Function of the muscles of the upper limb in car driving.

The function of (I) the deltoid muscle, (II) the trapezius muscle, and (III) the three main elbow flexors as well as the triceps brachii muscle were tested during driving in a simulator I.The anterior and middle portions of the deltoid muscle work during contralateral rotation of the steering wheel, while the posterior portion does not work at all. The deltoid muscle seems to have a purely phasic action in ear driving II.The upper portion of the trapezius muscle works more or less statically with a weak contraction. There is no correlation between the periods of contraction and the angular movements of the steering wheel. The middle and lower portions of the muscle show much less activity than the upper portion, III.The three main elbow flexors, i.e. the brachialis, biceps brachii and brachioradialis muscles, and the triceps brachii muscle show some activity during driving, but without any meaningful correlation between the periods of activity and the deviation of the steering wheel.