Kb. Hagen et al., INFLUENCE OF WEIGHT AND FREQUENCY ON THIGH AND LOWER-TRUNK MOTION DURING REPETITIVE LIFTING EMPLOYING STOOP AND SQUAT TECHNIQUES, Clinical biomechanics, 10(3), 1995, pp. 122-127
Changes in kinematics as a function of lifting weight and frequency wa
s investigated in sagittal symmetric repetitive lifting. For every lif
t cycle (lowering and lifting) the motion range between the upright po
sition (0 degrees) and the maximum angular displacement of the thigh a
nd lower-trunk body segments was recorded. Ten subjects performed five
repetitive lifting bouts with different weight/frequency combinations
, using both stoop and squat lifting techniques. In total, 6384 lifts
were analysed. The lifting weight or frequency did not influence the m
otion ranges in stoop lifting. In squat lifting the weight lifted did
not appear to have any influence on the motion ranges, while the thigh
motion range was significantly smaller at lifting frequency of 20 lif
ts min(-1) than at a frequency of 10. A significant gradual decrease i
n the thigh motion range and corresponding increase in the lower-trunk
motion range were seen for a majority of the subjects during squat li
fting at frequency 20. These changes suggest that quadriceps muscle st
rength is the limiting factor in repetitive squat lifting. Also the va
riation in motion ranges was greater in squat lifting than in stoop li
fting.