When you're expending energy at a very high rate, non of the energy systems (Alactic, Lactic or Aerobic) can keep up
with the demands you are putting on your body. The body is designed to fatigue
long before the muscles or heart rate runs out of ATP (ATP is the bodies
petrol). Even at the highest levels of intensity, the bodies ATP levels don’t
drop below 60%. Dropping below 60% would be very damaging to the muscles. In
order to stop that, the body has a few defence mechanisms in place to allow the
body to maintain homeostasis (normal living state).
Central and Peripheral
Fatigue:
- · Brain turns “off” muscles, which decreases power output, and slows down your rate of energy expenditure.
- · Fewer motor units are recruited > less muscles fibres firing > less energy used > less decrease in ATP percentage.
Peripheral
- · Decrease in contractile properties – i.e. the muscles cant produce as much force.
- · Likely to come about due to environmental changes within the cells.
In reality, no one
knows exactly why the body fatigues. I don’t care what they say, there is yet
to a be a study that has shown 100% certainty as to why we fatigue. If anyone
tells you that “lactic acid” is the reason why, they’re a jackass. If anyone says
that it is due to a build up of phosphate, they’re an even bigger jackass.
Some studies have shown that a build up of hydrogen ions COULD be the reason,
but again, it’s the best explanation for a topic we do not fully understand.
What we can be certain of, is that the body fatigues on purpose. It needs to
fatigue to survive. Once we understand the central and peripheral fatiguing
systems, then we may be closer to finding the actual reason! I guess the title was misleading and you may feel that you are no closer to realising the truth than you were when you hadn't read this. I can only apologise, but I feel there will be more apologise to come, from a variety of coaches and scientists, as we endeavour to find the reason.
Until next time
Stay Strong
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