Muscle architecture of biceps brachii, triceps brachii and supraspinatus in the horse.

This research article explores the composition and functionality of three muscles in the horse’s front limb, namely the biceps brachii, triceps brachii, and supraspinatus, with a focus on their potential to contribute to the mechanics of this limb.

Objective and Methodology

• The aim of the study was to investigate the attributes and potential contributions of three muscles – biceps brachii, triceps brachii, and supraspinatus – to the mechanics of a horse’s proximal forelimb.
• The researchers dissected these muscles from the proximal equine forelimb and measured their muscle mass, fibre length, tendon mass, and tendon length.
• The physiological cross-sectional area (PCSA) and maximum isometric force were also estimated for each muscle to provide insight into their strength and functionality.
• Additionally, measurements of the moment arms were taken at the shoulder and elbow joints to understand their contribution to these joints’ movements.

Findings

• The biceps brachii demonstrated a greater capacity for isometric force-generation than the supraspinatus, and a larger shoulder moment arm. This suggests that it could potentially make a bigger contribution towards the movement (or moment) of the shoulder than the supraspinatus.
• The study suggests the supraspinatus likely serves mainly as a stabilizer for the shoulder, rather than a shoulder extensor, due to its smaller capacity for force generation and movement contribution.
• The biceps brachii was also found to function as an elbow flexor and showed a greater PCSA and force-generating capacity than the triceps brachii, implying that it could impact the flexion and movement of the elbow more than the triceps brachii.
• Tendon force calculations revealed that the biceps tendon is capable of withstanding much greater forces than the lacertus fibrosus, the broad, flat tendon of the biceps brachii.

Impact of the Study

• This work sets the foundation for further research into how energy recycling in elastic tissues interacts with the generation and absorption of mechanical work by adjacent muscle groups in the horse’s forelimb.
• Understanding these specific muscle groups’ roles, strengths, and interactions could be particularly useful for equestrian sports, veterinary care, and equine physiotherapy.