High- and low-carb diet and fasting state modify alternative maximal accumulated oxygen deficit.

This investigation aimed to assess if alternative method to estimate the maximal accumulated oxygen deficit (MAOD_alt) can detect changes in energy system contribution in different substrate availabilities. Following a graded exercise test to determine maximal oxygen uptake intensity (iVO_2max), 26 recreational runners performed a time to exhaustion effort (TTE) as baseline at 110% iVO_2max. The same TTE was performed in fasting state, then, a muscle glycogen depletion protocol was executed. Subsequently, participants received low-carbohydrate diet and beverage containing high (H-CHO, 10.8±2.1g·kg^-1), moderate (M-CHO, 5.6±1.1g·kg^-1), or zero (Z-CHO, 0.24±0.05g·kg^-1) carbohydrate. Another TTE was performed 24h later. Each energy system contribution was assessed. Generalized linear mixed models were used for statistical analysis (p<0.05). H-CHO increased relative anaerobic capacity (slope effect [baseline-intervention]x[H-CHO-M-CHO]) due to the relative lactic contribution maintenance (slope effect [baseline-intervention]x[H-CHO-Z-CHO] or [H-CHO-M-CHO]) and increase in relative alactic contribution (6.3±3.5kJ·min^-1). The aerobic contribution was lower (-8.7±4.0kJ·min^-1), decreasing performance (-34±16s) for H-CHO. M-CHO and Z-CHO maintained anaerobic capacity due to increase in alactic contribution (slope effect [fasting-intervention]x[M-CHO-H-CHO]; and Z-CHO was 7.3±3.4kJ·min^-1 higher than baseline). Fasting increased relative alactic (2.9±1.7kJ·min^-1) but decreased aerobic contribution (-3.3±2.3kJ·min^-1), impairing performance (-17±12s). In conclusion, MAOD_alt can detect changes in energy system supply in different nutritional states. Therefore, participant's nutritional state must be considered prior to conducting the test.