The Harvard Business Review has an https://hbr.org/2013/07/if-you-want-to-motivate-someone-shut-up-already. Basically, they find that the method of exercising with a silent partner is more effective than when using an encouraging partner.
The team interpreted this as people wanting to compare favorably with others. Superior exercise partners are strong motivators for this purpose – you’re going to have to practice hard to eventually reach their level. But if they are very vocal and encouraging, you will tend to consider them their equals and perhaps not try as hard.
Interesting observation, not causal, but might be worth trying.