Fatigue Flashcards
Fatigue
A reduced capacity to complete work
Muscle fatigue
A reduction of muscle performance and inability to maintain expected power output
> Imbalance between ATP requirements of a muscle and its ability to resynthesise ATP
Onset and rate of fatigue depends on:
> Type of activity (aerobic/anaerobic)
Muscle fibres being used
Types of muscle contraction
Intensity and duration of activity
Fitness levels (more conditioned = delayed onset)
Why does fatigue occur?
> Energy depletion
Dehydration
Build up of waste products
Energy depletion
(Primary factor)
> ATP-PC system is exhausted due to PC depletion
Glycogen issued as an energy source
Glycogen is used in the anaerobic and aerobic pathways depending on duration and intensity
Glycogen depletion
> Stored ATP is used up
PC is used up
Muscle glycogen is used up
Liver glycogen is broken down and glucose is transported to muscles via blood
Fat metabolism
> When liver glycogen levels are depleted, there is a feeling of lethargy and fatigue
Fat can be metabolised if intensity is low enough
Fat can only be burned in the presence of some glycogen
Dehydration
> When fluid loss is greater than fluid intake
Accompanied by loss of salt and calcium (electrolytes)
Leading to cramps and loss of muscle efficiency
Reduction of blood plasma volume
Reduction of blood plasma volume
> Increased thirst
Decreased blood pressure
Decreased tissue fluid formation
Increased heart rate
Declining performance
Retention of body heat
Effects of dehydration
> Decreased reaction time
Loss of concentration
Poor decision making
Elevated body temperature - increased blood redistribution to skin
Decreased blood to muscle
Decreased O2 availability
Blood thickens - becomes harder to pump - less to muscles - less O2 available for glycolysis and oxidising lactic acid
Build up of waste products
During intense exercise, (7-45 seconds), accumulation of lactic acid and CO2 in muscle cells causes extreme fatigue and complete loss of muscle function
Increased lactic acid > decreased pH > inhibition of anaerobic and aerobic enzyme activity required for ATP regeneration
Onset of blood lactate accumulation (OBLA)
OBLA is the point at which the muscle can no longer get rid of the lactic acid and it begins to pool in the blood
> occurs at 4mmol of blood lactate
inhibits oxygen being collected by haemoglobin
causes pH level of blood to lower causing pain in the working muscles
leading to loss of function
Lactic acid research
> DOMS, often blamed on lactic acid, is actually caused by microscopic tears and trauma to the muscles and inflammation
Other deflects of fatigue
> Decrease calcium levels - inhibits sliding filament theory
Decrease acetylcholine levels - decreased need to transmit nerve impulses across neuromuscular junction
Managing fatigue
> Ensuring training is optimal for performance at varying intensity
Periodisation
Diet (eatwell + carbs)
Intermittent nature of some sports
Pacing strategies
Tactical strategies
Correct technique
Hydration (isotonic, hypotonic)
Energy drinks/gels
Supplements
Psychological factors
