Table 2.

Gas exchange, metabolite, and hormone variables measured during isotope tests

Day 1Day 18
RestExerciseRestExercise
o2, l/min0.27±0.061.87±0.280.27±0.031.82±0.28
RER0.89±0.060.93±0.030.85±0.060.90±0.03
Glucose, mM4.8±0.64.4±0.64.6±0.64.3±0.3
Lactate, mM0.4±0.082.1±1.10.4±0.081.5±0.6
FFA, mM0.32±0.110.61±0.260.36±0.250.74±0.20
Leucine, μM78.3±8.785.0±6.277.6±12.676.5±7.3
KIC, μM10.6±3.112.7±5.611.5±2.511.3±4.2
β-OHB, mM0.78±0.570.90±0.601.66±0.60*1.83±1.18*
Insulin, pM105±8251±2574±3537±9*
Cortisol, nM251±104328±154226±52303±33
  • Values are means ± SD. Exercise, last 30 min of a 50-minute exercise bout at 50% Vo2max, RER, respiratory exchange ratio; FFA, free fatty acid; KIC, α-ketolsocaproate; β-OHB, β-hydroxybutyrate.

  • * Significantly different from day 1 at P < 0.05.

  • Significantly different from rest at P < 0.05.