Peripheral Fatigue Flashcards
Physiological definition of fatigue
Failure to maintain the required or expected force or power
Definition of weakness
Failure to generate the required or expected force or power
Marks of fatigue
Can’t reach the same force level
Shape of tetanus curve changes - takes longer to reach the plateau and also takes longer for the muscle to relax
Excitation-contracting coupling
ATP dependent processes
Myosin head force development
3Na out, 2K in results in resting potential
Calcium pump
Excitation-contraction coupling in fatigue/energy crisis
If there is little energy, these systems can be a source of fatigue because the pumps in these systems need ATP to work
Which type of muscle fibres are ‘unfatigueable’
Type II because they have mitochondria
What does caffeine do?
Facilitates the opening of ryanodine receptors in the sarcoplasmic reticulum
Inhibitory effects of calcium release
High AMP
High ADP
Very low ATP
Mg concentration doubles at fatigue because ADP, AMP and IMP have lower affinity for Mg than ATP
Calcium re-uptake
Evidence in amphibians (none in mammalian muscle) that calcium re-uptake is the cause for slower relaxation
The quicker the calcium is taken up, the quicker the muscle can relax
Potassium gradients during fatigue
Accumulation of K in extracellular space because T-tubular membrane has a large SA and the T-tubular network has a small volume.
More difficult to induce action potentials
Inorganic phosphate inducing fatigue
Phosphocreatine level go down (hydrolysed into inorganic phosphate and creatine).
Ph also drops a lot in fatigue which causes an increase in protons.
Inorganic phosphate bind to the calcium in the cell - calcium can’t help with muscle contraction = fatigue
ATP Depletion
Studies show that ATP in a cell does not drop below 60% f resting levels (whole muscle)
Isolation fibre: down to 20%
Localised ATP depletion possible in the space between T-tubule and sarcoplasmic reticulum (Triad junction)
What is compartmentalisation?
where metabolite vary within different compartments of the cell
What is compartmentalisation used to explain?
ADP tightly regulated and does not acculumate
ATP average levels do not fall enough to affect cross-bridge function
H+ plays a minor role in physiological condition (PH, temperature)
Metabolism for runners
The better trained you are, the better your fat metabolism
It is advantageous for a runner to have a higher metabolism because it slows down fatigue
