Whether they be a weekend fitness enthusiast or elite athlete, most sports people have at one time or another during their exercise career suffered a leg injury - described in the early 1900s as 'spike soreness' in runners - more commonly known as shin splints. According to one recent study in the US, this pain in the shin accounted for 13 per cent of all running injuries.
The proper medical term is 'medial tibial stress syndrome' but the more generic term of shin splint has been adopted to describe any exercise-related pain in the lower leg. Regardless of which term you prefer, it's applied to three causes of pain along the inside of the lower leg.
The first cause is by inflammation of the periosteum - the fibrous sheath of collagen and connective tissue which covers the bones of the lower leg. Stress causes the inflammation at the point where the muscles fascia (tissue surrounding the muscle) joins the periosteum. Often someone whose feet turn inward during running or other repetitive activities will stretch certain tendons in the lower leg causing friction and inflammation of the bone.
The second cause is a stress fracture of the tibia or the inside of the shin bone. These are actually tiny microscopic breaks in the bone - often too small for x-rays or bone scans to pick up - as a result of too much stress placed on it. The third cause is thought to be a type of compartment syndrome on the outside (posterior) part of the lower leg. This is caused by pressure that builds up inside the muscle fascia to the point of restricting the extra blood the muscle needs during exercise. With a lack of blood, the muscle becomes suppressed, which causes an aching after exercise has begun.
Most often, the cause of shin splints is excessive running on hard or uneven surfaces. Usually, first-time runners, high on enthusiasm, experience these pains in the lower legs, but experienced runners aren't exempt. Often shin splints can result if an athlete suddenly increases the intensity, volume or training surface (going from soft to hard surfaces) of their workouts, or change to a different type of running shoe.
Of course prevention is better than cure. If you've recently taken up running or have changed your exercise patterns, do so gradually. Vary the surfaces you run on. And if you run frequently, check your shoes at least every six months for wear and tear.