by Melanie McQuaid

For the last many years that I have trained, first as a mountain bike athlete and more recently as an off road triathlete, I would put about 80% of my riding hours on a road bike. This came naturally as I have always done my interval training using a power meter, and up until 2008, I did not use a power meter on my mountain bike. The time I spent riding trails focused more on quality endurance and technical training.

This winter I started to employ the PowerTap SL 2.4 Disc Hub System off road. I have replaced one of my hill workouts with another off road workout on hills and have started the process of data collection and analysis to compare my ability in January to my hopefully improving ability in March. What is interesting is the comparison of the hill workouts done on the road to my hill workouts done on the mountain bike. I have no doubt that some of my observations can help me to better plan for these workouts and how to tailor my training program to better reflect what I am going to encounter racing. Many of these observations merely confirm what we already know are the differences between mountain bike racing and road racing. However, the actual quantification of these differences is of interest.

For example, one trainer workout I chose on the road bike was four to five minute intervals at 95 rpm and 85% of my maximum aerobic power. This workout is excellent for time trialling on the road and mountain biking, particularly in XTERRA, is a time trial. However, mountain biking is not as steady an effort as this. The hills I found for the mountain biking were uneven, at times very steep and at times it would level. My average was about 70 rpm for that climb at a much higher average power output than I would do on the trainer, particularly in the sections that were quite steep. This leads me to consider that the trainer workout I was doing would be great for long steady climbs at altitude when you want to keep your heart rate under control, but for mountain bike racing on rolling terrain, you will need to do intervals at much more than your maximum aerobic power. Using a powertap to measure the average watts you can hold and the cadence you can maintain will help you to gauge your improvements, whether by pedaling faster or by pedaling harder.

The other observation thus far has been that the average power output on a given mountain bike ride versus the average output for one of my road rides is much higher. This is obviously attributed to greater rolling resistance on fatter tires. It is true that after a mountain bike ride it may not feel like you have gone that hard because you are constantly distracted by the beauty of your surroundings, but the next day you are definitely more fatigued than you would be from a road ride. You also tend to maintain a much higher heart rate on the mountain bike without thinking about riding hard, which would give you better aerobic endurance gains if you incorporated off-road rides into your program throughout the winter. Effectively you will have painless harder training.

So although none of this is particularly new science, it is great to have a tool to help to quantify your efforts off-road. It has been very useful for me to have the Powertap when I am doing intervals, and now I can add greater specificity to my training by doing those intervals on my mountain bike. Training specific gets you fitter, faster and with the PowerTap SL 2.4 Disc Brake Hub, filthy. Happy trails!

--Melanie McQuaid