Is Stryd critical power a meaningful parameter for runners?

Abstract

Stryd is a foot pod that reliably estimates running power. Our objectives were to examine the efficacy of the website-generated Stryd critical power (CP_STRYD) as a meaningful parameter for runners. 20 runners performed their regular training while wearing Stryd for a minimum of 6 weeks to generate CP_STRYD. Runners completed laboratory graded exercise testing, and outdoor 1500 m and 5000 m time trails. CP_STRYD was most similar to the second ventilatory threshold (VT2) or the onset of blood lactate accumulation (OBLA) and is highly predictive of running performance. Stryd ground contact time (GCT) was a predictor of performance when comparing runners at the same submaximal treadmill speed. CP_STRYD generated from outdoor running is equivalent to that calculated using an established CP model. However, variance between different methods of CP estimation must be a consideration for runners and coaches. Stryd offers meaningful data for runners including a realistic estimate of CP.

Keywords: Anaerobic threshold; Athletic performance; Cardiorespiratory fitness; Endurance training; Running; Wearable technology.

FIG. 1

1a CPSTRYD is compared with vs CPCALC, Deming’s Regression Results: Slope = 0.97 ± 0.13, Y-intercept = 7.48 ± 39.98, SD of the residuals = 30.18, p<0.01. 1b There was no bias evident on the Bland Altman plot. 1c The two measures of CP appeared equivalent. Runs test p value = 0.77.

FIG. 2

Stryd CP is compared with power at VT2 with (2a) Linear regression (Best-fit values: Slope 0.77 ± 0.11, Y-intercept when X=0.0 66.70 ± 32.89, X-intercept when Y=0.-86.35) and (2b) non-linear regression (Polynomial: Second Order (Y=A + B*X + C*X^2), Best-fit values A = 265.2, B = -0.70, C = 0.00) are compared. 2c A Bland Altman plot was used to examine bias and individual athlete differences. Runs test p value = 0.87.