GLOSSARY

Type IIa fibres are fast oxidative-glycolytic (FOG) fibres with intermediate properties between type I and type IIx fibres: both fast and strong and fairly fatigue-resistant.

Characteristics

• Myosin isoform: MHC IIa with high contraction velocity.
• Metabolism: high glycolytic and moderate-to-high oxidative capacity, with relatively many mitochondria and capillaries.
• Colour: red to pink owing to moderate myoglobin.
• Motor unit: medium to large; recruited after type I fibres.

Adaptability

Type IIa fibres are the most adaptable