The entire recreational form of exercise known as ‘aerobics’ is based on the categorisation that certain activities are ‘aerobic’ and others are ‘anaerobic’, where the former term is applied to exercise which relies on continuous use of oxygen, whereas the latter refers to exercise which does not use oxygen.
This categorisation has led to the difficulty the layperson has in understanding that sprinting is not an aerobic event, even though the sprinter is obviously breathing oxygen very heavily throughout the race. All too often does one hear the comment that a sprinter does not breathe at all during a race. This is untrue and misleading. Sprints are ‘anaerobic’ because the inhaled oxygen is unable to be used immediately and directly during the sprint to metabolise stored fuels in the body.
Moreover, it needs to be pointed out that cellular oxidation by direct reliance on molecular oxygen occurs only at the end of a series of specific metabolic processes which remove hydrogen atoms in successive stages from the energy-producing substances derived from our food.
Today, the terms ‘aerobic’ and ‘anaerobic’ are regarded by the scientific community as archaic and somewhat inaccurate, and are often replaced by ‘oxygen-dependent’ (oxidative) and ‘oxygen-independent’ (non-oxidative), respectively. This change in terminology recognises the fact that oxidation does not refer only to the gain of oxygen by certain substances or compounds. Oxidation also occurs in a reaction in which hydrogen atoms are removed from a compound, a process which continually takes place in the human body. The acquisition of oxygen atoms or the loss of hydrogen atoms are both characterised by the oxidised substance losing negatively charged entities known as electrons. Thus, oxidation refers to any reaction whereby a chemical compound loses electrons.
The current Western craze of ‘aerobics’ drew its name from Kenneth Cooper’s early book entitled Aerobics, largely to emphasize the fact that this form of exercise was intended to enhance cardiovascular endurance. Today, the term ‘aerobics’ is applied loosely to all forms of exercise done to music in the health club environment, including ’stretch-and-tone’, which place no meaningful stress on the ‘aerobic’ (oxygen dependent) system.
True ‘aerobic’ exercise involves predominantly the long-term energy system (or pathway), which requires the continuous use of oxygen for the oxidation of glycogen (stored in the muscles and liver) or fatty acids (from stored body fats). When the exercise intensity increases, the two ‘anaerobic’ energy systems furnish the necessary energy: the short-duration system (high energy phosphate or ATP-CP system), and the intermediate energy system.
The short-term system used to be referred to as the ‘alactic anaerobic energy’ system. Its preferred name today is the phosphagen or high energy phosphate system. The intermediate system used to be known as the lactic acid (LA) system or the ‘lactic anaerobic’ (or anaerobic glycolytic) system. Now, the more accepted term is the oxygen-independent (or non-oxidative) glycolytic system.
What distinguishes these two systems from the ‘aerobic’ system is the fact that the higher intensity of muscular effort involved in both cases severely limits their duration. Thus, if one becomes breathless or the muscles are unable to continue operating without rest in a fitness class, it is a clear indication that the exercise is not ‘aerobic’. This should become most obvious to the aerobics instructor, who constantly has to talk to the class and give ongoing commands. If she cannot maintain a normal instructional conversation with her clients, she is no longer working in the ‘aerobic zone’. She will find that her pulse rate is beginning to fall beyond the recommended cardiovascular training heart rate.
This occurs at a point known formely as the anaerobic threshold. The more popular term now is the blood lactate turnpoint (or threshold) or OBLA (Onset of Blood Lactate Accumulation), since this marks the stage when the rate of lactate accumulation begins to exceed its rate of removal. Although this greater attention to scientific accuracy would appear to place ‘aerobic’ processes and cardiovascular training on a sounder footing, it should not obscure the fact that each energy system or pathway is simultaneously involved in all exercise. The degree to which any particular system predominates over a given period is determined primarily by the intensity of the muscle action involved.
Even then, one has to recognise that different energy pathways are involved at the same instant to sustain tonic (postural, stabilising) muscle action and phasic (dynamic) muscle action of different durations. Stated in another way, different energy pathways may be implicated at a systemic level and a local muscular level. In this respect, it is important to appreciate that all human movement involves muscle actions which simultaneously stabilise and move the muscles and joints, so that the body may rely on cardiovascular (oxygen-dependent) processes for its prolonged overall movement in a particular event, while the postural muscles may periodically draw upon oxygen-independent processes.
Thus, systemically, oxidative processes might be dominant, whereas locally, non-oxidative processes might also be highly active. It is incorrect to state that only one energy system or pathway is active during a specific activity. For example, marathon races between equally-matched elite performers may be won by the athlete who can make the most efficient use of oxygen-independent processes during crucial phases such as hill-climbing or concluding bursts of speed.
This emphasizes that successful physical conditioning for all sports depends on a good understanding of the energy processes of the body and how various dedicated or ‘cross-training’ exercise regimes contribute to developing the appropriate fitness profile required for each specific sport.
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Facts and Fallacies of Fitness
