1. SPORT MED 20L Mr. Giesbrecht
How a Muscle Works
SPORT MED 20L
Mr. Giesbrecht

2. MOTOR UNIT
A Motor unit consists of the motor neuron and the muscle fibers it connects to
Some motor units consist of only one muscle fiber while others consist of hundreds of muscle fibers

3. MUSCLE STRUCTURE AND SARCOMERES

5. MUSCLE CONTRACTION – SLIDING FILAMENT THEORY
Resting Phase
Very little calcium is present so few myosin cross-bridges are formed

6. MUSCLE CONTRACTION – SLIDING FILAMENT THEORY
Excitation-Contraction Coupling Phase
A signal (Action Potential) comes from the motor neuron to the muscle causing the release of calcium
Calcium stimulates the connection of the mysosin (Thick Filaments) cross bridges to the actin (Thin Filaments)

7. MUSCLE CONTRACTION – SLIDING FILAMENT THEORY
Contraction Phase
The cross bridges pull on the thin filaments bringing the ends of the sarcomere closer together
The energy for the puling action of the cross-bridges comes from the breakdown of adenosine triphosphate (ATP)
In order for contraction to continue calcium must be present and the cross bridge needs ATP

8. MUSCLE CONTRACTION – SLIDING FILAMENT THEORY
Relaxation Phase
Stimulus from motor neuron stops
Calcium is “pumped” back to storage
Cross-bridges release

9. MUSCLE TWITCH
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10. MUSCLE FIBER TYPES Fast Twitch Muscle Fibers Develop force fast
Relax fast
Fatigue quickly
Type IIx

11. MUSCLE FIBER TYPES Slow Twitch Muscle Fibers Develop force slowly
Relax slowly
Fatigue slowly
Type I

12. MUSCLE FIBER TYPE AND SPORT PERFORMANCE
Fast Twitch
Strength/Power/Speed sports
Slow Twitch
Endurance based sports

13. MUSCLE FIBER TYPE AND SPORT PERFORMANCE
Assignment – Classify the sporting events on the sheet provided as being either fast twitch or slow twitch activities.