Effects of resistance training intensity on the cardiovascular health of postmenopausal women with hypertension: a study protocol for the LOAD trial.

Resistance training (RT) reduces the cardiovascular risk in patients with hypertension, especially blood pressure (BP). Current guidelines suggest an intensity between 50% and 80% of the load for 1-repetition maximum (1RM) for the training prescription for this population. However, there is an absence of chronic studies designed to test the effect of different intensities on cardiovascular parameters. This study will investigate RT acutely and a 10-week intervention on BP, heart rate (HR), heart rate variability (HRV), endothelial function (EF), feeling responses and rate of perceived exertion (RPE) in postmenopausal women. Salivary samples will be collected to analyse stable metabolites of nitric oxide. The study will adopt two sequential phases: crossover (acute) and randomised controlled trial (10 weeks). 20 postmenopausal women (50-65 years old) diagnosed with hypertension will be enrolled to perform baseline assessments. In the acute test (phase 1), the participants will perform one RT session with 60%1RM (18-20 repetitions per set) and 80%1RM (8-10 repetitions per set) in a random order. BP, HR and HRV will be measured before and for 1 hour after the session. The feeling will be measured before each RT session and at the end, along with RPE. For the 10-week intervention (phase 2), participants will be randomly allocated to train for 10 weeks at 60%1RM or 80%1RM. BP, HR, HRV, feeling responses, RPE, EF and salivary samples will be measured at baseline, during and after all experiments. Intention-to-treat analysis will be adopted using the linear mixed model.