Polar h1

The above description of the HIIT intervention was presented elsewhere [20 (link)]. Here, briefly, a HIIT program was conducted in one (out of three) lesson per week for ten weeks. Ten-minute warm-ups consisting of jogging and stretching exercises preceded the main exercises. The central part of the program was the HIIT intervention with a total time of 14 min. The HIIT intervention consisted of three cycles based on the Tabata protocol (8 rounds of 20 s work/10 s rest). Between processes was a 1-min break. All the exercises were played on a screen to ensure that workout and rest were implemented accurately.
Evaluation of the intensity of the workout was based on the Tanaka formula:
Using the Polar H1 (Polar Electro, Kempele, Finland), participants’ heart rate was measured and was established in the range of 75–80% HRmax (145–157 heartbeats/min) to perform the HIIT.

The intervention lasted 10 weeks. Participants followed the HIIT intervention during the one PE lesson (45 min) per week. First, a 10 min warmup with jogging and stretching exercises conducted. Next, the HIIT intervention was performed and lasted 14 min, divided into three sessions based on Tabata protocol (20 s work/10 s rest) separated by a 1 min break. In the first session, participants performed: pushups, high knees; in the second session: dynamic lunges, spider crawling; in the third session: plank-to-pushups and side squeezes. All exercises were played on a screen to ensure that workout and rest were implemented accurately. After the HIIT intervention, stretching and breathing exercises were performed to calm down. The control group participated in a standard physical education program.
The participants’ heart rate was measured with a Polar H1 (Polar Electro, Kempele, Finland) and established the range of 75–80% HRmax (145–157 heartbeats/min) when performing HIIT. The Tanaka formula, HRmax = 208 − 0.7 × “age” (age = 16 years in this study), was used to verify the intensity of the workout. The subjects achieved an HR of 156.2 ± 17.8 bpm (CI 95%: 123.0–184.0).

The measurements were taken before and after the 10-week intervention on one day from 8:00 a.m. to 1:00 p.m. The intervention lasted 10 weeks. Participants followed the HIIT intervention during one PE lesson (45 min) per week. The HIIT intervention was performed and lasted 14 min, which was divided into three sessions based on the Tabata protocol (20 s work/10 s rest) and separated by a 1 min break. In the first session, participants performed pushups and high knees; in the second session, they performed dynamic lunges and spider crawling; and in the third session, they performed plank-to-pushups and side squeezes. The control group participated in a standard physical education program.
Each participant’s heart rate was measured using a Polar H1 (Polar Electro, Kempele, Finland), and a range of 75–80% HRmax (145–157 heartbeats/min) was established when performing HIIT. The Tanaka formula, HRmax = 208 – 0.7 × “age” (age = 16 years in this study), was used to verify the intensity of the workout. The participants achieved an HR of 156.2 ± 17.8 bpm (CI 95%: 123.0–184.0).