Different Effect of Local and General Fatigue on Knee Joint Stiffness.

Abstract

This study aimed to investigate the influence of locally and generally induced fatigue on the stiffness properties of the knee joint. Twenty-two male (24.9 ± 4.5 yr, 1.78 ± 0.06 m, 75.4 ± 6.4 kg, 23.9 ± 1.8 kg·m) and 18 female (21.1 ± 1.5 yr, 1.66 ± 0.05 m, 63.4 ± 6.5 kg, 22.9 ± 2.5 kg·m) amateur athletes participated. Peak torque (PT) of the knee extensor musculature, muscle stiffness (MS) of the vastus lateralis, and musculoarticular stiffness (MAS) of the knee joint were assessed pre- and postlocally and generally induced fatigue (undertaken on two separate days with a 1-wk interval). Males were characterized by higher values of MAS, relaxed and contracted MS, normalized PT (PT/body mass), and normalized MAS (MAS/external load) irrespective of time point (P < 0.05). Contracted MS increased more (P < 0.01) and normalized PT decreased more (P = 0.03) in males than in females postfatigue. Significant increases occurred in MAS in females (P = 0.01); relaxed MS (males, P < 0.001; females, P < 0.001), contracted MS (males, P < 0.001; females, P = 0.04), and normalized MAS (males, P = 0.001; females, P = 0.01) in both sexes; and normalized contracted MS (contracted MS/external load) in males (P < 0.001). Normalized PT decreased significantly in males (P < 0.01) postfatigue. Contracted MS (P = 0.01) and MAS (P = 0.05) decreased significantly in males post-fatigue. The stiffness properties of the knee joint are influenced by locally and generally induced fatigue, with different responses being observed in males and females.