FEATURE ARTICLE
LIMITATIONS OF GLOBAL POSITIONING SYSTEMS ON THE TRAINING AND TESTING EFFECTS OF CYCLING
analysis software leverages the powerful capability of applying the power measurement with GPS. Several different types of software exist; however, they all provide the same type of analysis of the data. The software organizes the data in a descriptive format for easy analysis. For example, Figures 1 and 2 show two different layouts of cycling workouts with measurements of GPS and power. Figure 3 demonstrates the power of using the software to zoom in on a particular portion of the data file to analyze a certain section of the ride. Let’s revisit our previous cyclist. He performed a “sweet-spot” workout (1). Essentially, the cyclist rode a predetermined interval period at 88 – 92% of his FTP (Figure 4 depicts the workout). During the first interval, he can see his power range was significantly lower than his predicted range; he only produced an average power of 226 W over the 18-min interval. Additionally, his average wattage for the second interval was only 218 W and he can see he is significantly below his targeted power range. Using the same data, he can analyze the effects of elevation change on his power output (Figure 4 shows how his power spikes during even the smallest of elevation changes). Additionally, he was unable to keep the wattage level in the targeted power zone during the descents in the terrain. Several conclusions can be made from this basic analysis of this one workout. The best conclusion is that fatigue affected the cyclist as he may not have fully recovered from previous workouts. This explains why he was unable to reach the targeted power zones, and why his power was not as consistent during the changes in elevation. With this analysis and conclusion, the cyclist can better plan his workouts to allow for recovery in order to get the maximum benefit of his training.
The cyclist conducts a laboratory LT test and his results show he reaches LT at 200 W while his FTP is 300 W. He knows that his RER is equal to 1.0 at 200 W since this was the point he reached his lactate threshold. Using Table 1, he can read that he is burning roughly 5 calories per min and that he is using all carbohydrates (CHO). Additionally, the LT test will tell him what other percentages of the RER he rides. For instance, the cyclist’s LT gave the following RER values: RER .70 .80 .90 1.0 1.0+ WATTAGE 170 180 190 200 200+ CALORIES CONSUMED/MIN 6.6 = 100% fats 6.0 = 33% CHO / 66% fats 5.4 = 67% CHO / 33% fats 5 = 100% CHO Moving to anaerobic energy system
With this information, the cyclist can gauge how much he needs to consume during a long time trial. Think of this scenario: the cyclist is going to perform a fairly flat 40-km time trial. Since he has traversed the course before, he knows he can ride the entire course at an average of 190 W at an average speed of 40 km/hr. By gathering this information from his power meter and GPS unit, he can gauge his nutritional needs during the race. Since he knows his RER at 190 W is 0.90, he is burning 5.4 calories/L of O2 (8). This level of work rate requires the cyclist to breathe 2 L of O2/min. This rate means he is burning 10.8 calories/min; of th ??????????????????????????????????
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