Injury Rate and Patterns in Group Strength-Endurance Training Classes

To identify the injury rate during high-intensity functional training.

Adults (N=100; 82 [82%] female) in group strength-endurance training at the Dan Abraham Healthy Living Center from January 9, 2017, through April 19, 2018, were recruited for the study. Participants were recruited before the class start date. Those who consented received a preclass survey and another survey 6 weeks after the class started to obtain data on demographic characteristics, baseline joint problems or pain, injuries in the preceding 6 weeks, class satisfaction, and exercise habits. Classes lasted 6 weeks and were led by a trainer for 60 minutes, once weekly. Participants were encouraged to perform similar exercise on 2 additional nonconsecutive days throughout the week. Injury was self-reported and defined as experiencing new pain or sustaining injury while exercising during the 6-week time frame. The primary outcome measure was the number of injuries per 1000 training hours.

The injury rate was 9.0 injuries per 1000 training hours (95% CI, 5.8-13.4 injuries per 1000 training hours) during the 6-week training and 5.0 injuries per 1000 training hours (95% CI, 2.8-8.2 injuries per 1000 training hours) during the 6 weeks preceding enrollment (P=.08). Injury occurred in 18 (18%) of participants during the 6-week training, and 9 of 24 injuries (37.5%) occurred during a training class. The most commonly injured regions were knees (n=7) and back (n=6). Burpees and squats were the most common movements causing injury.

The increased injury rate during the study was not statistically significant. It was higher than rates reported in previous retrospective studies of high-intensity functional training, weight lifting, or power lifting but comparable with rates reported in prospective studies of novice and recreational runners.