20 players allocated to the Copenhagen adductor exercise group complete a progressive strengthening programme comprising of the Copenhagen adductor exercise over a period of 6 weeks. They will complete two exercise sessions a week consisting of one set of the Copenhagen adductor exercise. The exercise will be performed on each side. The training load will increase from 5 repetitions in week 1, to 15 repetitions in week 6. The exercise programme is performed at the end of the warm-up of a regular football training session.

19 players allocated to the control group will be asked not to perform the Copenhagen adductor exercise or any other specific strength training for the adductor muscles and to continue to play football as usual.

The active player is supported on one forearm on the floor and the upper arm is resting along their side. The supporting partner places their hands at the ankle and the knee of the upper leg. The active partner raises their body from the floor and adducts both legs in a three second movement until the body reaches a straight line. The body is then lowered to the ground in a three second movement, the foot of the lower leg touches the ground before performing another repetition.

Lafayette handheld dynamometer (model: 01165) will be used to produce force values in Newtons.

Lafayette handheld dynamometer (model: 01165) will be used to produce force values in Newtons.