Emotion affects torso force production during flexion and extension movements: implications for spine loading

Abstract

Psychosocial variables have long been linked to injury risk but it has not been clear how these might influence the mechanical parameters associated with injury. This study aimed to clarify the relation between emotional states and the force produced for voluntary torso motion. A total of 15 subjects were tested. Subjects were exposed to images ranging from pleasant, unpleasant, neutral and blank for a 5 s duration, at which time a tone sounded. They were required to exert a force in flexion or extension, at the tone, to change the images. Exposure to unpleasant emotional stimuli increased muscle force production in flexion movements when compared to all other stimuli used (pleasant, neutral and blank). Friedman rank sum test revealed a significant main effect of emotion intensity and flexion, (Friedman chi-square = 12.3405, p = 0.006. It is proposed that this connection would increase muscle force production during, for example, lifting tasks in an unpleasant environment thereby leading to increased in spine compression.