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Fatigue or exhaustion is part of the 3 phase process our bodies go through when we overload/ stress them out. This process is called General Adaptation Syndrome or GAS for short, a 3 phases process your body goes through when you are under stress. Hans Selye a scientist in the 1950’s defined stress as the nonspecific response of the body to any demand put upon it. So, when you exercise, and you put your body under stress it goes through the 3 phases of GAS.


  1. Alarm – reaction
  2. Resistance – adaptation
  3. Exhaustion

Your body is remarkable, but it doesn’t like change. It constantly works to keep you at rest. Every time you ‘stress’ your body, for example by doing a longer than normal bike ride or run or add in a gym workout you are not used to, the body enters the first stage of GAS releasing Epinephrine which is your fight or flight hormone, Aldosterone which maintains blood volume and salt balance and cortisol which increases blood glucose for energy. This added training stress disturbs your natural homeostasis and moves you out of your comfort zone. If this stress continues your body works had to adapt (phase two) to this ‘new normal’.

In an ideal training world you would just repeatedly take your body through steps one and two… Phase three however is somewhere every athlete is probably going to wander at some point in their training, we have all been there, those days when your legs feel like they are made of led and your so tired your reaching for the coffee pot at the same time as trying to pin your eye lids open with match sticks. This your bodies exhaustion phase, there is a fine line between load and overload make sure you give your body adequate rest and recovery time, it’s always worth remembering when you are at rest your body recovers.

If you are struggling on your rest days, why not turn to Pilates to help! Not only a great all over body workout Pilates can help to stretch out tired muscles, increase your strength and coordination which in turn are going to help you feel stronger, fitter and faster when you do get back out for a run or turning the pedals.