The effects of combined creatine monohydrate supplementation and resistance training on body composition, muscle strength, and markers of satellite cell activity in older males.

摘要

Aging is associated with gradual loss of muscle mass, termed sarcopenia, which often leads to progressive disability and loss of independence. Though resistance exercise has shown to be an effective method at reducing the rate of age-related muscle loss and decline in force output; when combined with well known muscle building agents [such as creatine monohydrate (CrM)], these training-induced improvements are enhanced. To explore this idea further, a double-blind, randomized, controlled trial was conducted on 20 males aged between 55-75 yrs at Baylor University, Waco TX. Particpants were randomly assigned to consume either CrM [20g/d CrM + 5g Carbohydrate (CHO) x 7 days, then 5g/d CrM +5g CHO x 77 days] or carbohydrate placebo (20g/d CHO x 7 days, then 5g/d CHO x 77 days) while participating in a high intensity resistance training program (3 sets x 10 repetitions at 75% of 1RM), 3 days per week for 12 weeks. Testing sessions were complete prior to, 4 weeks, 8 weeks and 12 weeks post resistance training and supplementation. Each testing session included body composition measurement as determined by Dual Energy X-Ray Absorptiometry (DEXA), muscle strength measurement as determined by 1 repetition maximum (RM) on leg press and bench press, blood collection and vastus lateralis muscle biopsy. The blood serum was analyzed for insulin-like growth factor 1 (IGF-1), free testosterone and hepatocyte growth factor (HGF) and the muscle tissue for phophorylated mesenchymal-epithelial transition factor (c-Met), myogenic regulatory factors (MyoD, myogenin, Myf-5, MRF-4), and total myofibrillar protein. A significant time effect was observed for 1RM bench press (p=0.016), leg press (p0.05), body mass (p=0.030) and fat free mass (p=0.005), HGF (p0.001), phosphorylated c-Met concentration (p=0.008), myogenic regulatory factors Myf-5 (p0.001) and myogenin (p0.001), and total myofibrillar protein (p=0.005). A significant group (p=0.040) and group by time interaction (p=0.023) was revealed for MRF-4, suggesting CrM supplementation significantly increased MRF-4 following 12 weeks of resistance training. Notwithstanding, results from the current study suggest that CrM supplementation, when combined with 12-weeks of high intensity resistance training does not enhance body composition, muscle strength, and biochemical mechanisms regulating skeletal muscle hypertrophy compared to resistance training alone.