Being asked to blow into a plastic bag took on a whole new meaning during a Science Week presentation at Waterford Institute of Technology. The bag was hooked up to a person pedalling an exercise cycle to measure fitness levels.
The lecture, "Oxygen, energy and endurance performance", was presented yesterday by Dr Michael Harrison of Waterford institute's department of health, sports and exercise science.
The talk was for secondary school students and was closely related to their curriculum in discussing the Krebs Cycle and aerobic respiration.
"It highlighted the importance of oxygen for energy production and demonstrated that athletes with a high ability to take oxygen from the air are more successful in endurance sports," Dr Harrison explained.
The gradually expanding 150 litre bag, filled by the hapless cyclist Tomás Delahunty, provided a real and visual demonstration of respiration and energy production.
Dr Harrison was able to provide an on-the-spot assessment of fitness by analysing the chemical mix of oxygen and carbon dioxide in the bag and by calculating the amount of work being done on the cycle.
He found that towards the end of the experiment Tomás was producing about 300 watts of energy, enough to illuminate three standard light bulbs or about 20 long-life fluorescent bulbs.
At this point he was using up some four litres of oxygen per minute and burning up about 19 calories a minute. And for the record, the performance indicated Tomás was aerobically fit, Dr Harrison added.
Training can improve a person's sports performance and typically careful training will boost fitness by 25 per cent.
He also talked about a person's genes and their influence on sports performance.
"The big difference in your ability to improve is genetic," Dr Harrison stated. Typically half of the ability to improve through training is dependent on a person's genes.
"Genetically some people have a massive ability to improve," Dr Harrison added, but we are nowhere near being able to understand the genetics associated with this.
So far no fewer than 100 genes have been shown to have an influence on improvements to fitness and more will be discovered.
What changes take place inside the body in response to sports training is well known however. Participation in exercise increases the number of red blood cells, the cells that transport oxygen through the body, he said.
The heart muscle also strengthens, allowing it to pump the red blood cells through the circulatory system more efficiently.
The network of fine blood vessels, the capillaries, also develops in the muscles, improving access for the red cells and the delivery of oxygen.