Functional and Morphological Adaptations Following Four Weeks of Knee Immobilization

Abstract

Immobilization of the knee as part of the treatment in bone or joint lesions leads to atrophy and consequently loss of functionally. In patients this atrophy and loss of functionality is difficult to quantify because of interfering symptoms and missing baseline data. In the present study structural and functional changes in thigh muscles were examined in eight healthy volunteers of whom one leg was immobilized in a cast for four weeks. Quadriceps cross-sectional area determined with computed tomography was 21% +/- 7% diminished after four weeks immobilization (p < 0.05). Muscle biopsies from the musculus vastus lateralis revealed an 16% decreased fiber diameter (p < 0.05) and no significant shift in fiber types. Isokinetic strength measurements of knee extensors and flexors demonstrated a fall in peak torque of 53% +/- 9% and 26% +/- 13% at an angular velocity of 60 deg.s-1 (p < 0.01). Aerobic power in one-leg-cycling exercise was not significantly affected, but isokinetic quadriceps endurance work decreased from 9.1 kJ to 5.6 kJ (p < 0.05). Despite the fall in quadriceps performance the subjects had only minor functional complaints for a few days. It is concluded that immobilization of the knee is an important factor in the development of thigh muscle atrophy in patients and should therefore be diminished as much as possible.

Neural activation of the triceps surae is impaired following 2�weeks of immobilization

“…We expected that the use of eight subjects would lead to insufficient statistical power. However, in previous immobilization studies using fewer or the same number of subjects, a significant decline of muscle strength was demonstrated Hainaut 1987, Duchateau andHainaut 1990;Kitahara et al 2003;White et al 1984;Thom et al 2001;Veldhuizen et al 1993). Consequently, we concluded that eight subjects would be sufficient for this study.…”

“…Many studies have shown that such impairment is typically associated with significant loss of muscle mass (Hespel et al 2001;Miles et al 1994; Thom et al 2001;Veldhuizen et al 1993). For example, Veldhuizen et al (1993) found that the strength of the quadriceps femoris muscle decreased by 53% after 4 weeks of knee immobilization, whereas the decrease in the anatomical crosssectional area (CSA) assessed by computed tomography was 21%.…”

“…Many studies have shown that such impairment is typically associated with significant loss of muscle mass (Hespel et al 2001;Miles et al 1994; Thom et al 2001;Veldhuizen et al 1993). For example, Veldhuizen et al (1993) found that the strength of the quadriceps femoris muscle decreased by 53% after 4 weeks of knee immobilization, whereas the decrease in the anatomical crosssectional area (CSA) assessed by computed tomography was 21%. The same discrepancies between strength and anatomical CSA reductions, measured by ultrasonography or nuclear magnetic resonance imaging, have been observed following 10 and 14 days of knee immobilization respectively, by Thom et al (2001) and Hespel et al (2001).…”

Disuse of the musculo-skeletal system in space and on earth

“…In contrast, Veldhuizen et al (1993) reported that VL fibre type IIx showed the greatest atrophy, followed by type I and type IIa. Greater atrophy of fast fibres was also reported by Jaweed (1994) following 42 days of ULLS as the decrease in VL fibre CSA was 12% for type I and 15% for type II fibres, respectively.…”

Hand immobilization affects arm and shoulder postural control

“…Over the past few decades, several authors have documented modifications in skeletal muscle properties such as atrophy (White et al 1994;Hather et al 1992), increasing in the intramuscular connective tissue (Józsa et al 1990) and reduction in the maximal voluntary contraction strength (Veldhuizen et al 1993;Hortobàgyi et al 2000) after cast immobilization.…”