In just a few years, we went from having to do stress tests in a laboratory to being able to do them daily on our own bikes.
Most cyclists know that using a power meter while training is much more precise than taking your pulse and measuring your rating of perceived exertion (RPE).
Until the 1980s, cyclists competed and trained “based on feeling,” and were subject to all the errors entailed by this. Cyclists’ temperaments, social environment, weather conditions, motivation, and other factors directly impact perceived exertion, so the margin of error on RPE can be quite high.
In 1982, the first wireless heart rate monitor was put on the market by a well-known Finnish brand and pulsometer use increased exponentially until the mid-1990s, when any cyclist who didn’t use a pulsometer was labelled old-fashioned. Indeed, the use of one’s pulse for training purposes also has a margin of error. Factors like ambient temperature, muscle fatigue, altitude, etc. significantly influence cyclists’ heart rates.
In the 1990s, a renowned German company began selling power meters for road bikes. Although the first models where cost-prohibitive, in just a few years, technological advances and competition in the sector pushed prices down and there are now a number of affordable power meters available.
Training with a power meter is more precise. In fact, the wattage is so sensitive to the force leveraged each time the cyclist pedals that the very first time cyclists begin training with a power meter, they are able to become more efficient or at least more aware of the energy required for each working area.
This high watt sensitivity causes cyclists who pedal at 200 watts (W) on flat land to be amazed when they see that they expend 400 W when they stand on a steep slope, even though they may not feel like they are expending double the energy as when they were riding at 200 W.
Notably, average wattage (W.avg) will be undervalued the more the pace changes. For instance, during a two-hour flat training session, if a cyclist rides constantly at 200 W, their average will be 200 W. However, during a training session in which a cyclist takes an hour riding up a mountain pass at 400 W and rides down at 0 W for another hour, their average wattage would also be 200 W. Naturally, the training session in which the cyclist rode up the pass is harder than training on flat land, even if both training sessions have an average wattage of 200 W. So, the limited reliability of average wattage for quantifying the robustness of a training session gave rise to the concept of Normalized Power (NP). This concept was defined by Allen and Coggan (2010) as “an estimate of the power an athlete could have maintained at the same physiological cost if their power had been perfectly constant.” Returning to the previous example, training on flat land will yield an NP close to 200 W (given the constancy of the instantaneous power), but the session of going up and down the pass may yield an NP of up to 250 W (due to the inconsistency of the power data).
Another vitally important concept is the power to weight ratio (watt/kilogram). Cyclists can appreciate this figure when they compare their power meter data from the same training session with another cyclist of a different weight. If one cyclist weighs 130 lbs and another weighs 175 lbs, both will see very similar wattage on flat land, as inertia makes cyclists’ weights less determinant. However, once the road begins to slope upwards, the 175-lb cyclist will need to apply a great deal more wattage to pedal. If they go up at a rate of 5 W/kg, the lighter cyclist will go up at 300 W, while the heavier cyclist will need to exert 400 W to climb at the same rate. If one of the cyclists loses 20 lbs, they would exert 50 W less, but still go up at the same rate.
Finally, I’d like to highlight that although the use of power meters has revolutionized training sessions and competitions and most trainers closely follow each cyclist’s power data, they also continue to monitor cyclists’ heart rates and ratings of perceived exertion (RPE) during each session.
We’ll delve into greater detail on different power training concepts in coming posts. For now, we hope this post has served as an enriching introduction to the exciting world of power meters.