Health Hub
Survival of the Fittest: The Strong Survive!
The upper most graph was available when I did my weeklong training in Age Management Medicine in 2013. This impacted my decision to train the rest of my life for fitness. Since that time, two more studies have recently come out that demonstrate very similar outcomes. The conclusions of these graphs don’t require an MD or PHD degree. They compared the fitness of individuals at times zero on the horizontal axis. They then followed the individuals for mortality shown on the vertical axis over a period of time demonstrated in years on the horizontal axis. All graphs revealed a similar pattern. First of all, those in the most fit group had remarkably lower mortality than those in the least fit group. Note that mortality for the fittest individuals is generally less than 5% in 10 years. Note that mortality for the least fit individuals is always greater than 20% in 10 years. This can serve as motivation to move from any fitness group to the next most fit group. But the greatest motivation should lie in the recognition that if you are in the least fit group, the largest reduction in mortality occurs with the smallest increase in fitness. In other words, if you can move from the least fit group to the second least fit group there is an approximate 50% reduction in risk of mortality. Fitness can only be achieved through physical training, not diet, drugs, meditation, beating
drums or incantations. Sad story, but that’s how it is. If you want to figure out how to have a lower chance of dying, less chance of having cancer or becoming a cardiac cripple through some sort of event, or worse yet having a severe neurological event that renders you no longer yourself, I can help you figure out your best strategy for moving up the graph, so to speak.
Looking at the three graphs above, each one depicts the reduced risk of an outcome based on adherence to both Resistance training and Aerobic guidelines, or each one alone. The outcome is compared to the referenced non-exercisers. It’s easy to see that exercise is important as outcome (A) mortality, outcome (B) cardiovascular mortality, and outcome (C) cancer mortality were all reduced in all three exercise categories compared to non-exercisers. But since we’re talking about Resistance training here note how Strength training tended to outperform aerobic only. Muscle mass appears to be extremely important in reducing risk of cancer.
Simple either/or: Muscle Strengthening Exercise or Not?
The information above comes from a meta-analysis of a bunch of different studies that were able to determine whether or not the participants followed in the study for the outcomes above exercised or didn’t with regards to muscle strengthening activities. If you look at each graph, the outcome is bold at the top. Crossing the X axis is a vertical line representing 1.0 which would be the reference rate for the outcome in those that did not do muscle strengthening activities. Each graph has several different studies that were able to answer this question. Notice that in every study for every outcome, those that did strength training had a risk of the outcome less than that of those that did not.
The Diamond in each graph represents the relative risk of the outcome in strength trainers across all the studies combined.
All cause mortality was reduced by 15%. Cardiovascular disease was reduced by 17%. Total cancer was reduced by 12%. Diabetes was reduced by 17%.
In this narrative literature review below they summarized the existing evidence from large prospective cohort studies on muscle strengthening activities and risk of major chronic diseases and mortality in adults generally free of major Non-Communicable Diseases at baseline. In comparing the highest quartile of users of strength training exercise to the lowest quartile, where the lowest quartile represents the Hazard Ratio of one for the given outcome, nearly all studies revealed that exercise results in reduced risk. Though not represented in this chart, they report that epidemiologic evidence suggests that engagement in muscle-strengthening activities over 1–2 sessions (or approximately 60–150 min) per week was associated with reduced risk of cardiovascular disease (seven studies; approximately 20%– 25% reduction), type 2 diabetes (four studies; approximately 30% reduction), cancer mortality (four studies; approximately 15%–20% reduction) as well as all-cause mortality (six studies; approximately 20%-25% reduction).
