The heart is mainly a muscle, but unlike a nice and round Gluteus
Maximus, you cannot display a well-trained Heart on social media for personal
gains. Well, maybe Hanuman was the only guy who managed to display his heart in
order to impress his Boss and Boss’ Wife (Ram and Sita). He had eyes on the ‘Best Employee of the Ever
Award’.
As with any muscle, the heart also adapts to training stress from
exercise and eventually becomes more efficient at supporting the enhanced
cardiovascular requirements of exercise. But all is not good in the domain of
cardio because most of the protective cardiovascular benefits from
cardiovascular exercises such as running and cycling, wane away after a certain
point as per The Copenhagen City Heart Study (referred to as “the CCH
Study” below).
In the year 2015 when the CCH Study was published, suddenly
excessive and hard running was labelled dangerous for cardiac health, based on
the exercise related findings in the CCH Study. Not wanting to lose out
commercially, immediately Runner’s World published a very poorly written rebuttal, and then after 1 year
they came out with a more nuanced article which admitted the relevance
of the findings in the CCH Study. Competitor Running, in contrast, wrote a balanced article without any attempt to
debunk the study and protect its customer base.
The CCH Study was launched in the year 1975 by Dr. Peter Schnohr, to
understand physical activity and athleticism as tools for cardiovascular
disease prevention, and it involved a starting sample population of 20,000 men
and women. The Study grew over the years to include the effects of alcohol,
education, smoking, diabetes, sleep etc. on coronary heart diseases and strokes
in humans. Do note that Dr. Schnohr was amongst the top 10 runners in Denmark
at that time and he initiated the entire study based on the unpleasant symptoms
he experienced during his strenuous training and to understand whether
excessive running could be unhealthy.
For the past several decades, it is common knowledge and obvious
through medical evidence that our bodies need the effects of regular and
vigorous exercise, and that physically active people have a significantly lower
risk of death compared with inactive people. However, no upper threshold for
physical activity has ever been recommended.[1]
The CCH Study reported that both duration and intensity of walking,
running and cycling were important factors in relation to coronary heart
disease related mortality, with intensity of exercise playing a stronger role
in increasing the chances of cardiovascular issues.
There appears to be a U-shaped association between all-cause
mortality and dose of jogging as calibrated by pace, quantity, and frequency of
jogging. As per Dr. Schnohr, light and moderate joggers have lower mortality
than sedentary non-joggers, whereas strenuous joggers have a mortality rate
which is not statistically different from that of the sedentary group.[2]
Long-term strenuous endurance exercise might induce
pathological structural remodelling of the heart and large arteries. Current
data suggests that long-term training and competing in extreme endurance
events such as marathons, ultra-marathons, ironman distance triathlons, and
very long distance bicycle races can cause physical abnormalities and
malfunctions in the heart and elevate cardiac biomarker levels. Additionally,
long-term excessive exercise may be associated with coronary artery
calcification, diastolic dysfunction, and large artery wall stiffening.[3]
A similar finding[4]
on cardiac dysfunction and injury from marathon training was reported in this
study labelled “Myocardial Injury and Ventricular Dysfunction Related to
Trailing Levels Among Nonelite Participants in the Boston Marathon”. The
findings of this study are more relevant to the sensationalised stories we keep
hearing about in the media about runners suffering heart attacks during or
after a marathon, but which instances as per this study are mostly attributable
to the lack of proper training in such runners i.e. low mileage in training for
a long distance race.
 |
| Best Employee of the Ever |
As per the jogging/running part of the CCH Study, the findings for
the relationship between running and mortality when adjusted for various
factors is as follows:
Note:
Hazard Ratio (HR) below represents the chance of an event occurring.
A HR of 1 means that there is no difference in survival between the two groups.
A hazard ratio of greater than one or less than one means that survival was
better in one of the groups. So in the CCH Study a HR of 1 represents that the
chance of death is certain. Therefore, the HR for understanding the numbers
below is to be compared with a ‘sedentary nonjogger’ whose HR is 1 i.e. a
‘sedentary nonjogger’ will die (HR = 1), and anything less than 1
represents that the chance of mortality has decreased in the exercise group as
compared to a ‘sedentary nonjogger’ group.
Quantity of Jogging (adjusted for age and sex):
Hours of jogging per week
|
HR
(Hazard Ratio)
|
Remarks
|
Sedentary
nonjogger
|
1
|
Certainty
of mortality at a given point time.
|
Less
than 1 hour per week
|
0.32
|
68%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
1 –
2.4 hours per week
|
0.18
|
82%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
2.5
– 4 hours per week
|
0.38
|
62%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
More
than 4 hours per week
|
0.35
|
65%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
Quantity
of Jogging (adjusted for age, sex, smoking, alcohol intake, education, and
diabetes):
Hours of jogging per week
|
HR
(Hazard Ratio)
|
Remarks
|
Sedentary
nonjogger
|
1
|
Certainty
of mortality at a given point time.
|
Less
than 1 hour per week
|
0.47
|
53%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
1 –
2.4 hours per week
|
0.29
|
71%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
2.5
– 4 hours per week
|
0.65
|
35%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
More
than 4 hours per week
|
0.60
|
40%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
Frequency
of Jogging (adjusted for age and sex):
Frequency of jogging per
week
|
HR
(Hazard Ratio)
|
Remarks
|
Sedentary
nonjogger
|
1
|
Certainty
of mortality at a given point time.
|
Less
than or equal to once per week
|
0.19
|
81%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
2
to 3 times per week
|
0.20
|
80%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
More
than 3 times per week
|
0.48
|
52%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
Frequency of jogging per
week
|
HR
(Hazard Ratio)
|
Remarks
|
Sedentary
nonjogger
|
1
|
Certainty
of mortality at a given point time.
