Types of Skeletal Muscle Fibres
Skeletal muscle compositions vary.
Variables
Size (small, intermediate, large)
Myoglobin content (red muscle fibres=more myoglobin, white muscle fibres=less) Rate of contraction (fast, slow) ATP production (glycolytic, oxidative) Rate of fatigue (fast, slow)
Slow Oxidative
Smallest, least powerful fibres
Dark red due to high myoglobin and blood capillaries content Many large mitochondria and slow rate of contraction due to aerobic cellular respiration (reason they are called oxidative). Twitch contraction lasts 100 – 200msec and take longer to reach peak tension. Fatigue-resistant; prolonged, sustained contractions for many hours Ideal muscles for posture and endurance activities
Fast Oxidative–Glycolytic
Intermediate size
Dark red due to high myoglobin content and blood capillaries content. Intermediate rate of contraction due to aerobic and anaerobic cellular respiration Twitch contraction reaches peak tension faster than so fibres but are briefer in duration < 100msec. Intermediate fatigue–resistance Ideal for walking or sprinting
Fast Glycolytic
Largest, most powerful fibres (contain the most myofibrils) White due to few myoglobin molecules Large amounts of glycogen and generate atp mainly by glycolysis Fastest rate of contraction due to anaerobic cellular respiration Low level of fatigue resistance Ideal for explosive movements
111
Made with FlippingBook Publishing Software