Insulin-Like Growth Factor-1 and Resistance Exercise in Community Dwelling Old Adults.

BACKGROUND: Insulin-like growth factor-1 (IGF-1) is related to the preservation of lean body mass. Its decline during ageing is thought to make old adults more susceptible to sarcopenia and functional dependency. The aim of the present study was to investigate circulating total IGF-1 in old adults who engaged in a 12-weeks of progressive resistance training. DESIGN: Intervention study. SETTING: Community. PARTICIPANTS: Old Icelandic adults (N = 235, 73.7 ± 5.7 years, 58.2% female). INTERVENTION: Twelve-week resistance exercise program (3 times/week; 3 sets, 6-8 repetitions at 75-80% of the 1-repetition maximum) designed to increase strength and muscle mass of major muscle groups. MEASUREMENTS: IGF-1. RESULTS: At baseline IGF-1 was significantly associated with lean body mass and appendicular muscle mass (also when corrected for age, gender and various covariates). After the training IGF-1 decreased significantly from 112.1 ± 35.6 to 106.1 ± 35.2 µg/L during the course of the study. On and individual level, IGF-1 decreased in 59% and increased in 39% of the participants. Changes in IGF-1 were inversely related to changes in lean body mass (rho = -0.176, P = 0.013 ) and appendicular muscle mass (rho = -0.162, P = 0.019) also when corrected for protein intake, age, gender, and other covariates. CONCLUSION: Serum total IGF-1 decreases after 12 weeks of resistance exercise in community dwelling old adults. When looked at IGF-1 changes for participants individually it becomes clear that IGF-1 response to resistances exercise is highly variable. Changes in IGF-1 are negatively related to changes in lean body mass during training, which supports the hypothesis that IGF-1 is redistributed from circulation into tissue during periods of active muscle building.

Effects of whey proteins and carbohydrates on the efficacy of resistance training in elderly people: double blind, randomised controlled trial.

BACKGROUND/OBJECTIVES: A few previous studies indicate that protein supplementation increases gains in muscle mass and strength during a resistance exercise program. The purpose of this study was to investigate whether whey protein supplementation results in greater increases in lean body mass, muscle strength and physical function in elderly individuals during 12 weeks of resistance exercise when compared to isocaloric carbohydrate supplementation. SUBJECTS/METHODS: A total of 161 men and women, 65-91 years old, participated in a randomized, controlled, double-blind intervention study, involving dietary supplementation and a 12-week resistance exercise program, designed to increase muscle mass and strength of all major muscle groups. Participants exercised three times a week and received either 20 g of whey protein (n=83) or isocaloric carbohydrate (n=78) in liquid form immediately after each workout. Data were obtained at baseline and end point. RESULTS: The primary outcomes, lean body mass, strength and physical function increased significantly during the course of the study. Type of dietary supplementation did not influence gains in lean body mass (P=0.365), quadriceps strength (P=0.776) or performance during a 6-min walk (P=0.726) or a timed up-and-go test (P=0.151). Twenty participants discontinued the intervention. CONCLUSIONS: Ingestion of 20 g of whey protein immediately after resistance exercise three times per week, does not lead to greater gains in lean body mass, strength and physical function in elderly people with sufficient energy and protein intakes when compared to isocaloric carbohydrate.