Building Your Bones


Too often, female runners ignore strength work that could complement a running programme and reduce the risk of stress fractures that may otherwise be caused by muscle weakness. To avoid brittle bones, it’s important to give your body the calcium it needs as well as do sufficient strength work to protect them. – BY LAUREN VAN DER VYVER

A common injury complaint amongst female runners is shin splints, especially as they build up their mileage or pick up speed to chase a PB or attempt a new, longer distance – and the cause of this pain is all too often attributed to a decrease in bone density. However, Dr Lisa Micklesfield, senior researcher at the UCT/MRC Research Unit for Exercise Science and Sports Medicine in Cape Town, says that this is due to a common misconception: “Women runners don’t lose bone density any faster than women who don’t run, unless they have reduced energy availability – a symptom of which is menstrual irregularity, which may be due to reduced energy intake or excessive energy expenditure. Shin pain, for example, is the response of the muscle and bone of the lower leg to an increase in weight-bearing exercise, but with constant monitoring and adaptation to one’s training programme, and the correct footwear, this type of injury shouldn’t become problematic.”

Many women focus on cardiovascular instead of strength work in training, focusing on weight-loss instead of increasing muscle mass – especially when they hit the gym. Quite simply, to keep your structure sturdy, it’s important to introduce sessions that focus on building muscle in your legs and core to minimise the strain of your body hitting the ground when running. “Muscle mass is directly proportional to bone mass, largely due to the pull of the muscle on the bone” says Lisa, who therefore recommends strength training, but points out that it is just one of a number of factors associated with stress injuries in women runners. Training surface (tarmac versus gravel), biomechanics and possibly incorrect footwear should also be taken into account, if necessary.

Regular weight-bearing like walking, hiking, dancing, stair climbing, weight-lifting and racquet sports can all build the muscle you need, while swimming and cycling can improve your endurance, but they’re not the ideal sports to improve bone mass density.

As women, we also have to consider the impact pregnancy and breastfeeding has on the body. In the latter stages of pregnancy, maternal bone loss may occur, as this is the time when the fetal skeleton is being rapidly mineralised, but this bone-loss is temporary and is recovered after the birth and lactation, says Lisa. “While breastfeeding does decrease bone density, as the calcium is mobilised from the maternal skeleton for breast milk, the 3% to 7% lost is rapidly regained after weaning,” explains Lisa,
“and breastfeeding is not associated with
an increased risk of osteoporosis, either.”

Whether they run or not, women should be getting around 1000mg of calcium on a daily basis, and during pregnancy, Lisa recommends an extra 200mg of calcium on top of the 1000mg. “It all depends on how long the
woman breast feeds and how long amenorrhea – loss of menses – continues for. Evidence does suggest that it recovers fully even with short-spaced pregnancies.”

All in all, women runners need to stick to a lifestyle that includes sufficient calcium intake, whether pregnant or not, as well as introducing strength training in their weekly training programme – one to two sessions a week as a base. Naturally, we all lose bone mass as we age, but a healthy mix of physical activity and a nutritious diet can help you beat brittle bones – and avoid shin splints!