Using the 3-Minute All-Out Test to Explore the Durability of the Speed-Duration Relationship in Endurance Running

Critical power and critical speed (CS) are key markers in exercise physiology for distinguishing between heavy- and severe-intensity domains and are useful for training prescription and performance prediction. Durability, defined as the rate and extent of physiological decline during prolonged exercise, has become a focus in endurance sports. This study aimed to investigate whether an hour of heavy-intensity running induces a decline in CS and other performance parameters using GPS-based assessments.

Seven trained runners completed a set of 3-minute all-out tests to measure CS and its reliability. On a subsequent visit, they ran for 1 hour at 85% of their CS while wearing a portable GPS device. After the run, they performed another 3-minute all-out test to assess CS under fatigue.

The average speed during the fatiguing run was 3.6 (0.4) m·s-1, representing 78% of CS and 86% of maximal heart rate. CS and D' significantly declined by 6% (4%) and 68% (26%), respectively (P = .0039 and P = .0033). Total running distance, maximal speed, and time to reach maximal speed were also significantly reduced.

These findings demonstrate that 1 hour of heavy-intensity running impairs CS and other performance metrics in amateur runners, highlighting the importance of developing durability in endurance exercise.