Data Analysis from the Jeantex Bike Transalp 2009 An exclusive look at the hardest Mountain bike race there is. How hard must you pedal in order to stay with the Transalp leaders? The SRM-Data from Günter Sandmann – Masters racer, give you the answer.
Power output measurement is common in road racing. Many top riders train with power meters and in the all-comer categories too it is getting more common to find these devices, which show you to the nearest Watt, how hard you are pedalling. Many 2PEAK athletes depend upon the precise evaluation of power data to plan their training. But off road, there are not too many riders using power metering, so it is not easy to find data from these races and to understand their power structure. What is the difference between marathons on and off-road as regards performance? How hard are the climbs ridden? Günter Sandmans' data throw light in the dark zone of MTB marathons.
Due to bad weather the first stage was cancelled and the second stage was shortened, because there was still snow on the Geiseljoch. These data come from an SRM system.
Ambitious and fast starting Günter und Reinhard from the Team Black Forest Ultra1 on the second stage, which consisted of two climbs (grey line: vertical profile, green: power, blue: cadence, red: pulse frequency). Right from the first climb,marked by an interval, the tempo was high. The average power of 279 W for 35 Minutes wasn't reached again during the rest of the stage. On the second climb, the pair went more easily and finished in an excellent 2hrs 45m in place 11 in the masters category. On the shortened stage the energy used was a moderate 2245kj.
The analytical view from the SRM software shows the rate of distribution of the samples. Because of the long climbs, there are definite peaks in the speed – at just over 10kmh. The power curve is very steep too; the most common power sampled was 270w, the most common cadence a supple 80 RPM – fast for a mountain biker. Here we can see that Günter had been training on climbs in the correct gears.
If you go more into detail, you can see that not only the average power but also the power variations were initially greater than on the second hill. This is indicative of the onset of fatigue at these continuously high power levels. The cadence falls off as well, with increasing fatigue.
2PEAKs analysis of the ride shows clearly that on this stage the hammer was down: there is not so much orange (for Z4 intervals) to be found later in the race.
The team had a testing time on the second stage, where it became clear, that Günter was the stronger rider in the Schwarzwald team. This is quite normal in the Transalp race. You almost never find two riders of the same ability. These unequal teams have to accept the situation and work together to get the team through as well as possible.
On the first section of the long climb to the Pfitscherjoch Günter and his partner hammered up at a good 258w average power, later had to get off and push a few times – noticeable where the power curve runs flat along the bottom. Of course pushing is also hard work but less of an effort for the heart, than riding at high speed, as can be seen from the pulse curve, which drops in this phase.
On the long descent with counter-climbs, Günter raced in front and his partner was able to ride in his wake. The effect of the slipstream, which, as in road events is dependent upon the speed, can clearly bee seen with a powermeter. At the end, the Black Forest men got 12th place for the day.
The "stage royal”: four climbs and more than 3,600 meters climbing are a clear challenge. So in the power data we find the highest energy expenditure. 3800 kJ and five and a half hours' riding is a tall order. But Günter and Reinhard took the first hill without consideration of what was to follow and with over 270 W average power for over 1:15 hours, reached their highest continuous power for this long duration in the whole of the Transalp. After that they had to curb their effort and Günter rode from here on mainly in the endurance zones. For the continuous power phases, upper Z3 is the typical cut off point. und Günter fuhr fortan überwiegend im Grundlagenbereich die Etappe zu Ende. Für Dauerbelastungen ist ein GA2-Leistungsniveau die typische Belastungsgrenze. Only really good athletes can produce Z4 power day after day and keep it up for long periods. Usually it is paid for the following day by tired legs. Z5 is not really relevant in marathons.
The fifth stage had a large portion of cross country and although the profile was straight forward, with only one long climb, still had 3,200 meters climbing. At the beginning of the long climb, Günter and Reinhard started with around 250 W, but couldn't hold the tempo all up the brutal 1,700 meter climb, as can be seen by the fall off in the power curve. Apart from this, Reinhard had a crash. At the finish the pair had a rather moderate average speed and landed in place 15 in their competition – an indication that the other teams were just as tired, or that the profile, with a lot of short counter climbs, prevented a high continuous performance level. Günters average pulse fell to 152, which is clearly below the level of the previous days.
The previous days, with an energy level of over 3.000 kJ have taken their toll. On the third hard day in a row, the average output falls to 165 W. Nevertheless Günter and Reinhard placed better than the day before and finished in 14th place.
Hills, hills and more hills; Günter took the 1.400 meter climb from Kaltern to the Grauner Joch in sporting fashion: 1h 45m uphill with an average 230 W are no small matter following the exertions of the previous days, even if it was in Z3 for him. Later on group riding on asphalt played its part, until the finishing climb to Andolo gnawed at the reserves and the cadence dropped down the scale.
Now they could smell the Gardasee – the classification was clear – accordingly Günter and his colleague took it a bit more easy. The last hard descent spoiled the average speed clearly. That the legs are working hard too is not shown – as static loads don't get noticed by the power meter.
Günter und Reinhard finished the as 14. in the Masters competition with a deficit of 5h 48m to the category winners. from the power data we can see, that that the long climbs, which dominate the vertical profile in the Bike Transalp, have to be climbed at high and constant power in order to get into the first ten. So the training has to be geared to optimising tempo stability on long climbs. It is not the top power level which counts – but the ability for endurance power. Power peaks are only needed in the technical passages, in order to ride through.
The time differences to the best teams permit a rough calculation of the top performance levels. This gives a value for the best Master riders of around 320 W on the climbs, with the best men close to 350W
Cross country energy expenditure is higher than on the road
Is the Bike Transalp - a high standard event - harder than a comparable road marathon like the TOUR-Transalp? The data show, that the power needed to obtain a similar placing is somewhat lower in cross country. But on the road, the descents are more relaxing and in any case the whole body is less stressed than off road. So it is logical, that at the same level of fitness, pedalling output can be higher on the road than off road. Günter got values in training of up to 25% higher energy use with a pulse meter than with the Powermeter. That isn't unrealistic, because all the extraeneous work done - for instance standing on the pedals in the descents - doesn't register on the Powermeter but of course still costs energy. Then there are the pushing phases, which the Powermeter can't sense.
Off road descents are not just harder - they present an opportunity to gain a more time with good handling skills than on the road. In the final trail to Lake Garda, there were 20 minute differences in a single descent. So the challenge to mountain bike riders is wider than to road marathon racers. despite almost the same pedalling power output, riding off road clearly eats up energy and strength, because the body has to work more.
The stages in overview
The tabels show the average performance data during the Transalp week (First stage was cancelled due to bad weather).
The maximum values are highlighted in colour. The effective power value P_eff (normalized power) shows better than the average power,how high the real load on the rider is. The effective scale rates the quality in peaks higher than in the lower values. To calculate the relative climbing performance the complete system weight is used. In Günters case this was as follows:
By dividing the power by the system weight you get the system power/weight ratio (not to be confused with the personal power/weight ratio). This is what decides how fast you can climb with your complete equipment. It is no surprise, that the highest power was reached on the shortened second stage.
The severity of the stages can well be deduced from the energy requirements, which are calculated here from the pedalling output, although the actual energy used is up to 25% more off road.
The "stage royal" (stage 4) leads in this respect. A typical sign for stage races is the higher pulse rate on the second day, together with a generally falling pulse tendency overall (caused by fatigue and/or economical riding).
Günter, who has ridden the Bike Transalp several times, found the Powermeter a good help during the event, to judge the effort better on the long climbs: " I wouldn't want to be without it in future, neither in training or in competition," concludes the knobbly tyred pioneer.
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