Friday, April 10, 2009

Tired? It's All In The Head

I was trailing in 2nd place in the last 100 metres of my maiden 1500 metre race on the track at the Singapore National  Stadium when I was 13. My legs were shot, my lungs were screaming from the effort and my brain was telling me to stop. I told myself that it ain't over til the fat lady sings and I certainly did not see nor hear no fat lady singing. Suddenly, I was able to summon up my one final push, I dug into my reserves and was able to out kick my opponent. I won the race. Where did that burst of strength come from, I kept asking myself? Wanna know? Please read on.

There is growing evidence that when your muscles, lungs etc scream for you to stop taxing them during exercise, it is just one factor out of many that the brain takes into account when determining how tired or fatigued we feel.

The brain actually uses a mixture of conscious, sub-conscious and physiological cues to control our muscles and hold them back from reaching a truly exhaustive stage. Hence, when the brain "decides" that your muscles had enough stress, the brain causes the distressing sensations that you and I interpret as "heaviness" or muscle fatigue.

In the study reviewed,the researchers studied cycling performances in 2 groups of elite cyclists. One group was given just 10 mgs of amphetamines (or stimulant) while the other group received a placebo. The cyclists worked at a level of exertion that felt the same to them (on a scale known as the Rate of perceived exertion scale).

The results were fascinating, to say the least. Brace yourself for this. The group receiving the stimulant rode 32% longer before their power output fell to 70% of their start values. Comparing with the placebo group at the same time which the test ended, the group receiving the stimulant had significantly higher levels of power output, oxygen consumption, heart rates, ventilatory volumes and blood lactate concentrations.

The findings provide proof that there must still be a "reserve store" even when our muscles scream out asking us to stop. If the muscles were really fatigued (or tired) because they were at the point of "exhaustion or empty" then the stimulant wouldn't have produced any improvement in the group of cyclists receiving it.

What does this mean for you and I? It means that even when we feel tired (in the muscles) during endurance exercise (be it running, cycling or swimming etc), it doesn't mean we're gonna have to stop (or lose your race, game etc). If we can override the brain, we can often push on. So don't give up til the fat lady sings.


Swart, J, Lamberts, RP, Gibson, A et al (2008). Exercising with reserve: Evidence that the CNS regulates prolonged exercise performance. BJSM. 43(10): 792-8. DOI: 1136/bjsm.2008055889.

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