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Tone Your Heart with Moderate Exercise

For a person intent on staying in shape, it seems there's always something new to isolate and tone: the abdominals, the quadriceps, the biceps. A new study suggests that we may also want to tone the parasympathetic nervous system. This part of the nervous system runs many functions in the body, including the beat of the heart.

Scientists can indirectly check heart health by measuring the difference--or variability--in heart rate with each breath of air. A lower variability is associated with common heart problems like coronary artery disease, congestive heart failure, and angina. Moderate amounts of aerobic exercise appear to improve the tone of the parasympathetic nervous system, thereby increasing heart rate variability.
 
This study looked at how different amounts of exercise affect heart rate variability. Thirty seven men between the ages of 25 and 49 volunteered. They were asked how much they exercised, and then placed in a low, moderate, or highly active group depending on their answers. Activity levels were based on calories burned in a week doing aerobic exercise, since aerobic activities relate best to heart rate variability. 

The low (sedentary) group spent less than 1,000 calories per week during aerobic exercise. Moderate equaled 1,000 to 2,000 calories per week, and high indicated over 2,000 calories per week. The high-level group tended to be endurance-trained athletes such as swimmers, triathletes, long distance runners, and martial artists. Participants took part in a 10-minute test every day for five days. This test was used to judge the men's existing  level of heart rate variability. Their heart rates were monitored while they matched their breathing to the beat of a metronome set at 10 breaths per minute.

The results showed that heart rate variability was better in both the high and moderate exercise groups when compared with the low-activity group. Yet no marked difference appeared between the high and moderate exercisers. It was no surprise that resting heart rate was lower in both the moderate and high exercisers compared to those in the low-activity group.

If you are hoping for improved heart health, at least a moderate level of exercise seems to be the key. In this study, aerobically active men showed better heart rate variability, which was likely due to good parasympathetic tone. It didn't seem to make a difference whether the exercisers were trained athletes or moderate exercisers. Toning up the parasympathetic nervous system may make a difference in heart health.

References: Edward L. Melanson. Resting Heart Rate Variability in Men Varying in Habitual Physical Activity. In Medicine & Science in Sports & Exercise. November 2000. Vol. 32. No. 11. Pp. 1894-1901.

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