Diagnostics with isokinetic devices in shoulder measurements -- potentials and limits

Abstract

The correction of muscular imbalances is assumed to be important in therapy of shoulder pathologies and muscular strengthening. However, it is not clear how these imbalances should be defined and the extent to which conclusions can be drawn, relevant to therapy and training. Statements on physiological strength ratios and deviations from these are only possible using a valid and reliable measurement. Isokinetic shoulder strength measurements can be considered validly isokinetic up to 180 °/s, Differentiation between the various types of work and movements is reliable within a test-retest variability of 15-20%. The maximum torque serves as a reliable parameter and additional information is obtained by determination of local muscle fatigue. In this context important considerations are the test method and especially positioning and fixation. However, the direct application of isokinetically determined strength values in training and rehabilitation is only possible when the exercise position agrees with the position during measurement. This is usually not the case. Since isokinetic movements are rarely if ever encountered in everyday living or sports, data obtained by these methods can hardly be used for training management and should mainly be used as a therapy control. Adequately reliable data on the strength ratio of shoulder movements can be obtained within narrow limits by isokinetic strength measurements. However, in spite of critical assessment of the methods, it is recommended that isokinetic measurements should be uniformly performed in accordance with the queries in order to guarantee comparability and interpretation. In addition stress in everyday living and sports lead to specific changes which should always be interpreted on the basis of method-specific criteria and exercise-specific movements. Taking functional-anatomical and methodical considerations into account, isokinetic measurements deliver valuable information for training and therapy within the framework of medically and scientifically founded strength diagnostics.