A study on risk factors inducing stress fractures in young Japanese long-distance runners -effects of training distance and intensity-

Abstract

The purpose of this study was to examine the risk factors of stress fractures in terms of training distance and intensity in young male Japanese high school long-distance runners. Nine hundred and twenty-five runners from high schools, colleges, and work teams responded to our questionnaire. Our analysis of the questionnaire found that the onset rates of stress fractures in males were 25.0%, 40.2%, and 55.3% in high school runners, collegiate runners, and work team runners, respectively, suggesting that young Japanese long-distance runners are more likely to suffer from stress fractures than European and American runners. Stress fractures occurred in male high school and collegiate runners after training that had increased running distance (24.7% and 33.1%, respectively) or running intensity (17.0% and 9.6%), or both increased running distance and increased running intensity (29.8% and 34.6%), suggesting that an increase in running distance at moderate intensity might be a major risk factor in stress fractures in young male long-distance runners. Data from college and work team runners that ran all three years of high school show that stress fractures are most likely to occur in May of the high school freshman year. These results suggested a need to reconsider training programs for freshmen to prevent stress fractures in young runners.