Being part of the Marvel Cinematic Universe certainly looks like hard work. Playing a superhero requires constant hours in the gym. It means doing a lot of physically exhausting work on set. It means wearing a potentially uncomfortable superhero costume. However, for Chris Hemsworth, it turns out that the hardest part of the job isn’t all the physical exertion, it’s when you do the audio recording of all the physical exertion.

Playing Thor requires more than a few grunts, groans, screams and shouts. And because a lot of those noises are needed for off-camera scenes, or because an actor is running around or getting punched in the face, the audio recording for them is usually done after the fact. This ADR is referred to in the industry as “efforts” when an actor comes in to record all the various noises their character makes while they are exerting effort. CinemaBlend caught up with Chris Hemsworth on the red carpet at SDCC and he told us efforts were the most exhausting part because of the way they destroy his voice.