Does Overexertion Correlate with Increased Injury? Determining the Relationship between Training Load and Soft Tissue Injury in NFL Players using Wearable Technology

OBJECTIVES: The development of injury prevention strategies is important in maximizing athlete health and safety. Increased training loads have been associated with increased odds of injury in collision sports during all phases of training. To date, the relationship between training load and injury has not been investigated in NFL players. The primary objective of this study was to determine the correlation between player workload and soft tissue injury utilizing wearable GPS technology. METHODS: Player workloads were assessed during training sessions during the preseason and regular season using GPS and triaxial accelerometer from 2014-2016. Soft tissue injuries were recorded during each season and were divided into ligamentous and myotendinous injuries. Player workload during the week of injury and mean weekly workload in the 4 weeks prior to injury were determined for each soft tissue injury. These variables were also determined in uninjured position-matched controls during the same week. Descriptive statistics were used to summarize player workload for injuries and controls. Subgroup analysis was also conducted to determine whether observed effects were confounded by training period and type of injury. RESULTS: Data was obtained over 2 NFL seasons from 2014-2016. A total of 136 lower extremity injuries were recorded. 62/136 (45%) of injuries were sustained during the preseason. Ankle sprains were the most common type of ligamentous injury (60%) while hamstring strains were the most common type of myotendinous injury (49%). 100 injuries that had a set of GPS data were included in the analysis. Injuries were associated with greater increases in player workload during the week of injury compared to uninjured individuals (193.6, 95% CI 104.6-282.5 versus 101.2, 95% CI 27.7-174.8, p = .0038). Injured players were associated with a 110% increase in training load during the week of injury compared to uninjured players, who were associated with a 73% increase (p = .032). This effect was most pronounced with myotendinous injuries during the preseason as these injuries were associated with significantly greater increases in workload during the week of injury compared to uninjured controls (617.0, 95% CI 318.4-915.6 versus 384.1, 95% CI 137.5-630.8, p = .0095). Injured players were associated with 260% increase in training load during the week of injury compared to uninjured controls who were associated with 165% increase in workload (p = .012). CONCLUSION: Soft tissue injuries in professional football are associated with large increases in training load during the week of injury. This effect seems to be especially pronounced during the preseason when workloads are generally higher and is primarily applicable to myotendinous injuries. These results suggest that a gradual increase in training intensity is a potential method to reduce risk of soft tissue injury. Preseason versus regular season specific training programs monitored with wearable technology may assist team athletic training and medical staff with developing programs to optimize player performance.