Recurrance of hamstring strain is quite often a problem for soccer players. It is always important to strengthen your hamstrings, giving importance to flexibility of the muscle group. Eccentric exercises are prefered under physio supervision.

Before return to sports an isokinetic strength testing would be prefered.
Isokinetic strength testing is used as an indicator of recovery following muscle injuries. This test is done using isokinetic dynamometer. This equipment should be available at your sports medicine clinic. This machine allows the hamstrings to be tested through the full range of knee movement. All concentric, eccentric, and isometric (static) strengths are tested. The muscle endurance of the hamstrings may be assessed, which together with the eccentric strength and the quadriceps/hamstring ratio, is particularly relevant for runners (important for football). Isokinetic testing gives specific muscle strenght and weakness can be identified. An apt individual strengthening programme can be planned to treat your specific problems, and will assist in effective rehabilitation.