Kevin Hart Praises Mark Wahlberg's Grueling 4 AM Gym Routine

Kevin Hart’s preaching the gospel of gains -- but he’s giving all the credit to his guy Mark Wahlberg ... saying nobody’s doing it like the king of those brutal 4 AM workouts.

TMZ caught up with Kevin at Wally’s in Beverly Hills Wednesday -- and he kept it playful, clowning Mark’s routine as "s***" before flipping it, joking the 54-year-old’s actually 75 and deserves even more credit.

Check the video -- Kevin goes full fanboy over Mark’s grind, which he recently told us is so intense even Druski had to tap out when he joined him for a session.

But Kev’s not just hyping his boy -- he also gets into his own health kick, showing love to the gym life and shouting out his workout circle along the way.