Preworkout dietary nitrate magnifies training-induced benefits to physical function in late postmenopausal women: a randomized pilot study

To inform end points for future work, we explored the utility of preworkout (i.e., an acute dose before training) beetroot juice (BRJ) combined with exercise (BRJ + EX) to augment indices of physical function in postmenopausal women compared with exercise only (EX). A two-arm pilot study was used to compare 24 postmenopausal women following an 8-wk, circuit-based exercise intervention. Participants were randomized to BRJ + EX (<i>n</i> = 12) or EX (<i>n</i> = 12). BRJ + EX participants consumed 140 mL of BRJ 120-180 min (only) before training for 7 wk, then discontinued during the final week to mitigate carryover effects. Physical function indices were 6-min walk test (6MWT), estimated V̇o_2peak, heart rate recovery (HRR), and maximal knee extensor power (P_max). A treadmill task was used to measure V̇o₂ on-kinetics wherein mean response time (MRT) coincided with the duration to reach 63% of steady-state V̇o₂. Results showed greater changes (Δ) among BRJ + EX participants for 6MWT distance (40 ± 23 m vs. 8 ± 25 m; <i>P</i> = 0.003, <i>d</i> = 1.35), ΔV̇o_2peak (1.5 ± 0.9 mL·kg^-1·min^-1 vs. 0.3 ± 1.0 mL·kg^-1·min^-1; <i>P</i> = 0.008, <i>d</i> = 1.20), and ΔHRR (-10 ± 6 beats/min vs. -1 ± 9 beats/min; <i>P</i> = 0.017, <i>d</i> = 1.05). Large and medium effect sizes favoring BRJ + EX were detected for ΔP_max (<i>P</i> = 0.07, <i>d</i> = 0.83) and ΔMRT (<i>P</i> = 0.257, <i>d</i> = 0.50), respectively. In postmenopausal women, BRJ + EX appears to magnify some adaptive benefits to physical function including aerobic capacity and recovery beyond that of training without BRJ. Investigation into contributing mechanisms is needed.<b>NEW & NOTEWORTHY</b> Though exercise training represents the principal strategy to combat age-related decline, the attendant effects of menopause weaken aspects of exercise adaptation compared with premenopausal women and age-matched men. Here we provide important initial evidence that preworkout (i.e., an acute dose before training) beetroot juice coupled with an 8-wk, circuit-based exercise training intervention may uniquely benefit late postmenopausal women by enhancing indices of physical function including aerobic capacity and recovery.