The acute effect of exercise and nutrition on respiratory exchange ratio in women

Methods Twenty recreationally active women (Mean ± SD; age 24.6 ± 3.9 yrs; height 164.4 ± 6.6 cm; weight 62.7 ± 6.6 kg; %fat 28.2 ± 4.8 %) participated in this randomized crossover, double-blind study. After preliminary body composition and maximal strength testing, each participant completed six exercise sessions, consisting of three exercise modalities: aerobic endurance exercise (AEE; 30 min, 50% heart rate reserve), high-intensity interval running (HIIT; 10 x 1min on: 1min off, 90% HRR), and high-intensity resistance training (HIRT; 6 exercises: 3 sets, 20 sec rest), and two acute nutritional interventions: 25 grams of CHO (maltodextrin) and PRO (whey protein isolate). Salivary samples were collected before each exercise session to determine estrogen. RER was analyzed via indirect calorimetry (Parvomedics TrueOne 2400) at: baseline, immediately post (IP), 30 minutes (30min) post, and 60 minutes (60min) post-exercise. Subjects were seated and connected to the metabolic cart by a tube for 15 minutes at each time point. A mixed level model [modality (AEE vs. HIIT vs. HIRT) × treatment (CHO vs. PRO) × time (base vs. IP vs. 30min vs. 60min)] covaried for estrogen was used to evaluate RER. Consent to publish the results was obtained from all participants. Results Significant two-way interactions existed between modality and time (p<0.0001) and time and treatment (p<0.0001). Significant modality differences existed between HIIT and AEE (p<0.0001), HIIT and HIRT (p<0.0001), and AEE and HIRT (p=0.0024). RER was significantly higher from HIIT than AEE and HIRT IP exercise (p<0.0001), and significantly lower from HIIT 30min and 60min post exercise (p<0.0001-p=0.0020) than AEE. RER was significantly lower 30min (p=0.0169), but not 60min post (p=0.3603) HIIT vs. HIRT. No significant differences existed between HIRT and AEE IP exercise (p=0.3370); RER was significantly lower for HIRT than AEE 30min and 60min post exercise (p=0.0004-0.0265). For time and treatment, RER was not significantly different between CHO and PRO IP exercise (p=0.1150), but was significantly lower for PRO 30min and 60min post (p<0.0001p=0.0012).