Field-based Determination of Critical Power and Critical Speed Among Recreational Runners

Background Critical power (CP) is a highly regarded threshold, delineating the boundary between heavy and severe intensities of exercise. Determination of CP has long been hindered by testing protocols that are time consuming and require maximal effort. The aim was to investigate the relationship and reliability of field-based methods of determining CP/critical speed (CS) among recreational runners. Method 23 participants (women n = 4, male n = 19; age = 45 ± 7 years, height =178 ± 7 cm, mass = 83.3 ± 22.6 kg) completed six weeks of habitual training (HAB), consisting of the participant continuing their preexisting program. This was then followed by three individual time trial (TT) efforts across a one week period, the durations of which being 3, 7 and 12 minutes for all participants. Then three, two 3-minute all out tests (3MT) were completed across another one-week period, these consisted of running for 3 minutes at a maximal sprint from start to finish. A leading foot pod was worn during all activities, allowing for data to be recorded remotely and trials to be self-administered by participants due to COVID-19 restrictions. CS, CP, W′ and D′ was calculated from each of these sets of data and compared. Results No significant difference was observed between CSHAB (3.44 ± 0.47 m·s-1) and CSTT (3.50 ± 0.53 m·s-1), CPHAB (282 ± 42 W) and CPTT (288 ± 44 W), D′HAB (113 ± 75 m) and either D′TT (141 ± 35 m) or D′3MT (81 ± 42 m), and W′HAB (7.73 ± 4.63 kJ) and either W′TT (9.32 ± 3.46 kJ) or W′3MT (5.03 ± 2.77 kJ) (p > 0.05). Of these, a good level of agreement was observed between CSHAB and CSTT (r = 0.858, p < 0.001, CoV = 5.6 %) in addition to between CPHAB and CPTT (r = 0.869, p < 0.001, CoV =6.0 %). A lower level of agreement was observed between D′HAB and D′3MT (r = 0.478, p = 0.021, CoV = 50.6 %) with all other pairs showing no significant correlation (p > 0.05). No significant difference was observed across 3MT1 and 3MT2 for CS (3MT1: 3.75 ± 0.57 m·s-1, 3MT2: 3.78 ± 0.57 m·s-1),CP (3MT1: 305 ± 53 W, 3MT2: 307 ± 51 W), D′ (3MT1:87 ± 45 m, 3MT2: 75 ± 45 m) or W′ (3MT1: 5.21 ± 2.86 kJ, 3MT2: 4.86 ± 3.17 kJ) (p > 0.05). Agreement was high across 3MT1 and 3MT2 for CS and CP (CoV = 4.3 % and 3.7 % respectively), but lower for D′ and W′ (54.7 % and 113.3 %). Conclusion Estimating CS and CP from HAB training data appears to be a valid method of determination that requires no intentional bouts or expensive equipment. Determination of D′ and W′ using this method, however requires great caution. The 3MT was found to be reliable for CP and CS but not D′ and W′, however the 3MT should not be administered without proper supervision.