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Background: Despite the fact that patients with obstructive sleep apnoea syndrome (OSAS) often have symptoms at the level of skeletal muscle such as fatigue, the question of whether the structural, cellular and functional properties of limb skeletal muscles are affected have not been fully examined.

Objective: The aim was to examine physiological and muscular parameters in patients with OSAS and to assess the relationship between these parameters and the clinical symptoms.

Method: Eighteen patients with OSAS and 16 controls participated. Aerobic capacity was assessed using a sub maximal test. Fibre type distribution and fibre area were analysed on muscle biopsies taken from the tibialis anterior, The microvascularisation was assessed using the following parameters: 1) the number of capillaries per fibre (CAF), 2) CAF per fibre area (CAFA), 3) CFPE-index, which represents the interface between muscle fibre and capillaries, 4) LC/PF-index or capillary tortuosity, which represents the percent of muscle fibre perimeter in contact with the wall of the microvessel.

Results: The OSAS group had significantly lower predicted relative maximal oxygen uptake (p = 0.0047) which was inversely correlated to AHI (apnoea/hypopnoea-index) (r = -0.6, p = 0.017). There was a significantly higher CFPE-index for slow type I fibres (p= 0.007) and fast type II fibres (p= 0.0126) and significantly higher LC/PF-index for type I fibres (p=0.0003) and type II fibres (p= 0.0285) in OSAS patients compared to controls.

Conclusion: OSAS patients have a higher muscle microvascularisation and a lower aerobic capacity than controls. Furthermore the aerobic capacity was inversely correlated to AHI.