Once you’ve been training at the same gym for many years, you tend to see the same people over and over again. And I must admit, as a coach/trainer in this industry for nearly 30 years, I often find myself observing others as they work out (between my own sets, of course), and wondering why they never seem to change.

I think back to the way they looked several years earlier and realize that the vast majority carry about the same amount of muscle now as they did then despite spending hours each week pushing and pulling on barbellsdumbbellscablesOpens, and machines. Does this scenario describe you? If so, read on to discover six ways that may be limiting your muscle growth.

1. Not Enough Sleep

This is something I find myself reminding my clients and fellow gym rats about all the time. If you’re not getting enough sleep, you won’t build very much muscle, regardless of whether or not you’re training intensely each day, eating a proper diet, and taking all of the right supplements. Why? It’s simple: Sleep is the period of time that our body uses to recuperate, recover, repair, and rebuild.

We don’t grow muscle tissue while in the gym, or even at the dinner table, but in bed while we rest. Suboptimal recovery equals suboptimal hypertrophy. Sleep at least seven to eight hours each night if you want to get the most out of your hard work.

2. You’re Not Getting Enough Calories

While I am no way an advocate of bulking up, or eating everything in sight to gain mass, I can tell you that if you eat too little, you’ll remain stuck in neutral. Quality foods, in ample amounts, act as the building blocks for creating new lean tissue, aka muscle.

Just as a house can’t be erected without cement, bricks, or wood, the body cannot be built without enough protein, nor energized without enough carbohydrates and fats. Shoot for a minimum of one to 1.5 grams of protein and carbs per pound of body weight, along with another 300 to 400 calories from essential fatty acids each day if you’re looking to add lean muscle.

3. Cardio Overload

I recommend that every bodybuilder (recreational or competitive) perform at least some cardio exercise (20 to 30 minutes or so) three to five days per week, year round, because it is heart healthy and helps keep body fat levels in check.

However, there are those that are obsessed with the treadmill, bike, elliptical machine, or stair climber, performing more than an hour on one of these contraptions each day and still wondering why their legs still look like sticks or why their arms are never worthy of a gun show. Too much cardio not only cuts deeply into our overall recovery abilities, but also sends mixed signals to our body about what we are trying to accomplish. These two things combined may not only slow muscle growth, but in extreme cases, even reverse it. So yes, do some cardio, but in reasonable amounts.

4. Poor Technique

Even if the dedication, effort, and intensity are there, if proper exercise form is not, you can fail to make the gains you desire. The movements we perform in the gym act as the stimulus, or signal, for hypertrophy, but only when the target muscle receives enough overload and tension to set things into motion.

Cheating, swinging, body English, and even lack of concentration will all negatively affect muscle fiber firing, increasing your chance of injury more than your chance of building lean tissue. Master correct form on all movements while focusing on feeling the muscle work, not how much weight you’re moving from point A to B.

5. You’re Bored

In the early stages of lifting weights, almost any workout program will help to build more muscle, even if utilized week after week. But as you grow more experienced, the body becomes more stubborn and far less responsive to doing the same things time and again in the gym.

However, either because of laziness, lack of knowledge, or simple habit, most trainees perform the same exercises, for the same reps, in the same order at every workout. And the result? Little to no progress is realized. Because the human body is literally an adaptive machine, it needs to be constantly challenged with unique stimuli, or it will remain in a state of homeostasis.

If you have been training more than two straight years, make sure to switch things up in the gym at least every few weeks. Use different exercises, rep ranges, intensity techniques, and rep tempos to keep the body off balance.

6. You’re a Phone-y

No, I do not mean you’re fake, but rather a person who cannot put the phone down, even while attempting to get in a good workout. Trust me, I understand that social media has become a huge part of our lives. It’s fun, rewarding, and sometimes necessary—especially for those employed in the fitness industry—to take videos and photos at the gym.

But some take it too far, to the point that they are more worried about their best camera angles than hitting their muscles from all right angles. Sure, take a video or two and post to your favorite media accounts, but then put the phone away, turn up your headphones, and get to work.

The bodybuilders of the ’70s, ’80s, and ’90s are often considered the best ever. Perhaps this is because when they entered the gym, they only had muscle on their mind.