Proposal for scientific comparison of bicycle hill-climbing performance

November 26, 2010/ Jim Parker

Many Cruzbike owners have made the observation that they climb faster on a Cruzbike vs. other rear wheel drive (RWD) recumbent bicycles. Clearly, there are complex biomechanics involving the upper and lower body when hill climbing on a regular road bike (watch this video of Lance Armstrong climbing for an example). The Cruzbike pivoting-boom front wheel drive (PB-FWD) bicycle has some obvious similarities to the road bike when hill climbing: both make use of rhythmic pulling on the handlebars to angle/lean a compact tetrahedral drivetrain, and both take a slightly sinusoidal wheel path during maximum hill-climbing effort. Based on these observations and testimonials from Cruzbike cyclists, we have reason to believe that the Cruzbike PB-FWD design climbs faster than a standard RWD recumbent. Now let’s look at what would be required to prove this hypothesis scientifically.

First, the research would need to be conducted by an independent researcher. Some people have called for Cruzbike, Inc., to conduct the research. However, if we did, and the hypothesis was confirmed, many people would consider the results biased, and disregard them. Secondly, a good research protocol needs to control for many variables, and have enough data points to have statistical power. In short, a scientific, randomized, controlled study would require considerable planning and proper execution to have merit. However, the effort may be worthwhile. Recumbent bicycles are acknowledged to offer many advantages over the standard safety bike, but they have a reputation for being slow when climbing hills. If it could be proven that the PB-FWD recumbent design climbed significantly faster than other recumbent designs, it could greatly widen the acceptance and popularity of recumbent bicycles.

Here is a suggested proposal for such a research project that attempts to control for all the important variables, including physical fitness, age, body weight, bicycle weight, and adaptation to the unique pedaling characteristics of each format.

Proposed Method:

Recruit 40 active adult cyclists from the same geographic area with no recumbent riding experience. They could be volunteers or paid a small fee for participating. Basic demographic information of the riders would be collected (age, weight, height, gender, etc.) At the initial meeting of the recruited cyclists, they would each perform a time trial on their regular DF bike climbing up a reference hill with approximately an 8 to 12% grade and 1000 meter length. Heart rate would be monitored. Next, randomly assign each cyclist to one of the test groups (i.e. PB-FWD or RWD recumbent).

Each cyclist would receive a 30 minute introduction to the bike, and would agree to train on the bike 6 to 10 hours per week for 12 weeks, keeping a log of their training. A research affiliate would check in by telephone or email weekly to make sure cyclists were putting in the required training.

At the end of the first six weeks, the cyclists would re-convene with their assigned recumbent bicycle and repeat the time trial, climbing the same hill, again monitoring heart rate. The bikes would have approximately the same gear ratios and similar tire tread and air pressure. The weight of the bicycles would be equalized by adding weight to the lighter bicycles. Training would continue for another six weeks and the time trials would be repeated at 12 weeks, concluding the study. Standard statistical analysis would determine if there was a significant difference in climbing speed between the two test groups.

Key points here are 1) the randomization of the participants so that both groups would have the same probability of having participants of equal age, fitness, level, body weight, etc.; 2) by having participants with no recumbent experience, there will be no advantage from a longer adaptation period; 3) by equalizing bicycle weight, tires, and gearing, the only variable left is the actual bicycle drive system, and 4) by having one long hill-climb as the test course, speeds will be low and advantages from aerodynamic differences will be minimized. High-tech monitoring of power output and/or oxygen consumption is not needed to test the hypothesis and has been intentionally omitted to reduce the cost and complexity of the study.

If an independent researcher would like to lead such a research project, Cruzbike, Inc., will gladly cooperate and loan up to 20 FWD bicycles for up to 20 weeks for the project. An alternative to this fairly large study would be to conduct a much smaller “pilot” study with only four cyclists. Selection of the cyclists would have to be more carefully performed to get cyclists of the same cycling/climbing ability and no recumbent experience before they were randomly assigned to one of the two test groups. With a small number of test subjects, more repetitions of the time trial may be required to get enough data points.