Lower-limb asymmetries in early and late middle age

The present study examined the relationship between upper- and lower-limb laterality and the difference in kinaesthetic function between lower limbs. A total of 360 early and late middle-aged people from rural areas in Japan participated in the study. The first purpose was to describe upper- and lower-limb lateral preferences. Approximately 80% of the population showed uncrossed lateral preference between hand and foot (i.e., right-handed and right-footed or left-handed and left-footed). Furthermore, the proportions of uncrossed type population were similar among the four age groups (30s-40s, 50s, 60s, and 70s). The second purpose was to examine the lateral differences in leg muscle strength in order to seek possible reasons for a leftward bias in the occurrence of hip fractures. Leg muscle strength was measured by a strengthergometer. The muscle strength of the left leg (non-preferred) was stronger than that of the right (preferred) leg in the 50s age group, whereas there was no significant difference between the two lower limbs in the other age groups (30s-40s, 60s, 70s). This finding suggests that greater fatigue on the left leg bone system might induce the high occurrence of left hip fractures.