Actin, alpha skeletal muscle

Alpha-skeletal muscle actin is the predominant actin isoform in striated skeletal muscle, forming the thin filaments of the sarcomere and being essential for force generation during contraction. Its appearance in saliva indicates muscle fibre structural disruption, as actin is released from myocytes following sarcomeric damage caused by eccentric exercise, high mechanical load, or muscle injury. As a structural contractile protein, salivary alpha-skeletal actin provides direct evidence of myofibrillar damage distinct from enzymatic markers.