Everyone has probably heard of watts. However, not all cyclists are aware of how this unit of measurement for power can be used in their own training. Power describes how much mechanical work the body performs over a certain period of time and is perhaps the most important optimisation screw that road cyclists can turn if they want to control their performance and, above all, increase it efficiently. A power meter is used to measure how hard the rider is pedalling. Recorded and correctly interpreted, the data guarantees consistently accurate training documentation and allows progress to be recognised in real time. Watt values have revolutionised cycling. No other method can optimise form more efficiently than a data-based training plan based on performance in watts. The more ambitious the goals are, the more it is advisable to control training based on performance rather than heart rate, as the heart rate during cycling is subject to influencing factors such as temperature and wind conditions, emotions, fluid loss or nutrition. Even an espresso before training can influence the heart rate. In addition, our heart is a sluggish pumping muscle that reacts with a time delay to sudden changes in intensity, as is common during interval training. The wattage, on the other hand, is a real-time value and incorruptible.
In competitions, power values are indispensable for pacing, i.e. power distribution. They reveal the condition of the legs and determine more reliably than body feeling whether you can maintain your pace or not. After the race, analysing the performance data helps to identify development potential. This allows you to structure your further training in a targeted manner.
Cycling is better researched in terms of training science than almost any other endurance sport. Other key figures can be calculated from pedalling performance, such as training zones or energy requirements. Power can also be described as energy flow in joules per second. The energy in kilojoules corresponds to the product of power in watts and the corresponding time and this approximates the kilocalorie requirement.
In the realm of numbers
The Functional Threshold Power (FTP) allows numerous conclusions to be drawn about the individual training status. Also known as "threshold power", it describes the maximum average power over an hour in watts. Programmes with which the individual FTP can be mapped are integrated into almost every training app. As an FTP test requires conditions that are as constant as possible and requires a lot of energy, a test duration of 20 minutes is easier to implement than a full 60-minute test. The hourly performance can be approximately determined by multiplying the average performance over 20 minutes by a factor of 0.95. No matter how long the test lasts, don't forget to warm up! However, endurance tests also occur in training and competitions. Since training software can calculate automatically over a wide range of time periods, it will spit out an FTP value even without a test, which is already a good indication of the performance of frequent riders. However, the values are only really comparable if the tests are always carried out according to the same protocol, for example on an ergometer. Outdoors, however, slightly higher values are often possible with a power meter.
The FTP test cannot replace a professional performance diagnosis. However, it can be carried out at home without outside help and therefore provides simple information on personal long-term performance, such as that required for mountain rides. Focussing on a single key figure makes training control easier. If you ride with wattage measurement and know your FTP, you can regulate your training based on performance ranges. The figures on the bike computer tell you exactly when you are regenerating or training base, speed or sprints. In addition, the FTP value helps to assess the feasibility and the difference to other participants when preparing for a race.
Professional values
The peloton is spread out on the flat stages of the Tour de France. The captain is shielded by his helpers and hardly has to exert any power on the flat (around 140 watts), whereas a rider at the front of the peloton has to exert around 245 watts. If the captain of a team wears the yellow jersey, the unwritten laws of cycling demand that his team rides a lot at the front in order to control the race and defend the leader's jersey. Because the slipstream effect at the front is less than in the middle of the pack, the captain in the slipstream, for example, pedals around 250 watts, while his helper at the front of the field pedals around 355 watts.
In the individual time trial, the captain has to show what he can do. No team-mate can provide him with a slipstream. To do this, he has to deliver a high continuous wattage - which translates into even more speed thanks to good aerodynamics. Many racing drivers therefore go to the wind tunnel to optimise their seating position in the battle against the clock. As a rule of thumb: if you need more than 300 watts to reach 45 km/h, you will lose time compared to the best riders. A typical continuous time trial power output is 460 watts. Converted, the racer needs 288 watts for 45 km/h.
On the climbs, the favourites are among themselves: uphill resistance dominates. As the best riders also ride at high speeds on the climbs and the wind often blows, there are slight slipstream effects. Those in the lead therefore have to invest a little more energy compared to a rider on the rear wheel (around 540 watts to 460 watts) and may end up losing out. As soon as you start going uphill, your performance depends on your weight (watts per kilogramme of body weight).
Measurement technology
Coaches and engineers recognised early on that watt training for cyclists could take performance analysis and control to a new level. Uli Schoberer and his SRM powermeter are regarded as pioneers of the technology in cycling. Professional cyclist Greg LeMond described the device as "my best training partner" back in the early 1990s.
In almost 40 years of development, the technology has been significantly reduced in size, and current models are only a few grams heavier than conventional cranks or pedals. Unlike their predecessors, the current devices also measure accurately and reliably. Both are essential for accurate training control. An inaccuracy of just five per cent can render the performance data unusable.
Power meters can be categorised into different types with different strengths and weaknesses. There are systems that measure on the crank, in the crank spider or on the pedal. Devices that only measure on one side are cheaper but less accurate than models that measure on both sides. In past tests, a difference of 20 watts and more was not uncommon. With many crank-based power meters, the performance of the legs in the pulling phase of the pedalling movement remains unclear. This makes inaccuracies in the right-left distribution more likely.
Powermeter variants
The original: SRM power meter with precise measurement in the crank spider. The measuring spider can be combined with bottom bracket shafts of different diameters. There is also a choice of different blades, meaning that more or less all common gear groups can be covered.
Our tests confirm that pedal power meters have good accuracy. The advantage: they can be used on several bikes and have no compatibility problems. The Favero Assioma has proven itself in long-term use, weighs 304 grams, measures accurately and is comparatively inexpensive. Favero also offers a robust off-road/gravel version.
The SRAM Rival Dub Wide (see above) is an inexpensive crank power meter that measures on one side on the left and starts at 274 euros. The double-sided pedal version from Garmin is available for around €1,100 (see below).
Jan Timmermann
Editor
