Dependence of the maximal lactate steady state on the motor pattern of exercise.

BACKGROUND

Blood lactate concentration (BLC) can be used to monitor relative exercise intensity. The highest BLC representing an equilibrium between lactate production and elimination is termed maximal lactate steady state (MLSS). MLSS is used to discriminate qualitatively between continuous exercise, which is limited by stored energy, from other types of exercise terminated because of disturbance of cellular homoeostasis.

AIM

To investigate the hypothesis that MLSS intraindividually depends on the mode of exercise.

METHODS

Six junior male rowers (16.5 (1.4) years, 181.7 (3.1) cm, 69.8 (3.3) kg) performed incremental and constant load tests on rowing and cycle ergometers. Measurements included BLC, sampled from the hyperaemic ear flap, heart rate, and oxygen uptake. MLSS was defined as the highest BLC that increased by no more than 1.0 mmol/l during the final 20 minutes of constant workload.

RESULTS

In all subjects, MLSS was lower (p < or = 0.05) during rowing (2.7 (0.6) mmol/l) than during cycling (4.5 (1.0) mmol/l). No differences between rowing and cycling were found with respect to MLSS heart rate (169.2 (9.3) v 172.3 (6.7) beats/min), MLSS workload (178.7 (29.8) v 205.0 (20.7) W), MLSS intensity expressed as a percentage (63.3 (6.6)% v 68.6 (3.8)%) of peak workload (280.8 (15.9) v 299.2 (28.4) W) or percentage (76.4 (3.4)% v 75.1 (3.0)%) of peak oxygen uptake (60.4 (3.4) v 57.2 (8.6) ml/kg/min).

CONCLUSIONS

In rowing and cycling, the MLSS but not MLSS workload and MLSS intensity intraindividually depends on the motor pattern of exercise. MLSS seems to decrease with increasing mass of the primarily engaged muscle. This indicates that task specific levels of MLSS occur at distinct levels of power output per unit of primarily engaged muscle mass.