Unfit marathon runners face heart risk

Marathon runners who are not fully fit can cause damage to their heart that takes up to three months to repair, according to a new study.

A team of researchers and runners from the Heart and Stroke Foundation used data from magnetic resonance imaging (MRI) to find out what is going on in the athletes' hearts as the runners pounded out the 26 miles.

Cardiologist Eric Larose told the Canadian Cardiovascular Congress: "Marathon runners can be a lot less fit than they think. Lack of real aerobic fitness may directly impact the ways the heart organises itself to survive the stress of marathon running."

His research found that the magnitude of abnormal heart segments was more widespread and significant in a group of less fit runners.

During the marathon, they had signs the heart might be at greater risk of damage than that of runners who had better training or at least had better exercise capacity.

Dr Larose said: "Without proper training, marathon running can damage your heart. Fortunately the exercise-induced injury is reversible over time, but it could take up to three months to completely recover."

His team studied the effects using MRI measurements, which propel research beyond the traditional stethoscope as a means of estimating and measuring heart function.

The left ventricle of the heart is divided into 17 segments that make up the heart as a whole. When a segment is injured or stressed during the marathon, its neighbours on either side can take over to perform the function of the damaged area.

This makes the heart as a whole appear stronger and fitter than is really the case when considering each individual segment.

It also makes it practically impossible for physicians to arrive at an accurate assessment of the heart health of the marathon runner when only considering the whole heart.

Dr Larose took healthy amateur runners and performed a full evaluation on them six to eight weeks before, and then immediately after, they ran a marathon.

They underwent exercise tests and blood analysis as well as MRI.

Some of the effects:

COLD - training too hard can make runners susceptible to colds

HEART - undetected heart conditions can sometimes lead to death in seemingly fit marathon runners

GASTRO - intestinal problems. Many runners experience intestinal cramp and even diarrhoea, thought to be caused by changes to the blood flow to the intestines

CRAMPS - sudden pains in the legs caused by dehydration and lack of glycogen in the blood

RUNNERS KNEE - sharp pain in the knee cap. May need surgery

SHIN SPLINTS - pain near the shin bone, can take weeks to heal

BLISTERS - most marathon runners end up with blisters at some point

ACHILLES TENDINITIS - acute pain in the heel caused by running on hard surfaces