Cardiorespiratory Fitness And Microvascular Function Responses To 4 Weeks Of Single-Sprint Training

BACKGROUND: Cardiorespiratory fitness (CRF) and microvascular function (MVF) are associated with multiple health outcomes. Investigations of high-intensity, low-volume exercise suggest that CRF improves after a 2x20s sprint training intervention, but a 1x20s sprint training intervention is ineffective. PURPOSE: To corroborate evidence that a 1x20s sprint training intervention is ineffective for improving CRF, and to explore the effect of this training intervention on MVF. METHODS: 46 healthy, untrained participants ages 18-35 were randomized into a training or time-matched negative control group. Training consisted of a 20s maximal cycling sprint, 3 days/week for 4 weeks. CRF was assessed via VO2peak (L/min) pre- and post-intervention. MVF was assessed via post-occlusive reactive hyperemia for the arm and leg using ultrasound (cm/s) and near-infrared spectroscopy (NIRS, %/s) at pre-, mid-, and post-intervention. Bayesian RMANCOVA, with pre- values as covariates, were used to assess the probability of a group x time interaction. Results presented as observed mean (SD), BF10 (likelihood of the group x time interaction model versus the null), and BFincl (change in model probability by adding the group x time interaction). RESULTS: Pre-post changes in CRF were 0.05 (0.14) for training and 0.00 (0.19) for control with evidence against a group x time interaction (BF10 = 0.046, BFincl = 0.388). Pre-post changes in arm MVF via ultrasound were -0.35 (11.61) for training and -1.59 (10.06) for control with evidence against a group x time interaction (BF10 = 0.007, BFincl = 0.166). Pre-post changes in arm MVF via NIRS were -0.03 (0.61) for training and -0.13 (0.49) for control with evidence against a group x time interaction (BF10 = 0.005, BFincl = 0.155). Pre-post changes in leg MVF via ultrasound were 0.16 (11.67) for training and 3.51 (15.92) for control with evidence against a group x time interaction (BF10 = 0.064, BFincl = 1.205). Pre-post changes in leg MVF via NIRS were 0.15 (0.38) for training and -0.02 (0.29) for control with evidence against a group x time interaction (BF10 = 0.058, BFincl = 0.429). CONCLUSIONS: The evidence suggests that a 4-week intervention consisting of 1x20s maximal sprint 3 days/week is ineffective for increasing CRF, systemic MVF, and local MVF in untrained, but otherwise healthy individuals. Supported by: Mississippi Center for Clinical and Translational Research - Pilot Projects Program