Maximal lactate steady state (MLSS) presumably corresponds to the high
est constant workload that can be performed by oxidative metabolism. T
he anaerobic and, to a minor extent, the oxidative metabolism have bee
n reported to be affected by age. The second decade of life is the key
period in the change in energy metabolism between children and adults
. The aim of this study was to evaluate the effects of age on MLSS in
34 male subjects (age: 15.4 +/- 2.8 yr, range: 11-20 yr; height: 171.8
+/- 14.9 cm, range: 134-191 cm; body mass: 59.6 +/- 15.5 kg, range: 2
7-90 kg) performing an incremental load test to determine maximal work
load and several constant load tests for MLSS measurement on a cycle e
rgometer. MLSS (4.2 +/- 0.7 mmol . l(-1), range: 2.8 to 5.5 mmol . l(-
1)) and MLSS intensity related to maximal workload (66.5 +/- 7.7%, ran
ge: 50-84%) were independent of age. MLSS heart rate (180.1 +/- 10.1 m
in(-1), range: 156-208 min(-1)) decreased (P < 0.01) with increasing a
ge, whereas absolute (157.2 +/- 54.8 W, range: 65-240 W) and relative
MLSS workload (2.6 +/- 0.5 W . kg(-1), range: 1.5 to 4.1 W . kg(-1)) a
nd absolute (236.9 +/- 79.0 W, range: 100-350 W) and relative maximal
workload (3.9 +/- 0.6 W . kg(-1), range: 2.7 to 5.5 W . kg(-1)) increa
sed (P < 0.001) with age. The age independence of MLSS supports the th
eory that neuromuscular factors may contribute to the frequently obser
ved changes in response to given exercises with physical maturity more
than changes in oxidative metabolism and/or glycolysis.