Why everything hurts when you start running — and what's normal

When you start running, your body hurts in new places, and it's hard to know which aches are part of the process and which are a problem. Most of them are normal. Here's the field guide.

Delayed-onset muscle soreness (DOMS). The deep, stiff ache that shows up a day or two after a run — especially your calves, quads, and glutes — is your muscles responding to an unfamiliar load. It's normal, it shows up on both sides fairly evenly, and it fades on its own within a few days of easy movement and rest. As your muscles adapt over two to three weeks, it gets noticeably milder. DOMS is the most reassuring kind of running pain.

Shin splints (medial tibial stress syndrome). Aching along the inside edge of your shinbone is the classic beginner complaint. It happens because muscles, tendons, and bone all adapt at different speeds — and when you ask them to absorb more pounding than they've toughened up for, the tissue along the shin protests. The key fact: shin splints are a mismatch signal. They mean you progressed faster than your body could remodel. Most cases settle with rest, ice, and a slower ramp. But ignored and run through, they can progress to a tibial stress fracture — which costs you months. So shin pain is the one to respect, not push through.

The side stitch. That sharp cramp under your ribs is usually your diaphragm and the connective tissue around it complaining, often tied to breathing rhythm or eating too close to a run. It's harmless and transient — slow down, breathe deep into your belly, and it passes.

The general rule that separates adaptation from injury:

• Probably normal: dull, achy, on both sides, fades within a day or two, doesn't get worse week over week.
• Back off: sharp, in one specific spot, lingers, or gets worse run over run. Pain that changes how you move is always a stop sign.

Underneath all of it is one principle: your muscles toughen up in weeks, but your bones and tendons take months. The lungs and legs that feel "ready" are running on a faster clock than the tissues actually absorbing the impact. That gap is where almost every beginner injury lives.

What to do with this: expect general soreness and keep showing up. But when pain gets specific, sharp, or one-sided, treat it as information — slow the progression and let the slow-adapting tissue catch up.

Source: Cleveland Clinic — Shin Splints