A bodybuilder said he follows the '2x2' rule to avoid losing muscle without spending long hours in the gym

• You can shorten your gym sessions without losing gains, according to bodybuilder Marcus Filly.
• The 2x2 rule of two exercises, two intense sets each, can help you get the most out of the gym, he said.

A simple training technique can help you avoid derailing your muscle gains while cutting back on gym time, according to Marcus Filly, a bodybuilder and six-time CrossFit Games athlete.

The 2x2 rule can help you ditch a long, complicated workout routine with "max results" and "minimal time in the gym," with 45 minute workouts, four to five times a week, Filly said in a video posted on his YouTube channel.

The formula involves picking just two exercises per day, and completing two or three sets of each exercise at a high intensity level. Filly said the sets should be performed at 90% of your all-out effort, and can help you maintain muscle.

"What most people don't realize is that the most impactful and effective lifting that you do in the gym happens when you hit these higher effort sets that get you close, but not all the way, to failure," he said.

The catch is, you'll also need to warm up first to avoid injury and perform your best, so anticipate three to five additional sets to work up to your more intense efforts, he said.

"I'm not saying you need to go to the gym, do four to six sets, and then leave," he said. "In order to give that level of effort you need to do sufficient warm-up and sub-maximal sets beforehand."

You also need to rest enough between sets to maintain high intensity, according to Filly.

Altogether, expect to take about five minutes warming up, 15-20 minutes for the high intensity lifts, and then plan to 15-20 minutes working on accessory or conditioning exercises at a lower effort, about 50%.

"Consistency and effort — those two variables are way more important than the volume that you do in the gym or the total time you spend there," Filly said.

If you're looking to gain, not just maintain, you can continue to build muscle with only two days a week per muscle group using a similar strategy, strength coach Mike Boyle previously told Insider.

He recommends three sets of 10 reps each as an effective baseline workload. For overall muscle growth, opt for compound movements that work multiple muscle groups at once, such as squats, deadlifts, pull-ups, and presses.