In an age when looksmaxxing influencers have greater social reach than board-certified medical professionals, and the conversation about arbitrary self-improvement is increasingly becoming more granular and scientific-feeling (see: the PSL scale), it's getting harder to differentiate between actual health advice and subjective rules made up by literal teenagers.

Take, for instance the topic of back chain vs. front chain dominance, which posits the notion that the muscles along the back of your body deserve more of your attention than the ones on the front, and becoming “back chain dominant” will inherently make you more attractive. The mere suggestion would be swiftly tossed out the window of any physical therapist’s office. Online, meanwhile, it’s striking a chord.

The thing is, there’s actually some value to this idea, or at least part of it. The problem is that social media doesn’t do nuance. To explain, we thought we’d catch up with a few qualified experts, for old time’s sake.

What does ‘back chain’ and ‘front chain’ actually mean?

Technically speaking, nothing. If we’re being scientific, which we should, considering we’re talking about dishing out consequential health advice, let’s at least use the proper terminology. What we’re actually talking about here are the body’s posterior and anterior muscle chains.

"Your posterior chain is the group of muscles running along the back of your body,” says Katie Cyrana-Hillery, PT, DPT, OCS, CSCS, physical therapist at Evolve Physical Therapy and Performance. The posterior chain, or what social media is calling the “back chain,” includes muscles like your calves, hamstrings, glutes, lats, traps, and delts, as well as some of your deeper abdominal muscles. While these are all individual muscles, “they work together to power almost everything you do,” Dr. Cyrana-Hillery says. “Walking, running, jumping—even just standing up from a chair.”

In the same way that your biceps and triceps work in opposition to one another so that your arm can both flex and extend, your posterior chain is complemented by the muscles on the front of your body—including your quads, hip flexors, and pecs—which are known collectively as the anterior chain. “Efficient movement depends equally on both chains,” Dr. Cyrana-Hillery says. “When one breaks down, movement gets less efficient and your risk of pain and injury goes up.” Essentially, they are two sides of the same coin.

Is it better to be back-chain or front-chain dominant?

For the average person looking to live a healthy, active, pain-free life, the answer, unequivocally, is neither. “We don't really want dominance in one of them,” Dr. Cyrana-Hillery says. “We want evenness. It's not about being posterior-chain dominant or anterior-chain dominant. What actually matters is recruiting the right muscles at the right time and getting both chains to work together.”

The exception (sort of) would be elite athletes, who naturally tend to drift towards posterior or anterior dominance as a result of the inherent mechanics involved in their sport. "Look at the difference between sprinters and marathon runners,” says Zaki Afzal, DPT, physical therapist and owner of Optimize Physical Therapy and Performance. “Their bodies literally couldn't be more different, because the demands of their sport are completely different.” While both types of athletes in this analogy are technically running, the sprinter is asking far more of their hamstrings, glutes, and adductors, and therefore more likely than the marathoner to fully develop those muscles. “When you look at the energy demands during walking, running, and sprinting, the faster you go, the more your posterior chain gets involved,” Dr. Afzal says.

But even elite athletes aren’t aiming for posterior or anterior chain dominance. In fact, a lot of how the pros train is geared towards evening out imbalances in order to avoid injury. "Truthfully, there's not a case where it's better to be more dominant in one,” says Dr. Cyrana-Hillery. “Even in running, you want that posterior chain to be strong, because you want it to propel you forward, but if you don't have stability from your anterior—your core, your quads, your hip flexors—you're not going to be able to perform.”

What should you focus on?

Regardless of whether you’re a sprinter, running ultras, or just hitting the weight room a couple of times a week to stay in shape, your primary goal should be maintaining a healthy balance of posterior and anterior training. "Training both together is what's most important,” says Dr. Cyrana-Hillery. "For every pulling exercise you do, do a pushing exercise. For every glute-dominant exercise you do, do a quad-dominant one.”

For the majority of folks, that probably means focusing more on your posterior-chain muscles than you currently are. They’re the muscles you don’t see in the mirror, and the same ones that pay the price of most desk jobs. "A lot of the attention on the posterior chain comes down to modern life,” says Dr. Cyrana-Hillery. “When you sit eight-plus hours a day, those muscles get weak and stop activating properly.”

“Most desk-bound people are front-loaded and underbuilt in the back, so the practical guidance is usually to train your posterior chain more, but not because the posterior chain is morally superior,” Dr. Afzal says. “It's because that's where you’re probably weaker, and closing that gap is where athleticism and pain relief live. If someone had a huge posterior chain and skinny, weak quads, I'd tell them the opposite. It's about balance and what your body actually has to do—not picking a team.”