Poor cardiorespiratory fitness could increase your risk of a future heart attack, even if you have no symptoms of a lifestyle illness today, a new study has found.
A strong link was found between higher fitness levels and a lower risk of heart attack and angina pectoris over the nine years following the measurements that were taken in a study by the Norwegian University of Science and Technology’s (NTNU) Cardiac Exercise Research Group (CERG).
The study results have been published in the European Heart Journal.
Even among people who seem to be healthy, the top 25 per cent of the fittest individuals actually have only half as high a risk as the least fit 25 per cent.
Between 2006 and 2008, CERG researchers measured the cardiorespiratory fitness of 4527 men and women who participated in the HUNT3 population-based health survey in Nord-Trøndelag. None of the subjects had cardiovascular disease, cancer or high blood pressure, and most were considered to be at low risk of cardiovascular disease for the next ten years.
Nevertheless, 147 of the participants experienced heart attacks or were diagnosed with angina pectoris by 2017. These diseases signal that the coronary arteries in the heart are narrowed or completely blocked.
The researchers analysed the participants in groups based on their level of fitness in relation to others of the same age and gender. The risk proved to decline steadily as patient fitness increased. The correlation between fitness and cardiovascular risk also held after adjusting for other factors that differed between the most and least fit participants.
One of the greatest strengths of the study is that the test used maximum oxygen uptake to measure participant fitness. Earlier studies that have linked fitness level to disease risk in healthy populations have largely been based on less precise calculations of fitness, or on self-reported physical activity information.
Our body uses oxygen to drive metabolic processes that create energy for the muscles. Maximum oxygen absorption is simply the maximum amount of oxygen the body is able to absorb during physical activity. Heart, blood vessel and muscle functioning are all important for oxygen uptake.
The study suggests that even a small increase in fitness can significantly improve health. For each increase of 3.5 fitness points, the risk of heart attack or angina decreases by 15 per cent.
Even if you never get in such good shape that you can say you have optimal protection, the study shows that participants’ risk was lower the more fit they were.
To measure maximum oxygen uptake accurately, you have to breathe into a mask while running on a treadmill, where the speed increases or the incline gets steeper every minute. As you work at higher and higher intensity, your body needs more and more oxygen. The test ends when you can’t run anymore, or when measurements show that the oxygen uptake is no longer increasing even though the treadmill speed is.
But why does the fitness number mean so much for your future health?
Researchers use a treadmill and a special mask to measure a person’s maximum oxygen uptake, which is considered an important measure of fitness.