Four factor model to describe an isoinertial lift.

The objectives of the study were threefold: (1) to develop an empirical description of dynamic factors involved in a test of lifting performance on an Incremental Lifting Machine (TLM) through application of principal components analysis; (2) to conduct gender analyses of the factor structures; and (3) to determine the stability of the structures with repeated sampling. An initial sample of 175 participants (79 females and 96 males) completed a maximal isoinertial lifting test from a starting height of 0·34 m to a target height of 1·83 m. A confirmatory sample of 132 participants (33 females and 99 males) completed the same 1LM test under identical conditions. A force transducer attached to the back of the armature provided continuous displacement data from which displacement, velocity, acceleration, force, and power profiles were determined. These data were summarized into 32 lift parameters, and then subjected to principal components analyses. For the dynamic parameters recorded for the initial sample, a four factor solution accounting for 78·9% of the variance was found to be optimal. Factor one (named Mid-Body Coordination and accounting for 24·7% of the variance) related to the timing and displacement of maximum velocity and power. Factor two (named Maximum Strength) contained maximum force and power measurements and accounted for 22·5% of the variance. Factor three (named Minimum Strength) related to minimum measures of force and power and accounted for 17·2% of the variance. Finally, factor four (named Lower Body Co-ordination and accounting for 14·4% of the variance) related to the timing and displacement of maximum force. Descriptions of the factors were developed in terms of their underlying biomechanical relationships. The four factor solution was found to be stable across genders, and it was replicated for the confirmatory sample. It was concluded that these dynamic factors possessed considerable scientific utility for future research.