FEATURE ARTICLE
LIMITATIONS OF GLOBAL POSITIONING SYSTEMS ON THE TRAINING AND TESTING EFFECTS OF CYCLING
efficiency at his current power level. This is an oversimplification of creating a training plan from submaximal FTP, but it does illustrate how much more objective power analysis can be compared to just time and distance produced by the GPS. Using power alone for training is a wonderful tool, however, combining it with heart rate and GPS provides even more information to improve training. Using the same data, the cyclist can analyze particular portions of the ride in order to see what affects performance the most. Another aspect this technology gives a cyclist is the ability to calculate other physiological factors. The foremost of these factors is maximal oxygen uptake. According to the American College of Sports Medicine (ACSM), the formula to calculate relative VO2 is as follows (2): Relative VO2 = [(10.8 x work rate)/mass] + 7 Where: W = watts M = cyclist’s weight in kg VO2 = mL/kg/min The difference between the equations is how the wattage is measured. The power from the submaximal field test is considered a steady-state peak output. In addition to knowing the cyclist weighs 75.9 kg (167 lb), the power output from the field test concluded a FTP of 300 watts. Armed with this information, the cyclist can calculate his relative VO2 for his submaximal field test. The calculation would look like the following: Relative VO2= [(10.8 x 300 W)/75.9] + 7 = 49.7 mL/kg/min The cyclist can use this information to compare his physical condition to other cyclists within his racing category. With this comparison, he can determine if he needs to increase his relative VO2 compared to his competition. This calculation tends to overestimate, but it gives the cyclist a close approximation without the expensive laboratory testing. If an elite cyclist can afford to perform the expensive laboratory testing, he or she is then able to leverage this GPS enabled technology even more. Laboratory testing of VO2max and lactate threshold assists in giving the cyclist’s true FTP. Additionally, the cyclist can use this information to monitor nutritional needs. Table 1 shows respiratory exchange ratios (RER) based on lactate threshold (LT) testing with an open spirometer. A RER value of 1.0 indicates LT. Through performing this test in a laboratory, the cyclist will know what wattage to ride at in order to reach LT. Additionally, most LT testing protocols use ramp-testing protocols that will give differing wattages at differing RER values. Once again, let us use the previous cyclist as an example.
performed the same test on the same course in which he or she had wind at their back. The cyclist rode the 10-km course in 18 min due to the “push” given by the wind. The increase in speed was not due to increased performance but due to environmental factors. Without this information, the cyclist is not seeing the “true” picture of their performance. The cyclist needs a more honest metric to make the correct analysis because power does not measure speed and t