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As we have seen in the previous few blogs, oxygen is vital for survival as we need it to make energy to keep all our systems functioning, and to keep the oxygen energy system going. The use of O2 in the cells of the body is known as O2 uptake or consumption. When the body is at rest oxygen uptake (VO2) is approximately 3.5 millilitres per kilogramme of body weight per minute (ml/kg/min). This value of oxygen uptake at rest is also known as 1 metabolic equivalent or 1 MET. Exercise can therefore be categorised into light, medium or heavy depending on the amount of O2 uptake required or the METs. The maximum amount that a person can take in (respiratory) transport (cardiovascular) and use (muscular) will therefore provide an indication of their fitness. The more O2 that they can take in, transport and use, the higher intensity they can work at and the fitter they will be. This maximal oxygen uptake is called VO2max and is generally accepted to be the best guide to assessing someones fitness levels, and can be directly measured using various aerobic tests. Accurately measuring VO2max involves a physical effort sufficient in duration and intensity to fully tax the aerobic energy system. In general clinical and athletic testing, this usually involves a graded exercise test (either on a treadmill or on a cycle ergometer) in which exercise intensity is progressively increased while measuring ventilation and oxygen and carbon dioxide concentration of the inhaled and exhaled air. VO2max is reached when oxygen consumption remains at steady state despite an increase in workload. We could do the bleep test (a 20m shuttle run, timed by a recording over 23 minutes, with a faster pace each minute), the slightly less harsh Rockport walking test, or an expensive session on a bike with a BUPA team. If you really want to know how fit you are your Diets Don’t Work personal trainer can do one of these tests with you.
The important thing to recognise is that we can improve VO2 max through cardiovascular training, and that your body will adapt and change to stresses and overload placed upon it. At the correct intensity of cardiovascular training there are a number of adaptations that happen, which we will go through in the next blog. In the meanwhile even just a short burst of activity a few times daily will be enough to start these adaptations, making you fitter, lighter and even healthier!!