Abstract
INTRODUCTION: Cocoa flavanols (CF) may exert health benefits through their potent vasodilatory effects, which are perpetuated by elevations in nitric oxide (NO) bioavailability. These vasodilatory effects may contribute to improved delivery of blood and oxygen (O(2)) to exercising muscle. PURPOSE: Therefore, the objective of this study was to examine how CF supplementation impacts pulmonary O(2) uptake (V˙O2) kinetics and exercise tolerance in sedentary middle-aged adults. METHODS: We employed a double-blind cross-over, placebo-controlled design whereby 17 participants (11 male, 6 female; mean ± SD, 45 ± 6 years) randomly received either 7 days of daily CF (400 mg) or placebo (PL) supplementation. On day 7, participants completed a series of 'step' moderate- and severe-intensity exercise tests for the determination of V˙O2 kinetics. RESULTS: During moderate-intensity exercise, the time constant of the phase II V˙O2 kinetics (τV˙O2) was decreased by 15% in CF as compared to PL (mean ± SD; PL 40 ± 12 s vs. CF 34 ± 9 s, P = 0.019), with no differences in the amplitude of V˙O2 (AV˙O2; PL 0.77 ± 0.32 l min(-1) vs. CF 0.79 ± 0.34 l min(-1), P = 0.263). However, during severe-intensity exercise, τV˙O2, the amplitude of the slow component (SCV˙O2) and exercise tolerance (PL 435 ± 58 s vs. CF 424 ± 47 s, P = 0.480) were unchanged between conditions. CONCLUSION: Our data show that acute CF supplementation enhanced V˙O2 kinetics during moderate-, but not severe-intensity exercise in middle-aged participants. These novel effects of CFs, in this demographic, may contribute to improved tolerance of moderate-activity physical activities, which appear commonly present in daily life. TRIAL REGISTRATION: Registered under ClinicalTrials.gov Identifier no. NCT04370353, 30/04/20 retrospectively registered.