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Background and Objective: Aging reduces cardiac autonomic function parameters such as heart rate response to exercise and heart rate recovery after physical activity. This study aimed to determine the parasympathetic nerves reactivation after upper body exercise among young and middle-aged men.
Methods: In this quasi-experimental study 24 active men based on their age were divided into two groups including 30-35 (young) and 55-60 years old men (middle-aged). Participants performed upper body exercise on a Monark arm ergometer. During the test, heart rate was recorded continuously by electrocardiogram. Also, participants' heart rate was recorded for 10 minutes after completion of the test. In order to measure the time domain parameters of heart rate variability (PNN50 and RMSSD), one-minute successive RR waves intervals collected in 5 minutes and 10 minutes after the completion of the test and then were transmitted to the heart rate variability software for analysis. Also, heart rate recovery was measured in one minute and two minutes after the test by the difference between the maximum heart rate during the test with heart rate in one and two minutes after the completion of the test.
Results: There was a significant difference between PNN50 in minutes 5 and 10 after the test in young men (P<0.05). Young men also had higher values of RMSSD in minutes 5 and 10 compared to middle-aged men. The heart rate recovery in the 2 minutes after test was significantly higher than 1 minute after test in both groups (P<0.05). Heart rate recovery was higher in young people than in middle-aged people at 5 and 10 minutes after high-intensity exercise due to faster withdrawal of sympathetic nerves.
Conclusion: Changes in the autonomic nervous system is dependent on the type, duration of activity, and the age of the participants.