Allowing the rehabilitation of acute hamstring strain injuries (HSIs) to be guided by the pain threshold did not reduce the time to return to play (RTP).

However, it did lead to a greater recovery of isometric knee flexion strength and improved biceps femoris long head fascicle length at the 2-month follow-up.

Thus, applying early eccentric loading and long-length exercises to the pain threshold may help manage deficits in knee flexor strength and help maintain gains in biceps femoris fascicle length without influencing the RTP timing.