Energetically optimal stride frequency is maintained with fatigue in trained ultramarathon runners

Area of Science:

• Exercise Physiology
• Biomechanics
• Human Performance

Background:

• Humans naturally select an optimal stride frequency to minimize metabolic cost during running.
• Previous research indicates self-optimization of stride frequency persists during fatiguing tasks up to 1 hour.
• The capacity for self-optimization after prolonged endurance events remains less understood.

Purpose of the Study:

• To investigate whether runners can maintain optimal stride frequency selection after a 6-hour ultramarathon.
• To determine if prolonged running impacts the ability to self-optimize gait for metabolic efficiency.

Main Methods:

• A controlled pre-post study design was employed.
• Temporal stride kinematics and metabolic data were collected from male runners before and after a 6-hour running bout.
• A control group of ultramarathon runners engaged in normal daily activities for 6 hours.

Main Results:

• No significant differences were observed in preferred and optimal stride frequencies between pre- and post-ultramarathon conditions.
• The relationship between metabolic cost and stride frequency remained consistent.
• The energetically optimal stride frequency did not substantially change after 6 hours of running.

Conclusions:

• Runners demonstrated similar stride frequency adjustment dynamics post-ultramarathon as in a non-fatigued state.
• This suggests that the capacity for self-optimization of gait for energetic efficiency is preserved after prolonged endurance running.
• The findings indicate runners can automatically adjust their gait to converge on the energetically optimal pattern even after extreme fatigue.