different water-based exercises.