Incidence of injuries and associated factors in treadmill runners: a prospective cohort study

Abstract Aims: To determine the incidence of injuries in exclusive treadmill runners and the main associated factors in 24 weeks. Methods: The incidence of injuries was investigated every two weeks by an electronic form. To analyze the associated factors, muscle force output, range of motion, and flexibility were investigated. To perform a descriptive analysis (baseline) and injury predictive factors (regression), we divided runners into two groups, injured and uninjured. Comparisons between groups were assessed evaluated by Student's t-test, Mann-Whitney, or Chi-square test. The relationship between associated factors and incidence of injuries was estimated by Logistic regression analysis. The model's accuracy was assessed by the receiver-operating characteristic curve (ROC). Thirty-seven runners completed the study. Results: The incidence of injuries was 6.8 per 1,000 hours of exposure. Among the associated factors, we highlight that runners with higher hip flexor force output were 4 times more likely not to injure (OR 4.0; CI 95% 1.03 -16.23) and lower knee extensor force output was related to a greater chance of injury (OR .24; 95% CI .65 - .93). The area under the ROC curve was 0.84. Conclusion: The incidence of injuries in treadmill runners was high. The factors associated with the injuries were the output of the flexor strength of the hip and the extensor force of the knee.

摘要 研究目的：旨在明确纯跑步机跑者的损伤发生率，以及24周随访周期内与损伤相关的主要危险因素。
研究方法：通过电子问卷每两周开展一次损伤发生率调研。为分析损伤相关危险因素，本研究对受试者的肌肉力量输出、关节活动度（range of motion, ROM）及柔韧性进行了检测。为完成基线描述性分析与损伤预测因素的回归分析，我们将跑者分为损伤组与未损伤组两组。组间比较采用学生t检验、曼-惠特尼检验或卡方检验进行评估。采用逻辑回归分析估算危险因素与损伤发生率之间的关联关系，并通过受试者工作特征曲线（receiver-operating characteristic curve, ROC）评估模型的预测准确度。最终共有37名跑者完成全部研究。
研究结果：跑步机跑者的损伤发生率为每1000小时暴露量6.8例。在相关危险因素中，值得注意的是，髋屈肌力量输出较高的跑者未发生损伤的概率是其他跑者的4倍（比值比OR=4.0；95%置信区间CI：1.03~16.23）；而膝伸肌力量输出较低则与更高的损伤风险相关（比值比OR=0.24；95%置信区间CI：0.65~0.93）。本研究构建的ROC曲线下面积为0.84。
研究结论：跑步机跑者的损伤发生率较高。与损伤相关的危险因素为髋屈肌力量输出与膝伸肌力量输出。