LAUSR

Abstract This investigation aimed to assess whether the alternative method of estimating 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 a low-carbohydrate diet and beverages containing high (H-CHO, 10.8±2.1 g·kg − 1 ), moderate (M-CHO, 5.6±1.1 g·kg − 1 ), or zero (Z-CHO, 0.24±0.05 g·kg − 1 ) carbohydrates. Another TTE was performed 24 h 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±3.5 kJ·min − 1 ). The aerobic contribution was lower (− 8.7±4.0 kJ·min − 1 ), decreasing performance (− 34±16 s) 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±3.4 kJ·min − 1 higher than baseline). Fasting increased relative alactic (2.9±1.7 kJ·min − 1 ) but decreased aerobic contribution (− 3.3±2.3 kJ·min − 1 ), impairing performance (− 17±12 s). In conclusion, MAOD alt can detect changes in energy system supply in different nutritional states. Therefore, participantʼs nutritional state must be considered prior to conducting the test.