Fitness: use it or lose it
Forget the hype, says ADF Physiotherapist Lt Rob Orr, in the second of a two-part series on health and fitness fact and fiction.
Volume 11, No. 50, August, 24, 2006

FOLLOWING our look last edition at some of the myths and misconceptions regarding health and fitness, this edition we continue to delve into the fitness facts vs fantasy.

Muscle turning to fat
There is a common misconception that when you cease training, muscle turns to fat (or the chest slips to the stomach). Just as an apple cannot change into an orange, the protein strands that make up muscle tissue cannot turn into fat tissue. The misconception arises from two effects that come from a cessation in activity.

The first comes from disuse. When not needed, muscle tissue atrophies or decreases in size – use it or lose it.

The second comes from a calorie surplus with less calories being used because of the decrease in activity. This surplus leads to an increase in fat storage. These two effects combine to decrease muscle size while fat size increases.

The fat burning zone
The fat burning zone is claimed to be a training intensity, between 60–70 per cent of your predicted maximum heart rate (PMHR) – a range optimal for utilising fat as energy. The reasoning behind this argument lies in the fact that the lower the exercise intensity the greater the percentage of energy requirements that are met by fat. Whereas, higher intensities utilise more carbohydrates than fat.

Therefore, the lower the exercise intensity, the more the energy requirements come from fat stores; the higher the intensity, the more the energy requirements come from carbohydrates.

Unfortunately, fat loss is not so simple. More important than the fuel source is the overall amount of energy used. Fat loss comes from creating a calorie deficit, where more energy is used than consumed. With this in mind, the higher the intensity, the more calories used in total.

Compare:
Subject A runs at 65 per cent of their PMHR (fat burning zone) for 30 minutes and utilises an estimated 300 calories – if 60 per cent of these calories are made up from fat, 180 calories of the overall 300 calories burnt are from fat stores.

Subject B runs at 75 per cent of their PMHR (cardio zone) for 30 minutes and utilises an estimated 500 calories – if 40 per cent of these calories are made up from fat, 200 calories of the overall 500 calories burnt are from fat stores. Furthermore, and more importantly, the total calorie count is higher.

There are benefits of low intensity training, but that is a subject for later discussion.

Spot reduction
A common misconception is that spot-reduction, or the loss of fat from one specific part of the body is possible; for example the use of sit- ups to flatten the stomach. However, if spot-reduction were possible, wouldn’t a runner or cyclist have thin legs with fat upper bodies?

Losing fat from one specific body area alone is not possible as the body draws fat stores from around the body and transports them through the blood to the working muscles. Furthermore:

• The muscles often targeted for spot-reduction tend to utilise minimal fat stores (the burning feeling) when trained in isolation (leg lifts and sit-ups).
  
• Due to the isolated training load, these muscles may actually grow in size. This gives them a larger appearance, in turn leading to more repetitions being conducted to decrease size.
  
• The isolated actions leads to a rapid increase in lactic acid and hydrogen, which inhibits fat
  utilisation.

In a nutshell, keep training to prevent muscle mass loss and fat gain, train at intensities specific to what you wish to achieve, and utilise compound exercises involving numerous muscle groups and joints rather than trying to target that single muscle to enhance fat loss.

Forget the hype and go with fact.

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