Objective: To investigate relationships between training mileage and intensity, and the type, incidence, severity, and duration of respiratory illness in distance runners, and the impact of illness on submaximal and maximal running performance.
Design: A longitudinal observational study of distance runners with serial monitoring of training loads and clinical patterns of illness.
Setting: A 4-month winter training period in the Southern Hemisphere.
Participants: A total of 20 highly trained (elite) male middle-distance and distance runners competing at the national and international levels.
Main outcome measures: Training was quantified by mileage (km), intensity (scale, 1-5), and load (volume x intensity). Symptoms and signs of respiratory illness (type, duration, and severity) were verified by a physician at a weekly review. Performance was monitored by measuring submaximal and maximal oxygen uptake and time to exhaustion on a incremental treadmill test.
Results: A majority of subjects (15/20) experienced 1 or more episodes of respiratory illness (mean, 2.5 episodes; range, 1-5), with 79% of symptoms classified as upper respiratory in origin. There were no significant differences in mean weekly mileage (P = 0.43), training intensity (P = 0.85), or training load (P = 0.45) between healthy runners and those affected by illness. Mean weekly (88 +/- 46 km) and mean monthly (373 +/- 163 km) mileages prior to each episode of illness were similar to the overall study means (95.5 +/- 36.4 km and 382 +/- 146 km). There were no substantial relationships between mean weekly training mileage, intensity, or training load and the number of illnesses reported (all r < 0.20). Neither submaximal nor maximal running performance was significantly affected by the presence of illness.
Conclusions: Differences in training mileage, intensity, and load were not associated with the incidence of respiratory illness in highly trained middle-distance and distance runners. Runners with mild illness can be reassured that symptoms will not necessarily impair submaximal and maximal performance.