Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis

Abstract

Quantity and timing of protein ingestion are major factors regulating myofibrillar protein synthesis (MPS). However, the effect of specific ingestion patterns on MPS throughout a 12 h period is unknown. We determined how different distributions of protein feeding during 12 h recovery after resistance exercise affects anabolic responses in skeletal muscle. Twenty-four healthy trained males were assigned to three groups (n = 8/group) and undertook a bout of resistance exercise followed by ingestion of 80 g of whey protein throughout 12 h recovery in one of the following protocols: 8 × 10 g every 1.5 h (PULSE); 4 × 20 g every 3 h (intermediate: INT); or 2 × 40 g every 6 h (BOLUS). Muscle biopsies were obtained at rest and after 1, 4, 6, 7 and 12 h post exercise. Resting and post-exercise MPS (l-[ring-(13)C6] phenylalanine), and muscle mRNA abundance and cell signalling were assessed. All ingestion protocols increased MPS above rest throughout 1-12 h recovery (88-148%, P < 0.02), but INT elicited greater MPS than PULSE and BOLUS (31-48%, P < 0.02). In general signalling showed a BOLUS>INT>PULSE hierarchy in magnitude of phosphorylation. MuRF-1 and SLC38A2 mRNA were differentially expressed with BOLUS. In conclusion, 20 g of whey protein consumed every 3 h was superior to either PULSE or BOLUS feeding patterns for stimulating MPS throughout the day. This study provides novel information on the effect of modulating the distribution of protein intake on anabolic responses in skeletal muscle and has the potential to maximize outcomes of resistance training for attaining peak muscle mass.

Figure 1

Schematic representation of the experimental protocol. Negative time points indicate before exercise, positive time points indicate after exercise. LBM, lean body mass; REX, resistance exercise.

Figure 2

Plasma insulin concentration following a bout of leg extension resistance exercise (4 sets × 10 repetitions at 80% one repetition maximum) and post-exercise ingestion of 80 g whey protein consumed using a BOLUS (2 × 40 g every 6 h), INT (4 × 20 g every 3 h) or PULSE (8 × 10 g every 1.5 h) ingestion protocol during a 12 h recovery period. −0 and +0 h are pre- and post exercise, respectively. Data were analysed using a 2-way ANOVA with Student–Newman–Keuls post hoc analysis. Values are mean ± SD. Different vs.§, all other time points within treatment; a, rest; †, Intermediate and *, Pulse, at equivalent time point (P < 0.05).

Figure 3

Plasma essential amino acids (EAA; A), branched-chain amino acids (BCAA; B), and leucine (C) concentration following a bout of leg extension resistance exercise and post-exercise BOLUS, INT or PULSE ingestion protocol during a 12 h recovery period, as described in Fig. 2. Data were analysed using a 2-way ANOVA with Student–Newman–Keuls post hoc analysis. Values are mean ± SD. Different vs. a, rest; *, Pulse; †, Intermediate; and ‡, Bolus, at equivalent time point (P < 0.05).

Figure 4

Myofibrillar fractional synthetic rate (FSR) between time points (A) and mean FSR throughout 1–12 h (B) following a bout of leg extension resistance exercise and post-exercise BOLUS, INT or PULSE ingestion protocol during a 12 h recovery period, as described in Fig. 2. Data were analysed using a 2-way ANOVA with Student–Newman–Keuls post hoc analysis. Values are mean ± SD expressed as %· h⁻¹. Different vs. a, Rest; b, 1–4 h; ‡, Bolus and *, Pulse at equivalent time point (P < 0.05).

Figure 5

Phosphorylation of Akr^Ser473 (A), TSC2^Thr1462 (B), mTOR^Ser2448 (C), PRAS40^Thr246 (D), following a bout of leg extension resistance exercise and post-exercise BOLUS, INT or PULSE ingestion protocol during a 12 h recovery period, as described in Fig. 2. Data were analysed using a 2-way ANOVA with Student–Newman–Keuls post hoc analysis. Values are mean ± SD expressed as arbitrary units. Different vs.§, all time points within treatment; a, rest; b, 1 h post exercise; c, 4 h post exercise; d, 6 h post exercise; e, 7 h post exercise; f, 12 h post exercise; *, Pulse; †, Intermediate; and ‡, Bolus at equivalent time point (P < 0.05).

Figure 6

Phosphorylation of p70 S6K^Thr389 (A), rpS6^Ser235/236 (B), eEF2^Thr52 (C) and 4E-BP1^Thr37/46 (D) following a bout of leg extension resistance exercise and post-exercise BOLUS, INT or PULSE ingestion protocol during a 12 h recovery period, as described in Fig. 2. Data were analysed using a 2-way ANOVA with Student–Newman–Keuls post hoc analysis. Values are mean ± SD expressed as arbitrary units. Different vs.§, all time points within treatment; a, rest; d, 6 h post exercise; f, 12 h post exercise; *, Pulse; and †, Intermediate; at equivalent time point (P < 0.05).

Figure 7

MuRF-1 (A) and SLC38A2 (B) mRNA expression relative to GAPDH following a bout of leg extension resistance exercise and post-exercise BOLUS, INT or PULSE ingestion protocol during a 12 h recovery period, as described in Fig. 2. Data were analysed using a 2-way ANOVA with Student–Newman–Keuls post hoc analysis. Values are mean ± SD. Different vs.§, all time points within group; ¶, all time points within group and Bolus at equivalent time point (P < 0.05).