What question did this study set out to answer?

This study aims to understand how different forms of exercise affect muscle protein synthesis in older men.

February 2, 2015The Journals of Gerontology Series A119 citationsOpen Access

Day-to-Day Changes in Muscle Protein Synthesis in Recovery From Resistance, Aerobic, and High-Intensity Interval Exercise in Older Men

KBKirsten E. Bell CSChristopher Séguin GPGianni Parise

Key Points

This study aims to understand how different forms of exercise affect muscle protein synthesis in older men.
22 sedentary men aged 67±4 years completed resistance exercise, aerobic exercise, or HIIT in a randomized design.
Participants used a stable isotope tracer (D2O) for 9 days, measuring tracer incorporation in saliva and muscle biopsies.
Muscle biopsies were taken on Days 5-8 to assess responses at rest and after exercise bouts.
Myofibrillar protein fractional synthetic rate was significantly elevated at 24 and 48 hours after resistance exercise and HIIT.
The increase in myofibrillar synthetic rate was greater in resistance exercise compared to HIIT at both 24 and 48 hours.
HIIT uniquely increased sarcoplasmic protein fractional synthetic rate 24 hours postexercise (2.30±0.34% d(-) (1) vs 1.83±0.21% d(-) (1)).

Abstract

BACKGROUND: Resistance exercise (RE) and aerobic exercise are recommended for older adults for fitness and strength. High-intensity interval exercise (HIIT) is an understudied but potent potential alternative to aerobic exercise. This study aimed to determine how each mode of exercise affected the integrated day-to-day response of muscle protein synthesis. METHODS: Sedentary men (n = 22; 67±4 years; body mass index: 27.0±2.6 kg m(-) (2) mean ± SEM) were randomly assigned to perform RE, aerobic exercise, or HIIT. Participants consumed a stable isotope tracer (D2O) for 9 days. Daily saliva samples were taken to measure tracer incorporation in body water. Muscle biopsies were obtained on Days 5-8 of D2O consumption to measure tracer incorporation into muscle at rest, 24 hours, and 48 hours following each exercise bout: RE (3 × 10 repetitions: leg extensor and press, 95% 10RM), HIIT (10 × 1 minute, 95% maximal heart rate HRmax), or aerobic exercise (30 minutes, 55%-60% HRmax). RESULTS: Myofibrillar protein fractional synthetic rate was elevated, relative to rest, at 24 and 48 hours following RE and HIIT. The increase in myofibrillar fractional synthetic rate was greater following RE versus HIIT at both time points. HIIT was the only mode of exercise to increase sarcoplasmic protein fractional synthetic rate 24-hour postexercise (2.30±0.34% d(-) (1) vs 1.83±0.21% d(-) (1)). CONCLUSIONS: This study shows that in older men, changes in muscle protein synthesis in response to certain exercises are long lasting and that HIIT significantly increases myofibrillar and sarcoplasmic fractional synthetic rate in this population.

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