Impact of dairy protein during limb immobilization and recovery on muscle size and protein synthesis; a randomized controlled trial.
Study Goal
The researchers aimed to determine whether 20 g of daily dairy protein supplementation could attenuate muscle loss during immobilization or enhance recovery during ambulatory movement and resistance training in middle-aged men.
Results Summary
Dairy protein supplementation did not prevent muscle size or function loss during immobilization or improve recovery, but it increased myofibrillar protein synthesis during ambulatory recovery without affecting phenotypic recovery.
Population
Thirty middle-aged men (49.9 ± 0.6 years)
Effective Dosage
20 g daily
Duration
14 days of immobilization, 14 days of ambulatory recovery, and 14 days of resistance training (6 sessions)
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
14 days of unilateral leg immobilization | decrease | isometric knee extension strength | thirty men (49.9 ± 0.6 yr) | -24.7 ± 2.7% | reduced | #1 |
14 days of ambulatory recovery | increase | isometric knee extension strength | thirty men (49.9 ± 0.6 yr) | -8.6 ± 2.6% | partially recovered | #2 |
six resistance training sessions over 14 days | increase | isometric knee extension strength | thirty men (49.9 ± 0.6 yr) | -0.6 ± 3.4% | fully recovered | #3 |
20 g of dairy protein supplementation | no change | isometric knee extension strength | thirty men (49.9 ± 0.6 yr) | - | no effect | #4 |
14 days of unilateral leg immobilization | decrease | thigh muscle cross-sectional area | thirty men (49.9 ± 0.6 yr) | -4.1 ± 0.5% | decreased | #5 |
14 days of ambulatory recovery | increase | thigh muscle cross-sectional area | thirty men (49.9 ± 0.6 yr) | -2.1 ± 0.5% | partially recovered | #6 |
six resistance training sessions over 14 days | increase | thigh muscle cross-sectional area | thirty men (49.9 ± 0.6 yr) | +2.2 ± 0.5% | increased above baseline | #7 |
20 g of dairy protein supplementation | no change | thigh muscle cross-sectional area | thirty men (49.9 ± 0.6 yr) | - | no treatment effect | #8 |
14 days of unilateral leg immobilization | no change | myofibrillar muscle protein synthesis | thirty men (49.9 ± 0.6 yr) | - | unaltered | #9 |
20 g of dairy protein supplementation | no change | myofibrillar muscle protein synthesis during immobilization | thirty men (49.9 ± 0.6 yr) | - | no effect | #10 |
20 g of dairy protein supplementation | increase | myofibrillar muscle protein synthesis | thirty men (49.9 ± 0.6 yr) during ambulatory recovery | - | increased | #11 |
20 g of daily protein supplementation | no change | loss of muscle size and function induced by 2 wk of muscle disuse | middle-age men | - | does not attenuate | #12 |
20 g of daily protein supplementation | no change | recovery | middle-age men | - | does not potentiate | #13 |
immobilization | decrease | average mitochondrial muscle protein synthesis | thirty men (49.9 ± 0.6 yr) | - | attenuated | #14 |
20 g of dairy protein supplementation | no change | average mitochondrial muscle protein synthesis during immobilization | thirty men (49.9 ± 0.6 yr) | - | no effect | #15 |
20 g of dairy protein supplementation | increase | myofibrillar protein synthesis | thirty men (49.9 ± 0.6 yr) during a 2-wk period of ambulatory recovery following disuse | - | increased | #16 |
20 g of dairy protein supplementation | no change | phenotype recovery | thirty men (49.9 ± 0.6 yr) | - | without group differences | #17 |
Muscle disuse results in the loss of muscular strength and size, due to an imbalance between protein synthesis (MPS) and breakdown (MPB). Protein ingestion stimulates MPS, although it is not established if protein is able to attenuate muscle loss with immobilization (IM) or influence the recovery consisting of ambulatory movement followed by resistance training (RT). Thirty men (49.9 ± 0.6 yr) underwent 14 days of unilateral leg IM, 14 days of ambulatory recovery (AR), and a further six RT sessions over 14 days. Participants were randomized to consume an additional 20 g of dairy protein or placebo with a meal during the intervention. Isometric knee extension strength was reduced following IM (-24.7 ± 2.7%), partially recovered with AR (-8.6 ± 2.6%), and fully recovered after RT (-0.6 ± 3.4%), with no effect of supplementation. Thigh muscle cross-sectional area decreased with IM (-4.1 ± 0.5%), partially recovered with AR (-2.1 ± 0.5%), and increased above baseline with RT (+2.2 ± 0.5%), with no treatment effect. Myofibrillar MPS, measured using deuterated water, was unaltered by IM, with no effect of protein. During AR, MPS was increased only with protein supplementation. Protein supplementation did not attenuate the loss of muscle size and function with disuse or potentiate recovery but enhanced myofibrillar MPS during AR. NEW & NOTEWORTHY Twenty grams of daily protein supplementation does not attenuate the loss of muscle size and function induced by 2 wk of muscle disuse or potentiate recovery in middle-age men. Average mitochondrial but not myofibrillar muscle protein synthesis was attenuated during immobilization with no effect of supplementation. Protein supplementation increased myofibrillar protein synthesis during a 2-wk period of ambulatory recovery following disuse but without group differences in phenotype recovery.