1. Playing all the right notes, but not necessarily in the right order: unravelling the mechanisms limiting human oxygen uptake
V. Merzbach, D. Gordon, J. Baker
Sport and Exercise Science Research Group
Pushing the Boundaries - 4th Annual Research and Scholarship Conference 14th May 2014
Introduction
In an incremental test to volitional exhaustion, a levelling off or plateau-like response in VO2 is the primary criterion for a maximal effort. Previous work has shown that the plateau in VO2 is related to the finite anaerobic capacity. The anaerobic work capacity (AWC) (W’) which integrates anaerobic substrate metabolism as well as the metabolite accumulation can be derived from the power-time relationship in conjunction with critical power (CP).
Therefore the purpose of this study was to examine if W’ predicts the incidence of plateau at VO2max. A
Method
15 male participants reported to the laboratory on 5 separate occasions where visits 1 and 5 were used for the measurement of VO2max and the remaining 3 tests, time trials to exhaustion, for determination of CP and W’. A pre-calibrated metabolic cart was used to analyse VO2 responses and a ΔVO2 < 1.5 ml∙kg-1∙min-1 was applied as plateau criterion. The participants had to exercise at 95, 100 and 120% of Pmax from VO2max 1 for the time trials. CP and W’ were derived using a linear P -1/t model and solving the equation P=AWC∙(1/t)+CP.
Figure 1 A: Incidence of plateau (%) for the whole group, responders (RE) and non-responders (NRE) between trial 1, 2 and mean, B: anaerobic work capacity [W’ (kJ)] and C: critical power (W) shown as mean ± SD.
Conclusion
Previously used methods such as the MAOD have certain limitations to measure anaerobic capacity and predict the incidence of plateau as they do not integrate the accumulation of pain and fatigue. The data from this study suggests that W’, derived as AWC from the non-invasive CP method, is somehow correlated to plateau response. However, further research should seek to assess this relationship in more depth.
Results
No significant differences were observed for the whole group in any variables. When the group was split into responders (RE) who exhibited a plateau response in VO2 there was a significant positive correlation between ΔVO2 ml∙kg-1∙min-1 (mean difference in VO2 for the last 2 consecutive 30s blocks) and W’ (P= 0.030) but not for non-responders (NRE) (p> 0.05). The mean ΔVO2 for the whole group was 0.60 ± 1.83 ml∙kg-1∙min-1 and for RE and NRE it was 0.27 ± 0.91 and 0.90 ± 2.40 ml∙kg-1∙min-1, respectively.
References
Gordon, D. et al. Incidence of the plateau at VO2max is dependent on anaerobic capacity. Int J Sports Med, 2011, 32, 1-6.