After pumping himself up to huge proportions to play a bodybuilding criminal in Pain & Gain, Mark Wahlberg had to trim himself back down to play a Navy SEAL in Lone Survivor – Peter Berg’s Afghanistan-set thriller that tells the real-life story of a group of marines who soon turn from hunters to hunted during a mission to take down a notorious Taliban leader.

Ditching the isolation machines altogether, Wahlberg hired long-time trainer and Brian Nguyen – a key member of the 42-year-old actor’s entourage since working with him on 2006’s American football drama Invincible – to prepare him for the rigourous marine bootcamp he was about to embark on. MF caught up with Nguyen to find out how he used functional training to get Wahlberg battle ready…

Mark only had four weeks in between finishing Pain & Gain and starting on Lone Survivor. We got him back down to around 185lbs [84kg] from 210lbs [95kg] by cutting out the weight training and switching his diet from eating heavy to eating clean. After all the bench pressing and heavy squatting he was doing for Pain & Gain, we also had to reestablish his shoulder and hip mobility as he was dropping weight.

As soon as he got to the Lone Survivor set in New Mexico he went straight into marine training, which involved a lot of functional work – running up and down hills with a gun and a heavy backpack – so if he didn’t have that mobility it would have been a disaster.

Bobby Strom is a personal trainer who has worked with a host of celebrities, including Britney Spears, Ryan Reynolds and Scarlett Johansson. Here he talks to MF about training actor Joel Kinnaman for his leading role in last year’s Robocop remake.

He was lean and fit because he’d been doing a little training already. We just made him leaner, bigger, stronger and in superior condition.

I’ve been working with him since January 2013, when he had to get in shape for filming, but we’ve continued to the present day.

The Robocop suit that he had to wear was heavy, so we did a lot of core and stability work to protect his back, using a TRX, a Bosu ball, stability boards and resistance bands. We also did a lot of high-intensity interval workouts that I call ‘mash-ups’. The aim is to move hard and fast through the entire workout, and never do the same workout twice.

He really did and still does – we’re training together six days a week at the moment.

How long did you spend training Pratt?

We worked together for six months before he began shooting Guardians Of The Galaxy.

What did his workout regime look like?

He’d lift weights four or five times a week for an hour at a time. For the first few months it was mainly traditional bodybuilding sessions to add size, targeting specific muscle groups on separate days (the actual splits changed from month to month). Towards the end we started mixing things up and adding in circuit training and P90X workouts to help get him lean.

Did he do anything else outside of the gym?

Yeah, he was really active. He did a lot of mountain biking, running, swimming and kickboxing. Adding these kinds of sports helped to keep things varied and enjoyable.

What was the secret to his success?

Hard work, dedication and making the right choices, which is all you can ask for as a trainer. If I could do the training for my clients I would, but I can’t. The discipline and drive has to come from them, and Pratt was excellent in this regard.

Performing heavy Olympic lifts can be problematic – not only because you’re lifiting massively weighty plates but also because most gyms frown when you drop a 100kg bar on the floor after you’ve finished a set.

The four moves in the Olympic lift assistance section on the right will help you perfect the form you need to go bigger, avoid injury and, due to the fact that you’re using lighter weights, stop you getting told off by nearby personal trainers because you're no longer making an awful racket when you drop the bar.

MF cover model star David Peters wowed the ladies on ITV’s hit show Take Me Out with his big arms, wide chest and rock-hard abs. Here’s how he got his lady-pleasing body – follow his workout to improve your chances of getting the girls too.

The workout
Perform the exercises (right) in the order listed, resting for 60 seconds between each set and 90 seconds between each move.

Most people focus on biceps and triceps during their arms workouts, but targeting your forearms as well will help to build strength in your wrists and help protect them from injury.

Do the following exercises in order, resting for two minutes between them. You can easily build these into your regular workouts, but remember to leave two or three days before repeating them to allow your muscles to recover.