Comparison of Critical Speed and D' Derived From 2 or 3 Maximal Tests

Purpose: The hyperbolic distance-time relationship can be used to profile running performance and establish critical speed (CS) and D'. Typically, to establish these parameters multiple (3+) performance trials are required, which can be highly fatiguing and limit the usability of such protocols in a single training session. This study aimed to compare CS and D' calculated from a two-trial (2-point model) and a three-trial (3-point model) method.
Methods: 14 male distance runners completed three fixed-distance (3600, 2400, 1200 m) time trials on a 400 m outdoor running track, separated by a 30-minute recovery. Participants completed the protocol nine times across a twelve-month period, with approximately 42-days between each test. CS and D' were calculated using all three distances (3-point model) and also using the 3600 and 1200 m distances only (2-point model).
Results: Mean (±SD) CS for both 3-point and 2-point models was 4.94 ± 0.32 m.s, whilst D' was 123.3 ± 57.70 m and 127.4 ± 57.34 m for 3-point and 2-point models, respectively. Overall bias for both CS and D' between 3-point and 2-point model was classed as trivial.
Conclusions: A 2-point time-trial model can be used to calculate CS and D' as proficiently as a 3-point model, making it a less fatiguing, inexpensive and applicable method for coaches, practitioners and athletes to monitor running performance in one training session.