HSIs remain a major cause of loss of participation across various sports. Functional deficits, such as decreased knee flexor strength, may increase the risk of reinjury if present at the time of RTP. Although eccentric load helps address this issue and reduce the risk of reinjury, the frequent practice of performing exercises pain-free may delay the introduction of this type of exercise.
Forty-six males with acute HSI were randomly allocated to pain-free and pain-threshold rehabilitation groups. The outcome measures were days from HSI to RTP clearance, isometric knee flexor strength, biceps femoris long head fascicle length, fear of movement, and reinjury occurrence at the six-month follow-up. Both groups completed a standardised progressive rehabilitation protocol, differing only in the level of pain allowed during exercise.