What causes shin splints in runners?
Shin splints are caused by overloading the lower leg muscles and bone, usually from increasing mileage too fast, running on hard surfaces, worn shoes, weak calves, or poor running form. They cause aching pain along the inner shin bone and are most common in new runners.
Shin splints — medically called medial tibial stress syndrome — are inflammation where the muscles and connective tissue attach to the inner shin bone. The direct cause is repetitive impact that exceeds your tissue's current capacity to absorb load. The contributing factors stack: rapid mileage increases (more than 10% per week), running on hard surfaces like concrete, worn-out shoes past 800 km, weak calf and tibialis anterior muscles, flat feet or high arches without proper support, and overstriding with a heavy heel strike. Beginners are especially vulnerable because untrained bone hasn't yet developed the density to handle running impact. The fix: reduce running volume by 30-50% for 1-2 weeks, ice the shin area 15 minutes after running, do calf raises and toe raises daily (3 sets of 15), replace shoes if they're over 500 km, and return to running gradually. If pain persists for 2+ weeks despite rest or localizes to a single point, see a sports physio — it could be progressing to a stress fracture, which takes 6-12 weeks to heal. Prevention: increase mileage slowly, strengthen calves, run on softer surfaces when possible, and never run through sharp shin pain.