1. Muscle Responses to Training
Objectives:
Define key terms hyperplasia, hypertrophy.
Explain how training increases muscle strength

2. Homework: Long Answer Question:
A tennis player needs to use their muscles to exert different amounts of force throughout a match.
Use your knowledge of muscle contraction to explain how this is possible.
(12 marks)

3. A tennis player needs to use their muscles to exert different amounts of force throughout a match.
Use your knowledge of muscle contraction to explain how this is possible.
(12 marks)
What should be included in a good answer?
mechanism of muscle contraction – sliding filament theory
different fibre types
explanation of motor unit
methods of changing amount of force:
number of units recruited
type of units recruited
frequency of stimulation

4. Mechanism of muscle contraction
Action potential arrives at neuromuscular junction
ACH released
Binds to receptors on sarcolemma
wave of depolarisation in muscle
t-tubules
Sarcoplasmic reticulum releases Ca2+
Ca2+ binds to troponin
moves tropomyosin
this leaves the binding sites on the actin free
Myosin heads attach to actin binding site to form cross bridges
ATP required to form cross bridge.
Myosin head moves towards the centre/power stroke occurs
Actin slides over the myosin/actin moves towards the centre of the sarcomere
Cross bridge then broken but can be recreated if calcium ions are still present
ATP is also required to allow the myosin to break the cross bridge
Muscle shortens and movement generates force
Max 7

5. Different fibre types:
Type I / slow twitch fibres are aerobic
contract slowly
do not fatigue
produce low force
Type II b / Fast Glycolytic fibres are anaerobic
contract quickly
produce high / highest force
fatigue quickly
Type IIa / Fast Oxidative fibres are anaerobic
Contract quickly
Have some resistance to fatigue
Max 5

6. Explanation of motor unit
Each nerve innervates a number of muscle fibres / definition of motor unit
Same type of fibre in each motor unit
All or None / Nothing law
Methods of changing amount of force:
more units recruited means more force
larger units recruited means more force
ST units produce lowest force / FT units produce highest force
All units recruited for maximum force.
Max 5

7. Frequency of stimulation:
Single nerve impulse produces twitch
Wave summation – several impulses in quick succession increases strength of contraction
Tetanic contraction – sustained stimulation reaches maximum force of contraction but fatigues quickly
Spatial summation – different motor units contracted at different times to maintain level of force without fatigue.
Max 6

9. What happens in / to your muscles when you train?
It depends…
What does it depend on?
Type of training
Type of muscle fibre

10. Nature vs Nurture

11. Aerobic Training of Type I fibres
Muscle fibre hypertrophy (fibres get larger)
in mitochondrial size and density
in activity of oxidative (aerobic) enzymes
in muscle myoglobin
triglyceride and glycogen stores
capillarisation

12. Resistance training of Type II fibres
Hypertrophy of Type II fibres
Hyperplasia (splitting and production of new) of Type II fibres
activity of glycolytic (anaerobic) enzymes
muscle ATP and PC stores
Improved buffering capacity (tolerance of lactic acid)

13. Aerobic Training of Type II Fibres
Conversion of Type IIb fibres to Type IIa fibres through:
mitochondrial density
capillarisation
triglyceride stores
myoglobin

14. CELLULAR ADAPTATION PRODUCED BY AEROBIC TRAINING
AFTER SEVERAL WEEKS OF AEROBIC TRAINING
BEFORE TRAINING
glycogen
fats
oxygen uptake
glycogen
fats
oxygen uptake
= SLOW TWITCH MUSCLE FIBRE (type I)
= FAST TWITCH MUSCLE FIBRE (type II) (do not increase in size)

15. CELLULAR ADAPTATIONS PRODUCED BY STRENGTH TRAINING
AFTER SEVERAL WEEKS OF STRENGTH (ANAEROBIC) TRAINING
MUSCLE CELL
BEFORE TRAINING
ATP PC
glycogen
glycolytic
enzymes
lactic acid
ATP PC
glycogen
glycolytic
enzymes
lactic acid
= SLOW TWITCH MUSCLE FIBRE (type I) (starts small gets smaller)
= FAST TWITCH MUSCLE FIBRE (type II) (starts big gets bigger)

16. Read the review article on the evidence for hyperplasia
Pick out what you think are the 5 most important/interesting/relevant pieces of evidence supporting the occurrence of muscle hyperplasia.

17. A2 revision guide