Important thing to check is psoas involvement. Get the patient to hold hand behind head and see if they can actively hip flex beyond 90 degrees and hold it there. Early fatigue or spasm may mean increased tone (overactivity) of hip flexors due to overuse/strain. The hip flexors although appearing tight, may simply be overactive or spasming due to weakness. If this is the case they would need to be re-strengthened especially above 90 degrees of hip flexion