Effect of 3-week high-intensity interval training on VO2max, total haemoglobin mass, plasma and blood volume in well-trained athletes.

Abstract

This study examined the haematological adaptations to high-intensity interval training (HIT), i.e. total haemoglobin mass (tHb-mass), blood volume (BV), and plasma volume (PV), and its effects on VO2max in well-trained athletes. Twenty-seven male and eight female well-trained (VO2max 63.7±7.7ml/min/kg) athletes were randomly assigned to the HIT (HITG, N=19) or the control group (CG, N=16). Over a 3-week period, the HITG performed 11 HIT sessions, consisting of four 4-min interval bouts at an exercise intensity of 90-95% of the individual maximal heart rate (HRmax), separated by 4-min active recovery periods. Before and 5±2days after the intervention, tHb-mass, BV and PV were determined by the CO-rebreathing method. VO2max was assessed in a laboratory treadmill test. tHb-mass (from 753±124 to 760±121g), BV (from 5.6±0.8 to 5.6±0.9l) and PV (from 3.2±0.5 to 3.2±0.5l) remained unchanged after HIT and did not show an interaction (group×time). Within the HITG, VO2max improved from baseline by +3.5% (p=0.011), but remained unchanged in the CG. No interaction (group×time) was seen for VO2max. The HITG showed a significant reduction in HRmax compared to the baseline measurement (-2.3%, p≤0.001), but HRmax remained unchanged in the CG. There was a significant interaction (group×time) for HRmax (p=0.006). Also, oxygen pulse significantly increased only in HITG from 22.9±4.4 to 23.9±4.2ml/beat, with no interaction (p=0.150). Eleven HIT sessions added to usual training did neither improve VO2max nor haematological parameters compared to the CG.