Bow and muscles: Observed muscle activity in archers and potential implications for habitual activity reconstruction

Abstract

Previous research has suggested that reduced humeral asymmetry in robusticity in European Late Pleistocene and Early Holocene populations may be a result of increased left humeral robusticity due to muscle loading from increased use of bow hunting. This paper provides a basis for considering the causes of such changes by assessing the overall intensity and level of asymmetry in the distribution of muscle activation and muscle force among living male archers. In this experiment, 20 right-handed archers drew a replica of the self bows characteristic for the Upper Paleolithic and Neolithic. We measured activation of eight muscles (biceps, triceps [long head], triceps [lateral head], deltoid [anterior part], deltoid [middle part], deltoid [posterior part], infraspinatus, and latissimus) using surface electromyography. We observed about a 15%–28% left bias in total maximum muscle force. The main muscles employed were triceps (lateral head), deltoid (middle part), and deltoid (posterior part) on both sides and triceps (long head) on the left arm. The most asymmetrical toward the right arm was the activation of biceps (123% right bias in mean muscle activation) and toward the left was triceps (long head) and triceps (lateral head) (70%–110% left bias in mean muscle activation). We conclude that left biased asymmetry in maximum muscle force produced during bow shooting may be responsible for the increase in robusticity of the left humerus and that the pattern of activation of specific individual muscles suggests that archery may be identifiable in the prehistoric record using skeletal features associated with muscle activity.