Journal Title (Medline/Pubmed accepted abbreviation):Am. J. Clin. Nutr.
Page Numbers :1403-1412
Background: Muscle tissue in older adults exhibits a weaker anabolic response to amino acids and insulin in the blood, leading to sarcopenia, or a reduction in muscle mass and strength. It has been shown that: 1) a supplement with essential amino acids (EAA) and sugar and 2) aerobic exercise can independently stimulate anabolism in muscle.
Hypothesis: Aerobic activity will augment the response of muscle tissue to an EAA+sucrose supplement in older adults.
Subjects: Sedentary adults, age 70 ± 3 y, 3 male and 3 female
Experimental design:randomized, cross-over
Treatments : Aerobic exercise or no exercise the evening before consumption of an EAA+sucrose supplement
Protocol : The participants reported to the laboratory on two evenings, 4-6 weeks apart. On one day, they followed an aerobic exercise routine, and on the other day they did not exercise. Meals around the exercise session were controlled. The next morning, the participants consumed a beverage with 20 g EAA and 35 g sucrose over the course of 3 hours. Using controlled intravenous infusions of isotopically labeled amino acids, the rate of protein synthesis and protein breakdown was monitored. During the evaluation, blood flow, plasma glucose concentration, and plasma insulin concentration were also monitored. Muscle biopsies were acquired to assess protein concentration and concentration of enzymes involved in protein synthesis and breakdown.
The anabolic nature of amino acids was indeed observed
when exercise was performed the evening before consumption of the amino acid beverage. An increase in blood flow and amino acid delivery to muscle cells was key in the mechanism by which exercise enhanced these anabolic effects. Routine aerobic exercise can help older adults build and maintain muscle mass, thereby preventing debilitating age-related muscle loss.