One of the articles talked about this. That it's literally the power of positive thinking.
During our conversation, Kamm described a demonstration he witnessed at a sports psychiatry lecture. Before an audience of 75 people, the presenter had a volunteer, a woman who had been an elite athlete, leave the room. While she was gone, the presenter instructed the audience members to think “horrendously negative thoughts” about her once she returned. So they did.
After a few minutes of speaking to the volunteer on stage, the lecturer stopped the conversation and said, I want to try an experiment. He stretched his arms forward until they were as straight as ramrods, and he asked the volunteer, the ex-athlete, to try to push his arms down.
“She couldn’t,” Kamm said. “As strong as she was — she was bigger than him, stronger than him — she could not get his arms to budge much.”
Then the lecturer repeated the entire sequence, with one big difference. This time, when the volunteer re-entered the room, the audience was to think “incredibly positive thoughts about her.” And this time, when the lecturer extended his arms, “it was like she was pushing on a feather,” Kamm said.