Power on the Bike
It is very common to hear athletes talk about their fitness using sentences such as ” I rode 50 minutes at an average HR of 180, pretty good eh? Also the average speed of a ride is often quoted: ” We recently rode at an average speed of 22 mph ( or 33 km/h)!” unfortunately the truth is both statements are not really meaningful by themselves. A high heart rate is an indication of a strenuous workout, but that’s it. Without a context such a statement is worthless. The same is valid for the average speed conversation: was it uphill or slightly downhill, or flat with a tailwind? Alone or in a group ride? Often the average speed we log falls as the season progresses, because our training rides and races become more demanding – but the power output improves. The average speed does not contain any evidence of the real performance if we do not improve the information content.
The goal of training is not to develop the ability to work at an increasing heart rate. The goal is to improve performance, in other words the output. Heart rate is often used and sometimes abused as a performance indicator is because the measurement technology is available. Heart rate monitors are relatively inexpensive and therefore relatively widespread. On the other hand, the direct measurement of power output can only be achieved using relatively more complex and therefore more expensive equipment, which is in turn relatively rare. But it is given that the muscle work determines the workout intensity and the measured heart rate is only one of several indicators that reflect that intensity.
For the muscle to produce a certain amount of power, it needs to be nourished (“fueled”) and supplied with oxygen. The transportation system is provided by the blood stream. The quantity of the oxygen that can be made available depends on the number of heart beats (frequency) and the volume of the heart. Then other factors have an influence such as the oxygen saturation of the blood cells (hematocrit). The real pumping performance of the heart can therefore not be measured by the heart rate alone. In any case, the increased pumping action of the heart does reflect the increased muscle work during the exercise, but it is not the only cause. Sounds complex? Yes, it is, but it also simple. At the end it is only the output that matters.
Performance can be defined in scientifically exact terms. For a cyclist, this is the product of leg force times leg turnover (cadence) and is expressed in watts (watt = joule/seconds= energy per time unit). A small force times a high cadence can therefore equal a bigger force times a slower cadence. A good example is Lance Armstrong’s “spinning”-style. Lance produces a remarkable power output by multiplying a very high cadence with an average force. A rider like Jan Ullrich on the other side produces an identical performance by applying an average cadence to a remarkable force.
Power output is therefore the key to speed. Under the assumption that the external conditions remain unchanged (wind, gradient, riding position, etc.), only an increased power output leads to a faster speed. The best rider does not win, because he has the highest heart rate, the biggest oxygen intake, or pushes the biggest gear. He wins because in relation to his total system weight (rider + bike + all other equipment) and/or his systems aerodynamic coefficient he expresses the highest power output. Exceptions to this rule are luckily very common and things such as tactics and other parameters influence a race outcome substantially. Good, then otherwise road racing could end up being pretty boring..
Weight and Relative Power Output
Absolute power output itself misses the point as well. Only when power gets divided by the weight, you really get a relevant measurement, the power to weight ratio. The power to weight ratio defines how fast a cyclist can ride up a climb. The amplitude goes from 1 W/lbs (2 W/kg) to 14 W/lbs (7.2 W/Kg) for pro riders.
If we watch the pros, we can easily see how this correlation dictates the way they look: first they train to achieve a maximum of force and then they try to lose as much weight as possible without losing leg strength. Since losing weight contributes to increase the ratio. Before Bjarne Rjis succeeded in winning the Tour de France in 1996, he had to lose 11 lbs (5 Kg). Losing 5 to 10% of body weight is still easier than to increase the power output in the same range, especially when you already are at a very high level.
Like the power to weight ratio for a climber, the power to aerodynamic ratio is what matters most for a time trialist. This is a quotient as well: power divided by drag area (cwA). This value expresses how good the “engine” power output is in relation to the “bodywork” quality. An athlete who sits extremely aerodynamically on the bike, rides much faster with the same power output. Riders who have a high power to weight ratio as well a good power to aerodynamic ratio, are equally qualified for the flats as well as for the climbs. Good riders like Armstrong or Ullrich are good examples. But specialists can also be good in both disciplines. The time trial world champion of 2002, Santiago Botero already won the climbers polka dot jersey at the Tour de France.
