Estimating Anaerobic Capacity Using Post-Exercise Measures: ‘MAOD_alt’ Is Valid, Even In Hypoxia

The gold standard measure of anaerobic capacity is the maximal accumulated oxygen deficit (MAOD), which represents the difference between the estimated oxygen cost of exercise and the aerobic contribution to that exercise. An alternative to MAOD, ‘MAOD_alt’, is calculated as the sum of the glycolysis contribution, which is estimated from peak post-exercise blood lactate concentration, and the phosphocreatine concentration, which is estimated from the post-exercise VO2 response. MAOD_alt has been validated in several studies. However, there is only limited evidence of its validity in exercise that is performed in hypoxia. PURPOSE: The purpose of the present study was to determine the validity of MAOD_alt as a measure of anaerobic capacity in cycle ergometer exercise that is performed in moderate hypoxia. METHODS: Two women (mean ± SD: age 22 ± 1 y, height 160 ± 7 cm, weight 56 ± 7 kg, VO2max 40 ± 5 mL/kg/min) and five men (23 ± 2 y, 174 ± 5 cm, 75 ± 7 kg, and 45 ± 8 mL/kg/min) performed constant power, severe intensity, cycle ergometer exercise tests to exhaustion in hypoxia (FIO2 = 0.106 ± 0.006). VO2 responses in 7 min of recovery were fitted to a two-component model (fast and slow phases) and the area under the fast phase was taken to represent the phosphocreatine contribution. The peak blood lactate value was determined from the blood samples that were collected 4 to 6 min after exercise, and the increase in concentration from baseline was multiplied by 3.3 mL/kg/mM to estimate the glycolysis contribution. The criterion measure, MAOD, was calculated using published methods that assume that the oxygen demand can be estimated by extrapolation of the sub-threshold VO2:work rate relationship and that the slow component of the VO2 response reflects an increase in oxygen demand. MAOD_alt and MAOD values were compared using paired-means t-tests, with significance set at p < 0.05. RESULTS: The mean time to exhaustion was ~4½ min, indicating that the intensity was in the severe exercise intensity domain, and, thus, suitable to elicit a maximal anaerobic contribution. The values for MAOD_alt (58 ± 6 mL/kg) and MAOD (58 ± 9 mL/kg) did not differ (p = 0.83), and were strongly correlated (r = 0.74). CONCLUSION: The results of the present study support the validity and use of MAOD_alt as a measure of anaerobic capacity, even in hypoxia.