In science there are two measures by which data is assessed: reliability and validity.
Reliability in statistics and psychometrics is the overall consistency of a measure. A measure is said to have a high reliability if it produces similar results under consistent conditions. “It is the characteristic of a set of test scores that relates to the amount of random error from the measurement process that might be embedded in the scores. Scores that are highly reliable are accurate, reproducible, and consistent from one testing occasion to another. That is, if the testing process were repeated with a group of test takers, essentially the same results would be obtained. Various kinds of reliability coefficients, with values ranging between 0.00 (much error) and 1.00 (no error), are usually used to indicate the amount of error in the scores.”  For example, measurements of people’s height and weight are often extremely reliable.
Validity is the extent to which a concept, conclusion or measurement is well-founded and corresponds accurately to the real world. The word “valid” is derived from the Latin validus, meaning strong. The validity of a measurement tool (for example, a test in education) is considered to be the degree to which the tool measures what it claims to measure; in this case, the validity is an equivalent to accuracy.
Problem with power is that it is less reliable and valid when applied to the testing of novice and intermediate/sport athletes, and more reliable and valid when applied to the training and testing of expert or professional athletes. Overall, power may be objective (as all the online paid advertising states by both coaches and the manufacturers), but it makes power data unreliable and invalid.
With professional athletes who have a keen awareness of how their body functions, how their body generates force, from where force is generated, and how to modulate and regulate movement to change their power output, the measurement of power will be more reliable and more valid because it is an actual measurement of the forces they can generate, consistently with specific technique.
With amateur athletes, those who lack self awareness, lack a deep understanding of technique, lack technique, lack the ability to modify technique in real time while training or competing, whose life focuses primarily around home and work, which is then followed by sport, you cannot be sure what exactly the power meter is measuring? Is it the stress of work impeding their ability to generate power, is it fatigue because they were up all night with their sick child, exhaustion because a project deadline got moved up, because home renos are growing from a minor to a major issue, or perhaps they overdosed on coffee and energy drinks and are having a mild PED fueled burst? You don’t know, and if you don’t know what you are measuring, then irrespective of how objective the number may seem, it isn’t.
If you cannot specifically identify what the power data represents, then the data is meaningless. With novice and intermediate athletes, power values are more often than not, random points achieved at a point in time, where the athlete has little to no idea of how they generated, or how to replicate generating that power level under varying conditions. Worst, athletes and coaches don’t know that they don’t know, and proceed to depend on data simply because they have a solid number to establish training and racing parameters.
Curious isn’t it… hack coaches depend on data, but Daniela Ryf, and her coach Brett Sutton do not depend on power data. When the 3x Ironman World Champion and Ironman WC course record holder doesn’t use power as a staple in her training, you would think that it would make athletes and coaches rethink their approach.
When the 4x Ironman World Champion Chrissie Wellington, who was undefeated at the iron distance of triathlon states that she did not rely on power to compete, instead honed her skills of self awareness in order to execute racing strategies, you would think that it would have athletes and coaches throwing away their power meters.
But the temptation of a number is just to much for most to let go. Problem is that for most athletes, their power meter is a random number generator, not an objective measure of anything because what is being measured is not consistently reproducible by the athlete.
So why is power heralded as the new metric for training? Because online/spreadsheet coaches need something by which to measure progress, and power has become the data point. Why? Unfortunately because… the average coach cannot tell the difference between valid and invalid data, between reliable and unreliable data. The mindset is… its data, hurray! Now go harder and produce data with bigger numbers.
As an athlete, if you do not have proper technique (be it cycling, running, or whatever), if you do not know what proper technique is, if you do not have the awareness to feel whether or not you are executing good technique, when and how your technique breaks down, then there is absolutely no reason to have a power meter.
What is a power meter going to tell you? It will only tell you the power you generate with ineffective and inefficient technique; technique which limits your potential and places you at risk of injury.
What will a power meter not tell you? That you are riding with ineffective and inefficient technique, what aspect of your technique is ineffective and inefficient, how to fix your technique, or the fact that chasing power with ineffective and inefficient technique is a dead end.
What will a power meter not tell your coach? What sort of technique you train with, compete with, train with when you are tired, done in, fueled poorly vs fueled properly, etc…
Only one on one coaching, where the coach observes, adjust, teaches through drill and skill work can technique be assessed, improved, developed, and hence power be generated efficiently, effectively and with the potential to increase without jeapordizing the athlete with injury, burn out or a blow up.
But what will an athlete (unaware of their lack of technique) do with a power meter? They will train and train trying to squeeze more and more power out of ineffective and inefficient technique, because they were told that this is proper “training” and the way to becoming a competitive athlete.
And what will the outcome be for this athlete? By squeezing more and more power out of poor technique, they will fail to progress past a point without having to compromise their health and as a result will become frustrated, disappointed, probably suffer an injury and/or a bout of over-training, and if pushed too hard, too long, will likely come quit the sport.
If you want to develop as an athlete the starting point is not power, it is technique. In swimming, in cycling, in running, in any sport, the starting point is the technique of that sport, or perhaps the athlete needs to take go back to an earlier starting point and learn basic movements fundamentals prior to being able to start sport specific technique.
If you seek your potential, then stop working with coaches who want to take the easy way out, who seek short cuts in their approach, because they will seek short cuts in your training. If your coach is an expert in “copy, paste, and send”, then perhaps you want to consider changing your coach.
If you seek your potential, find a coach who works one on one with athletes, developing their abilities from the beginning, not from where its convenient and cost effective for the coach to begin.
Find a coach with a long term perspective, who cares about you as a human being, not just you as an athlete, a coach who cares about your health, and wants you to succeed equally in sport, and more importantly at home and work too.