Effects of successive periods of detraining and retraining in males with whey protein or carbohydrate supplementation on body composition, muscle performance, and mTOR and ERK 1/2 intracellular signaling responses to resistance exercise.

Resistance exercise and nutritional strategies involving carbohydrate (CHO) and whey protein (WP) can stimulate muscle protein synthesis (MPS) via the mammalian target of rapamycin (mTOR) pathway. Currently, it’s unknown if short-term detraining (DT) can restore blunted anabolic responses to induce robust effects during a subsequent retraining period. Twenty resistance-trained males were randomized to consume 25 grams/day of WP or CHO. Both groups followed a 4-week weight-training program, detrained 2 weeks, and retrained for 4 weeks. Body composition, muscular strength and endurance, and MPS markers were measured throughout the study. Leg press strength (LPS) increased (p < .05), and both groups retained lean mass and LPS following DT. Greater group and time differences for PRO were observed for total protein content. Phosphorylation levels of MPS markers exhibited significant group by time interactions,with higher levels in the CHO group. It’s concluded that resistance-trained males can retain muscle following 2 weeks of DT.