Purpose: A previously established Step-Ramp-Step (SRS) exercise protocol was able to accurately predict the work rate associated with the maximal metabolic steady state (MMSS) in cyclists. The purpose of this study was to determine whether a modified SRS protocol could predict the running speed and power associated with the MMSS. Methods: Fifteen (8 male; 7 female) runners ( VO 2max 54.5 [6.5] mL•kg −1 •min −1 ) were recruited for this investigation composed of four to five visits. In the first visit, runners performed a moderate intensity step (MOD), an incremental exercise test, and a heavy intensity step (HVY), on a motorized treadmill. This SRS protocol was used to predict the running speed and power associated with the MMSS (i.e., the SRS-MMSS), where running power was assessed by a wearable device (Stryd) attached to each runner's shoe. Subsequent visits were used to confirm the maximal lactate steady state (MLSS) as a proxy measure of the MMSS (i.e., the MLSS-MMSS) and to validate the SRS-MMSS speed and power estimates. Results: The estimated SRS-MMSS running speed (7.2 [0.6] mph) was significantly lower than confirmed running speed at MLSS-MMSS (7.5 [0.8] mph; bias = 3.6%, P = 0.005); however, the estimated SRS-MMSS running power (241 [35] W) was not different than the MLSS-MMSS confirmed running power (240 [37] W; bias = −0.6%; P = 0.435). VO 2 at SRS-MMSS (3.22 [0.49] L•min −1 ) was not different than respiratory compensation point (3.26 [0.58] L•min −1 ; P = 0.430). Similarly, VO 2 at MLSS-MMSS (3.30 [0.54] L•min −1 ) was not different than respiratory compensation point ( P = 0.438). Conclusions: The SRS protocol allows MMSS, as measured by MLSS, to be accurately determined using running power (Stryd), but not speed, in a single laboratory visit.

Purpose: Although running traditionally relies on critical speed (CS) as an indicator of critical intensity, portable inertial measurement units (IMUs) offer a potential solution for estimating running mechanical power to assess critical power (CP) in runners. The purpose of this study was to determine whether CS and CP differ when assessed using the Stryd device, a portable IMU, and if two running bouts are sufficient to determine CS and CP. Methods: On an outdoor running track, ten trained runners (V̇ O2max, 59.0 [4.2] ml/kg/min) performed three running time-trials (TT) between 1200 and 4400m on separate days. CS and CP were derived from two-parameter hyperbolic speed-time and power-time models, respectively, using two (CS2TTCP2TT) and three (CS3TTCP3TT) time trials. Subsequently, runners performed constant intensity running for 800m at their calculated CS3TTand CP3TT. Results: Running at the calculated CS3TTspeed (3.88 [0.44] m </ s) elicited an average Stryd running power (271 [28] W) not different from the calculated CP3TT(270 [28]; p=0.940; d=0.02), with excellent agreement between the two values (ICC=0.980). The CS2TT(3.97 [0.42] m/s) was not significantly higher than CS3TT(3.89 [0.44] m/s; p=0.178; d=0.46); however, CP2TT(278 [29] W) was significantly greater than CP3TT(p=0.041; d=0.75). Conclusion: The running intensities at CS and CP were similar, supporting the use of running power (Stryd) as a metric of aerobic fitness and exercise prescription, and two trials provided a reasonable, albeit higher, estimate of CS and CP.