The Importance of your Cardio Fitness and Preventing MORTALITY
With everyone's New Years Resolutions in full swing (and hopefully not tossed to the side already!), I think it is important to take time to realize that not only is looking good for the beaches in a few months important, but we should also consider our overall health and wellness goals as well.
Many Americans know that risk factors such as smoking, hypertension, obesity, diabetes, etc. are known to increase your risk of cardiovascular disease. However, many studies have indicated that your Cardiorespiratory Fitness (CRF) is "at least as important as the traditional risk factors, and is often more strongly associated with mortality". While this may seem obvious ("better shape, of course I'll live longer!"), what does being in shape actually look like and what are some of the mechanisms that keep us alive?
What is CRF?
One would imagine the CRF is linked with having good conditioning (running a lot, not getting tired that easily, having endurance) but what exactly does that mean? CRF is defined by Duck-chul Lee et al. as " the ability of the circulatory, respiratory, and muscular systems to supply oxygen during sustained physical activity".
This includes a few parts besides just the heart and lungs (although that is part of the equation). This definition goes into the body as a whole, speaking to the heart, vascular system (think veins and arteries), lungs, muscles, even down to the cellular level with the mitochondria in the muscles-which provide all the energy for every living cell.
There are several factors that play into your current CRF levels, including non modifiable and modifiable. The non modifiable factors include AGE. GENDER, and GENEOTYPE (your genetics- thanks mom and dad...) and the modifiable factors include PHYSICAL ACTIVITY, SMOKING, OBESITY, and MEDICAL CONDITION (wash your hands!). With all that said, the number 1 factor is without a doubt your physical activity, meaning that with the hand you were dealt, with what you have already done to your body- by simply putting in the concentrated effort to get active you get modify your current health status (...shocker).
We usually label CRF in terms of METS (metabolic equivalents) or maximal oxygen uptake (VO2 Max). A MET can be thought of as the equivalent as you burning 1 calorie (kcal), per kilogram of body weight, per hour. This is equivalent to the amount of energy it costs you to sit down quietly watching TV. Some examples of other activities and how much METS they are equivalent to can be found at http://www.cooperinstitute.org/2012/04/met-minutes-a-simple-common-value-to-track-exercise-progress/.
VO2 Max is simply a measure of how much oxygen your body can take in and utilize during maximal aerobic (with oxygen) exercise. Once you cross the threshold of the intensity of the exercise exceeding your bodies ability to take in and use the oxygen, you now switch the primary energy driver for your body to your anaerobic systems- one of which produces the lactic acid that builds up and makes your workouts extremely uncomfortable. So, when we talk about VO2 Max, even though it pushes you, it is just another measure of your aerobic fitness.
Some Numbers on CRF
So now we have a firm definition of CRF and how to measure it, how good is it really at protecting us from death? Here are a few quick numbers to run by according to the Aerobics Center Longitudinal Study (ACLS) done by Stofan et al., which examined the exercise habits of over 13,000 men and nearly 4,000 women from ages 20-87...
-Fit men had a 43% lower risk for all cause mortality, and a 47% lower risk for CVD related mortality when compared with unfit men
-Fit women had an even bigger advantage- 53% for all cause and 70% for CVD related mortality vs being unfit!
-Fit men were categorized as burning anywhere from 525 to 1650 kcals/wk during leisure time activity
-Fit women were categorized as burning anywhere from 420 to 1260 kcals/wk during leisure time activity
-Becoming fit after being unfit reduced the risk of all cause mortality by 44% and CVD related mortality by 52% (applies to males only in study, but one could safely assume similar benefits would be present in females)
So you incorporate some cardio or regular exercise into your everyday routine- all the sudden you live longer? What exactly does having an increased CRF do to your body that would effect mortality rate?
1) Increased Insulin Sensitivity
When you eat- sugar (glucose) is released from the food source and flows through your body. Insulin comes along and essentially "unlocks" your cells to suck up the sugar for energy to continue to do the functions that allow you to live. Eventually the "lock and key" mechanism would wear out and the insulin would no longer unlock the cells to allow uptake of the glucose. With all that glucose chronically floating around unchecked and not entering the cells to provide energy, you essentially are now diabetic.
