Maximal but not submaximal performance is reduced by constant-speed 10-km run

Area of Science:

• Exercise Physiology
• Biomechanics
• Sports Science

Background:

• Understanding the physiological and biomechanical adaptations to endurance exercise is crucial for optimizing training and performance.
• Investigating how running economy, mechanics, and force production interact during fatiguing exercise provides insights into fatigue mechanisms.

Purpose of the Study:

• To examine the effects of endurance exercise on running economy, mechanics, and force generating capacity.
• To identify adaptive mechanisms during a fatiguing run by recording metabolic, kinetic, and kinematic variables.
• To assess maximal force and power production before and after endurance exercise.

Main Methods:

• Seven untrained men completed a 10 km run at a self-selected pace.
• Measurements included 3D ground reaction forces, electromyography (EMG) of leg muscles, gas exchange, heart rate, and kinematics.
• Maximal voluntary contraction (MVC) and double twitch (DT) tests were performed pre- and post-run.

Main Results:

• A significant reduction in maximal running speed, MVC, and passive DT was observed post-run.
• Despite fatigue, subjects maintained relatively constant oxygen consumption and running kinematics during the submaximal run.
• The most substantial changes in EMG activity and kinetics occurred within the first 2 km of the run.

Conclusions:

• Submaximal running speed, economy, kinetics, and kinematics are largely maintained after initial adjustments during prolonged exercise.
• Fatigue-induced impairments in contractile force generating capacity are evident in maximal performance tests.
• These findings highlight the body's ability to sustain submaximal effort while revealing limitations in maximal force production under fatigue.