title: Maximal lactate steady state declines during the aging process.
abstract: Increased participation of aged individuals in athletics warrants basic research focused on delineating age-related changes in performance variables. On the basis of 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 yr, middle-age athletes (MA), 43.2 +/- 1.0 yr, and older athletes (OA), 64.6 +/- 2.7 yr] of male, competitive cyclists and triathletes matched for training intensity and duration were studied. Subjects performed a maximal O2 consumption (V(o2 max)) test followed by a series of 30-min 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 V(o2 max) among all age groups (YA = 67.7 +/- 1.2 ml x kg-1x min-1, MA = 56.0 +/- 2.6 ml x kg-1x min-1, OA = 47.0 +/- 2.6 ml x kg-1 x min-1). When expressed as a percentage of V(o2 max), 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 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. Although 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.
authors.affiliation: Sport and Exercise Science Program, The Ohio State University, Columbus, OH 43210-1284, USA.
authors.forename: Craig O
authors.initials: CO
authors.lastname: Mattern
authors.forename: Margaret J
authors.initials: MJ
authors.lastname: Gutilla
authors.forename: Darrin L
authors.initials: DL
authors.lastname: Bright
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Kirby
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Hinchcliff
authors.forename: Steven T
authors.initials: ST
authors.lastname: Devor
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism*; D015308:Anaerobic Threshold / Q000502:physiology; D001823:Body Composition / Q000502:physiology; D002950:Citrate (si)-Synthase / Q000378:metabolism; D003430:Cross-Sectional Studies; D004032:Diet; D005260:Female; D006801:Humans; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000378:metabolism; D009929:Organ Size / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology; D013177:Sports
chemical_list: D019344:Lactic Acid; D002950:Citrate (si)-Synthase; D018995:Myosin Heavy Chains