If you’re putting effort into going to the gym, you should at least be getting something out of it. But if you’re not seeing the definition in your arms or that coveted peach-shaped booty, you’re probably thinking, what the heck am I doing wrong?

Well, you may need to start lifting heavier, increasing your reps, or relying on more compound movements to get out of your workout rut. To help you cut down on your gym time while netting bigger muscle-building results, we asked top trainer, Jess Allen, CSCS, for the mistakes she most commonly sees. Plus, we consulted research to find out how you can tweak your routine to maximize strength and muscle.

6 Reasons You’re Not Building Muscle

1. You’re repeating the same tried-and-true moves.

We love squats and lunges, bicep curls and overhead presses, but it’s time to shake things up. Two reasons doing these movements repeatedly don’t work: One, you need to give muscles time to recover and heal, so they can build, says Allen. “If you repeat the same movements, there’s no recovery time,” she says. Two, your muscles adapt quickly to exercise. “Our bodies essentially figure out how to do less work while doing the same routines,” she explains. Varying your training will keep your body guessing and your muscles building.

2. You’re sticking to the same weights.

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If you graduated to a 20-pound medicine ball long ago and are still hoisting the same weight, it’s time to move up. Additional stress on your muscles is essential for repairing and rebuilding, which is what makes them stronger. Follow this advice from Allen: If repetition one and 10 feel similar, increase your load (aka increase the weight you’re lifting). “Lifting heavier loads also allows you to do more work in the same amount of time,” she says. Shorter, more effective workout sessions? Yes, please. (Check out this guide to picking the right weights for you.)

3. You’re sticking to the same reps.

You don’t always have to increase your load. If you want to increase strength, doing more reps can be just as effective, according to 2016 research in the Journal of Applied Physiology. In a study on men who did full-body resistance training, those who performed 20 to 25 reps with lighter weights saw equal strength gains as those who lifted heavier weights and completed eight to 12 reps. As long as you lift until your muscles are fatigued, you can get just as good results. The benefit about structuring your workout as you like it is that you’re more likely to stay consistent with your routine — and that’s what will help you build muscle.

4. You’re hyper focused on abs.

Separate ab workouts are OK, but they may not be the best use of your session. If you’re crunched for time, it may be more effective to build core strength with compound movements that work multiple muscles at once, says Allen. For instance, squats, kettlebell swings, renegade rows, deadlifts and thrusters may not seem like classic ab moves, but they all engage the core. “Overhead movements are also a great way to ‘turn your abs on,’” she says, including push presses or overhead walking lunges.

5. You have too many cardio workouts in the books.

If you’re a stickler for worrying about cardio first, strength training second, you may want to flip that thinking. “Evaluate your fitness goals. If you want to reduce body fat and gain lean muscle, it’s best to incorporate weights and ditch long steady-state cardio sessions because the two are working against each other,” she says. To keep up your cardiorespiratory fitness and ensure the top-notch calorie-burn of cardio, two or three days of a high intensity interval training session (HIIT), can get the job done. And if activities, like running longer distances, are meaningful to you, then you may have to readjust your goals, which is totally fine, too.

6. You’re not varying the intensity.

Speaking of HIIT, if you roll into the weight room and toggle through the same exercises at the same clip, it may help to kick it up a notch. According to a study in Physiological Reports, doing eight weeks of high-intensity, low-rep resistance training boosted strength and lean muscle mass gains better than moderate intensity, higher-rep workouts. In the high-intensity group, participants did four sets of three to five reps at 90 percent of their one-rep max. In between sets, they rested for three minutes. The moderate-intensity group did four sets of 10-12 reps at 70 percent of their one-rep max. On the other hand, they rested for one minute in between sets. Why the better results? The authors say that the multi-joint movements the high-intensity group used (deadlifts and bench presses) improved strength gains, and the higher-intensity movements recruited more muscle fibers.

This article originally appeared on Life by Daily Burn.

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