In an interesting study Jim Martin, Ph.D. of the University of Utah, and Waneen Spirduso, Ed.D of The University of Texas at Austin, found that crankarm length had little to do with maximum power output. They tested cranks from 120mm to 220mm in length at different power outputs and cadences. While the 145mm to 170mm cranks produced the greatest power (no 175 or 180mm cranks were tested), overall the differences were small. They also found that amount of energy each cyclist had to expend did not vary with either crankarm length, or with cadence. According to their research the perfect crankarm length would be either 20% of leg length or 41% of tibia length. For most people thatâ€™s a 160-185mm crankarm. Keep in mind, this study looked at maximum power, not sustained power, which I have not seen any studies of.
Does that look like 41%?
The situation when it comes to cadence is much less clearcut. Some early studies seemed to suggest that the optimal cadence was actually much lower than the 90-100rpm that cyclists typically ride, more like 50-60rpm. The limitation of these studies was that they were done with relatively untrained cyclists at low power outputs. More recent studies published in the Journal of Sports Medicine show that at higher power outputs, cadence has less effect. Researchers have also learned that the more trained the athlete is, the less effect higher cadence has. Since most racing takes place at higher power outputs, and with well trained athletes, cadence is not a big factor. This is actually good news for singlespeed riders. As long as you can keep your cadence above 50-60rpm having one gear should not be a disadvantage, until you are spinning so fast that you are not able to deliver power to the pedals. But, thatâ€™s a topic for latter when we talk about training. The biggest difference in cadence is what type of muscle fibers you are using at different speeds. At a lower cadence you are using more fast-twitch fibers, similar to sprinting, and at a higher cadence you are using more slow-twitch endurance fibers. Assuming that in a typical ride or race most geared bike riders try and keep spinning at the same rpm, they use mostly slow-twitch fibers. A singlespeed riderâ€™s cadence is more affected by the terrain, and will likely spend more time in the high rpm and low rpm ranges. By spending more time in the low rpm ranges a singlespeed rider is using more of the fast-twitch fibers then the geared rider. There is a possibility that this more balanced use of the two muscle fiber types is an advantage.
Unfortunately, not enough studies have been done in this field for the results to be conclusive, although some of the more recent studies have had unexpected results. To me knowledge no studies have been done specifically on singlespeed vs. geared bikes. As always, the real testing is in actually riding and racing.
In the next installment we will look at the role training plays in getting the most out of you singlespeed.