The time course of physiological adaptations to high-intensity interval training in older adults.

Abstract

ObjectiveHigh‐intensity interval training (HIIT) has been shown to be more effective than moderate continuous aerobic exercise for improving cardiorespiratory fitness (CRF) in a limited time frame. However, the length of time required for HIIT to elicit clinically significant improvements in the CRF of older adults is currently unknown. The aim of this study was to compare changes in the CRF of older adults completing identical HIIT protocols of varying durations.MethodsForty healthy, community‐dwelling older adults completed a cardiopulmonary exercise test (CPET) before and after 2, 4, or 6 weeks of fully supervised HIIT on a cycle ergometer, or a no‐intervention control period.ResultsAnaerobic threshold (AT) was increased only after 4 (+1.9 [SD 1.1] mL/kg/min) and 6 weeks (+1.9 [SD 1.8] mL/kg/min) of HIIT (both P < 0.001), with 6‐week HIIT required to elicit improvements in VO2 peak (+3.0 [SD 6] mL/kg/min; P = 0.04). Exercise tolerance increased after 2 (+15 [SD 15] W), 4 (+17 [SD 11] W), and 6 weeks (+16 [SD 11] W) of HIIT (all P < 0.001), with no difference in increase between the groups. There were no changes in any parameter in the control group.ConclusionImprovements in exercise tolerance from HIIT precede changes in CRF. Just 4 weeks of a well‐tolerated, reduced‐exertion HIIT protocol are required to produce significant changes in AT, with a further 2 weeks of training also eliciting improvements in VO2 peak.