Validity of V̇O estimates from the forerunner 245 smartwatch in highly vs. moderately trained endurance athletes.

PURPOSE

Assessing the validity of maximum oxygen uptake (V̇O₂) estimates provided by a commercially available smartwatch (Garmin Forerunner 245, Garmin Ltd., Olathe, USA) compared to laboratory-based respiratory gas analysis in moderately-to-highly trained athletes.

METHODS

Thirty-five endurance athletes (Tier 2-3 athletes, 24 males, 11 females; age: 25.1 ± 3.5 years; V̇O₂: 60.1 ± 8.2 ml·min⁻·kg⁻) completed a treadmill ramp test with respiratory gas analysis to determine criterion V̇O₂. Additionally, each athlete performed two submaximal 15-min outdoor runs at > 70% of maximum heart rate, during which the smartwatch estimated V̇O₂. Athletes were stratified into moderately trained (V̇O₂ ≤ 59.8 ml·min⁻·kg⁻) and highly trained (V̇O₂ > 59.8 ml·min⁻·kg⁻) subgroups.

RESULTS

Across all athletes, the smartwatch underestimated V̇O₂ [mean differences: - 4.73 ml·min⁻·kg⁻ (run 1), -4.05 ml·min⁻·kg⁻ (run 2)]. Intraclass correlation coefficients (ICC) indicated moderate agreement between smartwatch and laboratory values (run 1: ICC = 0.71 [95% CI: 0.03-0.90]; run 2: ICC = 0.75 [95% CI: 0.17-0.91]), with mean absolute percentage errors (MAPE) of 7.9% and 7.2%. Subgroup analyses revealed better accuracy of smartwatch estimated V̇O₂ in moderately trained group (MAPE: 4.1-2.8%; ICC: 0.63-0.66 [95% CI: 0.09-0.87]), whereas in highly trained athletes, the smartwatch underestimated V̇O₂ by 6.3 ml·min⁻·kg⁻ (MAPE: 10.4-9.4%; ICC: 0.34-0.41 [95% CI: - 0.11-0.75]).

CONCLUSION

Smartwatch-derived V̇O₂ estimates are valid in moderately trained athletes but less valid in highly trained individuals. While smartwatches are useful for general monitoring, caution is warranted in their interpretation, particularly in highly trained individuals. Laboratory-based gas analysis remains the preferred method when precision is required.