# Heart Rate Index as a Measure of Physical Workload in Chainsaw Operations
## 2 Materials and Methods
### Experimental Data Collection  
We collected the data on 27 August 2022 in the South Moravia location, tree area Vetefov, Czech Republic. The respondent signed an informed consent. The respondent's ability to perform the required work activity was verified. Before starting the entire study, he was asked to fill out a questionnaire with the data needed for this study. Based on this data, the technical side of the measurement was prepared, including the setting of the participant's parameters. The experiment took place outdoors, 264 m above sea level, and was performed in the average meteorological conditions of 22.8 \({}^{\circ}\)C/53% humidity, wind 4 km/h, and light values 730 lx. To carry out the measurements and evaluate the results, it was necessary to enter data into the wearable measuring devices that can affect the measurement results, such as the age, height, and gender of the person being monitored. Several wearable sensors were used for the measurements themselves--the Whoop device (Whoop--41.11.4.0. v 17.2.1.0) (fitness and health wearable monitor WHOOP, Boston, MA, USA) and the Biostrap device (Biostrap EVO Recovery set--fitness and health wearable monitor, Biostrap, Duarte, CA, USA, LLC) (Biostrap--EVO--51C6A85F--V1.1.33). A Garmin Fenix 3 HR device (Software: 5.60) (Garmin company, Olathe, KS, USA) was also used. Individual sensors were located on both wrists with rubber wrist bands and on the forearm. Whoop and Biostrap were located on the left hand, Biostrap on the left forearm, and Garmin on the right hand. These wearable sensors were used to monitor workload and to eliminate data distortion and possible loss of data. It also increases the accuracy of data, as Biostrap monitored the rest mode before the workload. We also wanted to be sure that there would be no loss and distortion of data that could arise from the placement of the sensor, movement, sweating, or changes in measurement [39; 40; 41]. The Whoop wearable device allows you to measure sleep duration, sleep stages, strain, recovery, heart rate, resting heart rate, heart rate variability, respiratory rate, workouts, and calories burned. The Biostrap wearable device provides the following information usinga three-axis accelerometer and a three-axis gyroscope: the measurement of sleep phase, resting heart rate, heart rate variability, blood oxygen saturation, respiratory rate, arterial elasticity, and peripheral elasticity. The Garmin Fenix 3 HR wearable device allows you to monitor heart rate, running dynamics, step length, vertical ratio, and VO2 max, as well as a three-axis compass, altimeter, and barometer options. As part of this study, the subject was monitored 5 days before the start of the actual experiment and also 5 days after its end to determine the resting value of the heart rate and determine the usual behavior and performance behavior during the performance of work activities and regeneration for the work activities performed. Long-term behavioral measures were not evaluated and were not included in the study itself. In this case study, physiological parameters were monitored following the required work activity, both during the actual work activity and during breaks and the preparation for the work activity. The course of the actual measurement and the individual measured values were checked and monitored remotely during the measurement using applications for the individual monitoring devices used. A working and video recording of the performed activities was kept. To compare the load, the use of two different types of saws and two different types of cutting sets was chosen. Measurements were carried out during the processing of already felled Populus Alba white poplars. Cross-sections were performed in both vertical and horizontal orientations. Populus Alba is one of several species of poplar whose original area of distribution includes most of central, eastern, and southern Europe. In the Czech Republic, it is native to the Moravian valleys, and it is the predominant type of poplar in floodplain forests.