Transcript Muscle Fibre Types - Blyth-Exercise

Muscle Fibre Types
Muscle Fibre Types
Slow twitch fibres:
Slow Oxidative (Type I)
Fast twitch fibres:
Fast Glycolytic (Type IIb)
Fast Oxidative Glyc. (Type IIb)
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
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
Myoglobin
• Protein that delivers oxygen to muscles
• Slow-twitch muscles are _____ in
myoglobin
• Fast-twitch muscles are ______ in
myoglobin
Approximate Distribution of Muscle Fibre
Types for Different Sports
Slow-Twitch
• Most active during: long-distance running, swimming,
and cycling
• Red or dark in colour
• Generate and relax tension slowly; able to maintain a
lower level of tension for long durations
• Low levels of myosin ATPase and glycolytic enzymes
• High levels of oxidative enzymes
Fast-Twitch
• Ideal for: short sprints, power lifting, and
explosive jumping
• Pale in colour
• Ability to tense and relax quickly; generate large
amounts of tension with low endurance levels
• High levels of myosin ATPase and glycolytic
enzymes
3 Fibre Types
 Type I or Slow-Oxidative (SO)
 Generate energy slowly
 Fatigue-resistant
 Depend on aerobic processes
 Type IIA or Fast-Oxidative Glycolytic (FOG)
 Intermediate-type muscle fibres
 Allow for high-speed energy release
 Allow for glycolytic capacity
 Type IIB of Fast-Glycolytic (FG)
 Store glycogen and high levels of enzymes
 Allow for quick contraction without the need for oxygen
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
Muscle Biopsy
• Muscle stained with
myosin ATPase
• Black = Type II
• Light = Type I
• Proportion is
genetically
determined
Oxidative fibres
Small diameter
Characteristics of Different Muscle Fibre
Types
Distribution of Muscle Fibre types
• Tonic muscles
– Maintain posture
– Type I
– Soleus (for dorsi flexion)
• Phasic muscles
– Type IIA and IIB
– biceps