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Clin J Sport Med. 2000 Oct;10(4):279-85.

Reversal of runner's bradycardia with training overstress.

Author information

1
Division of Cardiology, William Beaumont Hospital, Royal Oak, Michigan, USA. penloom@jps.net

Abstract

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.

PMID:
11086755
[Indexed for MEDLINE]

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