You can build muscle and endurance at the same time. A former US Army Ranger turner ultramarathon runner explains how.

• You don't need to choose between training for strength and endurance, provided you eat enough, Nick Bare said.
• Bare is an ex-Army Ranger turned fitness professional who has run a sub three-hour marathon.
• Bare's military experience gave him the resilience to achieve his fitness goals, he told Insider.

It's a commonly held belief that you have to choose between endurance and strength, but this is a myth, according to US Army Ranger turned personal trainer Nick Bare.

Bare, who has run sub three-hour marathons, completed Ironmans and ultramarathons, and also competed as a bodybuilder and powerlifter, believes it's entirely possible to build muscle even if you run long distances. He calls it "hybrid training."

Bare studied nutrition at university, during which time he started his supplement company Bare Performance Nutrition, before joining the US Army for four years.

It was Bare's time in the military that taught him the mindset that he says led to his fitness and athletic success, he told Insider, and his motto "go one more."

Bare has a workout app that features various different training programs involving running, strength, and mobility, and he encourages his community to test their limits.

"You'll never know where your full potential exists unless you test it," Bare said. "And doing really hard things is a great way to test your full physical and mental potential."

You don't have to sacrifice strength for running

In his younger years, Bare's main focus was muscle-building.

"I used to have this mindset where I just wanted to put on size and strength. I was afraid of cardio because I thought it would burn my muscle up," he said. "I thought it would limit my potential to gain muscle." 

Bare wanted to build his endurance, but was worried about becoming a "small, skinny runner."

But through self-experimentation, research, and studying, Bare learned he could do both.

The trick is not to do too much too soon, and eat enough, he said.

"You realize that cardiovascular training can only benefit your ability to build muscle and strength and vitality in life," he said. 

You can be a good runner and build endurance without running 70 plus miles a week, and if you want to hold on to strength and muscle it's crucial not to do too much, Bare said. 20 miles or less can be enough. 

"Are you going to be the best bodybuilder, the best strength athlete while still running? Maybe not," Bare said. "Are you going to be the fastest runner in the world if you still want to hold onto size and strength? Maybe not. But if you want to balance those two and be good at both running and strength training, there is a way to do it."

It's key to increase your training volume gradually. Don't simply add cardio on top of your usual strength training (or vice versa), cut back on strength training by 20-25% and use that time and energy for running. This prevents overtraining and should allow your body to recover, Bare said.

Autoregulation, which means listening to your body and using common sense, is important too, he said.

Diet also plays a huge role in hybrid athlete training, and not eating enough is one of the biggest mistakes people make when trying to simultaneously build muscle and endurance, Bare said. 

The military helped Bare build his mental resilience 

Bare had always been interested in fitness, but his time in the military showed him his potential, he said.

To become an Army Ranger, Bare had to complete an intense 61-day tactical and leadership course. He failed two phases so it took him 145 days, he said.

"They're evaluating you based off your leadership potential when you're tired and hungry and you're leading other people who are very tired and very hungry," Bare said. "I spent four and a half months in Ranger school. I lost over 30 pounds, essentially all my muscle, because you're not working out, you're just running missions all the time."

But that experience taught him that nothing is "unbelievable" and you can push your body beyond what you think it is capable of, Bare said. 

This "competitive mental advantage" was much more important than his physical fitness when it came to pushing his body in extreme sports, he said.

That mindset has influenced Bare's training programs now.

"All these things I do, it goes back to that military mindset of 'where does my full potential exist in terms of physical performance?'" he said.