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Lateral asymmetry in grip strength: utility of the ten per cent rule.

OBJECTIVE
To measure asymmetry in grip strength between hands in left, right and mixed handers and to test utility of the ten per cent rule.


DESIGN
A cross sectional study.


SETTING
Queen Elizabeth Central Hospital, Blantyre, Malawi.


SUBJECTS
One hundred and seventy six healthy volunteers (102 males and 74 females) aged 15 to 66 years were selected from visitors to the patients admitted at the hospital.


MAIN OUTCOME MEASURES
Bilateral measurements of maximal grip strength, assessment of handedness using a questionnaire incorporating questions on hand preferred for six habitual activities.


RESULTS
In about 70% of males and females, the right hand was stronger than the left hand while frequency of left, mixed, and right handers was 5.7%, 4.5% and 89.2%, respectively. Significant association (chi2 = 6.43, n = 2, p<0.05) was found between handedness and stronger hand with preferred hand being stronger in most subjects. However, for about 40% of left and mixed handers and 27% of right handers, the non-preferred hand was stronger. The mean differences between grip strengths varied between 10% and 20% in different categories of handers when stronger hand was taken into consideration. Without considering the stronger hand, the mean bilateral difference in maximal grip strength in the three categories of handedness was between three and six per cent..


CONCLUSION
Distinction between stronger hand and hand preferred for skilled activities should be made and considered when assessing limitations in hand strength in clinical practice.