Wednesday, September 28, 2011

Hard To Kill

These days you can’t watch TV or listen to the radio for more than a couple of minutes without hearing about the latest thing that causes this or that chronic disease such as cancer or Alzheimer’s disease. All you really ever hear is about how this or that environmental factor or dietary practice or supplement reduces or increases your chances of acquiring said disease. The list of things goes on and on ad infinitum. But the real message is essentially, “Do this and not that so that you don’t die earlier than you were supposed to.” But maybe there is something simple you can do that reduces your chances of early death without all the contradictory evidence of environmental factors and food choices. There is. It’s called being strong.

Many studies have been performed on the old (age 65-80) and the very old (85+) that look at strength levels and mortality rates. What the researchers basically do is test the old people’s strength levels (most often hand-grip or leg extension maximal efforts) and then follow them around for a specified period of time and see who dies and who doesn’t. This is science at its most complex, folks. What they’ve found a lot of the time is that the people that were the strongest at the beginning were more likely to still be alive at the end. These studies are compelling but do have their drawbacks. First of all are the confounders. Are people stronger because they happen to be in good health or are they in good health because they are stronger? And on the flip side, are older people weak because of their failing health or is their failing health due to them being weak. It’s hard to separate and show causality of the strength level from the health level. But the proof is still in the pudding. The strong survive.

So that’s the old people. But what about young, robust characters that are in the prime of life? A huge study was performed at The Cooper Clinic in Dallas, Texas in the 80’s. If you ever had to do the Pacer (beep) test in gym class you can thank the Cooper Clinic. This study was a longitudinal study like the ones done on the elderly, but on a much bigger scale. When it was all said and done there were over 8,000 participants. And when the researchers controlled for variables that would skew data they found much the same thing. Those that were in the strongest third of study participants lived longer. For all the runners out there they even controlled against cardiovascular fitness and found the same thing.

In fact, muscular strength has been shown to be a great predictor of risk of cardiovascular disease in young adulthood. In two studies done on younger Swedish men, baseline levels of strength were assessed and were then followed up on later in life. Researchers found that muscular strength was inversely associated with risk of fatal and nonfatal heart disease and stroke, meaning that the stronger you were the less likely you were to have incidents of fatal or non-fatal cardiovascular disease or stroke. But why is that?

The studies, to my knowledge, didn’t take into account current levels of physical activity. They just made the association between current health statuses and where they end up. This means that someone who is just naturally strong has more protection against these diseases than someone else. This is my theory and I may be off, but it makes sense to me. In order to lift a heavy weight you must have a high tolerance to elevated blood pressures. Normal resting blood pressure is around 120/80. When lifting weights, that pressure can sometimes get to around 200/75. This is dependent on the weight lifted and the intensity of the weight relative to the trainee’s strength level, but that’s a lot either way. The same goes for heart rate. I was once working with a client who was wearing a watch with a heart rate monitor on it. During her squat workout I would glance at the watch to see how much her heart rate had climbed and at one point it had gone up about 45 points in a span of about 15 seconds.

What the studies seem to indicate is that it’s not so much that you do this on a regular basis, but that you have the ability to do it. They only measured strength levels at the beginning, waited a specific amount of time, and checked to see who was alive, who was dead, and who had had any instances of heart disease or stroke. The protective effects lie in the ability, not so much the doing. Now this is not to say that if you belong to the strongest third of the population you can put things on cruise control and ride in the easy lane until you kick the bucket at a robust 112 years old. It doesn’t work that way. Very few people have the ability to maintain a lot of strength and cardiovascular fitness if they all of a sudden stop doing the things that got them strong and fit in the first place. You still need to train and you need to maintain some type of cardiovascular fitness. Because if those things aren’t a big part of your life then what’s the point of living anyway?

Sources:
Association of body size and muscle strength with incidence of coronary heart disease and cerebrovascular diseases: a population-based cohort study of one million Swedish men. Silventoinen K, Magnusson PK, Tynelius P, Batty GD, Rasmussen F. Int J Epidemiol. 2009 Feb;38(1):110-8.

Muscle strength and body size and later cerebrovascular and coronary heart disease. Shrier I. Clin J Sport Med. 2010 Mar;20(2):131.

Physical fitness and 6.5-year mortality in an 85-year-old community-dwelling population. Y. Takata, et al. Arch Gerontol Geriatr. 2011 May 16.

Objectively measured physical capability levels and mortality: systematic review and meta-analysis. Cooper R, Kuh D, Hardy R; Mortality Review Group; FALCon and HALCyon Study Teams. BMJ. 2010 Sep 9;341:c4467.

Association between muscular strength and mortality in men: prospective cohort study. Ruiz, J.R. et al. BMJ 2008;337:a439

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