Characterization of electrocardiogram changes throughout a marathon.
OBJECTIVE
There are few data examining cardiovascular physiology throughout a marathon. This study was devised to characterize electrocardiographic activity continuously throughout a marathon.


METHODS
Cardiac activity was recorded from 19 subjects wearing a Holter monitor during a marathon. The 19 subjects (14 men and 5 women) were aged 39 ± 16 years (mean ± SD) and completed a marathon in 4:32:16 ± 1:23:35. Heart rate (HR), heart rate variability (HRV), T-wave amplitude, T-wave amplitude variability, and T-wave alternans (TWA) were evaluated continuously throughout the marathon.


RESULTS
Averaged across all subjects, HRV, T-wave amplitude variability, and TWA increased throughout the marathon. Increased variability in T-wave amplitude occurred in 86 % of subjects, characterized by complex oscillatory patterns and TWA. Three min after the marathon, HR was elevated and HRV was suppressed relative to the pre-marathon state.


CONCLUSIONS
HRV and T-wave amplitude variability, especially in the form of TWA, increase throughout a marathon. Increasing TWA as a marathon progresses likely represents a physiologic process as no arrhythmias or cardiac events were observed.
Department of Emergency Medicine, University of Pittsburgh, Iroquois 400A, 3600 Meyran Avenue, Pittsburgh, PA, 15261, US, vfranco@mednet.ucla.edu.
Vanessa
V
Franco
Clifton
C
Callaway
David
D
Salcido
Serina
S
McEntire
Ronald
R
Roth
David
D
Hostler
D000328:Adult; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D012420:Running / Q000502:physiology*