31P MRS evaluation of fatigue in anterior tibial muscle in postpoliomyelitis patients and healthy volunteers.

Changes in concentration of high energy phosphates and pH were studied during rest, exercise and subsequent recovery in the anterior tibial muscle of 10 patients with late effects of poliomyelitis and 10 age- and sex-matched healthy volunteers using 31P MRS. The exercise was dynamic and isometric, and the force levels were individually adapted to each subject and stepwise increased. In general, there were no differences in metabolite changes between the groups, except for lower Pi and Pi/PCr for the volunteers during the recovery phase, also reflected by shorter recovery half-time for Pi. The interindividual variation was much higher for the patient group. Some of the patients showed deviating results probably because of differences in muscle fibre type.