Can you exercise with muscle aches and how can you avoid them?

Yesterday's session was good: intense, rhythmic, and satisfying. But when you wake up, it's a cold shower, both literally and figuratively. Your legs are heavy, your whole body is stiff, and every movement makes you wince. The aches and pains remind you that your body wasn't quite ready for the outpouring of energy you've put it through. Small consolation: you're far from alone in this situation. These little aches and pains due to exertion have already affected everyone, from amateurs to champions such as Carlos Alcaraz or Kevin Mayer .

Muscle aches are familiar to us, yet they remain somewhat mysterious. Science defines them as "muscle inflammation due to the elimination of waste during exercise," as detailed by the Pasteur Institute. In concrete terms, physical activity burns away toxins, residues from processed foods or pollution that disrupt the body, causing fatigue, lack of concentration, and even swelling. However, it also causes the release of lactic acid, a substance well-known to 400m and 800m runners, produced by red blood cells and muscle cells when they lack oxygen, such as during intense exercise.

The elimination of this lactic acid can cause more or less unpleasant discomfort. The sensation of contracture comes a little later and originates from "the reconstruction of damaged elements in muscle cells" . Understand: your body works to repair the muscle fibers torn during the effort. The first pains occur a few hours later, or one night (the peak occurs between 24 and 72 hours after the session), while the body tries to rebuild its health.

But while the presence of muscle aches can hinder daily movements, it's not a medical concern. It simply signals that the muscles are well warmed up and it's time to take it easy. Because to relieve discomfort, the best remedy is still rest. Unless you have a professional masseur on hand to improve blood circulation or a cryotherapy machine to more easily eliminate lactic acid, it's not for everyone.

A pain reliever or heat packs can also help, but to get rid of the stiffness, you need to wait between two and five days. After that, it's advisable to consult a doctor, as the injury could be a sign of a muscle tear.

Until then, rest, then. "Sore, the muscle is in a state of reconstruction: doing another intense session on top of that is really not a good idea," insists Martin Barillon, sports physiotherapist. If you really can't stay still, the doctor recommends practicing a sport that doesn't put stress on your aching limbs. In concrete terms, no football matches if your legs hurt or tennis if your shoulders are causing you pain!

Regardless of your chosen discipline, micro-injuries will negatively impact your performance. "Severe muscle soreness leads to a loss of maximum strength and therefore a loss of overall strength," summarizes Martin Barillon. Forget about chasing records, so you'll already be weakened.

Munich, May 27, 1993: A light refresher for the OM players who have just been crowned European champions (from left to right, Jean-Jacques Eydelie, Didier Deschamps and Éric Di Meco). (Alain De Martignac/L'Équipe)

Patience is especially recommended because once the tissues have reformed, they will theoretically be stronger than before. To avoid being left slumped on the couch, the ideal is a short walk around the house or a light jog to detoxify - between 20 and 25 minutes at a pace that allows you to hold a conversation.

Although there is no scientific consensus on the physical effectiveness of this detox, researchers have shown that it aids psychological recovery. This explains why fitness coaches in professional clubs, across all sports, plan very light sessions the day after competitions. Or why cyclists gently pedal on their home trainers for just a few minutes after clocking up hundreds of kilometers.