Kumail Nanjiani walked into his workout regimen for "Eternals" as one big softy and emerged totally yolked thanks to high-intensity training, and a major focus on 2 key body parts.
Check out these workout videos of Kumail pumping iron with Grant Roberts ... the celeb trainer tells TMZ Kumail's transformation from scrawny to sculpted was all about intensity, and they trained for a little over an hour a day, 5 times a week for 10 months.
Kumail hit every body part training with Grant, but we're told the actor needed the most work on his shoulder and biceps, which were physically lacking when he started hitting the gym back in January -- Grant's words, not ours.
As you know, Kumail's super proud of his new look for the upcoming Marvel movie. He just pulled the curtain back on his transformation, showing off his guns and ripped torso.
Kumail's trainer tells us they did all the muscle sculpting with dumbbells -- raising sets and overhead pressings in every angle imaginable -- and that's where most of his energy went.
Grant, who also trained Hilary Swank for "Million Dollar Baby," mostly worked with Kumail at his studio in Bev Hills, but when Kumail was on the road filming other projects this year, he kept up his routine with a boost from Grant's workout videos.
Kumail came to Grant at 150 lbs. and 20% body fat, and we're told he got up to 174 lbs. and down to a very lean 10% body fat.
And, you can look like Kumail too ... Grant says anyone can achieve his physique if you put in the hard work -- no Peloton required.