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Reversal of Runner's Bradycardia with Training Overstress

Dressendorfer, Rudolph H. PhD; Hauser, Andrew M. MD; Timmis, Gerald C. MD

Clinical Journal of Sport Medicine: October 2000 - Volume 10 - Issue 4 - p 279-285
Clinical Investigations

Objective To elicit a criterion elevation (>10%) in resting heart rate (HR) with training overstress, and subsequently test the hypothesis that such “reversed bradycardia” (RB) negatively affects running performance.

Design Prospective before-and-after intervention with a comparison group.

Setting General community.

Participants 21 healthy male marathon runners.

Intervention Voluntary doubling of training miles on 14 consecutive days.

Main Outcome Measures Left ventricular (LV) function by echocardiography, HR, and plasma epinephrine (PE) at rest and during submaximal exercise, and 15 km road run performance.

Results Two days after the training overstress, 12 runners met the criterion (RB group), showing an average elevation in resting HR of 16% (range: 11 to 23%). The RB group also exhibited hyperkinetic LV shortening (p < 0.05), elevated exercise HR (p < 0.001), increased PE at rest and during exercise (p < 0.05), and reduced 15 km performance (p < 0.05). The other nine runners who maintained a stable resting HR during the intervention showed no significant outcome changes.

Conclusions In addition to muscular overuse, heightened sympathetic drive likely contributed to the observed reversal of bradycardia. The development of this stress-related cardiac perturbation was associated with a decrement in running performance, confirming the hypothesis.

Division of Cardiology, William Beaumont Hospital, Royal Oak, Michigan, U.S.A.

Received January 21, 2000; accepted August 9, 2000.

Address correspondence to Rudolph H. Dressendorfer, PhD, 6025 Colwell Rd., Penryn, CA 95663, U.S.A. E-mail: penloom@jps.net

© 2000 Lippincott Williams & Wilkins, Inc.