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Fast twitch fibres: Fast Glycolytic (Type IIb) Fast Oxidative Glyc. (Type IIb). Slow twitch fibres: Slow Oxidative (Type I). Muscle Fibre Types. A. Slow Twitch Fibres. Suited for repeated contractions during activities requiring a force output of < 20-25% of max force output
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Fast twitch fibres: Fast Glycolytic (Type IIb) Fast Oxidative Glyc. (Type IIb) Slow twitch fibres: Slow Oxidative (Type I) Muscle Fibre Types Sport Books Publisher
A. Slow Twitch Fibres • Suited for repeated contractions during activities requiring a force output of < 20-25% of max force output • Examples: lower power activities, endurance events Sport Books Publisher
B) Fast Twitch Fibres • Significantly greater force and speed generating capability than slow twitch fibres • Well suited for activities involving high power • Examples: sprinting, jumping, throwing Sport Books Publisher
The Muscle Biopsy • Used to determine muscle fibre type 1. Injection of local anesthetic into the muscle being sampled 2. Incision of approximately 5-7mm is made in the skin and fascia of the muscle 3. The piece of tissue (250-300mg) removed via the biopsy needle is imbedded in OCT compound 4. The sample is frozen in isopentane cooled to –180C Sport Books Publisher
Muscle Biopsy Sport Books Publisher
The Histochemistry • The biopsy samples are first sectioned (8-10 μm thickness) • Sections are processed for myosin ATPase: Fast twitch fibres – rich in myosin ATPase – white in colour Slow twitch fibres – low in myosin ATPase – Red in colour Sport Books Publisher