Resistance exercise enhances myofibrillar protein synthesis with graded intakes of whey protein in older men.
Level 2 - randomized trial
Controlled clinical physiology trial with graded dose allocations and within-subject unilateral exercise control
PubMed 22313809 · doi:10.1017/S0007114511007422
What was done
Thirty-seven older men (mean age 71 ± 4 years) completed a single bout of unilateral leg resistance exercise before ingesting 0, 10, 20, or 40 g of whey protein isolate (W0, W10, W20, W40). Using infusions of L-[1-13C]leucine and L-[ring-13C6]phenylalanine with bilateral vastus lateralis muscle biopsies, researchers measured whole-body leucine oxidation and 4-hour post-protein consumption myofibrillar protein synthesis (MPS) in both exercised and non-exercised legs.
What was found
Whole-body leucine oxidation increased in a stepwise, dose-dependent manner. In resting muscle, MPS increased above basal fasting values by approximately 65% for W20 and 90% for W40 (P < 0.05), with no significant increase at lower doses. In exercised muscle, W20 and W40 ingestion increased MPS above W0 and W10 exercised values (P < 0.05), and W40 produced a greater response than W20 (P < 0.05).
Why it matters
This study shows that exercised muscles in older adults require higher doses of protein (up to 40 g of whey) to maximize myofibrillar protein synthesis, contrasting with younger adults whose post-exercise response saturates at 20 g.
Limits
The study was conducted exclusively in non-frail older men, limiting generalizability to older women or frail populations. It measured acute 4-hour fractional synthetic rates after isolated whey ingestion rather than long-term muscle mass gains or responses to whole-food protein sources.
Cited by
- supports Consuming proportionately higher amounts of protein can restore a normal muscle protein synthesis response in older adults.
- supports In younger individuals, 10 grams of protein can stimulate muscle protein synthesis, whereas older adults require closer to 20 to 40 grams per meal.
- supports Performing an exercise session prior to food intake restores the postprandial muscle protein synthesis response in older adults to an almost completely normal level.