Austrian Championships Cross-Country 2009
Karl Markt (SRM Stevens Team) won silver at the Austrian MTB Championships in Walding, which was nine laps of 2.7 kilometers on a tough, muddy course for a total of 1:46 h riding and running. He was riding with the new SRM FSA k-force light Mountain Bike PowerMeter.
If you compare the SRM data of a mountain bike race to a road race there are obviously some differences due to the character of the competition.
- Speed is significantly slower: average 14 km/h
- Time and distance: a typical cross country mountain bike race is about 1.5 to 2 hours, which is much shorter than a 200k (eg. National Championships) road race that takes 5-6 hours.
- Power is about the same: average 219 watts (2.9 W/kg), that's a little lower than on the road, but a closer look shows why: about 1/3 of the time Karl wasn't pedalling at all, in the downhills and the running sections. Downhills are much more demanding than on the road, they are technical, and bike handling skills - not just on the downhills -- need good upper body and core strength. There are high peaks of power causing a high variability of power, with high demands in max power and anaerobic endurance.
- Heart rate is much higher and more stable than on the road. The demanding downhill and running sections leave no time to really recover like on the fast downhills on the road when you don't.
- Cadence is lower than on the road. The average is about 70 rpm while riding (don't bee fooled by the 44.4 rpm average for the file, that's for the whole time - including when the cadence is 0 rpm because of running).
- Energy consumption is difficult to compare. The time when you don't pedal does not mean that the metabolism is going down. Downhills and running sections also demand a high energy output. Because a lot of energy is metabolized anaerobically, the relation between fat and carbohydrate to cover the needs is different to the road. On the road, also due to the length of the competition much more fat is metabolized. Mountain bike races are on a much higher level fired with carbohydrates. Also, because of the high total body demands the efficiency factor in a MTB race can't be roughly 20-25% like it is in a road race, so an estimation of the calories burned is not possible.
If you have a look at the data: the first lap is vital for the final result. If you ride the difficult technical sections and single trails ahead of the bunch you can ride the best line and don't have to be careful of the other riders as much. There is also no wasted energy for passing or stopping because of crashes.
 Zum Click on graph to enlarge
Karl's first lap was the most intense in the race: 255 watts average for a little less than 10 minutes, then 2 ½ minutes without a cadence, which means downhill or running.
Karl's average heart rate for the first lap was 160 bpm and didn't get much lower until the end of the race.
His average power decreased to just above 200 watts from lap 5 on, but that does not mean that his intensity level was significantly lower.
The non-pedalling time got longer too, up to 4:16 minutes in lap 5.
His average speed doesn't change that much, maybe his experience level on that course got better and he found his perfect line to ride.
Click on graph to enlarge
Many cross-country mountain bike races have no final sprint, as was the case in this race. That's also a reason why the last lap is not on a higher intensity than the other laps - which is what you normally see in a road race.
Karl said that Johannes Metzler (Vaude Simplon Team), the winner of the race, was a better runner and therefore he had no chance. Longer running sections are not typical for Cross Country-races, but it can happen when it has rained and the mud is too deep to ride - like in Walding.
How can an SRM PowerMeter help to increase performance for mountain bikers? To answer this, we need to look at the max power values - especially for the short time intervals.
Karl's max power values are:
| 2 sec |
|
1.024 watts |
|
13.5 w/kg |
| 10 sec |
|
797 watts |
|
10.5 w/kg |
| 20 sec |
|
682 watts |
|
9 W/kg |
| 40 sec |
|
579 watts |
|
7.6 w/kg |
| 1 min |
|
505 watts |
|
6.6 w/kg |
| 4 min |
|
407 watts |
|
5.4 w/kg |
| 20 min |
|
304 watts |
|
4 w/kg |
| 60 min |
|
242 Watt |
|
3.2 w/kg |
Considering these values, Karl now knows what he is able to push and can simulate his individual power demands in training to increase his max power - with short sprints and different cadences, his anaerobic endurance with short intervals between 20 and maybe 90 seconds, different cadences, different times and ways of rest between the intervals.
Power is the best way to control the intensity of intervals - heart rate has a delay in adaptation to workload. That makes it impossible to find the perfect intensity especially in the short intervals.
Heart rate can be very helpful to control the length of the rest between the intervals, so the combination of both make training more effective.
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