High Volume Running Versus Cycling on Immune Function
Date: Oct. 28, 2013
Motivation for exercise should be a good thing, but having too much motivation can lend itself to an increased risk for overreaching.
Overreaching occurs when the body is put under levels of physical stress that it cannot recover from prior to the next training bout. This creates an accumulative effect that manifests into overreaching before eventually becoming a chronic condition of overtraining syndrome.
Overreaching has been linked to alterations in immunity and increased risk for illness; and while endurance athletes seem to be at higher risk, little is known as to the specific response in running versus cycling.
Researchers compared inflammation, muscle damage and soreness, as well as innate immune function responses to a 3-day period of intensified exercise in experienced long distance runners and cyclists. Subjects were tracked over 12 weeks using a specific Upper respiratory tract infection (URTI) model. During week five, test subjects exercised continuously for 150 minutes each day for three days at 70% VO2max. In addition, blood samples were collected before and after the 3-day period of exercise. Researchers analyzed the blood samples for markers of muscle damage, inflammation, and innate immunity and oxidative burst activity. By comparison, runners experienced significantly more muscle damage, inflammation, and delayed onset of muscle soreness.
Interestingly, the 3-day period of exercise caused significant downturns in the innate system, but between groups there was no difference in the response pattern. Due to the fact that no group differences were measured in either 12-week URTI severity or symptom scores, it would seem both modes of exercise create an increased risk for illness when overreaching occurs in response to training volume.
The severity though for overtraining syndrome may be higher for runners as the 3-day period of functional overreaching resulted in substantially more muscle damage and soreness, and systemic inflammation. The impact of running compared to non-weight bearing exercise warrants consideration when training at higher volumes. (Brain Behavior and Immunity, 2013)