Optimizing Anabolic Response In Older Adults: The Role Of Muscle Capillarization In Different Exercise Modalities

The aging process leads to a decline in muscle mass and functionality, accompanied by morphological and structural changes in muscle fibers. Resistance training plays a primary role inducing muscle accrual and counteracting sarcopenia, however recent evidence suggests that muscle fiber capillarization has also a key role in the maintenance of muscle size and functionality in older adults. PURPOSE: To determine whether a period of aerobic training prior to resistance training can effectively enhance muscle mass in older adults by stimulating angiogenesis. METHODS: To date, 19 healthy older adults (70.6 ± 4.5 years) were randomized to either a progressive resistance training group (RR, n = 10) or a combined resistance and aerobic training group (AR, n = 9). RR protocol consisted of 3 lower limb and 3 upper body exercises (3 and 2 sets). AR protocol included 40 minutes of cycling at 60%VO2max and 3 upper body exercises. Both protocols were performed 3 times a week for 8 weeks. Isometric muscle strength, assessed through maximal voluntary contraction, and body composition, measured using DXA, were evaluated before and after the training period. Additionally, muscle biopsies of vastus lateralis were taken to analyze fiber cross-sectional area (CSA), fiber distribution, and capillary density. RESULTS: Statistical analysis revealed that muscle strength significantly increased in RR (p = 0.03 p < 0.001, +21%), while AR tends towards statistical significance (p = 0.05, +11%). Total body lean soft tissue did not change significantly, while a time x group interaction was observed in leg lean soft tissue (p = 0.02), with significant changes in RR (p = 0.004, +3%). No significant group effect was found for CSA type I (RR +27.1% AR +16.8%), type II (RR +24.3% AR +13.4%), or capillary density. CONCLUSIONS: These findings suggest that resistance training alone significantly enhances muscle strength and leg lean soft tissue in older adults, whereas combining aerobic and resistance training shows only a trend toward improving muscle strength. Neither training protocol leads to significant changes in total body lean soft tissue, muscle CSA, or capillary density. These preliminary data underscore the importance of resistance training in improving muscle strength and specific body composition parameters in older adults.