The acute effect of foam roller application on eccentric knee flexor strength in rugby sevens players: a randomised crossover trial

Background: Hamstring injuries account for approximately one in six injuries for rugby players. Contributing factors include poor eccentric strength and reduced range of motion (ROM) at the hip and knee joints. Beyond specific training methods, foam rolling is employed extensively to enhance ROM, joint mobility, general performance, and other outcomes pre- and post-physical exercise. The study aimed to investigate the acute effect of foam roller application on eccentric knee flexor strength, hip, and knee ROM in rugby sevens players. Methods: A total of 23 rugby sevens players (age: 24.16 ± 2.15 years, height: 177.0 ± 5.89 cm, body mass: 64.57 ± 6.65 kg) underwent two conditions in a randomised crossover experiment. The experimental condition included Foam Roller (FR) exercises (3 sets, 30 seconds each with 10-second recovery intervals) on the gastrocnemius and hamstring muscles of both limbs. The non-foam rolling (NFR) condition involved resting on the mat for the same time period as the foam rolling session. Maximal eccentric strength (MES), average eccentric strength (of three repetitions) (AES), active straight leg raise (ASLR), and active knee extension (AKE) tests were performed on both limbs pre- and post- each condition. Results: The present study revealed that FR improved MES and AES (~1.4–1.7%, p < 0.001), ASLR (~9–10%, p < 0.001), and AKE (~8–10%, p < 0.001) compared to the NFR condition. Conclusions: These findings confirm that FR is a viable strategy to improve eccentric knee flexor strength, hip, and knee ROM before other activities. Such applications may be useful in improving performance and reducing injury risk for athletes.