"He's yelling at me because he cares" is the same internal logic that keeps many women in abusive romantic relationships.
Sometimes kids overwork their heart and coach is supposed to stop the kid to protect their health. Coach can't tell the kid in front of the group "You worked too hard, come stand here and rest", this would make the whole group to feign being overworked. Instead the coach is saying "You're not working hard enough, come here and stand in front of the group as a punishment for being lazy".
The proper solution is just tell the kid to take a breather without stating a reason (maybe tell them privately how to notice on their own when they are overworking themselves). The other kids won't notice or care.
(And if some kid is looking for an excuse not to do the exercises... why are they even there? And who cares? It's an extracurricular, the point is to get out of it what you put in. It's not boot camp.)
First, you are literally punishing kid for being overworked, while claiming they are slackers are teaching them to overwork themselves even more next time.
The harder the kids try, the more the kid will be punished and claimed to be lazy.
Second, you are lying to the kids, they have no way to actually figure out rules.
Are you a professional coach or just think it would work this way?
The athletes we are discussing are already selected as fit for the specific sport. All of them are very tolerant to stress from the training and competition. Unless stress of not doing exercise (correctly) is higher than stress from doing it (correctly) there won't be progress.
What for an outsider looks like abuse, for athletes is within tolerable limits.
That doesn't sound like being selected for stress tolerance. That sounds a lot more like stress tolerance is being mentally beaten into them.
