The Invisible Hand in Performance Testing
Triphasic Principle 39 – Coaching Contamination Principle
You know, after all the years of testing athletes—measuring power output, vertical jumps, DC potential, even down to cellular energy—I came to a realization that hit me way back in 2008-09. It wasn’t about the tests, or the athletes, or even the training methods. It was about the people running the tests.
Here’s how it unfolded.
One day, I was overseeing a series of tests for a project. My main assistant wasn’t around that day, so I had a group of interns helping out. I didn’t have time to explain what we were doing, so I just ran the protocols myself. We tested, logged data, moved on—nothing out of the ordinary.
The next week, my assistant was back. This time, I let him take charge of the testing. And suddenly, the results were better. Significantly better.
At first, I thought, there’s no way this is a procedural difference. Everything was identical—the same athletes, same equipment, same warm-up, same testing environment. But then I noticed something: my assistant was talking to the athletes—encouraging them, telling them what we were measuring, hyping up the process, setting positive expectations.
The following week, I decided to observe carefully. Sure enough, he was radiating positivity—telling the athletes how much they’d likely improved and reinforcing their effort. It was great coaching energy… but from a testing standpoint, it was a variable.
So, I decided to run a controlled experiment. I took back over testing, but this time, I intentionally downplayed expectations. I told the athletes, “Hey, we’re not seeing much change, but let’s get one more round in.”
And just like that, the numbers dropped—right back to what they were on week one.
That’s when it hit me like a ton of bricks: the tester’s mindset and communication can influence the outcome. We all know the observer effect exists in psychology and physics, but I had just seen it firsthand in human performance testing.
From that point on, I realized if I wanted valid, repeatable results, I had to control the human influence—the expectations, the energy, even the tone in the room. It wasn’t about being secretive for the sake of ego; it was about scientific integrity.
Over the years, I probably owe a few apologies to my assistants. Some of them were frustrated that I didn’t share every detail of what I was testing. But the truth was, if they knew too much, their hopefulness—their good intentions—could change the outcome.
And that’s the paradox: in coaching, belief and motivation are essential. But in testing, they can be contaminants.
So I learned to draw a hard line: when it’s testing day, coaching stays outside the lab, and not include staff in the objectives of the testing.
