Maximal lactate steady state in trained adolescent runners

Area of Science:

• Exercise Physiology
• Sports Science
• Biochemistry

Background:

• The maximal lactate steady state (MLSS) is a key indicator of endurance capacity.
• Understanding MLSS in adolescent athletes is crucial for training prescription.
• Fixed blood lactate concentrations are often used as proxies for MLSS, but their validity in adolescents requires investigation.

Purpose of the Study:

• To determine the exercise intensity corresponding to MLSS in adolescent endurance-trained runners.
• To investigate potential sex differences in MLSS.
• To compare MLSS with commonly used fixed blood lactate reference points (2.0, 2.5, and 4.0 mmol/L).

Main Methods:

• Participants: 16 boys and 9 girls (endurance-trained adolescents).
• Protocols: Incremental treadmill test for peak oxygen uptake (VO2) and lactate profiling; four 20-min constant-speed runs to determine MLSS.
• Analysis: MLSS defined as the highest speed with <0.5 mmol/L lactate change between 10-20 min; comparison with fixed lactate concentrations via linear interpolation.

Main Results:

• Boys ran faster (15.7 km/h) than girls (14.3 km/h) at MLSS (P<0.01).
• When normalized to peak VO2 (85% for both sexes) and peak heart rate (92% boys, 94% girls), no significant sex differences were found.
• MLSS intensity (speed and %peak VO2) was similar to 2.0 and 2.5 mmol/L lactate, but lower than 4.0 mmol/L.

Conclusions:

• Adolescent endurance-trained runners achieve MLSS at a relative exercise intensity comparable to adult athletes.
• A fixed blood lactate concentration of 2.5 mmol/L during an incremental test serves as a reliable approximation for MLSS in both adolescent boys and girls.
• The findings support the use of 2.5 mmol/L as a practical reference for prescribing training intensity in young endurance athletes.