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.
Highlights
Running is considered a contemporary social phenomenon and it is one of the five most popular sports activities in the world[1]
Higher hip flexor force output was identified as 4 times more likely to have no injury in the final model and lower knee extensor force output as the highest chance of injury (OR .24; 95% CI (65-93)
Injuries incidence in treadmill runners was 6.8 per 1,000 hours of running, and the main associated factors were hip flexor and knee extensor isometric muscle force output
Summary
Running is considered a contemporary social phenomenon and it is one of the five most popular sports activities in the world[1]. The choice to run on a treadmill is related to convenience, social aspects, and climate[4]. Several studies report kinematic and kinetic differences between treadmill and overground running. The main differences mentioned in a recent systematic review[5] were: less vertical displacement of the pelvis, less range of motion of knee flexion during stance, less peak propulsion, and increased moment of the sagittal plane of the ankle in the treadmill run. Another point reported in the literature is the different muscle recruitment, due to the rigidity of the surface[6]. Treadmill running has less air resistance and energy cost[8], as demonstrated in a recent meta-analysis in which was pointed that the lactate concentration and oxygen consumption were lower in treadmill running at almost full speed[9]
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