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It is not unusual for athletes to exhibit an “abnormal” ECG due to the effect of exercise training on the anatomy and autonomic control of the heart. Up to 80% of highly trained athletes show some evidence of ECG changes. The most common training-induced ECG changes in athletes are sinus bradycardia, first-degree AV block, second-degree AV block (Mobitz type 1 only), incomplete RBBB (QRS duration <0.12 s), early repolarization, and isolated QRS voltage criteria for LVH.
Platelet activation and aggregation are reduced with training, while fibrinolysis is enhanced in trained compared to untrained individuals. The effect of chronic exercise on fibrinogen remains unclear, with data from cross-sectional studies supporting lower fibrinogen levels in trained compared to untrained subjects and data from training studies showing increased, decreased, or unchanged fibrinogen levels following training (Womack, Nagelkirk, and Coughlin, 2003). Endurance training, ...
Heart rate responses to resistance exercise have been more widely reported than changes in stroke volume and cardiac output. The small-to-modest increase in cardiac output during resistance exercise is the result of a modest increase in heart rate and an unchanged or decreased stroke volume. During resistance exercise, heart rate increases modestly but stroke volume decreases; thus cardiac output is only modestly increased.
“The phase of the menstrual cycle significantly affects a female runner’s hormonal environment and therefore her physiology,” Karp explains. In the forthcoming book Running for Women (Human Kinetics, 2012), Karp and coauthor Carolyn Smith, MD, explain how various aspects of physiology are affected by the phase of the menstrual cycle, including oxygen consumption, body temperature, and metabolism. Metabolism“Menstrual-phase variations in running performance may largely be a consequence of ...
