Acute tendon changes in intense CrossFit workout: an observational cohort study.

CrossFit is a fitness program that has become increasingly popular in the Western world, but as in other sports, the risk of injury is present. Only a few studies have addressed health benefits and injuries in CrossFit. It is known that chronically overloaded tendons will thicken and increase the risk of tendinopathy. However, it remains unknown whether acute overload caused by strenuous, high-intensity exercise will exert changes in tendons and if these changes can be detected and described by ultrasonography. The aim of this study is to evaluate the effects of acute overload on tendon thickness using ultrasonography. Standardized ultrasound measurements of the patella, Achilles, and plantaris tendons were performed before and after a specific workout in 34 healthy subjects. Significant increases were observed in patella tendon thickness before (M = 4.5, SD = 0.6) and after (M = 5.0, SD = 0.7) highly intense strenuous exercise, with an estimated mean differences of 0.47 mm (95% CI: 0.35-0.59 mm; P < 0.0001) and in Achilles tendon thickness before (M = 4.4, SD = 0.4) and after (M = 4.5, SD = 0.5) workout, with an estimated difference of 0.17 mm (95% CI: 0.04-0.29 mm; P < 0.01). However, there was no significant difference in fascia plantaris thickness before (M = 3.4, SD = 0.5) and after (M = 3.4, SD = 0.5) workout (P = 0.97). A significant increase in the thickness of the patellar and Achilles tendons was found in response to strenuous, highly intense CrossFit exercises. In order to understand the underlying mechanisms of the findings and possibly utilize this to gain a better understanding, further studies must be conducted.