The Effect of the Number of Carries on Injury Risk and Subsequent Season’s Performance Among Running Backs in the National Football League

Abstract

Background: In recent years, several studies have correlated pitch count with an increased risk for injury among baseball pitchers. However, no studies have attempted to draw a similar conclusion based on number of carries by running backs (RBs) in football. Purpose: To determine whether there is a correlation between number of carries by RBs in the National Football League (NFL) and risk of injury or worsened performance in the subsequent season. Study Design: Cohort study; Level of evidence, 3. Methods: The ESPN NFL statistics archives were searched from the 2004 through 2014 regular seasons. During each season, data were collected on RBs with 150 to 250 carries (group A) and 300+ carries (group B). The following data were collected for each player and compared between groups: number of carries and mean yards per carry during the regular season of interest and the subsequent season, number of games missed due to injury during the season of interest and the subsequent season, and the specific injuries resulting in missed playing time during the subsequent season. Matched-pair t tests were used to compare changes within each group from one season to the next in terms of number of carries, mean yards per carry, and games missed due to injury. Results: During the seasons studied, a total of 275 RBs were included (group A, 212; group B, 63). In group A, 140 RBs (66%) missed at least 1 game the subsequent season due to injury, compared with 31 RBs (49%) in group B ( P = .016). In fact, players in group B missed significantly fewer games due to injury during the season of interest ( P < .0001) as well as the subsequent season ( P < .01). Mean yards per carry was not significantly different between groups in the preceding season ( P = .073) or the subsequent season ( P = .24). Conclusion: NFL RBs with a high number of carries are not placed at greater risk of injury or worsened performance during the subsequent season. These RBs may be generally less injury prone compared with other NFL RBs.