As in all sprint related sport disciplines, maximal muscle force and power of the lower limbs are crucial during sprint cycling. Because such events require fast and forceful movements, it’s no surprise that especially the anaerobic, neuromuscular and mechanical systems will be stressed. But what is the relationship between velocity and power?
Power consists out of two major components: velocity and force. The basics of muscle physiology show us that a higher muscle contraction velocity results in a lower muscle force production! So, what’s the consequence for the power-velocity relationship? Since the force is down-sloping in relation to muscle contraction velocity, the power-velocity curve will be parabolic, which means that there will be an optimum: the maximal power production! At this point, the muscle force and contraction velocity will be balanced optimally.
Muscle power: the key to sprint cycling success?
When a muscle contracts, it produces a certain amount of force and torque or moment. The higher optimal and maximal torques are produced by cyclists with a higher lean leg volume (total weight – fat weight). This makes sense; the higher the muscle mass, the higher the force and torque production. This in turn, relates to the maximal power production.
“Conclusion; the maximal power output is obtained at an optimal cadence!”
Now, how’s muscle contraction related to cycling? After all, the bike velocity isn’t the same as the muscle contraction velocity. However, the bike velocity is dependent of the muscle contraction velocity, by means of the cadence. Conclusion; the maximal power output is obtained at an optimal cadence! Therefore, in theory, maximal power output and optimal cadence should be related to each other. Nevertheless, no such relationship could be found by scientific studies. So, there seem to be more factors which one needs to consider!
Air resistance: the missing key!
It’s well known that track sprinters can reach very high speeds. This might partly be the result of their very high maximal power production. This might be as high as 20 Watt /kg body weight! The maximal power output seems to be determined for a large part by the sprint training background and the genetics of a cyclist. However, the power production doesn’t seem to be the only contributor to speed. Some studies even seem to conclude that maximal power production isn’t directly related to sprint performance at all.
Because during track sprinting, the speed of the cyclist is very high (up to 18 m/s or 64.8 km/h), the main opponent of a track cyclists is the air resistance. Air resistance is known to comprise more than 90% of total resistance experienced by a cyclist. This air resistance consists of two parts: the drag resistance and the frontal area of the cyclist and his/ her bike.
“Because during track sprinting, the speed of the cyclist is very high, the main opponent of a track cyclists is the air resistance.”
The drag resistance is dependent of the shape of the cyclist. This is why professional time trial cyclists are eager to optimize their bike position and their materials during competition. Related to this, is the frontal area. The frontal area seems to be dependent of, amongst others, body height, mass and lean leg volume. This can be explained simply by the fact that the bigger the cyclist is, the greater frontal area he or she will have. This explains why maximal power production might not be related to sprint performance in a direct manner.
Instead, frontal area needs to be taken into account as well! Indeed, sprint performance is related to maximal power production when corrected for frontal area! This introduces a new paradox: bigger muscles are required to produce high torque values, which are required for maximal power output. But at the same time, this increases your frontal area! Once again, it’s important to find the right balance.
Even though optimal cadence isn’t directly related to maximal power production, it’s still valuable, since it’s directly related to the sprint performance. But how? Studies indicate that the optimal cadence is halfway the maximal cadence. In other words: the optimal cadence is half of the cadence which can be obtained during non-loaded cycling (no resistance). A higher optimal cadence seems to be related to the percentage of fast muscle fibres. This is important in all-out, explosive events. A cadence close to its optimum lowers the energy costs, and improves the mechanical efficiency. Therefore, the right gear ratio is very important during sprinting! A higher gear ratio might result in a lower cadence, closer to the optimal cadence, in turn improving the sprint performance.
We can state that a (track) sprint performance is a multi-factorial process. Keep in mind that a high maximal power production, corrected for the frontal area, is very important. But also, that it’s not the only factor. Your training shouldn’t be focussed on power solely. Air resistance, by means of drag and frontal area and cadence are crucial as well. Therefore, sprint performance optimization is more of balance act than one expects!
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Dorel S, Hautier C, Rambaud O, Rouffet D, Van Praagh E, Lacour J-R, et al. Torque and power-velocity relationships in cycling: relevance to track sprint performance in world-class cyclists. International journal of sports medicine. 2005;26(09):739-46.