# Selection of Posture for Time-Trial Cycling Events
## 4 Discussion
With the results of this study, the characterization of comfort and wind speed are added to the variables defining optimal time-trial posture, and the characteristics of the rider are specified as the drag area and power delivery capacity. It is worth noting that for several race conditions, the less aerodynamic posture, ABh in this study, can be more advantageous than the aerodynamically efficient posture ABl. For example, when considering a race condition in flat terrain (i.e., zero road grade), ABh is the recommended posture at every wind speed for Riders 2, 3, and 5. Moreover, for Riders 1 and 4, the ABI posture is recommended for all of the displayed race conditions when the selection is performed based only on performance (i.e., in the area below the dotted line). Nevertheless, when the comfort constraints are considered, there is a range of wind speeds for which ABh is recommended instead of ABI. The race conditions for which ABh is recommended are found at higher headwinds. This can be seen in Figure 7 for a 0% inclination as the change from light to dark color when increasing headwind speed. The change is found at 13 km/h for rider 1 and 10.5 km/h for rider 4. This result can be counterintuitive because, at higher wind speeds, the aerodynamic drag gains relevance indicating that the more aerodynamically efficient posture ABl should be selected. Nevertheless, at higher headwinds, the race times also increase, leading to shorter pressure and vibration exposure thresholds, making ABI an unfeasible posture for some race conditions. Another example is a race condition with no wind speed. In this case, it can be observed that for each rider there are specific road inclinations in which the recommended posture changes from ABI to ABh. It is worth noting that the road inclination of posture change for each rider is the same if the selection is performed based on performance only or considering the comfort constraints. The road inclination of posture change varied over the riders between -3.6% and 1%, meaning that for some cyclists, even on descending roads, ABh is more advantageous than ABI (see Riders 2, 3, and 5). This phenomenon occurs because the power delivery capacity of these cyclists was significantly reduced when adopting the most aerodynamic posture. Hence, unless the aerodynamic advantage compensated the power delivery reduction, ABI would not be recommended. These results highlight that a more aggressive aerodynamic posture does not necessarily lead to race time improvements and, on the contrary, it can have adverse effects on the comfort of the riders. The results of the optimal posture selection when considering only performance permitted identifying that the relation \(C_{D}A/P_{1h}\), is relevant for the computation of the race time. More specifically, the difference between the ratios of the postures under comparison has a relationship with the tendency of the performance-only selection threshold (Table 6 and Figure 7). This means that the variation of the \(C_{D}A/P_{1h}\) ratio when changing the posture has a strong influence on the determination of the advantageous posture. The practical implications of the results of this study are that the optimal selection of posture should be performed considering the specific characteristics of the bicycle and the cyclist on the possible postures to be selected, and the race conditions. In particular, the power delivery capacity, aerodynamic drag, and vibrations on the saddle are characteristics of the rider that should be considered. The race distance, the road inclination, and the wind speed should be considered as well to represent the race conditions. Another practical implication is that the ratio between the drag area and the power delivery capacity has a strong influence on the overall performance of a cyclist understood as the race time when riding on a given posture. For this reason, the most aerodynamically efficient posture is not always the optimal posture. In the framework of this study different research directions were identified.