Stimulus Level during Endurance Training: Effects on Lactate Kinetics in Untrained Men

Area of Science:

• Exercise Physiology
• Sports Science
• Endurance Training

Background:

• High-Intensity Interval Training (HIIT) is gaining popularity in endurance sports due to its time efficiency.
• Untrained individuals are increasingly adopting HIIT for fitness benefits.

Purpose of the Study:

• To compare the effects of 16-week HIIT versus Moderate Intensity Continuous Exercise (MICE) running programs on lactate kinetics in untrained males.
• To determine how these training modalities influence the time to reach the individual anaerobic threshold (IANS) and time to exhaustion (TTE).

Main Methods:

• 65 untrained males (30-50 years) were randomized into HIIT or MICE groups.
• HIIT involved intervals at or above the individual anaerobic threshold (IANS), while MICE used continuous running at 70-82.5% of IANS-HR.
• Total workload was matched between groups, with performance assessed via stepwise treadmill tests.

Main Results:

• Both HIIT and MICE significantly increased the time to reach IANS, with HIIT showing a faster improvement.
• HIIT significantly prolonged the time from IANS to "time to exhaustion" (TTE), whereas MICE showed a significant reduction in this period.
• Both groups demonstrated similar significant increases in overall TTE, indicating comparable improvements in maximal exercise duration.

Conclusions:

• HIIT and MICE similarly enhance running performance in untrained males when total workload is equated, but through distinct physiological mechanisms.
• HIIT is a time-efficient alternative or supplement to MICE for improving both aerobic and anaerobic performance.
• This study did not confirm HIIT's superiority over MICE for the "time to exhaustion" parameter, contrary to some previous research.