Submitted on March 24, 2003
Accepted on August 22, 2003
MAXIMAL LACTATE STEADY STATE DECLINES DURING THE AGING PROCESS
Craig O Mattern1, Margaret J Gutilla1, Darrin L Bright2, Timothy E Kirby1, Kenneth W Hinchcliff3, and Steven T Devor1*
1 Sport and Exercise Science Program, The Ohio State University, Columbus, OH, USA
2 Department of Family Medicine, The Ohio State University, Columbus, OH, USA
3 Department of Veterinary Clinical Sciences, The Ohio State University, Columbus, OH, USA
* To whom correspondence should be addressed. E-mail: devor.3{at}osu.edu.
Increased participation of aged individuals in athletics warrants basic research focused on delineating age-related changes in performance variables. Based on potential age-related declines in aerobic enzyme activities and a shift in the expression of myosin heavy chain (MHC) isoforms, we hypothesized that maximal lactate steady state (MLSS) exercise intensity would be altered as a function of age. Three age groups [young athletes (YA), 25.9 ± 1.0 years, middle-age athletes (MA), 43.2 ± 1.0 years, and older athletes (OA), 64.6 ± 2.7 years] of male, competitive cyclists and triathletes matched for training intensity and duration were studied. Subjects performed a maximal O2 uptake (VO2max) test followed by a series of 30-minute exercise trials to determine MLSS. A muscle biopsy of the vastus lateralis was procured on a separate visit. There were differences (p<0.05) in VO2max among all age groups (YA=67.7 ± 1.2 ml.kg-1.min-1, MA=56.0 ± 2.6
ml.kg-1.min-1, OA=47.0 ± 2.6 ml.kg-1.min-1). When expressed as a percentage of
VO2max, there was also an age-related decrease (p<0.05) in the relative MLSS exercise intensity (YA=80.8 ± 0.9%, MA=76.1 ± 1.4%, OA=69.9 ± 1.5%). There were no significant age-related changes in citrate synthase (CS) activity or MHC isoform profile. The hypothesis is supported as there is an age-related decline in MLSS exercise intensity in athletes matched for training intensity and duration. While type I MHC isoform, combined with age, is helpful in predicting (r = 0.76, p<0.05) relative MLSS intensity, it does not explain the age-related decline in MLSS.
