Effects of Wearing N95 Respirators and Surgical Masks during Progressive Running Exercise and High-Intensity Interval Training on Time- and Frequency-Domain Indicators of Heart Rate Variability

Background and purpose: Wearing face masks has become popular during the COVID-19 pandemic as a measure to prevent the spread of the virus. Some studies have pointed out the intervening role of these masks in the effect of exercise on the cardiovascular system. This study aimed at examining and comparing the effects of masking (N95 respirators and surgical masks) and not wearing a mask during exercise on heart rate variability (HRV) parameters. Materials and methods: In this semi-experimental design, 15 healthy women were randomly placed into three groups: surgical mask, N95 respirators and no mask. The participants took part in a progressive running session and then two weeks of HIIT program (2-4 sets, 20-60 seconds with 15-60 seconds of rest between repetitions and 3-5 minutes between the sets) with 80-90% of HRmax. The time- and frequency-domain parameters of HRV were recorded during rest and recovery after exercises using electrocardiogram and then analyzed in Kubios HRV software. Results: Progressive running session before two weeks of HIIT training caused a significant decrease in parasympathetic time-domain parameter (RMSSD) and average RR in all groups in the fifth minute of recovery compared with rest values (P≤0.05). In addition, after HIIT training, sympathetic time-domain (SDNN) parameter and average RR significantly increased (P=0.01 and P=0.02, respectively) while a significant decrease was seen in the sympathetic frequency-domain (LF) parameter in rest and recovery compared with baseline values (P=0.01). No significant differences were observed between the two masked groups in parameters studied (P=0.43). Conclusion: Increase in parasympathetic parameters and decrease in sympathetic parameters improved HRV. Wearing surgical masks or N95 respirators during exercise did not have an intervening effect on the positive results of exercise, including improving the autonomic function of the heart and maintaining sympathovagal balance in healthy women.