A demonstration of level-anchored ratio scaling for prediction of grip strength
Level-anchored ratio scaling, such as the Borg CR10 scale and the Borg CR100 scale, uses verbal anchors in congruence with numbers to give ratio data together with natural levels of intensity. This presupposes that the anchors possess natural positions in the subjective dynamic range and also numerical inter-relations. In an experiment, subjects had to produce a force of handgrip corresponding to their conception of Strong, followed by a Maximal performance. By using the previously found relationship between Strong and Maximal of 1:2 together with knowledge of the exponent in the power S-R-function (R=cSn) for grip strength, n=1.8, predictions of individual maximal performances were obtained. The predicted values correlated 0.76 with, and deviated only 3% (ns) from, actual maximal performances of grip strength. This result as previously also found for aerobic capacitygives a strong support for the use of verbal anchors, so common in category scaling, also in ratio scaling and that the Borg CR-scales fulfill the requirements for ratio scales. For estimation of muscular strength, such as grip strength, this present study points to the value of using submaximal determinations as a compliment to maximal performances (e.g., to obtain measures of functional capacity). The results also support the increasingly common use of the CR-methodology in other ergonomic settings concerning suitable design of tools and equipment.
grip strength verbal anchors functional capacity borg cr scales