

You have 20 minutes to explain the assigned step of the
Sliding Filament theory.
Use the success criteria and SWEETS provided
Timer
Learning Outcomes



All able to remember
and understand the 3
different types of fibres
Most are able to apply
knowledge of the fibres
to sporting events.
Some are able to justify
the proportions of
muscle fibres in each
muscle



Answer exam questions 3 & 4 on p42 (sheet
from last week).
Using photos from starter activity display this
information in a way that you feel is most
appropriate to aid revision (flip book, poster,
instruction manual)
Complete flipped learning worksheet watching
video on weebly.




Within skeletal muscle there are 3 types of
muscle fibres. All contain a mixture of all three
but not in equal proportions.
This mix is mainly genetically determined.
These fibres are grouped into motor units, only
one type of fibre can be found in one unit.
(Motor unit – the motor nerve and the group of
muscle fibres that it controls)
Characteristic Slow
Oxidative
s
Twitch
Type I
Structural
Fibres per
motor
neurone
Motor
neurone size
Myoglobin
content
Type of
myosin
ATPase
Mitochondria
l density
Capillary
density
Sacroplasmic
reticulum
development
Glycogen
stores
Fast
Oxidative
Glycolytic
(F.O.G.)
Type IIa
Fast Twitch
Glycolytic
(F.T.G.)
Type IIb
10-180
300-800
300-800
Small
Large
Large
High
Medium
Low
Slow
Fast
Fast
High
Medium
Low
High
Medium
Low
Low
High
High
Low
High
High

In pairs look at
homework sheet on
characteristics of
muscle fibres. Are
your answers the
same? Justify your
decisions.
Characteristic
s
Force of
contraction
Speed of
contraction
Fatigability
Slow
Oxidative
Twitch
Type I
Low
Fast
Oxidative
Glycolytic
(F.O.G.)
Type IIa
High
Fast Twitch
Glycolytic
(F.T.G.)
Type IIb
High
Slow
Fast
Fast
Low
Medium
High
Aerobic
capacity
Anaerobic
capacity
High
Medium
Low
Low
Medium
High
Motor Unit
strength
Low
High
High
Muscles
 Questions are frequently asked on the characteristics
of muscle fibre types.
 If the question asks for fast-twitch characteristics,
learn the following as they are probably the most
straightforward to remember: low number of
mitochondria, low myoglobin, low capillary
density, low triglyceride stores, high glycogen
stores, high PC stores and low fatigue resistance.
 These characteristics can be used for slow-twitch
fibres — just reverse them!


Although fast twitch fibres generate much
greater forces they have a higher fatigue index
meaning shorter contraction time.
The relative proportion of each fibre type
varies in the same muscles of different people.


Elite endurance – greater proportion of slow twitch
fibres
Elite sprinter – greater proportion of fast twitch
fibres
Using the sporting pictures create a continuum
like the one shown below according to the fibre
type predominantly used by the selected
performer.
_________________________________
Type 1
Type 2a
Type 2b


Now look at Fig 2.09 to check your continuum
•
Answer and explain the following statement: “can
muscle fibre distribution predict success in certain
sporting activities?”
•
Generally true but there are other determining factors:
- length of lever
- VO2 max
- physique
- motivation
- confidence



In pairs attempt the exam question
Peer mark the answer in a different colour
Make your corrections using green pen


The motor unit is the basic functional unit of
skeletal muscle.
The motor unit is the motor nerve (neurone)
and the group of muscle fibres that it controls.


Stimulation of one motor neuron causes all the
muscle fibres in that motor unit to contract
simultaneously.
Each muscle is made up of a number of units.
The number recruited varies depending on
strength required.
 Number
of fibres within a motor unit is
dependent on control required.
Small muscle for fine motor skill may only require
one fibre per motor unit e.g. eye to focus
 Large muscle for gross skill may need 500 or more
fibres e.g. kicking a football



Motor units are usually made up of the
same muscle fibre.
So we see both fast and slow twitch
motor units in a muscle.
I am/can
Known
fibres
Look again at Who am I?,
using a green pen what can
you add to it now.
Learning Outcomes
All able to remember and understand the 3
different types of fibres
Most are able to apply knowledge of the
fibres to sporting events.
Some are able to justify the proportions of
muscle fibres in each muscle
I am Type ?
as
slow
twitch
I
manufacture and split ATP
at a fast rate so produce fast
strong contractions.
IIa
White in colour due to low
level of myoglobin and few
mitochondria
IIb
Red in colour due to
presence of high volumes
of myoglobin
I
Known as fast glycolytic
fibres
IIb
Produce ATP at a slow rate
by anaerobic metabolism
IIb
more prone to fatigue than
type I fibres.
IIa
very resistant to fatigue
I
Known as fast oxidative
fibres
IIa
contain a medium amount
of
myoglobin
and
mitochondria
IIa
break down ATP very
quickly resulting in short,
fast bursts of power and
rapid fatigue
IIb
be turned into type IIa by
resistance training
IIb
are capable of producing
repeated
low
level
contractions by producing
large amounts of ATP
I