For years Hailey Bieber was the face of Pilates. Not so much as an athlete as an aesthetic - tight clothing, a slim body, a studio full of mirrors. Now, in an interview with "Time", she has admitted that Pilates has become "a bit of a trend" for her and that she struggles to find instructors who genuinely pay attention to technique and posture. She trains with weights.

This is not a renunciation of Pilates. It is an admission that something which became a trend stopped being done properly - and that is the more interesting half of the story.

What actually changes when you switch to weights

Trainer Rober Fitness explains that the first thing you notice is an increase in muscle mass, or hypertrophy. In a person with a low body-fat percentage that shows in the silhouette: "She will feel more toned, more defined." The key is progressive overload - the load increases as the body adapts.

The second effect is more interesting because you cannot see it. Muscle is active tissue and burns energy even when you are sitting, resting or asleep. That is what people call a "faster metabolism", when it is really just more muscle demanding more fuel. The third effect is blood glucose control - muscles use it for energy, so strength helps the body manage it better.

The fear the industry kept alive for a long time

For decades, the image of a woman lifting weights was tied to bulk. In practice the result depends on load, frequency, nutrition, rest and genetics. In a woman with a slim frame and low body fat, more muscle means more definition, not more volume. How many years were cardio machines and "light dumbbells for women" sold on the back of a fear with no basis?

Rober Fitness puts the emphasis somewhere else - strength after childbirth. He talks about the pelvic floor and the core, but also about entirely everyday things: having the strength to carry your child, to get through the day, to endure a period defined by exhaustion and broken sleep. "In the end, to feel strong" is a key part of recovery.

There is also a part the eye cannot see. Strong muscle makes a joint more stable and safer, which helps with movement control and protects the knees, hips, shoulders and back. Working with load also helps bones retain density - something that matters more with age, and especially during menopause.

Hailey has not abandoned Pilates - she still does it, alongside yoga and mobility work. What she changed is the order. And that is the lesson: the disciplines are not the problem. The problem is that each of them became a brand before it became a training method.