2) Blood Lipid and Cholesterol Levels
Until recently, researchers weren't entirely sure why cardio affected cholesterol levels. Now we are getting some insight into the processes. One reason being that exercise stimulates enzymes that move cholesterol to be excreted through the liver. Another being that it stimulates HDL production (the good cholesterol) which is great for your vessel health and getting rid of the fats from sticking around (pun intended).
3) Body Composition
Again, this seems obvious, but worth mentioning. If you are engaging in regular CRF and exercise in general, you are burning calories and not storing them. When excess calories from any source are stored in the body (protein, carbs, or fats) they are stored in the body as FAT. There are different pathways to convert all these macronutrients to fat, but with nearly unlimited room in our body to store, this is the bodies most efficient way of storing the excess energy. Worth mentioning from a study done by DiPietro et al.- just a 1 min increase in maximal treadmill testing resulted in reduced the risk of gaining 10 lbs an average of 14% in men and 9 % in women, meaning CRF may be a good indicator of future weight gain.
Multiple studies (Aronson et al. 2004, Church et al. 2002, Kuo et al. 2007, Williams et all 2005) have demonstrated an inverse relationship between CRF and C reactive protein (a typical marker of inflammtion). Why is this so important? Inflammation causes damage and ruptures to vessels throughout the body and heart (not to mention everything else beside just the cardiopulmonary system). Many of our lifestyles promote this inflammation process, from our nutrition to stress to lack of sleep. Without getting into the exact causes of inflammation as it is an incredibly in depth topic, being able to mitigate the negative effects of inflammation is crucial.
5) Enhanced Nervous System Functioning
Again, too in depth of a conversation to get into, but if you want to be able to relax and "shut off", having better CRF will help boost your nervous system robustness. Constantly having your nervous system cranked up in "fight or flight" mode will keep your body in a state of alert and eventually exhaust you. Some of this is due to the actual mechanical benefits of CRF like a reduced heart rate, or the release of different neurotransmitters such as dopamine which help relax and create a sense of euphoria.
So whats your next move? Hop right on the next treadmill and push yourself until you pass out?
Not so fast (again, pun intended)- according to the ACLS study, all it requires for most health benefits is simply walking briskly for about 30 min a day most days of the week( >5). In fact, that is what a majority of the very fit men and women did just that- logging anywhere from 2 to 3 hours a week.
Like everything, start slow and work your way up. Use the following guidelines set by the Physical Activity for Americans.
Light-intensity aerobic activity = 1.1 to 2.9 METs
Moderate-intensity activity = 3.0 to 5.9 METs
Vigorous-intensity aerobic activity = 6.0 or > METs
Use the link from above http://www.cooperinstitute.org/2012/04/met-minutes-a-simple-common-value-to-track-exercise-progress/ to find some activities you enjoy and the Coopers Institutes website http://www.cooperinstitute.org/2012/04/met-minutes-a-simple-common-value-to-track-exercise-progress/ to calculate you total METs per day/week.
Related Articles/Further Readings
Stofan, J. R., Dipietro, L., Davis, D., Kohl, H. W., & Blair, S. N. (1998). Physical activity patterns associated with cardiorespiratory fitness and reduced mortality: the Aerobics Center Longitudinal Study. American Journal of Public Health, 88(12), 1807-1813. doi:10.2105/ajph.88.12.1807
Lee, D., Artero, E. G., Sui, X., & Blair, S. N. (2010). Review: Mortality trends in the general population: the importance of cardiorespiratory fitness. Journal of Psychopharmacology, 24(4 Suppl), 27-35. doi:10.1177/1359786810382057
MET minutes: A simple common value to track exercise progress - Cooper Institute. (n.d.). Retrieved January 05, 2017, from http://www.cooperinstitute.org/2012/04/met-minutes-a-simple-common-value-to-track-exercise-progress/
Activity Categories - Compendium of Physical Activities. (n.d.). Retrieved January 05, 2017, from https://sites.google.com/site/compendiumofphysicalactivities/Activity-Categories