CHANGES IN MUSCLE MORPHOLOGY, STRENGTH AND ENZYMES IN A 4-5-YEAR FOLLOW-UP OF SUBJECTS WITH POLIOMYELITIS SEQUELAE

Twenty subjects with polio sequelae were studied on two occasions 4-5 years apart by means of dynamometer measurements of knee-extension and flexion strength and muscle biopsy for histochemical and enzymatic an alyses. The subjects were divided into those who reported (unstable, n = 12) and did not report (stable, n = 8) new or increased muscle weak ness in the tested leg between the two examinations. Muscle strength d ecreased significantly in the unstable subjects, but only for knee-fle xion in the stable subjects. However, the endurance test comprising 50 consecutive knee-extensions at 180-degrees/sec showed increased fatig ability at the second examination only in the stable subjects. Most su bjects had markedly increased muscle fiber areas, which in some subjec ts increased further, but in those already with very extreme hypertrop hy the fiber size decreased. Capillarization and activity of citrate-s ynthase were decreased at the initial examination, but no significant further reduction was observed at the second examination. The results demonstrate individual patterns in the compensatory process for the pr esumed loss of motor units.