HIIT-style combination exercises can waste your time if you're trying to build muscle, according to a personal trainer

• Combination exercises pair multiple movements together, often including both upper and lower body.
• But combo exercises aren't great for muscle-building, according to a personal trainer.

Combination movements that string together multiple weighted exercises are popular in HIIT classes and on social media, but they're not helpful for building muscle and strength, according to a personal trainer.

"I'm not a huge fan of most combo movements. They're very popular in group fitness and on Instagram to make exercises look cool and exciting, and people assume they're more effective," Miriam Fried, NYC-based personal trainer and founder of MF Strong, told Insider.

The problem is that many combo movements combine upper and lower body exercises with the same weight, which is likely to be either too light or too heavy to be effective for building muscle, she said. Examples include a lunge with a bicep curl or a squat with a triceps extension.

As a result, you may think you're doing double the workout, but won't get the most out of each movement, according to Fried. And you may get hurt, if the weight is heavy enough that it leads to bad form.

Instead, focus on classic tried-and-true compound lifts or supersets, and don't think your workout needs to be flashy or complicated to be effective.

Combo exercises can waste your time or lead to bad form if your goal is building muscle

Combination exercises aren't the same as compound exercise, like deadlifts or a push-up, that already work multiple muscle groups. Compound exercises use several body parts at once, such as your legs, back, and core, to complete one movement, helping to build full-body strength and muscle.

Combined exercises are multiple movements in sequence. They typically add an isolation exercise, often involving a smaller muscle group like the biceps, triceps, or shoulders, to a basic leg exercise like a lunge or squat.

However, the larger muscles of your lower body are able to lift much more weight than your arms. If you pick a weight heavy enough to challenge your legs, it's likely to be too much for your upper body to handle, and you might compensate with poor form or incomplete movements, according to Fried. A lighter weight, though, won't really work your lower body enough to build muscle.

"You're not getting much out of it or you're hurting yourself," Fried said.

Not all combination exercises are ineffective, since it makes sense to pair some movements together. For building muscle, however, you want to continually challenge yourself using progressive overload, which means selecting the right weight for your goals, Fried said.

There may be other reasons to combine movements together besides building muscle — linking exercises with little rest in between can help raise your heart rate and improve your cardio endurance using weights. Certain types of weight training link movements together to train explosive strength and power, like kettlebell complexes or barbell movements like the thruster (a squat to an overhead press).

To better target specific muscles, try a superset

If you do want to save time and get the most bang for your buck in the gym, you're better off sticking to supersets, Fried said.

A superset is two or more exercises performed back-to-back with little rest in between. You don't have to link the movements, though, which means you can choose a weight that's appropriate for each exercise.

Supersets can make your workouts more efficient by allowing one muscle group to rest as you're working another muscle group. You can also alternate between pushing and pulling movements, or isolation and compound movements.

Examples of useful supersets include a chest press to a bent-over row, a push-up to a pull-up, or single-leg deadlift to a back squat.