Decreased Muscle Speed, Strength and Fatigability Following two Hours of Tourniquet-Induced Ischaemia

Abstract

Contractile and morphological properties of the rabbit tibialis anterior muscle were measured 48 hours following a two-hour ischaemic episode. Ischaemia was induced using a specially-designed pneumatic tourniquet placed on the rabbit thigh. Maximum tetanic tension of muscle subjected to ischaemia (381 ± 77 g) was only about 30% of the tension generated by control muscles (1 212 ± 67 g). The rate of rise of tetanic tension of muscles subjected to ischaemia (15.9 ± 3 g/ms) was only 33% of control values (44.5 ± 5.9 g/ms). Muscle fatigue index increased significantly from 0.22 ± 0.7 in control muscles to 0.55 ± 0.09 in ischaemic muscles suggesting that muscles subjected to ischaemia had a greater endurance capacity than control muscles. Morphologically, focal necrotic regions and inflammatory cells were observed in ischaemic muscle fibers. Taken together, these data are consistent with selective damage to the fast glycolytic muscle fibers within the ischaemic tibialis anterior muscles. Thus, ischaemia results in overall decreased muscle speed, strength and fatigability.

Key Words:

• tourniquet
• ischaemia
• skeletal muscle
• fiber types
• fatigue