Concurrent Heart Rate and Energy Expenditure Validity of Polar Verity Sense Devices During Light and Moderate Intensity Resistance Training in Recreationally Active Adults: A Pilot Study

Wearable technology is again the top fitness trend from ACSM for 2024. Our lab recently found that bicep-worn devices (Polar Verity Sense) are valid for measuring average/maximal heart rate (HR) but are not valid for estimating energy expenditure (EE) during acute resistance exercise training (RT). We postulated that the errors may have been due to the device’s algorithms assuming higher intensity during RT, but no study has directly tested these outcomes with various RT intensities. PURPOSE: To determine the concurrent validity of identical Polar Verity Sense bicep-devices to record valid measures of average and maximal HR as well as estimated EE following light and moderately heavy RT. METHODS: Twelve recreationally active adults (n=5 females, n=7 males, age: 29.9±7.5 yrs; mass: 87.7±27.6 kg; height: 178.1±12.1 cm) completed 4 sets of 6 repetitions of the deadlift exercise at a light (3-4 on 0-10 RPE scale) and moderately heavy (6-8 on 0-10 RPE scale) intensity (8 total sets), with 1-1.5 min. rest between sets. Two Polar Verity Sense devices were evaluated, along with the Polar H10 chest strap (average/maximal HR criterion) and Cosmed K5 portable metabolic cart (EE criterion). Data were analyzed for validity (Mean Absolute Percent Error [MAPE] and Lin’s Concordance Coefficient [CCC]), with predetermined thresholds of MAPE<10% and CCC>0.70 (n=6 participants). A two-way ANOVA was used to determine differences between identical Polar devices, p<0.05 (n=12 participants). RESULTS: Independent of intensity condition, there were no differences between Verity #1 or #2 for average HR (p=0.85), maximal HR (p=0.58), or EE (p=0.52). Polar verity #1 and #2 were valid for light intensity average/maximal HR (MAPE range: 3.3-4.8%; CCC range: 0.89-0.95) but were only approaching validity for moderate intensity average/maximal HR (MAPE range: 7.9-10.6%; CCC range: 0.60-0.75). Moreover, neither device was valid for estimating EE at light (MAPE range: 45.4-51.0%; CCC range: 0.59-0.64) or moderate (MAPE range: 45.0-53.6%; CCC range: 0.48-0.58) intensities. CONCLUSIONS: The wearable bicep-worn devices tested herein can be utilized for measuring average/maximal HR but should not be utilized for accurate measurements of EE during RT at various intensities, and identical devices provide similar readouts for these parameters.