The Muscular System
Muscle Types
Major Muscles of the Human Body
Muscle Fibres
Antagonistic pairs
You may think there is only one type of muscle. However, muscles come in 3 main types and have different characteristics.
Cardiac Muscles
Found in the heart
Not under conscious control
Allows heart to beat with a continuous rhythm
Allows blood to be pumped around the body as we sleep
Very resistant to fatigue
High number of mitochondria
Very good blood supply
Voluntary Muscles
Under conscious control
Used for movement
All major muscle groups of the body are under voluntary control
Can become fatigued
Can be fast twitch or slow twitch
Involuntary Muscles
Not under conscious control
Responsible for breathing in order to assist exercise
Important for bodily functions
Assist digestion and breathing
Allow vital processes to occur at night when you're asleep
Resposible for moving the body in order to perform skills
Control our internal organs
Ensures that the oxygen demand of the body can be met
Muscles are made up of lots of tiny fibres. Each of the fibres can be classified into 3 types which impact on their use of physical activity.
Type I
Red in colour
AKA slow twitch
Dense supply of mitochondria
Aerobic respiration
Dense supply of myoglobin
Don't fatigue easily
Importance in sport
Useful to
Useful for long-distance performers such as marathon runners
Application to an athlete
The dense myoglobin content in the muscles means type I muscle fibres can store more oxygen for use during aerobic respiration.
This means they don't fatigue so easily and are especially suited to endurance suited to endurance-based athletes.
However, they don't enable quick, powerful contractions, so the runner may not be a quick sprint finisher.
Type IIa
AKA fast oxidative
Importance in sport
Dense supply of mitochondria
High density of myoglobin
Aerobic and anaerobic respiration
Not so easy to fatigue
Fast and strong contractions
Useful to
Application to an athlete
Type IIa muscle fibres have high density of myoglobin for aerobic respiration; however, they can also use anaerobic respiration and can produce fast contraction.
Useful for games players who use both aerobic and anaerobic respiration
This is beneficial for a footballer who will need to go through intervals of high-intensity sprints to the ball and lower-intensity jogging for the duration of 90 minutes.
Type IIx
White in colour
Easily fatigued
Importance in sport
AKA fat glycotic
Anaerobic respiration
Low density of myoglobin
Low density of mitochondria
Fast and strong contractions
Useful to
Application to an athlete
Useful for explosive events such as weightlifting and sprinting
These have a low myoglobin and mitochondria content, and have less oxygen stores, so they use anaerobic respiration.
This results in fast, powerful contractions, great for sprinters, but fatigue quickly due to lack of oxygen.
The voluntary muscles' main role is to allow movement by working with the skeleton. Each muscle is responsible for different movements
Muscles work together in pairs in order to cause movement. Each pair is called an antagonistic pair
The agonist
Also know as the prime mover, this is the muscle that contracts and shortens to allow movement by pulling on the bone
The antagonist
Examples of antagonistic pairs at different joints
The muscle works in the opposite manner and lengthens and relaxes to allow the joint to be moved
Joint - Hip
Movement - Flexion
Agonist - Hip flexors
Antagonist - Gluteus maximus
Movement - Extention
Agonist - Gluteus maximus
Antagonist - Hip flexors
Joint - Knee
Movement - Flexion
Agonist - Hamstrings
Antagonist - Qaudriceps
Movement - Extension
Agonist - Qaudriceps
Antagonist - Hamstrings
Joint - Ankle
Movement - Plantar flexion
Agonist - Gastrocnemius
Antagonist - Tibialis anterior
Movement - Dorsiflexion
Agonist - Tibialis anterior
Antagonist - Gastrocnemius