Introduction: The recovery of muscle size and function following musculoskeletal unloading has received little attention in the scientific literature. Nutritional factors such as total energy, protein intake, and the pre- and/or post-exercise consumption of amino acid-carbohydrate (AACHO) have been shown to be important for enhancing training adaptations in recreational exercisers.
Purpose: A preliminary study was conducted to explore the interaction between nutrition and resistance exercise during reconditioning from unloading.
Methods: Muscle CSA, strength, and endurance were measured during a control period following 30 d of unilateral lower limb suspension (Post-ULLS) and after 18 d of reconditioning (ReCon). Six participants consumed either AACHO (979 kJ, 36 g carbohydrate, 22.5 g protein) or placebo (PLAC) prior to resistance exercise (3 d x wk(-1)) during reconditioning. Total daily energy and macronutrient intake were evaluated from dietary journals.
Results: From Post-ULLS to ReCon, muscle endurance increased 1.1 +/- 0.6 min in AACHO and decreased 1.3 +/- 0.7 min in PLAC. Muscle CSA (6 +/- 2 vs. 5 +/- 3 cm2) and strength (105 +/- 53 vs. 81 +/- 37 N) increased similarly in AACHO and PLAC, respectively. When groups were pooled there was a significant correlation between daily protein intake and the recovery of muscle CSA (r = 0.81).
Discussion: Although our findings are preliminary, timing AACHO intake during reconditioning was beneficial for muscular endurance, while overall protein intake was associated with increased muscle size. A systematic evaluation into the synergistic relationship between nutrition and exercise during muscular recovery from prolonged unloading is warranted.