Effects of resistance training and dietary protein intake on protein metabolism in older adults. Campbell, Wayne W., Marilyn C. Crim, Vernon R. Young, Lyndon J. Joseph, and William J. Evans. Human Physiology Laboratory, USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111; the Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, MA 02142; and the Noll Physiological Research Center, The Pennsylvania State University, University Park, PA 16802.
APStracts 2:0003E, 1995.
Nitrogen (N) balance, fed-state leucine kinetics and urinary 3-methylhistidine (3-MeH) excretion were examined in 12 men and women, aged 56-80 y, before and during 12 wk of resistance training (RT). Subjects were randomized to groups that consumed diets providing either 0.80+/-0.02 g protein.kg-1.d-1 (lower protein, LP) or 1.62+/-0.02 g protein.kg-1.d-1 (higher protein, HP). At baseline, mean N balance was negative for LP (-4.6+/-3.4 mg N.kg-1.d-1) and positive for HP (13.6+/-1.0 mg N.kg-1.d-1). Nitrogen retention increased similarly in LP and HP at the 11th wk of RT by 12.8 and 12.7 mg N.kg-1.d-1, respectively. Thus, LP had an increased efficiency of N retention. LP had decreased leucine flux (P<0.001), oxidation, (P<0.001) and uptake for protein synthesis, (P<0.02), relative to HP, both at baseline and after RT. Leucine flux increased with RT in both diet groups (P<0.05), and was associated mainly with an increase in protein synthesis in LP (91 % of the change in flux), and an increase in oxidation in HP (72 % of the change in flux) (RT -by-diet interaction, P<0.05). RT increased actomyosin protein breakdown (increased 3-MeH/creatinine ratio, P<0.01). Diet-related differences in protein metabolism did not influence body composition changes with RT. These data show that the efficency of N retention and protein utilization during RT is higher in older people who consume 0.8 versus 1.6 g protein.kg-1.d-1 dietary protein. 

Received 13 September 1994; accepted in final form 13 January 1995.
APS Manuscript Number E377-4.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 February 1995.