The Best Workout Routine to Build Lean Mass - Muscle & Fitness (2024)

Gain muscle or get lean? It’s an age-old conundrum that plagues physique-builders the world over. To those looking for both it can often feel like the Judgment of Solomon—an agonizing choice that inevitably leads to an all-or-nothing scenario. However, there is a way, but it ain’t easy. yet if you’re willing to put in the effort, lean mass can be yours. The question is: Are you willing—and ready?

The Lean Mass-15 routine is a four-week plan that features a number of advanced training principles designed not just to build muscle, but increase cardio function and burn fat as well. That’s because, with its intense pacing and active rest periods, it’s partly a HIIT cardio routine—just one that also builds muscle.

Because of its intensity, this is not the type of routine you’ll want to follow for more than four consecutive weeks. A better strategy is to substitute it for your regular routine every four weeks, to give your body a chance to recuperate from this program, and because we always advocate switching things up on a regular basis. The body is always adapting to stress placed upon it (that’s exactly what’s going on with muscle growth), so when it begins to get used to LM-15, you’ll shock it with a new routine, and then go back again.

For the next four weeks, you’ll be moving a lot and resting little. Most of the rest periods, in fact, are active, which means about 95% of the 75 minutes you’ll spend in the gym each day will have you in motion. We understand a lot of guys find it hard to carve out 75 minutes for training, while others can manage 90 minutes or more. Don’t worry—this program packs maximum volume into minimum time for a workout that is as effcient as it is productive, and you can adjust the timing of it by slowing down or speeding up the pace. You’ll just need to adjust the weights used.

One other word about this routine: It is designed to elicit muscle hypertrophy, not necessarily strength, although increased strength is a natural by-product of any kind of resistance training. However, while it’s been said that a stronger muscle is a bigger muscle—and there is a general truth to this statement—it needs to be taken in proper context. A well-trained muscle is always going to be stronger and bigger than an untrained one, and it’s pretty safe to say that a guy who can squat 405 for 10 reps is going to have bigger quads than one whose 10-rep max is 135. But when it comes to volumizing muscles, heavier isn’t always better. Case in point: Ed Coan is arguably the strongest man, pound-for-pound, who ever lived. Standing 5’6″ at a bodyweight of around 220lbs, Coan squatted 1,019lbs, benched 584, pulled a 901 deadlift, and has held more than 70 world records. Yet while Coan is impressively thick, he’s never carried anywhere near the lean muscle mass of pro bodybuilders of similar height—guys like Dexter Jackson, Branch Warren, Shawn Ray, and Lee Labrada, who, alternately, couldn’t have come near a 1,000-lb squat on their best days. So don’t worry if you’re not turning heads in the gym with the weights you’re using here; you’ll turn them on the beach. Just remember: If you’ve got time to talk to your buddy about sports while doing the LM-15, you’re doing something wrong.

The Lean Mass-15 routine divides body-part training over three days. Day 1 focuses on back, biceps, and forearms. Day 2 is chest and triceps. Day 3 is thighs and shoulders, with abs done every workout and calves on Days 2 and 3. The split is 3 days on, 1 day off/2 days on, 1 day off—an old-school standard for an average of five training days out of every seven. You’ll note the deliberate use of the word focuses above, as opposed to “is devoted to,” because while each training day has its featured body parts, you’ll also reinforce the previous day’s emphasis and prime for the next workout with light “pumping” sets for the body parts you’re not targeting that day. Studies show that training a body part on consecutive days can lead to greater muscle growth, while working antagonistic muscle groups together elicits a stronger contraction from each. A win-win!

Generally speaking, the set-rep scheme for this routine follows a traditional pyramid format, in which weights increase while reps decrease over the course of each exercise. That being said, the rep range varies quite a bit, but on the whole is probably a little higher than you’re used to doing. In my personal experience, higher reps lead to denser, more detailed muscles, not to mention greater overall physical endurance.

The time between working sets is something often referred to as “active rest”. In other words, you’ll work through the set breaks, but at a lower level of intensity. Each active rest period will last for as long as it takes you to complete 15 reps of the ancillary exercise paired up with the primary exercise you’re performing. So, for example, after you finish a set of pulldowns you’ll pick up a pair of light dumbbells and knock out 15 reps of lateral raises at a leisurely pace, and an emphasis on deep breathing. The main goal here is to stay active until your lats have sufficiently recuperated for your next set. And even though you’re going to use a much lighter weight than you do on shoulders day (around 10-lb dumbbells are enough to do the trick), they’ll get a pump, helping accelerate recovery from your last shoulders workout while also stimulating some new growth. After you’ve completed 15 reps of the ancillary exercises, take a few deep breaths, prep mentally for the next move, and then get back to it. Notice that there is always one less active rest set than working set: You don’t need to do an active rest set after the final set of an exercise. That’s the time when you’re moving on to the next exercise.

While this routine’s theme is constant movement, it’s not meant to be frenetic. You don’t want to deplete your oxygen to a point where you’re on the verge of passing out—that’s not going to help you lift with any kind of authority. So, keep the rest active, but also make sure you’re ready to give it your all on each and every working set.

Now head to the gym to put the Lean Mass-15 routine to the test. if you’re currently doing cardio, you’ll probably want to cut it back. Also, be sure to stay well-hydrated through the workout, as you’ll definitely be sweating more than usual. We’ve also included a handy supplement recommendation list, to help power your way through the workouts and support muscle growth.