Neuromuscular Science Ch. 8 Study Guide

Chapter 8

1. What physiological processes are affected by temperature? What is affected by an increase in core body temperature during a warm-up?

• Increase oxyhemoglobin dissociation

• Augment biochemical reactions

• Facilitate blood flow

• Increase connective tissue extensibility

• Increase muscle elasticity

• Increase action potential conduction velocity

• Increase twitch force of motor units

2. Describe the effects of temperature on muscle strength, power, movement speed, muscle stiffness, and muscle metabolism.

With warm temperature there will be an increase on muscle strength, power, movement speed, and muscle metabolism with a lower of muscle stiffness and vise versa in cold temperature.

3. Explain the different effects of active vs passive warm up.

Passive is the use of a heating modality like a hot pack while active is the muscle activity that increases the muscle temperature.

4. Define muscle tone, hypotonia, and hypertonia. Differentiate between spasticity and rigidity.

• Tone - resistance to passive stretch in relaxed muscle

• Hypotonia – low muscle tone, decreased resistance to passive stretch

• Hypertonia – increased muscle tone, increased resistance to passive stretch

• Spasticity

o Velocity dependent enhanced resistance to passive stretch

o Mediated in part due to “pathologically induced state of heightened stretch reflex”; exaggerated tendon tap

o Can be seen in some cases of traumatic brain injury, stroke, spinal cord injury, multiple sclerosis

o Movement deficiency not due to spasticity in antagonist, but poor recruitment of agonist MUs.

• Rigidity (continuous tension in muscle)

o Not velocity dependent

o No exaggerated tendon tap

o Bidirectional resistance to stretch

5. Define flexibility.

The range of motion about a joint.

6. Describe the deleterious (negative) effects of acute static stretching when it is performed prior to athletic competition. Are dynamic sport-specific movements performed during a warm-up (prior to competition) more or less beneficial than acute static stretching for maximizing performance? If dynamic movements are more beneficial explain why.

It will inhibit the motor neurons giving you a less force production, power, and speed on the muscles, which can lower your maximal performance. Dynamic are more beneficial prior to the athletic competition because it increases intramuscular temperature and will allow for maximal muscle performance in comparison to doing static stretches prior to an activity.

7. Differentiate between static, ballistic, and PNF stretching techniques. Which stretching technique is more effective for long-term improvements in flexibility?

Static – lengthening the muscle to the limit of its ROM, and holding this position for several seconds (usually 10-30 s)

Ballistic (dynamic) – repetitive bouncing movements that extend the ROM

Proprioceptive Neuromuscular Facilitation (PNF) - stretching techniques that are intended to depress the responsiveness of spinal reflex pathways

PNF appears more effective for long-term improvements in flexibility.

8. Describe the three types of PNF stretching techniques, and explain the mechanisms that are responsible for increasing joint range of motion via PNF stretching.

Contract-Relax: initial maximal isometric contraction of the muscle to be stretched (target muscle), followed by relaxation, and then static stretch of the muscle

Antagonist-Contract: partner assisted; contract antagonist (e.g., quads) while partner stretches target muscle (e.g., hamstrings)

Contract-Relax – Antagonist-Contract: partner assisted mixture of both techniques.

9. How often (i.e., frequency) should stretch training be performed, and for how many weeks to initially improve flexibility? (Based off of research from Guissard & Duchateau, 2004)

To initially improve flexibility, 30 stretch training sessions performed 5 times/week for 6 weeks may need to be performed.

10. What are the mechanisms that limit flexibility?

• Passive tissue properties

• Spinal reflex excitability

• Tolerance to discomfort

11. Changes in passive tissue properties contribute to increased range of motion during a single stretching session. Describe the phenomena of “creep” and “stress relaxation.”

• Creep: gradual elongation of muscle and tendon due to constant force being applied

• Stress Relaxation: repeated stretches decreases resistance force needed to achieve a given level of stretch - Resistance force at the target joint angle will decline by 30% during the stretch

12. Describe the effect of vibration on acute stretching. How does vibration affect muscle spindle function, the monosynaptic reflex (H-reflex), and the overall effect on flexibility?

Vibration leads to ↓ spindle function (↓ H-reflex) and ↑ effect of stretching bout and ↑ flexibility is influenced by afferent feedback.

13. What are the effects of stretching on tendon tap, H reflex, and motor evoked potentials?

• Stretching decreases tendon tap reflex more than it decreases H-reflex

o H-reflexes sensitive to α-MN excitability and pre-synaptic inhibition of Ia terminals

o Tendon

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