Mechanical efficiency of locomotion in females during different kinds of muscle action.

The mechanical efficiencies (ME) of pure positive and pure negative work as well as of stretch-shortening cycle (SSC) exercise were investigated with a special sledge apparatus. The subjects were 20 young females who performed six different types of submaximal exercise: two of pure concentric exercise (positive work), two of pure eccentric exercise (negative work) and two SSC exercises. The work intensities were determined individually, from the recordings of distance obtained during a single maximal concentric exercise. Each exercise involved 60 muscle actions lasting a total of 3 min per testing condition. The MEs of pure positive work with intensities of 30% and 60% maximum (C30 and C60 respectively) were 15.5%, SD 2.6% and 14.3%, SD 1.9%, respectively. In pure negative work, when the dropping heights were 20 cm (E20) and 80 cm (E80), MEs were 28.4%, SD 6.9% and 47.9%, SD 10.1%, respectively. In SSC-exercise, the MEs during the positive phase of the take-off were 31.3%, SD 6.3% (E20/C90) and 35.0%, SD 7.0% (E80/C69). The total MEs in SSC-exercise were 29.1%, SD 4.0% (E20/C90) and 40.1%, SD 5.2% (E80/C60 x 100). In pure negative work, the increased stretching velocity increased the value of ME. In the concentric phase of SSC-exercise, the integrated electromyographic activity (iEMG) of vastus lateralis (VL) and vastus medialis (VM) muscles were lower (P less than 0.05) than in pure concentric work, when the mechanical work was the same (C60 vs E80/C60). During pure eccentric work, iEMGs were lower in comparison to the eccentric phase of SSC-exercise.(ABSTRACT TRUNCATED AT 250 WORDS)