Abstract: This paper presents the results of a comparative study of load
sharing among back and leg muscles during squat and half-kneeling lifts. 19
young and healthy subjects with no history of low back pain or other
musculoskeletal disorders participated in the study. Muscle activity was
measured using electromyography (EMG) technique. Surface EMG electrodes were
placed bilaterally at the erector spinae, quadriceps and hamstring muscles.
Muscle activities were determined at different force levels representing 40, 60
and 80 percent of maximal voluntary contraction (MVC). The results showed
increase in normalised mean RMS (root mean squared) values of EMG of for all
the muscles with increasing force levels in both squat and half kneeling lifts.
Contralateral and ipsilateral ratio parameters were used to determine the
degree of load sharing among the muscles in both lifting postures. Statistical
analysis of the mean RMS values and the contralateral and ipsilateral ratio
parameters revealed no significant differences between squat and half kneeling
lifts. The paper discusses the implications of the results for preventing
injuries during manual handling and provides suggestions for future