Can energetic expenditure be minimized by performing activity intermittently?

Area of Science:

• Exercise Physiology
• Animal Energetics
• Behavioral Ecology

Background:

• Animals often exhibit intermittent locomotion, alternating brief activity bouts with rest periods.
• Previous studies indicate short-duration activities have a higher energetic cost per distance than long-duration ones.

Purpose of the Study:

• To test the hypothesis that intermittent, multi-bout activity is energetically cheaper per unit distance than single, short bouts.
• To quantify the energetic cost of intermittent versus continuous locomotion in mice.

Main Methods:

• Mice performed intermittent sprints (15s) at maximal speed with varying frequencies (1-13 bouts) within a fixed time (375s).
• Excess post-exercise oxygen consumption (EPOC) and excess exercise oxygen consumption (EEOC) were measured using respirometry.
• Lactate concentrations were analyzed at rest, post-exercise, and post-recovery.

Main Results:

• EPOC constituted over 80% of the total metabolic cost during intermittent activity and was independent of activity frequency.
• The net cost of activity (C(act)) per unit distance significantly decreased with increased activity frequency.
• The energetic cost per distance for intermittent activity matched that of continuous activity.

Conclusions:

• Animals can minimize energetic expenditure by adopting intermittent movement patterns with higher activity frequencies.
• Increasing the duration of continuous behaviors also minimizes energetic costs, suggesting similar efficiency to frequent, brief movements.