Running power meters — specifically Stryd — are reasonably valid and repeatable for pacing, but different brands aren't interchangeable and power only partly explains running economy
Interpretation
Cerezuela-Espejo et al.'s head-to-head test of five commercial devices found Stryd (app and watch) the most repeatable (CV ≤4.3%) and most valid against VO2 (r≥0.911) of the group tested, with other brands showing weaker repeatability. Austin et al. found Stryd power explains only around 31% of the variance in running economy (r=0.6) in well-trained runners — the authors' own conclusion is the device may not be precise enough to distinguish economy differences between competitive runners. Berzosa et al.'s small trail-running comparison found high within-brand but poor between-brand agreement, especially uphill, confirming brands measure power differently enough that cross-brand comparisons aren't reliable.
Practical implication
Recommend running power meters (Stryd specifically has the strongest validity evidence) as a useful pacing tool, especially on variable terrain, but caution against switching brands mid-season and against treating small power differences as meaningful economy differences — the correlation with economy is real but modest.
Sources
3 sources, independently verified.
Comparing five commercial running-power devices for repeatability and validity against VO2: Stryd (both app and watch output) was the most repeatable (SEM ≤12.5W, CV ≤4.3%, ICC ≥0.980) and most valid (r≥0.911, SEE ≤7.3%). Polar Vantage, Garmin Running Power and RunScribe all related to VO2 to some degree but with notably lower repeatability — meaning not all running-power devices are equally trustworthy for pacing decisions.
Stryd-measured power correlated with running economy at r=0.6 (90% CI 0.2-0.8) — explaining only around 31% of the variance. The authors' own conclusion is that the footpod may not be accurate enough to reliably distinguish economy differences between competitive runners, a meaningful caveat against over-interpreting small power differences.
Within-brand consistency was high (the two Stryd units agreed with each other, as did the two Garmin units), but between-brand agreement was notably poorer — especially for uphill power. The brands are not interchangeable, which matters for anyone comparing power numbers across devices or switching brands mid-season. Small sample (5 runners); treat as directional.