Chris Hemsworth swears by ice baths for muscle building, but doing them wrong can kill your gains. Here's the right way, according to his trainer.

• Actor Chris Hemsworth uses ice baths as part of his fitness routine, his trainer said.
• Ice baths can reduce soreness and help muscles recover from intense exercise. 
• To build muscle, avoid ice right after a workout, which can prevent muscle repair, evidence suggests. 

"Thor" star Chris Hemsworth has regular ice baths to boost his muscle recovery from hard workouts, but timing is key to maximize muscle-building, according to his personal trainer.

The actor carefully times his ice baths to avoid the common mistake of jumping in too soon after a workout, which can stall muscle growth and repair, said Luke Zocchi, Chris Hemsworth's longtime personal trainer and head trainer at Centr, Hemsworth's fitness app. 

"If your main goal is to build muscle, you don't want to have an ice bath right after training. Going straight into an ice bath after heavy lifting can decrease your gains," Zocchi told Insider. 

According to a 2019 study, immediate cold therapy after exercise can interfere with your muscles' ability to use protein to repair, slowing their ability to grow back bigger and stronger. 

However, other evidence suggests ice baths can be beneficial for preventing excessive muscle damage and flushing out lactic acid to reduce soreness. As a result, some athletes swear by ice baths for helping them get back to the gym sooner. 

You can get the benefits of ice baths without stunting muscle growth by waiting at least four hours after training to jump in, Zocchi said. 

He said Hemsworth's routine typically involves ice baths in the morning, before training, for about three minutes at a time, followed by a post-workout sauna for 15-20 minutes. You can also alternate between hot and cold, but should start with the sauna for best results, he added. 

While weightlifting workouts help build muscle so Hemsworth looks like a superhero, strategic ice and sauna therapy are key for keeping him in peak physical shape, according to Zocchi. 

"You've got to do the hard work, but you grow and get bigger in the recovery," he said. "The older me and Chris have gotten, more than ever we focus on recovery."