Polar h10 hr monitor

Continuous monitoring of HR during the experimental sessions was done with the use of a Polar H10 HR-monitor (Polar Electro Oy, Kemple, Finland), with a recording interval of 1 s. The maximal heart rate was obtained from the 2-km row test that was used for the indirect assessment of the maximal oxygen uptake [16 (link)] of the subjects. The 2 km row test consisted in rowing 2 km with the maximal effort (power) possible. During the test, continuous monitoring of the HR was done, and the maximum HR during the test was used as the maximum HR of the subject.

For the indirect calorimeter method, the Cardiopulmonary Exercise Testing System (Vmax Encore 29 System, VIASYS Healthcare Inc., Yorba Linda, CA, USA) was employed to conduct the metabolic CM. Warming up of the Vmax system for at least 15 minutes and the calibration should be done before each test. Participants were equipped with a well-fitted, noses and mouths covering mask (Hans Rudolph Inc., Kansas City, MO, USA) which connected to flow sensor and sampling line was to collect the amount of oxygen consumption (VO₂) and carbon dioxide output (VCO₂) they breathed (breath by breath).
For the accelerometer method, all the test data was collected by an ActiGraph GT9X-Link (Actigraph Corporation, Pensacola, FL, USA), a tri-axial accelerometer (size: 3.5 × 3.5 × 1 cm, weight: ~14 g). The initialization of the ActiGraph accelerometer and chest mount Polar H10 HR monitor (Polar Electro Oy, Kempele, Finland) was done by ActiLife6 software (version 6.12.1, ActiGraph, Cary, NC, USA). In this study, the sampling frequency of the accelerometer and heart rate monitor was set to 30 Hz, and the physical activity parameters (i.e., calories, and VM), and HR data were collected in 10-second intervals set manually via ActiLife6 software. The ActiGraph accelerometer was attached to their right ankle, and the participants took one test at a time.

Heart rate was continuously monitored during each session with the use of a Polar H10-HR monitor (Polar Electro Oy, Kemple, Finland). Participants’ maximal heart rate was obtained following a 2-km rowing test, utilized to indirectly assess the participants’ maximal oxygen uptake (VO_2max; Klusiewicz et al., 2016 (link)). The test consists of rowing 2 km with the maximal effort (power) possible, aiming to complete the distance in the shortest time. Heart rate was continuously monitored during the test and the maximum HR observed during the test was used as the participants’ maximum heart rate. Maximal heart rate for every subject at the end of the test exceeded 90% of their age predicted maximum heart rate (HRmax = 220–0.64^*age; Nes et al., 2013 (link)), indicating that a maximal effort was achieved.