EFFECTS OF HIGH-INTENSITY INTERVAL TRAINING ON MUSCLE SIZE, STRENGTH AND PROTEIN EXPRESSION IN OLDER ADULTS

Introduction: Aging is marked by a loss of type 2 muscle fibers, which are essential for strength and anaerobic performance, and can hinder daily activities and increase the risk of injury. Vigorous exercise (i.e., high-intensity interval training [HIIT]) can help maintain muscle mass, strength, and independence in older adults; however, the underlying molecular mechanisms that explain this preservation are poorly understood. Purpose: To examine changes in SERCA 1 expression, vastus lateralis cross-sectional area (VLCSA), and lower body strength following 12 weeks of HIIT in older adults. METHODS: Seven untrained older adults (76 ± 7 yr; n = 4 females) completed the total body HIIT protocol (a circuit of 9 functional exercises followed by bike intervals) 3 x week (45 min/session) for 12 weeks, with progressive increases in the work:rest ratios: 20s:40s (weeks 1-4); 30s:30s (weeks 5-8); and 40s:20s (weeks 9-12). Panoramic ultrasound images of the right VL were collected at baseline (PRE) and following training (POST) to estimate VLCSA, and microbiopsies from the VL were obtained to examine changes in SERCA 1 using Western Blots. Muscular strength for each participant was assessed by estimating their one-repetition maximum (e1RM) using a belt squat. Starting weights were determined using a percentage of the participants body weight (males = 120%, females = 100%) and were gradually increased until they were unable to perform >3-5 reps. Differences (p < 0.05) between PRE and POST for each variable were identified using paired t-tests, and Hedges g was used to determine effect sizes. RESULTS: There was a significant increase in SERCA 1 expression from PRE to POST (p = 0.049), as well as significant improvements in VLCSA (11.32 + 1.10 cm2 vs.12.54 + 1.50 cm2, p = 0.03, g = -0.95), and e1RM (101.1 + 12.7 kg vs. 154.7 + 12.7 kg, p = 0.02, g = -1.04). CONCLUSION: These findings suggest that 12-wk of HIIT increased muscle size and strength in older adults which may be explained, in part, by an improvement in intramuscular calcium handling. Supported by: Health Sciences Strategic Investment Fund, The Dr. George F. Haddix Presidential Faculty Research Fund