1. Neuromuscular Adaptations to Conditioning
Chapter 2

2. The Nervous System Central (CNS) Peripheral Brain Spinal cord Nerves
Axons

4. Neuron and Motor Unit Neuron is a single nerve cell
1014 neurons in brain
Synapses convey information via chemicals
Afferent-from periphery to CNS
Efferent-from CNS to periphery
Neuron body, dendrites and axon (myelin sheath)

5. Action Potential Alteration in permeability
Sodium influx and potassium outflow
Negative to positive
Nerve conduction velocity
120 m/s or 270mph for myelinated
400 f/s
5 m/s or 2mph for unmyelinated

9. Phospholipid Bilayer

10. Slow or Block Nerve Conduction
Demyelination
Multiple sclerosis
Guillain-Barre syndrome
Parkinsons
ALS

11. Neural Components of Muscle Activation
Motor unit
Acetylcholine (ACH)- primary neurotransmitter at the neuromuscular junction
Frequency of nerve impulses
Twitch
Summation
Tetanus

12. Electrical Stimulation
Motor nerve innervation
Latent period (.01)
Contraction phase (.04)
Relaxation phase (.05)
Fast vs. slow time varies

15. Threshold
AP results from the quick and dramatic alteration to ionic permeability following chemical or electrical intervention. Muscle resting at -90 millivolts
After stimulation of an excitable cell membrane sodium ions move into the cell and the transmembrane potential is reduced - referred to as depolarization
When a critical voltage level called the threshold is reached, voltage-sensitive sodium gates are opened followed by slower acting potassium gates (move out)
At +35 millivolts the sodium channels and the potassium channels are fully opened, resulting in restoration of the negative transmembrane potential - called repolarization
The amplitude of voltage changes in response to stimulation is constant from stimulus to stimulus and is described as "all or none"
Electrical stimulation of excitable cells is possible up to 1000 pps.

18. Temperature Heat increases speed and force output.
Cooling increases relaxation time.
Heat may increase speed by 20%.

19. Size Principle of Muscle Recruitment% F I B E R S U D
TYPE IIb
TYPE IIa
TYPE I
MUSCULAR FORCE

20. Reflexes Sensory receptors send a signal to a motor neuron
Motor neuron sends signal to the effector
Stretch shortening cycle (SSC)?

22. Stretch Shortening Cycle
Concentric force is increased as a function of eccentric action or stretching.
Increased force with speed of the motion.
Stored elastic energy responsible.

23. Fatigue Repeated contractions diminish relaxation time.
Neural signals continue to propagate.
Contracture occurs at the muscle site.

24. Mechanical Factors
Angle of pull is optimum at right angles or 90 degrees to the bone.
Length is optimum at midpoint or resting length.

25. Exercise Modes Isokinetic=constant velocity.
Isotonic=constant resistance (DCER).
Isometric=static and without muscle movement.

26. Neuromuscular Adaptations to Exercise
Hypertrophy- enlargement and increase in number of muscle myofibrils (not fibers), increasing the size of actin and myosin
Hyperplasia-increase in the number of fibers (not in humans, only in birds).
Fast twitch muscle fibers hypertrophy to a greater extent than slow twitch muscle fibers
Early increases in muscle strength have a large neural component
Long term increases in strength also have a neural component

27. Moritani and deVries Hypertrophy vs. Learning

28. Atrophy vs. Hypertrophy

29. Electromyography (EMG)
Records electrical signals from the brain.
EMG reflects muscle activation.
Surface electrodes (summated) or fine needle electrodes (individual).
Amplitude increases with recruitment (summation).
Integration of signal equals true mean of firing (RMS).

30. EMG cont… Positive relationship between EMG and force/velocity.
A measure of intensity.
Efficiency of electrical activity = stronger individuals require less activation.
Learning curve demonstrates greater force with less EMG.

31. EMG and Fatigue EMG increases with fatigue. Recruitment responsible.
Local fatigue is a function of individual muscle and joint.

32. Resistance Training and Aerobic Power
Resistance training does not improve aerobic power
Resistance training does not impair an individual’s ability to develop maximal aerobic power
Aerobic training does not enhance muscle strength or size
Aerobic training may compromise the benefits of strength training on muscle force production

33. Next Class
Chapter 6 Endocrine