The Tampa Bay Buccaneers spent the past two years practicing in the heat in the afternoons, to get players used to heat they'll be playing at in actual games. Most coaches prior to Lovie Smith tended to practice out of the heat, and Dirk Koetter is moving back to that approach by moving practice to mornings. He noted that it's about 11 degrees cooler out there for his players in the morning compared to Lovie Smith's afternoon practices.
Here's what Koetter said after practice yesterday, via the Tampa Bay Times.
"Last 10 years I've been coaching in the South, and I really do believe there's a cumulative effect over the course of the season, from August until the end of the year," Koetter said. "When you're out here, even if it's for walk-through and it's 12, 1, 2 (p.m.) and it's 95 degrees and the sun's beating on you. I just think there's a cumulative effect, and we're going to try to do everything we can to chip away at that."
There are a lot of obvious, easy snarky comments to be made here, as there were when Lovie Smith moved to mostly afternoon practices. But honestly, I have no real way of evaluating which approach is the right one here. Fatigue can certainly build up, but heat acclimatization is also a thing. After all, players spend months working up to game-ready fitness for a reason. Why shouldn't they do the same for temperatures they'll be playing at?
A quick bit of googling suggests that practicing at temperatures is absolutely a thing that could be beneficial, and a paper called "Consensus recommendations on training and competing in the heat" published in the British Journal of Sports Medicine says that acclimatization is crucial.
The most important intervention one can adopt to reduce physiological strain and optimise performance is to heat acclimatise. Heat acclimatisation should comprise repeated exercise-heat exposures over 1-2 weeks
Of course, the Bucs can still do so in the run-up to the season and during the week leading up to a game at high temperature -- this research does suggest that starting acclimatization months in advance may not lead to any improvements. But that's my cursory read of a few papers, and not a thorough evaluation of all the research out there.
So who's right here? I don't know. I do know that all the snarky comments I keep seeing in either direction don't seem particularly well-informed on this issue. And I'd bet both Lovie Smith and Dirk Koetter had more than just gut feeling and common sense backing up their opinions.