Lecture 5

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

Decreased twitch potentiation

Changes in Ca2+ kinetics at the sarcoplasmic reticulum level (correct)

Myosin light-chain dephosphorylation during actin/myosin interaction

Reduction in motor unit firing rates

How are motor unit firing rates affected by potentiation?

Motor unit firing rates decrease significantly

Motor unit firing rates increase significantly (correct)

Motor unit firing rates become irregular

Motor unit firing rates remain unchanged

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

Enhanced neural input to the system

Decrease in twitch potentiation

Increase in Ca2+ concentration at the myofilaments (correct)

Reduction in myosin light-chain phosphorylation

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 (C) Signup and view all the answers

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 (C) Signup and view all the answers

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

Central nervous system fatigue (A) Signup and view all the answers

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

Reduced force/cross-bridge (B) Signup and view all the answers

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 (C) Signup and view all the answers

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 (D) Signup and view all the answers

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

Motor units not recruited (B) Signup and view all the answers

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

Increased inhibition (A) Signup and view all the answers

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

Unfavorable, as it may result in decreased force output (D) Signup and view all the answers

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

task specificity (C) Signup and view all the answers

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

Weakness (B) Signup and view all the answers

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

Compensatory mechanisms (B) Signup and view all the answers

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

Metabolic substrates availability (D) Signup and view all the answers

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

Firing rates decrease with slowed muscle speed. (C) Signup and view all the answers

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

Decreased motor unit firing rates (B) Signup and view all the answers

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

Recruitment and rate coding (C) Signup and view all the answers

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

Reduced sensitivity and release of Ca+2 (A) Signup and view all the answers

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

Decreased motor unit firing rates (C) Signup and view all the answers

During maximal sustained exercise, what happens to EMG activity?

It increases until the contraction becomes maximal. (C) Signup and view all the answers