Pre-sleep Or Post-exercise Protein Intake Does Not Augment Resistance Training Adaptations In Older Adults

Abstract

Resistance training (RT) and protein consumption are recommended to attenuate decreases in muscle mass and strength with age. Immediate post-exercise (Post-ex) protein intake has been regarded as optimal for augmenting RT adaptations. However, nocturnal sleep is the longest post-absorptive period with muscle protein synthesis lower than basal rates. Thus, pre-sleep (Pre-sleep) protein intake may be more advantageous for older adults, who display blunted muscle anabolism, than Post-ex protein intake. PURPOSE: To examine the effects of pre-sleep versus post-exercise protein intake during 12 weeks of RT on muscle thickness (MT) and one-repetition maximum (1RM) strength in older adults. METHODS: 30 healthy, sedentary older males (age: 65.7±4.0 yrs, body mass: 85.9±13.1 kg) underwent the same 12-week whole-body RT program (2x/wk) and were randomly assigned to 1 of 3 groups, 1) consumed 40 g of protein immediately Post-ex (n=9), 2) consumed 40 g of protein 30 minutes Pre-sleep (n=11), or 3) did not consume additional protein supplementation (Ex only, n=10). MT was measured via ultrasound as the added values of the right rectus femoris, vastus intermedius, and vastus lateralis muscles. 1RM strength was assessed on the leg press machine. A 3x3 mixed-model ANOVA was used to analyze outcomes at pre-, mid-, and post-testing with significance at p≤0.05. RESULTS: There were significant main time effects for both MT (Pre: 6.29±0.98; Mid: 6.63±0.86; Post: 6.75±0.94 cm) and 1RM strength (Pre: 155.9±30.0; Mid: 170.1±36.0; Post: 184.2±47.1 kg). There were no group x time interactions or main group effects. Interestingly, only Post-ex significantly increased MT from pre to mid (Pre: 6.14±0.91; Mid: 6.67±0.88; Post 6.70±1.16 cm). CONCLUSION: During 12 weeks of RT in older adults, Post-ex protein intake increased MT in the first 6 weeks; however, after 12 weeks, improvements were similar to Pre-sleep protein intake and Ex only groups. Further, neither Post-ex nor Pre-sleep protein intake augmented RT-induced improvements in 1RM strength. Supported in part by Dymatize/ISSN Research Grant and Florida State University College of Human Sciences.