Equipment and Other
This is by no means an exhaustive list since there are countless of other variables. Depending on the age and the level of fitness these power to weight ratios differ significantly. With 2PEAK you can calculate compare your power output with that from other athletes – and of course you can filter age and volume to insure a peer-to-peer comparison. Equipment also plays a very small part, as the speed calculator shows us. With this you will get to starting line well informed and with realistic expectations.
By now it should be clear that power measurement is crucial in the pursuit of determining fitness improvements. How do we do this? The most elegant solution is the use of a power-measuring device such as the Power Tap hub or the SRM crank. These instruments measure the effective power output during the ride. Your bike mutates to a mobile ergo meter. The data can be downloaded on your computer and analyzed. With this an objective analysis of the training intensities is achieved. This data can then be uploaded into the 2PEAK servers for further analysis and integration into your training plan.
These instruments are great to effectively keep an eye on the training progress. Combined with 2PEAK they become even more meaningful. Since 2PEAK not only analyzes the past but also and more importantly defines, based on the acquired knowledge, how the future training needs to be configured such to allow for a further fitness improvement. With 2PEAK the circle of performance improvement can be completed.
The downside is that they are expensive. As an alternative 2PEAK offers what we call the MP-test (Maximum Power), or a climbing test on a longer climb. Both methods are based on the calculation of the hoisting capacity. The data that is needed therefore are: the system weight, the ascension in feet or meters and the time. All of which are relatively easy to be determined.
The MP test accomplishes the same as a power measurement device as far as being able to monitor the fitness improvements, by simply providing an objective and accurate measurement clocking your effort on your favorite climb. If you want to improve your power output from say, 260 to 300 watts on your favorite climb (you can find out what this would mean in terms of a time gain using our speed calculator in the tools menu), you can easily use the MP test to check your improvements. A systematic training approach with a power-measuring device will however be easier and allow you an ongoing insight into the way your body reacts to training.
Another difficulty around the theme power output measures is its dependence from the time factor. The actual effort that the human body generates is always a function of time: if the time increases the power output decreases. Especially for efforts under one minute, the power that can be generated depends dramatically on the time. This is due to the dominant aerobic component. This is also the zone that has no real correspondent with a heart rate measure (the heart rate lags the effort and can therefore not be used as an accurate indicator for it). This is why 2PEAK defines the last training zone simply as the highest motivation zone. As time increases the aerobic component of the effort gains importance and so the output decreases slower over time: the 4 minute effort is closer to the 1 hour effort in terms of average power output then the one minute power output. The attached chart illustrates this correlation: Leistung als Funktion der Zeit (performance as a function of time)
The curve shows the power output drop of a well-trained athlete over time. Starting at the maximum 8 minutes output (MP8) the output drops by 7% with every doubling of the duration (red line). The gradient of the drop depends on the individual and his capacity to hold an effort for an extended period
Targeted workout management with the help of power measurement.
The power demands differ from race to race. A marathon or stage race requires excellent long-term endurance but very little anaerobic capacities or speed. This is very different if starting for a XC race, a criterium or a cyclocross race: if you want to be with the lead group, you need to be able to turn quite often in the “red zone” when climbing, cornering or sprinting. The talent required here is to get into a short-term oxygen dept and then recover during a short descent. Sprinters of course need explosive power bursts in order to leave the competition in the dust and time trialists need enormous aerobic capacities to be able to ride for long periods at threshold. Everyone that can’t respond to attacks in the field because they lack explosiveness will be dropped and can pack up in a stage race.
These differences in competition, lead to different requirement profiles for training, without, which you’re not going to succeed. 2PEAK’s race planning takes these requirements into consideration and with its option to include the race profile into your training it allows for an efficient and transparent method to systematically train for your individual objectives. Once defined the training zones as well as the intervals will be defined in watts per time units and can then document the training in watts as well. The training can therefore be managed directly from the source and the improvements can be seen instantly.