Integrated Myofibrillar Protein Synthesis in Recovery From Unaccustomed and Accustomed Resistance Exercise With and Without Multi-ingredient Supplementation in Overweight Older Men

Abstract

Background: We previously showed that daily consumption of a multi-ingredient nutritional supplement increased lean mass in older men, but did not enhance lean tissue gains during a high-intensity interval training (HIIT) plus resistance exercise training (RET) program. Here, we aimed to determine whether these divergent observations aligned with the myofibrillar protein synthesis (MyoPS) response to acute unaccustomed and accustomed resistance exercise. Methods: A sub-sample of our participants were randomly allocated (n = 15; age: 72 ± 7 years; BMI: 26.9 ± 3.1 kg/m2 [mean ± SD]) to ingest an experimental supplement (SUPP, n = 8: containing whey protein, creatine, vitamin D, and n-3 PUFA) or control beverage (CON, n = 7: 22 g maltodextrin) twice per day for 21 weeks. After 7 weeks of consuming the beverage alone (Phase 1: SUPP/CON only), subjects completed 12 weeks of RET (twice per week) + HIIT (once per week) (Phase 2: SUPP/CON + EX). Orally administered deuterated water was used to measure integrated rates of MyoPS over 48 h following a single session of resistance exercise pre- (unaccustomed) and post-training (accustomed). Results: Following an acute bout of accustomed resistance exercise, 0-24 h MyoPS was 30% higher than rest in the SUPP group (effect size: 0.86); however, in the CON group, 0-24 h MyoPS was 0% higher than rest (effect size: 0.04). Nonetheless, no within or between group changes in MyoPS were statistically significant. When collapsed across group, rates of MyoPS in recovery from acute unaccustomed resistance exercise were positively correlated with training-induced gains in whole body lean mass (r = 0.63, p = 0.01). Conclusion: There were no significant between-group differences in MyoPS pre- or post-training. Integrated rates of MyoPS post-acute exercise in the untrained state were positively correlated with training-induced gains in whole body lean mass. Our finding that supplementation did not alter 0-48 h MyoPS following 12 weeks of training suggests a possible adaptive response to longer-term increased protein intake and warrants further investigation. This study was registered at ClinicalTrials.gov. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT02281331.

Keywords: creatine; deuterated water; fractional synthesis rate; high-intensity interval training; n-3 PUFA; resistance exercise training; vitamin D; whey protein.

Figures

Figure 1

Overall study schematic (A) and acute MyoPS response protocol (B). (A) Participants were randomly assigned to consume a multi-ingredient supplement (SUPP, n = 8) or control (CON, n = 7) beverage twice per day for 21 weeks. Between weeks 8 and 19, inclusive, participants completed a 12 weeks combined RET (twice per week) + HIIT (once per week) exercise training program. Lean tissue mass (DXA) and strength (1RM) were assessed at baseline (week 0), as well as pre- (week 7; Phase 1: SUPP/CON) and post-training (week 20; Phase 2: SUPP/CON + EX). The integrated MyoPS response to acute resistance exercise was assessed during participants' initial RET session (UT, untrained; week 8) and 10 days following their last RET session (TR, trained; week 21). (B) Following a baseline saliva sample, participants consumed 150 mL 70% deuterated water (D2O; Day 0). On Days 2–4, we obtained a fasting muscle sample from the vastus lateralis. Immediately after their muscle biopsy on Day 2, participants completed a session of resistance exercise at 65% 1RM. Saliva samples were collected regularly throughout each acute response period to assess deuterium (2H) enrichment of total body water. Eight weeks prior to the untrained acute response (–8 weeks), we obtained an unenriched, fasted muscle sample for the measurement of resting FSR. SUPP, supplement; CON, control; RET, resistance exercise training; HIIT, high-intensity interval training; DXA, dual-energy x-ray absorptiometry; 1RM, one repetition maximum; MyoPS, myofibrillar protein synthesis; 2H, deuterium; D2O, deuterated water; UT, untrained; TR, trained; FSR, fractional synthesis rate.

Figure 2

Integrated day-to-day (A) and cumulative (B) myofibrillar protein synthesis in response to acute resistance exercise pre- and post-training. Individual day-to-day (i.e., temporal) data are presented on the inset line graph in (A). The SUPP group is presented in black; the CON group is presented in white. SUPP, supplement; CON, control; UT, untrained; TR, trained; FSR, fractional synthetic rate.

Figure 3

Correlation analysis. FSR 0–24 h after unaccustomed acute resistance exercise was positively associated with the change in (A) whole body and (B) leg fat- and bone-free (i.e., lean) mass during 12 weeks of multimodal (RET + HIIT) exercise training (Phase 2). Linear regression lines of best fit are shown in black. Dotted lines indicate 95% confidence intervals. UT, untrained; TR, trained; FSR, fractional synthesis rate; RET, resistance exercise training; HIIT, high-intensity interval training.