IELTS Matching Headings (8)

For almost a century, scientists have presumed, not unreasonably, that fatigue - or exhaustion in athletes originates in the muscles. Precise explanations have varied but all have been based on the ‘limitations theory’. In other words, muscles tire because they hit a physical limit: they either run out of fuel or oxygen or they drown in toxic by-products.

•  Puzzling evidence raises a question

• Interpreting the findings

• Traditional explanations

In the past few years, however, Timothy Noakes and Alan St Clair Gibson from the University of Cape Town, South Africa, have examined this standard theory. The deeper they dig, the more convinced they have become that physical fatigue simply isn't the same as a car running out of petrol. Fatigue, they argue, is caused not by distress signals springing from overtaxed muscles, but is an emotional response which begins in the brain. The essence of their new theory is that the brain, using a mix of physiological, subconscious and conscious cues, paces the muscles to keep them well back from the brink of exhaustion. When the brain decides its time to quit, it creates the distressing sensations we interpret as unbearable muscle fatigue. This ‘central governor* theory remains controversial, but it does explain many puzzling aspects of athletic performance.

• Description of a new test

• A new hypothesis

•  Developing muscle fibres

A recent discovery that Noakes calls the ‘lactic acid paradox' made him start researching this area seriously. Lactic acid is a by-product of exercise, and its accumulation is often cited as a cause of fatigue. But when research subjects exercise in conditions simulating high altitude, they become fatigued even though lactic acid levels remain low. Nor has the oxygen content of their blood fallen too low for them to keep going. Obviously, Noakes deduced, something else was making them tire before they hit either of these physiological limits.

•  Puzzling evidence raises a question

• Surprising results in an endurance test

•  Interpreting the findings

Probing further, Noakes conducted an experiment with seven cyclists who had sensors taped to their legs to measure the nerve impulses travelling through their muscles. It has long been known that during exercise, the body never uses 100% of the available muscle fibres in a single contraction. The amount used varies, but in endurance tasks such as this cycling test the body calls on about 30%.

• Avoiding tiredness in athletes

• A new hypothesis

•  Description of a new test

Noakes reasoned that if the limitations theory was correct and fatigue was due to muscle fibres hitting some limit, the number of fibres used for each pedal stroke should increase as the fibres tired and the cyclist’s body attempted to compensate by recruiting an ever-larger proportion of the total. But his team found exactly the opposite. As fatigue set in, the electrical activity in the cyclists' legs declined - even during sprinting, when they were striving to cycle as fast as they could.

•  Description of a new test

• Surprising results in an endurance test

•   Developing muscle fibres

To Noakes, this was strong evidence that the old theory was wrong. ‘The cyclists may have felt completely exhausted,’ he says, ‘but their bodies actually had considerable reserves that they could theoretically tap by using a greater proportion of the resting fibres.’ This, he believes, is proof that the brain is regulating the pace of the workout to hold the cyclists well back from the point of catastrophic exhaustion.

• Interpreting the findings

• Avoiding tiredness in athletes

•  Traditional explanations

The myth of scientific method is that it is inductive: that the formulation of scientific theory starts with the basic, raw evidence of the senses - simple, unbiased, unprejudiced observation. Out of these sensory data - commonly referred to as ‘facts’ — generalisations will form. The myth is that from a disorderly array of factual information an orderly, relevant theory will somehow emerge. However, the starting point of induction is an impossible one.

• Deducing the consequences of hypotheses

• The testing of hypotheses

• Explaining the inductive method

There is no such thing as an unbiased observation. Every act of observation we make is a function of what we have seen or otherwise experienced in the past. All scientific work of an experimental or exploratory nature starts with some expectation about the outcome. This expectation is a hypothesis. Hypotheses provide the initiative and incentive for the inquiry and influence the method. It is in the light of an expectation that some observations are held to be relevant and some irrelevant, that one methodology is chosen and others discarded, that some experiments are conducted and others are not. Where is, your naive, pure and objective researcher now?

• Deducing the consequences of hypotheses

• The testing of hypotheses

• The role of hypotheses in scientific research

Hypotheses arise by guesswork, or by inspiration, but having been formulated they can and must be tested rigorously, using the appropriate methodology. If the predictions you make as a result of deducing certain consequences from your hypothesis are not shown to be correct then you discard or modify your hypothesis. If the predictions turn out to be correct then your hypothesis has been supported and may be retained until such time as some further test shows it not to be correct. Once you have arrived at your hypothesis, which is a product of your imagination, you then proceed to a strictly logical and rigorous process, based upon deductive argument — hence the term ‘hypothetico-deductive’. 

• The testing of hypotheses

• How research is done and how it is reported

• Deducing the consequences of hypotheses

So don’t worry if you have some idea of what your results will tell you before you even begin to collect data; there are no scientists in existence who really wait until they have all the evidence in front of them before they try to work out what it might possibly mean. The closest we ever get to this situation is when something happens by accident; but even then the researcher has to formulate a hypothesis to be tested before being sure that, for example, a mould might prove to be a successful antidote to bacterial infection.

• The role of hypotheses in scientific research

• Anticipating results before data is collected

• Deducing the consequences of hypotheses