Lecture 5

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22 Questions

What is the main reason why the same input to a muscle (twitch) results in significantly more force output in the potentiated state?

Changes in Ca2+ kinetics at the sarcoplasmic reticulum level

How are motor unit firing rates affected by potentiation?

Motor unit firing rates increase significantly

What is the main factor that enhances the active state during a brief high-intensity tetanus or voluntary contractions?

Increase in Ca2+ concentration at the myofilaments

Which of the following statements best describes the effects of muscle potentiation on force production?

Potentiation allows greater forces to be achieved with less neural input

What are the two likely mechanisms responsible for muscle potentiation during high-intensity contractions?

Ca2+ kinetics at the SR level and myosin light-chain phosphorylation

What limits the ability to continually flex a finger under a fixed load according to the text?

Central nervous system fatigue

What is one of the factors affected by metabolic perturbations that can lead to reduced force output?

Reduced force/cross-bridge

What is the big controversy mentioned in the text related to when discussing metabolites and their impact on the fatigue response?

The relative contributions of metabolites

Why is it mentioned that finger flexion can still occur with electrical stimulation despite limitations within central systems?

To illustrate the impact of muscle fatigue on voluntary activation

What does an increasing superimposed twitch throughout a fatiguing task indicate?

Motor units not recruited

Which factor contributes to decreased muscle activation (reduced firing rates) with fatigue according to the text?

Increased inhibition

Is it favorable or unfavorable when firing rates decline as muscle contractile speed slows down?

Unfavorable, as it may result in decreased force output

What is the main reason for reduced ROM due to fatigue in the text?

task specificity

Which factor contributes to the inability to generate an initial force appropriate for a task in the text?


What is the primary reason why fatigue processes are not sustainable indefinitely according to the text?

Compensatory mechanisms

What contributes significantly to the reduction in muscle response force and contractile speed during maximal or high intensity exercise?

Metabolic substrates availability

What is the relationship between firing rates and muscle speed according to the text?

Firing rates decrease with slowed muscle speed.

What mechanism may lead to a loss of force during sustained maximal contractions?

Decreased motor unit firing rates

In sub-maximal tasks, what combination plays a role in generating force?

Recruitment and rate coding

What is one cause for loss of force during sustained maximal exercise according to the text?

Reduced sensitivity and release of Ca+2

What is the effect of task specificity on force generation during submaximal intermittent exercise?

Decreased motor unit firing rates

During maximal sustained exercise, what happens to EMG activity?

It increases until the contraction becomes maximal.

Test your knowledge on the impact of metabolic perturbations on force generation factors such as reduced force/cross-bridge, reduced Ca+2 sensitivity, and reduced Ca+2 release from the SR. Explore the controversies surrounding the contributions of metabolites and their effects on fatigue response.

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