Use of Isokinetic Strength Ratios to Discriminate between Maximal and Feigned Shoulder Extension Musculature Efforts

INTRODUCTION Occupational injuries of the shoulder joint are of growing concern due to work time loss, as well as increases in medical and restitution expenses [1]. The assessment of shoulder musculature strength may assist in decision making regarding the effects of interventions, as well as possible readiness to return to work. Current practices related to the use of strength scores for such purposes are based on the assumption that the patient exerted optimal effort during trial performance. In this context, an approach proposed for determining the type of effort recorded using isokinetic dynamometry is based on the ratio of eccentric and concentric strength scores [2].The supposition of the method relies on the moment-angular velocity relationship obtained in recordings of maximal efforts, whereas concentric strength declines as a function of increases in angular velocity, eccentric strength scores remain relatively unchanged [2]. The eccentric to concentric strength ratio, therefore, is greater than 1 irrespective of the angular velocity employed. In performance of submaximal or feigned efforts, it has been shown that there is a significant increase in the value of this ratio, and that it is more pronounced as a function of the increase in the angular velocity employed. The purpose of this investigation was to assess the ability of two indices utilizing this phenomenon, termed the DEC and SEC, to distinguish between maximal, submaximal, and feigned isokinetic shoulder extension efforts.