A single bout of high-intensity interval exercise increased plasma volume by 6.7% at 48 hours and reduced cardiovascular strain during a hypoxic cycling time trial, but did not improve performance.
RCT (n=8)
Open-label
Counterbalanced order
No
Does a single bout of high-intensity interval exercise (HIIE) increase plasma volume and improve cardiovascular strain and cycling performance during a hypoxic time trial in recreationally active males?
A single bout of high-intensity interval exercise effectively expands plasma volume and reduces cardiovascular strain during subsequent hypoxic exercise, though it does not significantly improve time-trial performance.
Absolute Event Rate: 6.7% vs 0.3%
p-value: p=0.006
The purpose of our study was to assess the influence of a single high-intensity interval exercise (HIIE) bout in normoxia on plasma volume (PV) and consequent cycling performance in normobaric hypoxia (0.15 FiO2, simulating ~2,500 m). Eight males (VO2peak: 48.8 ± 3.4 mL/kg/min, 24.0 ± 1.6 years) completed a hypoxic 15 km cycling time trial (TT), followed by a crossover intervention of either HIIE (8x4 min cycling bouts at 85% of VO2peak) or CON (matched kJ production from HIIE at 50% of VO2peak). 48 hours post intervention, an identical TT was performed. Cardiovascular parameters were measured via impedance cardiography during each TT. Changes in PV was measured 24 and 48 hours post HIIE and CON. HIIE increased PV at 24 (4.1 ± 3.9%, P = 0.031) and 48 (6.7 ± 1.7, P = 0.006) hours post, while no difference was observed following the CON (1.3 ± 1.1% and 0.3 ± 2.8%). The higher PV led to an increased stroke volume (P = 0.03) and cardiac output (P = 0.02) during the hypoxic TT, while heart rate was not changed (P = 0.49). We observed no changes in time to completion (-0.63 ± 0.57 min, P = 0.054) and power output (7.37 ± 7.98 W, P = 0.078) between TTs. In the absence of environmental stress, a single bout of HIIE was an effective strategy to increase PV and reduce the cardiovascular strain during a cycling TT at moderate simulated altitude but did not impact hypoxic exercise performance. Trial registration: Clinical Trials ID: NCT05800808.
Pereira et al. (Fri,) conducted a rct in Healthy recreationally active males (n=8). High-intensity interval exercise (HIIE) vs. Control cycling at 50% VO2peak matched for total kilojoules was evaluated on Plasma volume change at 48 hours post-intervention (p=0.006). A single bout of high-intensity interval exercise increased plasma volume by 6.7% at 48 hours and reduced cardiovascular strain during a hypoxic cycling time trial, but did not improve performance.