The effects of nutrient timing on training adaptations in resistance-trained females

The purpose of this study was to determine the effects of pre- vs. post-workout nutrition on strength, body composition, and metabolism in trained females over 6 weeks of high intensity resistance training (HIRT).

Forty-three trained females (mean±SD; age: 20.5±2.2 yrs; height: 165.2±5.7cm; body mass: 66.5±11.4kg) were measured for strength, body composition, and metabolic variables before and after a HIRT intervention. Participants were randomized using a 2:2:1 matched block randomization scheme by baseline leg press strength into a group that consumed a 1:1.5 carbohydrate-protein supplement (16g CHO/25g PRO) pre-training (PRE), post-training (POST), or no supplement (CON).

Dual-energy X-ray absorptiometry was used to evaluate fat mass (FM), lean mass (LM), and percent fat (%fat). Strength was analyzed using a one repetition max on the leg and bench press (LP1RM and BP1RM, respectively). Participants completed HIRT twice per week for 6 weeks. At the first and last trainings, metabolic variables [resting energy expenditure (REE) and respiratory exchange ratio, RER] were measured.

There were no significant differences between groups for any changes in body composition variables or LP1RM (p=0.170-0.959). There were significant differences for BP1RM (p=0.007), with PRE and POST experiencing greater increases than CON (p=0.010 and 0.015, respectively). REE changes were not significant between groups (p=0.058-0.643). PRE demonstrated greater fat oxidation (RER) at 30min post-exercise (p=0.008-0.035).

Peri-workout nutrition is potentially important for upper body strength and metabolism. PRE may be more effective for promoting fat utilization immediately post-workout.