“I can’t run anymore” – a well-recognised thought? Well if it is, and your legs ache and feel painful during exercise, then this may have been caused by fatigue!

So what is it? Fatigue is the inability to sustain a given power output or speed. It occurs when the supply of energy, as ATP, does not match the demand for energy in the working muscles and mainly when lactic acid builds up in the muscles. So, during explosive activities such as sprinting, fatigue develops due to ATP and Phosphocreatine (PC) depletion – This is simply running low on energy within your muscles. It definitely affects performance and performing at your peak with the least possible fatigue means you cross the finish line faster (if you are a runner that is).

Adenosine Triphosphate (ATP) is the body’s energy currency, found in all cells, and when broken down it releases energy. The body transfers chemical energy found in food, such as carbohydrates, into usable energy found in ATP.

Fuelling properly can help delay the onset of fatigue, but I’ll talk a bit more about that in another post, make sure to check that out soon!

If you are an athlete, you will have more than likely experienced fatigue during high intensity exercise, or a fast run, cycle or swim in other words. For me, as a long running sprinter (400m), I get this a lot as my event is very strenuous and I actually struggle to combat fatigue effectively. There are ways both you and I can delay the build-up of lactic acid and fatigue, which I’ll mention later. Lactic acid may also occur in all sports where some kind of speed is repetitively being used.

Fatigue can occur during anaerobic respiration (referring to a process without oxygen). This is when your body is working so hard and muscles demand more oxygen than can be supplied by the body. This lack of oxygen triggers the use of anaerobic respiration. The anaerobic system involves only the partial breakdown of glucose (sugar), as oxygen is not present. In anaerobic respiration a substance called pyruvate is made but, because as it is only the partial breakdown of glucose, pyruvate enters lactate fermentation instead – which, you guessed it, forms lactic acid! You understanding yet?

So, if anything, all you need to take away from that is that high intensity exercise can cause the build-up of lactic acid.

This is known as the lactate threshold – The point at which the lactic acid starts to accumulate is known as the Onset of Blood Lactacid Accumulation (OBLA). This means the anaerobic system produces more lactic acid that can be dealt with, and builds up in muscles. This build up is the ‘wall’ stopping us from running! The only way to get rid of it is to return to aerobic exercise, or rest… so the oxygen can flush out the lactic acid!

Fight Fatigue

So, you want to combat fatigue? There are simple ways such as dietary intake before exercise, but the method I’m going to explain is a bit more hard work than just eating right, but it is much more effective!

Training! Sounds easy, but training correctly is the best way. Increasing muscle strength and strength endurance can help slow to onset of lactic acid very slightly in explosive activities (200m).

It should be recognised that activity at maximal intensity (100m sprint) can only occur using the energy made from anaerobic energy systems and it is likely fatigue won’t occur at all in such a short amount of time. On the other hand if you are a games player running a lot or usually run longer distances then increasing stamina is the way forward as you will need the aerobic system to continue working. Stamina is often referred to as the ability to sustain stressful physical exertion for a period of time.

Stamina links with Maximal Oxygen Consumption (VO2 Max), defined as the maximum amount of oxygen that can be taken in, transported and used by the body in one minute. The higher the VO2 max the more oxygen that is supplied and used by working muscles, resulting in more energy being produced aerobically.

So, basically the long and the short of it is train well for stamina and your breathing and lungs and blood will all become more efficient, giving your body more oxygen. As you have (hopefully) learnt above more oxygen will prevent fatigue and lactic acid hitting your muscles so early, which can help us all!