Abstract
PurposeThe training response of an intensified period of high-intensity exercise is not clear. Therefore, we compared the cardiovascular adaptations of completing 24 high-intensity aerobic interval training sessions carried out for either three or eight weeks, respectively.MethodsTwenty-one healthy subjects (23.0±2.1 years, 10 females) completed 24 high-intensity training sessions throughout a time-period of either eight weeks (moderate frequency, MF) or three weeks (high frequency, HF) followed by a detraining period of nine weeks without any training. In both groups, maximal oxygen uptake (VO2max) was evaluated before training, at the 9th and 17th session and four days after the final 24th training session. In the detraining phase VO2max was evaluated after 12 days and thereafter every second week for eight weeks. Left ventricular echocardiography, carbon monoxide lung diffusion transfer factor, brachial artery flow mediated dilatation and vastus lateralis citrate maximal synthase activity was tested before and after training.ResultsThe cardiovascular adaptation after HF training was delayed compared to training with MF. Four days after ending training the HF group showed no improvement (+3.0%, p = 0.126), whereas the MF group reached their highest VO2max with a 10.7% improvement (p<0.001: group difference p = 0.035). The HF group reached their highest VO2max (6.1% increase, p = 0.026) twelve days into the detraining period, compared to a concomitant reduction to 7.9% of VO2max (p<0.001) above baseline in the MF group (group difference p = 0.609).ConclusionBoth HF and MF training of high-intensity aerobic exercise improves VO2max. The cardiovascular adaptation following a HF programme of high-intensity exercise is however delayed compared to MF training.Trial RegistrationClinicalTrials.gov NCT00733941.
Highlights
Maximal oxygen uptake (VO2max) is considered the best measure of aerobic capacity and an increase in VO2max is the most common way of demonstrating an effect of aerobic exercise training [1]
The moderate frequency (MF) group improved VO2max by 4.6% (p = 0.036) already after eight training sessions, whereas no significant improvement was seen in the high frequency (HF) group at the same time point (+2.3%, p = 0.128; between group difference p = 0.449)
In our study we found a quite different progression of the adaptation between MF- and HF-training, and the highest VO2max-values occurred at different time points
Summary
Maximal oxygen uptake (VO2max) is considered the best measure of aerobic capacity and an increase in VO2max is the most common way of demonstrating an effect of aerobic exercise training [1]. A recent study of Swiss alpine junior skiers found that 15 high-intensity exercise sessions at 90–95% of HRmax performed over 11 days improved VO2max by 6% when measured seven days after completing training [8]. Two earlier studies have reported a decrease in VO2max and work performance after two weeks of highly intensified training in competitive cyclists [9,10]. This indicates that the assessment of VO2max may be dependent of when the measurements are taking place after completing a highly intensified training period. A secondary aim was to study the cardiovascular, pulmonary, endothelial and skeletal muscle adaptation induced by the two training programmes
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