QUADRICEPS MUSCLE PERFORMANCE IN SITTING AND STANDING IN YOUNG-WOMEN WITH PATELLOFEMORAL PAIN SYNDROME AND YOUNG HEALTHY WOMEN

The aim of this study was to evaluate and compare muscular activation in sitting and standing in patients with patellofemoral pain syndrome and healthy controls. Eleven women with patellofemoral pain syndrome a nd nine healthy controls were evaluated regarding: (a) muscle performa nce in sitting compared to standing - knee extensor torque was registe red in sitting with a Kin Com dynamometer and in standing with a force plate, and quadriceps muscle activity was registered with EMG in both sitting and standing; and (b) ability to maximally voluntarily activa te during sitting isometric knee extension. Maximally tolerated single -twitch electrical stimulation was superimposed on 20, 40, 60, 80 and 100% of maximal voluntary activation. Additional torque from the singl e twitch was documented. Five patients and all nine controls were test ed twice (tests a and b) with 2 days between tests, and high reproduci bility could be demonstrated. A significantly higher torque during sit ting compared with standing was found in both patients and controls, b ut with a significant correlation between sitting and standing torque values. No significant difference was found between patients and contr ols. Single-twitch electrical stimulation superimposed on maximal volu ntary activation resulted in increased torque in two of the nine contr ols compared to 10 of the 11 patients. The average increased torque in the patients were significantly higher than in the controls and estim ated to 18%. It was concluded that sitting isometric measurements are representative of the ability to produce standing isometric knee torqu e. A moderate degree of inhibition was demonstrated during sitting str ength measurements in the patients (not studied in standing).