Rep per rep, nothing beats free-weight, compound movements. Think: squats, deadlifts, bench presses, and rows. These weight room staples tap multiple muscle groups at once, hike up your heart rate, and even train those little stabilizer muscles that help keep everything in alignment and working properly. They are efficient, effective, functional (meaning they prep you to be stronger in everyday movements)—basically everything you want when you’re grinding it out in the gym.
So then why would you ever want to sit your booty on strength machines and perform teeny tiny biceps curls or knee extensions? Well, that’s exactly the sort of thinking that has led to many gyms’ weight machines gathering dust, certified personal trainer Rain Burkeen, owner of POP Fitness and resident fitness expert for the Trainerize personal training app, tells SELF.
She says that while that thinking isn’t completely wrong—yes, compound, free-weight movements should be the bedrock of most people’s strength routines—strength machine moves that isolate specific muscles also have their benefits.
After all, even though sitting on a bench and straightening your leg (knee extensions, anyone?) is about the least functional move you can perform in the gym—seriously, when do you actually sit on a bench and straighten your knees in real life?—a paper published in the Strength & Conditioning Journal suggests that exercises like these can, in fact, improve total-body function both in and out of the gym. The authors of the paper found that performing single-joint isolation exercises in conjunction with compound movements could help people increase their strength and performance more than doing functional, compound exercises alone.
“Free-weight lifts are great because they activate more muscles, but sometimes you just want to really focus in and hone in on one group,” adds Beverly Hills–based trainer Mike Donavanik, C.S.C.S.
When’s that exactly? Here, experts share when you should integrate some machinery into your strength routine.