Physical activity and regular exercise has long been associated with good health and longevity. Observational studies and small trials also suggest that those who work out regularly are less at risk of developing chronic diseases or dying prematurely and high intensity exercises (HIIT) have more benefits than moderate intensity continous training (MICT).
However, there hadn’t been any randomized clinical trials so far to assess the effects of physical activity on morbidity and mortality.
In an observational study researchers just observe the effects of a factor (in this case exercise), on a group of people, without changing who is and who is not exposed to the said factor. Randomized controlled trials, on the other hand, are done to compare the effects of a factor by exposing a group of people to it and keeping another group as a control (who are not exposed to the said factor).
Now, a new research published in the British medical journal (BMJ) indicates that HIIT and MICT do not have any major effects on all-cause mortality. However, HIIT does seem to have a comparatively better effect on all cause mortality than recommended physical activity and MICT.
HIIT, MICT and recommended physical activity
As per the study, the guidelines for recommended physical activity are mostly the same throughout the world. The American College of Sports Medicine recommends that you do at least 150 minutes of moderate intensity cardio per week that can be broken down to 30 minutes per day, 5 days a week or 75 minutes of high intensity cardiovascular activity per week, broken down to 20 minutes per day for more than 3 days a week.
A mix of moderate to vigorous intensity exercises can also be done after consulting an experienced fitness trainer.
Twice or thrice a week, resistance training exercises targeting each muscle group (for at least one minute each) should be done along with neuromotor exercises that focus on balance, concentration and agility.
Some examples of moderate intensity exercises include brisk walking, vacuuming, washing windows and slow bicycling. Hiking, jogging, playing soccer and running are some type of high intensity exercises.
The trial involved 1,567 volunteers (about 790 women and 777 men) with an average age of 73 years.
All the participants were randomised into either HIIT, MICT or control (those who did 30 minutes of moderate physical activity every day) groups. The volunteers were asked to follow up at the end of one, three and five years.
After five years, the observed average mortality rate was 4.6% with the rate being 4.7% in the control group, 5.9% in the MICT group and 3% in the HIIT group.
No difference was found between any of the groups when it came to the development of cancer or cardiovascular diseases. About 15% people in the control group, 15% in the MICT group and 15.3% in the HIIT group had cardiovascular diseases after five years. Similarly, 12.8% people in the control group, 11% in the MICT group and 12% in the HIIT group had cancer after five years.
Limitations of the study
Despite their findings, the authors pointed out the following limitations in their study:
Most of the participants, even in the control group, were in good health to begin with.
The control group participants strictly adhered to their physical activity regimen. Some of them were doing HIIT while those in the HIIT group were not able to properly follow their regimes.
The results of the study hence do not negate the link between physical activity and longevity but question the role of exercise intensity when it comes to mortality and morbidity.