|
Less
than or equal to once per week
|
0.29
|
71%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
2
to 3 times per week
|
0.32
|
68%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
More
than 3 times per week
|
0.71
|
29%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
Jogging
pace (adjusted for age and sex):
Jogging Pace
|
HR
(Hazard Ratio)
|
Remarks
|
Sedentary
nonjogger
|
1
|
Certainty
of mortality
|
Slow
(9.66 km/h to 11.27 km/hour)
|
0.34
|
66%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
Average
(above 11.27 km/hour)
|
0.25
|
75%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
Fast
(threshold workouts)
|
0.54
|
46%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
Jogging
pace (adjusted for age, sex, smoking, alcohol intake, education and diabetes):
Jogging pace
|
HR
(Hazard Ratio)
|
Remarks
|
Sedentary
nonjogger
|
1
|
Certainty
of mortality
|
Slow
(9.66 km/h to 11.27 km/hour)
|
0.51
|
49%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
Average
(above 11.27 km/h)
|
0.38
|
62%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
Fast
(threshold workouts)
|
0.94
|
6%
lowered risk of mortality (as compared to a sedentary nonjogger)
|
When the findings of the CCH Study appeared for the first time on
various news outlets and health magazines, there was a general uproar in the
running community since most of the avid runners did not want to acknowledge or
believe that something which felt so good could also be bad for them. The U
shaped graph (namely, the diminishing returns from running distance and
intensity) was unbelievable to most since till the CCH Study, none of the
previous studies had categorically stated that hard running may be detrimental
to the human body to the extent that all the benefits may wane away after a
certain peak. Moreover many of the news articles based on the CCH Study
provided a very general analysis of jogging related findings of the CCH Study,
which needless to say sounded quite ridiculous to runners who were training for
races, and who, as human nature goes, obviously did not want to hear that
training for races would be counterintuitive.
The CCH Study was not anti-running. It was a comprehensive long term
study on the pros and cons of hard training on the human body. Dr. Schnohr and
others have stated that “….to our knowledge, there has been no study of the
longevity of marathon, half-marathon or triathlon participants, but such
studies would clearly be informative…”
The simplistic interpretation of the jogging related findings in the
CCH Study by news media and individuals was incorrect since if you carefully
see the above tables from the CCH Study, the following points emerge which
demonstrate that the CCH Study was pro-running:
- There are benefits from any duration, frequency and intensity of running since the HR (hazard ratio) declines for each category of runner as compared to a sedentary non-jogger.
- Notwithstanding the above, the benefits from running are maximized by slow jogging (9.66 km/h to 11.27 km/hour) when done for 1 to 2.4 hours per week and in less than 2 to 3 sessions per week, and if the runner does not smoke, consume alcohol or have diabetes.
- As compared to a sedentary nonjogger, a person who runs can reduce his mortality risk to almost 50% even if he/she trains hard i.e. for more than 4 hours per week at a fast pace and in several sessions. Hence, even hard running is beneficial, but it’s less beneficial than slow running.
- The risk of mortality is only 6% lesser in a runner as compared to a sedentary nonjogger when a runner, (i) runs for more than 4 hours per week; (ii) runs more than 3 times per week; (iii) runs at a fast pace; (iv) smokes and drinks; and (v) has diabetes.
Therefore, unless you have picked up a few vices (alcohol and
tobacco) and maybe have diabetes too, as per the CCH Study, even if you keep
training hard, your mortality risk will always be lower than a sedentary
nonjogger’s.
Also note that the CCH Study is only limited to determining
cardiovascular health, and it has not considered the mental benefits of
excessive/hard/intense/prolonged exercise (howsoever you may want to describe
it).
As science has shown and as you may have felt yourself, the mental
benefits from “excessive running” especially in treating the general
malaise/depression in contemporary society may most certainly cancel the higher
cardiovascular risks associated with hard running (marathons, ultramarathons,
triathlons etc.) if seen in terms of personal choice in improving lives.
Quality of Life, over Quantity of Life?
What you can do with the aforesaid data and analysis is decide what
you want from running and your running schedule. If you want to run only for
longevity then run less per week and run slow (less than 2.4 hours per week
and slower than 11.27 km/h) and spend a few hours every week on strength
training since strength training can reduce mortality risks significantly and
also reduce cancer cell growth. However, if you run long distances out of sheer
passion and mental health then keep training hard but reduce alcohol and
smoking to decrease your mortality risk which otherwise comes in close
proximity to a sedentary nonjogger due to these vices.
Finally, the findings of the CCH Study fit like a glove with
Professor Alexander Y. Bigazzi’s (Department of Civil Engineering, the
University of British Columbia) recent findings[5]
of the minimum dose speeds (MDS) for Walking, Running and Cycling at which the
amount of inhalation of pollutants is the lowest. Move faster than these recommended
speeds and you will expend dramatically more energy which in turn will increase
your heart rate and respiration and therefore you will inhale exponentially
higher amounts of air + pollution. I had written a blog on this last year since in highly
polluted placed like Delhi, during the months ranging from November-March, the
air quality is extremely poor and a slower exercise speed is necessary to
reduce air pollution. So a combination of the findings of the CCH Study and MDS
(minimum dose speed i.e. workout speeds) is a win-win formula for areas with
polluted air.
- Aman Yadav
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4625209/
[2] https://www.ncbi.nlm.nih.gov/pubmed/25660917
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4625209/
[4] http://circ.ahajournals.org/content/114/22/2325
[5] https://www.researchgate.net/publication/308535014_Determination_of_active_travel_speed_for_minimum_air_pollution_inhalation
