Shin splints develop when repetitive impact places more stress on your shinbone and the tissue surrounding it than your body can repair between workouts. The formal name is medial tibial stress syndrome, and it’s one of the most common overuse injuries in runners and athletes who do a lot of running or jumping. The core trigger is almost always doing too much, too fast, on legs that aren’t conditioned for the load.
What Happens Inside Your Leg
Your shinbone (tibia) is wrapped in a thin layer of connective tissue called the periosteum. Every time your foot strikes the ground, muscles in your lower leg pull on this tissue where they attach along the inner edge of the bone. The three muscles most involved are the soleus (the deeper calf muscle), the posterior tibialis (which supports your arch), and a smaller muscle called the flexor digitorum longus that runs along the bottom of your toes.
When you run or jump repeatedly, the tibia also bends slightly with each impact, then springs back. In small doses with adequate rest, this stress actually strengthens the bone. But when the repetitive load outpaces your body’s ability to repair the microdamage, the periosteum becomes irritated and inflamed. That’s the aching, tender pain you feel spreading along the inner border of your shin.
Training Errors Are the Top Cause
The single biggest reason people get shin splints is ramping up activity too quickly. Increasing your weekly running distance by more than 30% has been shown to significantly raise the risk of developing the condition compared to a gradual buildup. This applies whether you’re a new runner logging your first miles, a seasoned athlete returning from a break, or a military recruit thrust into high-volume training. In one study of nearly 2,800 U.S. Naval Academy recruits, 3.5% developed shin splints during training.
Specific training mistakes that set the stage include:
- Sudden jumps in mileage or intensity, such as doubling your long run in a single week
- Skipping warm-ups, which leaves muscles stiff and less able to absorb shock
- Switching surfaces, like moving from a treadmill to concrete without a transition period
- Adding hill work or speed sessions before your legs have adapted to your base volume
The common thread is that bone and muscle adapt slowly. Cardiovascular fitness often improves faster than your skeletal system can keep up with, so you feel ready to do more before your shins actually are.
Foot Mechanics and Arch Shape
How your foot moves when it lands plays a significant role. Overpronation, where your foot rolls inward excessively after contact, increases the traction forces on the inner shin. This pulls harder on the periosteum with every step.
One reliable predictor is how much your arch drops under your body weight. A larger drop (meaning a flatter, more flexible arch) has been identified as a risk factor for exercise-related lower leg pain in novice runners. Conversely, very high, rigid arches come with their own set of problems, including higher rates of ankle injuries and certain stress fractures, but they’re less commonly linked to shin splints specifically. If you’ve always had flat feet or notice your shoes wear down heavily on the inner edge, your foot mechanics may be contributing.
Who Gets Shin Splints Most Often
Runners and military recruits account for the largest share of cases, but shin splints also show up in dancers, basketball players, soccer players, and anyone whose sport involves repetitive lower-leg impact. New exercisers are especially vulnerable because their bones haven’t yet adapted to the forces involved.
Female athletes face additional risk factors tied to hormonal health and bone density. Among young women, the combination of low calorie intake, irregular or absent periods, and reduced bone mineral density (sometimes called the female athlete triad) weakens the skeleton’s ability to handle repetitive stress. In one study, 34% of female athletes surveyed had a history of stress fractures or shin splints, and 25% reported skipping a period for three or more months. Irregular menstrual cycles in adolescent athletes have been associated with a higher percentage of severe injuries overall.
How Shin Splint Pain Feels
The hallmark of shin splints is a dull, aching pain that spreads across a broad area along the inside of your lower leg. It typically starts during or after exercise and may ease up as you warm into a run, only to return afterward. In the early stages, the pain fades with rest. As the condition worsens, it can linger into daily activities like walking or climbing stairs. Pressing along the inner edge of your shinbone usually produces tenderness over a wide stretch rather than one sharp spot.
Shin Splints vs. Stress Fractures
Because both conditions involve the shinbone and result from overuse, it’s important to know how they differ. A stress fracture is an actual crack in the bone, and the pain behaves differently in a few key ways.
- Location: Stress fracture pain is pinpointed to one specific spot. Shin splint pain radiates across a larger area.
- Response to activity: Shin splint pain sometimes improves during exercise. Stress fracture pain does not; it stays consistent or gets worse.
- Pain at rest: Shin splints typically ease when you stop. Stress fractures can hurt even when you’re sitting still.
Red flags that suggest something more serious than standard shin splints include pain that doesn’t improve after rest and a gradual return to activity, pain concentrated in one small area, and sharp tenderness directly over the bone. If those apply, imaging can confirm whether a fracture has developed.
Reducing Your Risk
The most effective prevention strategy is controlling your training load. The 10% rule (increasing weekly volume by no more than 10% at a time) is a conservative but well-supported guideline. If you’re coming back from time off, start at a lower volume than where you left off, even if your cardio feels fine.
Footwear matters more than most people realize. Shoes lose their shock-absorbing capacity well before they look worn out, generally around 300 to 500 miles of running. If you overpronate, a stability shoe or custom orthotic can reduce the inward rolling that strains the inner shin. Strengthening the calf muscles, particularly the soleus and posterior tibialis, helps those muscles absorb more of the impact before it reaches the bone. Calf raises (both straight-leg and bent-knee variations) and toe curls with a towel are simple starting points.
Varying your running surfaces can also help. Softer terrain like trails or tracks distributes impact differently than asphalt or concrete, giving your shins periodic relief. And if you’re training for a race, building in rest days isn’t optional. Bone remodeling happens during recovery, not during the run itself.