EFFECT OF ENDURANCE EXERCISE TRAINING ON HEART-RATE-VARIABILITY AT REST IN HEALTHY-YOUNG AND OLDER MEN

Heart rate variability (HRV) (SD of the RR interval), an index of para sympathetic tone, was measured at rest and during exercise in 13 healt hy older men (age 60 to 82 years) and 11 healthy young men (age 24 to 32 years) before and after 6 months of aerobic exercise training. Befo re exercise training, the older subjects had a 47% lower HRV at rest c ompared with the young subjects (31 +/- 5 ms vs 58 +/- 4 ms, p = 0.000 2), During peak exercise, the older subjects had less parasympathetic withdrawal than the young subjects (-45% vs -84%, p = 0.0001), Six mon ths of intensive aerobic exercise training increased maximum oxygen co nsumption by 21% in the alder group and 17% in the young group (analys is of variance: overall training effect, p = 0.0001; training effect i n young vs old, p = NS), Training decreased the heart rate at rest in both the older (-9 beats/min) and the young groups (-5 beats/min, befo re vs after, p = 0.0001), Exercise training increased HRV at rest (p = 0.009) by 68% in the older subjects (31 +/- 5 ms to 52 +/- 8 ms) and by 17% in the young subjects (58 +/- 4 ms to 68 +/- 6 ms). Exercise tr aining Increases parasympathetic tone at rest in both the healthy olde r and young men, which may contribute to the reduction in mortality as sociated with regular exercise. (C) 1998 by Excerpta Medica, Inc.