MTB racing requires solid endurance, your best power to weight ratio, and the ability to repeatedly deliver short high powered efforts. The endurance part is the same as any other aerobic sport, if you want to race, you need good endurance. Power to weight ratio means you have your body conditioned to develop your best power at the lowest possible weight. With all the climbs and accelerations in MTB racing, power to weight ratio is VERY important. And man, its tuff maintaining a super lean physique for months on end. But probably least understood is the ability to repeatedly produce the short high powered efforts that are required to ride fast through roots, clear obstacles and ascend the countless rises and hills featured in MTB races.
When racers launch from the line and hit the single track it may or may not be apparent that they are basically pedaling a few times, coasting, pedaling, coasting, continuously throughout the event. They also most likely do not realize just how much power they are producing during the "pedaling" portion of the ride. When you look at a power file from an MTB race it becomes very apparent! Every corner, lump, root, whatever.. requires a surge of power to maintain speed and momentum throughout the race. These surges are generally quite short, but repeated continuously throughout most sections of a typical race course.
Quadrant analysis.. what? Within WKO+ power file software you can view "how" the rider is producing power. High revs low force, high revs high force, low revs low force, low revs high force. Each pedal stroke will fall into 1 of these 4 quadrants. Generally during your basic road bike endurance ride you will be riding at a fairly middle rev speed (cadence) of around 90rpms with moderate force on each stroke. Chugging along, doing the miles, building endurance. Now say you want to accelerate, you may shift to a bigger gear and stand on the pedals in a low rev/high force style. Or you may spin the gear up with high revs eventually producing less force per rev as the rpm's increase. But on a MTB when you go to clear that root or small rise it is almost always accomplished with a lower rpm and HIGH FORCE.
I often notice that when I spend a lot of time training on my road bike that the transition back to racing on trails is not so smooth. All that power I developed on the road bike is good for those steady climbs, but when the going gets technical, rooty, highly undulating, I seem to wear out a lot faster. All those short, sharp efforts become exhausting and the next day I have soreness.. everywhere! Beat up and beaten down by the demands of MTB racing!
Why is this? I have my own conclusions, its due to the low cadence high force efforts, repeated over and over as power eventually fades away. These short, sharp efforts require a hearty push with every pedal stroke that uses more core muscle, arms and parts of the legs that just don't get worked very hard when road riding. Repeatedly delivery robust pedal strokes causes muscle contraction throughout the entire body, not to mention the upper body abuse you endure chattering through the roots and rocks, jumps and stumps and whatever obstacle may be coming next. MTB racing is much more of a full body workout, and if I've spent to much time on the road, I am going to pay for it!
So how do we train this quality up? All sorts of methods have been used, including low speed big gear accelerations, short high powered intervals, and long tempo rides with a "burst" every 5 minutes. But IMO this is all weak compared to actually getting out on the trails and riding hard.. or even better RACING! We all hear how the Pro's need racing to bring their legs around, and it holds true for us. Get out and race.. push hard, work to exhaustion and push even harder. These all out efforts will signal the body to adapt and develop strength where it needs it. I can get a bit of this by special road exercises, but nothing tops the specificity of actually getting out on the trail and riding hard!
