During exercise the demand for oxygen increases as the respiring cells require more oxygen to meet the increased demand for energy, there’s also an increased removal of carbon dioxide, (Burton, Stokes, & Hall, 2004). Carbon dioxide is a byproduct of aerobic respiration (as well as water and heat). In this experiment Douglas bags were used to collect expired gas to be used for analytical purposes. Douglas bags enable readings of both carbon dioxide and oxygen to be taken with the use of a Servomex Analyser, as well as total gas content using a dry gas meter and pump.
The analysis of these results can be used to determine the gross efficiency of an athlete, Douglas bags are used as a gold-standard approach due to their high reliability (Gregson & Hannah, 2012). Efficiency in this sense refers to the ratio of work generated in comparison to the total metabolic energy usage, (obson S. A, Hopker, Korff & Passfield, 2012). Efficiency is a key factor of endurance performance, especially in cycling (Joyner & Coyle, 2008). The main aim of this experiment was to study the changes of the respiratory system during different effort loads, as well as at rest.
These results were then analysed to give physiological values which were then analysed to gain an understudying of the participants efficiency. The use of Douglas bags was appropriate due to the type of exercise being performed. This is because systematic increases in work rate were implemented (Winter, Jones, Davison & Richard, 2006) Hypothesis As the workload increases, the carbon dioxide level collected in the Douglas bags will increase. It will increase relatively to the participant’s efficiency. An athlete with higher efficiency will have lower carbon dioxide levels compared to an athlete with ower efficiency.
Materials This experiment needed various specialist pieces of equipment, without these you cannot perform this experiment. Firstly a cycle ergometer, a Douglas bag, on top of the Douglas bag there was a one way valve, the Douglas bag also had a stop cock which stopped air from escaping when the participant wasn’t cycling, a tube was used to connect the mouth piece to the Douglas bag, a sterile mouth piece, a nose clip, a Servomex Analyser, a dry gas measure, a pump (for the dry gas meter), a barometer, weighing scales, a tape measure.
Method Firstly the participant was chosen; the participant had to have no reason (medical, physical or mental) not to perform the test. This helped to keep the test risk free, because only suitable participants were performing and unsuited participants weren’t putting their health at further risk. Each group then collected three Douglas bags once the participant was picked. All three of the Douglas bags were then empty using the pump, the bags were folded up as much as possible to ensure there was no air left in the bag which would have influenced the results.
The mouthpiece, tube and Douglas bag were then assembled together, this was performed on all three bags before the test to ensure the assembly during the test didn’t give the participant extra rest time, which would have influenced the results. The use of the valve was then practiced to ensure when we were performing the test it would run smoothly and everyone knew how to open/close the valve efficiently. The room pressure and temperature was then taken from a barometer, this would later be used in the physiological calculations to help give validity to the results.
The participant’s height and weight were then recorded, for the same reason to be used in the physiological calculation. The cycle ergometer was then set up appropriately for the participant; the seat was adjusted to hip height of the participant. The participant then sat on the seat and performed a couple of pedals to ensure the seat bike was comfortable and suitable for them to perform the test. Finally the test started only when the participant was fully prepared for the physical activity.
At any point during the test the participant was allowed to stop, for their health and safety. Test Details The test itself lasted for 12 minutes: there was 4 minutes rest, followed by two stages of four minutes each. The tempo the participant had to maintain was 60 revolutions per minute (rpm). Females needed to cycle at 60 watts for the first stage and 120 watts for the second stage, males however had to cycle at 90 watts and 180 watts respectively.
To ensure the correct watts were being produced the watts were divided by the rpm, the result of the calculation gave you the weight that was needed to produce the desired watts. Note that the basket of the ergometer weighs 1 kilogram, ergo this value must be subtracted from the result of the equation. For example: 60watts/60rpm = 1, in this case no weight was added to the ergometer because there’s already one kilogram present because of the basket.
Once the participant had completed the test the three bags were taken to the Servomex Analysers to measure the oxygen and carbon dioxide percentage present. The sampling tube was used to measure this. The dry gas meter and pump were then used to determine the volume of gas inside each bag. Room temperature and pressure was taken so that the results could be standardised during the physiological calculations. Results Table one shows as the workload increased, so did the VSTPD and respiratory exchange ratio.
Table two shows heart rate, respiratory ventilation and tidal volume all increase also as the workload was increased. Table two shows that ventilation also increases substantially – more than doubling from rest to a work rate of 120watts, going from 13. 33 breaths/min to 26 breaths/ min. Figure 1 shows how VO2 and VCO2 increase as work rate increases. VO2 went from 0. 37L/min at rest to 1. 98L/min at 120watts work rate, the VCO2 went from 0. 35L/min at rest to 1. 89L/min at 120watts work load. Showing a similar increase in both.
