Validity of Stryd Running Power for Estimating Metabolic Demand During Incline Treadmill Running

Inertial measurement units, like the shoe-mounted Stryd running power meter, offer an alternative metric to guide endurance training. Despite its utility on level running surfaces, whether Stryd can accurately monitor training intensity for inclined running is unclear.

Ten (4 females) trained runners (28 [8] y, 55.9 [9.1] mL/kg/min) performed a Step-Ramp-Step exercise test to estimate the running power at the respiratory compensation point. On a separate visit, participants performed 5-minute running trials at 0%, 2%, 4%, 6%, and 8% inclines in a random order, with speed adjusted to elicit the running power 10% below respiratory compensation point. Metabolic power and mechanical efficiency were calculated for the final minute of each trial.

Metabolic power and oxygen uptake at 6% (1063 [191] W, 3.02 [0.53] L/min) and 8% (1079 [219] W, 3.05 [0.62] L/min) were significantly higher (P < .05 for all comparisons) than at 0% (1037 [191] W, 2.95 [0.53] L/min). Consequently, mechanical efficiency was significantly lower at 6% (21.6% [1.4%]; P = .024) and 8% (21.3% [1.3%]; P = .006) compared with 0% (22.1% [1.3%]). These variables were not different from 0% for the 2% and 4% running trials (P > .05). Ventilation (P = .550), breathing frequency (P = .273), heart rate (P = .924), and rating of perceived exertion (P = .709) were not different across inclines.

Although Stryd slightly underestimated metabolic power (∼2%-4%) at steeper inclines, running at a fixed Stryd power yielded relatively consistent indications of metabolic demand across incline conditions, suggesting it is a useful metric to guide training during incline treadmill running.