Head-down Tilt High Aerobic Intensity Training Effect On Vo2max And Stroke Volume Adaptations

Abstract

The majority of evidence points to the stroke volume (SV) of the heart being the major limiting factor for maximal oxygen uptake (VO2max) in healthy humans. High-intensity aerobic interval training has previously been found to improve VO2max more than low and moderate intensity aerobic training when matched for total work. Haemodynamics are affected by venous return and positioning of the working muscles in relation to the heart. PURPOSE: It is the aim of the present study to investigate the effects of interval training with the legs placed above the heart. METHODS: A total of 28 young, healthy, untrained males were randomly assigned cycle training of 4x4 min intervals at 90 - 95% of HRmax with their legs higher than the level of the heart (STG) or on a conventional upright cycle (UTG) for 24 sessions over 6 weeks. VO2max, maximal SV (SVmax), submaximal heart rate (HR100W), and maximal power output (MPO) were examined before and after the training period. RESULTS: No significant difference was apparent between the groups in VO2max-improvement for from pre- to posttest when tested in either postural position. Both groups increased absolute VO2max (L•min-1) significantly, by 15.3% in UTG and 16.5% in STG (P < 0.01) in upright cycling, and 9.4% (UTG) and 15.9% (STG) in supine cycling (P < 0.01). These adaptations were accompanied by increased SV of 8.9% and 10.6% for UTG and STG, respectively (P < 0.05), and reduced submaximal HR (P < 0.01). CONCLUSIONS: High-intensity aerobic interval training performed in a 4x4 min fashion in either the upright or supine position does not lead to different adaptations in VO2max. However, high-intensity interval training four times per week is an effective means to improve VO2max in young, untrained males. Also, since the improvement in SV did not differ between groups this is further testament to the heart being an important modulating factor for VO2max-improvements.Figure