Working out with weights can lower a specific inflammation signal in your muscles, especially in people who respond really well to exercise—but that drop in inflammation doesn’t seem to explain why some people get bigger muscles than others.

We analyzed the available evidence and found that resistance training is associated with a reduction in IL-1β mRNA in muscle tissue, particularly in individuals who respond strongly to weight training [1]. This signal is part of the body’s inflammatory response, and lower levels may reflect less local muscle irritation after exercise. However, we also found that this drop in IL-1β mRNA does not appear to explain why some people gain more muscle size than others after training [1]. In other words, while the change in this inflammation marker happens, it doesn’t seem to be the reason muscle growth varies between people. The evidence we’ve reviewed so far leans toward the idea that resistance training can lower this specific inflammation signal in certain individuals, but the connection between this change and muscle growth remains unclear. We did not find any studies suggesting the opposite, but we also didn’t find evidence showing that reducing IL-1β mRNA directly leads to bigger muscles. What we’ve found so far suggests this inflammation marker may be a side effect of training, not a driver of muscle growth. For someone lifting weights, this means that feeling less sore or seeing lower inflammation markers doesn’t necessarily mean you’re building more muscle — muscle growth likely depends on other factors, like how much stress you place on the muscle and how well your body recovers.