When they looked at extremely high volume of resistance exercise, there may be a little bit of good news for some of you. There does appear to be an upper limit of benefit. In fact, some outcomes looked to fair poorly if existing strength training regimens exceeded 2.5 hours per week. Note that the J shaped curve did not exist for type II diabetes risk, outlining the importance of muscle mass and improving insulin sensitivity. It may be that placing excessive demand on the cardiovascular system with a ridiculous amount of muscle mass might lead to unnecessary strain, overtraining could be related to excessive cortisol, etc. Note that cancer mortality doesn’t really behave much with regards to a decline in efficacy with increased use. If there is some risk to lifting too many weights and getting too muscular, it is likely tied to cardiovascular disease outcomes. My general guideline for myself is about three sessions a week 30 to 40 minutes each of moderately heavy weight resistance training (when not injured). I definitely exceeded the 2.5 hours for much of my training career.
This meta-analysis was not yet available for free public access but the abstract explains the gist of this important and redundant information. Resistance training decreases mortality. In this particular study, they did a meta-analysis of studies that reported resistance training exposure and either all cause mortality, cardiovascular disease specific mortality and or cancer specific mortality as outcomes. Comparing resistance trainers to no resistance training there was a 15% reduction in all cause mortality, a 19% reduction in cardiovascular disease mortality and a 14% reduction in cancer disease mortality, all of which met statistical significance. Maximum risk reduction for all cause mortality was 27% observed around 60 minutes per week of resistance training. They once again demonstrated a reduction in the benefit of resistance training and all cause mortality with excessive implementation.
In the studies reviewed thus far, it is clear that those that reported resistance training live longer, get less cardiovascular disease and less cancer and clearly have less risk of diabetes. But so far, all we’ve looked at is reported training volume. Kind of like nutritional science, there’s room for recollection bias and outright lying. But it’s pretty hard to fake strength, so let’s take a look at some studies that would presume to imply a commitment to remaining strong, because the participants demonstrated strength as the variable and then they looked at similar outcomes. This handgrip study that recently published demonstrated findings in the table and graphs above. They utilized grip strength measured by a device that I have in my clinic, as this is a biomarker of function that I utilize in my clinical practice. Incidentally, in my currently weakened postoperative state, not upper body resistance training for almost a year now, I was able to maintain a grip strength that was almost off the chart for this study (weakest quartile <28.5 kg, 28.5–32.7 kg, 32.8–37.2 kg, and ≥37.3 kg strongest quartile for male). My current right hand grip strength (the non-injured side) is 120 pounds or 55 kg. At a current weight of 150 pounds, it is remarkable that my grip strength in a non-trained state was far above their highest quartile strength range. Lifelong training apparently pays off!
Look at the table from the grip strength study, above. Examine the grip strength quartiles, top left. Note that the strongest persons are in quartile four (Q4) and they represent the reference risk of death as 1 to the right, as this table examines mortality rates as Hazard Ratios (HR). Note that being in quartile one (Q1), the weakest quartile, or quartile two (Q2), the second weakest, results in statistically significant increased risk of death, approximately two times greater in the weakest quartile (HR of 2.06) and 1 1/2 times greater in the second weakest quartile (HR of 1.45). The second strongest quartile (Q2) had a tendency towards increased mortality compared to the strongest, but it didn’t meet statistical significance.
Let’s look at the graphic representation below that now. Look at the graph (A) examining all cause mortality. Let’s first look at the male patient breakdown which shows that it is extremely important to maintain strength to prevent death. Looking at females, they appear to be less affected by weakness as a risk marker for mortality until they become excessively week (Q1). Note that the pattern of decreased mortality holds across all quartiles whether you are younger or older than age 65. There appears to be a trend towards decreased mortality with increasing Grip strength in the healthy without chronic disease, but it is especially important to maintain physical strength if you have multiple comorbidities. Weakened and sick has a three times greater mortality (HR 2.94) than sick with strength.
Grip strength is an easily obtained biomarker, and has been validated to be a good surrogate marker for overall body strength and function. But let’s take a look at larger muscle group strength analysis and correlations to health outcomes in the study below.
In this study, almost 9000 adult men age 20 to 80 were followed for an average of 18.9 years. They were placed in three categories based on muscular strength, quantified by one rep max for leg press and bench press. They were also evaluated for cardiovascular fitness by maximal exercise test on a treadmill. The group rankings were age specific, dividing the participants according to strength into 1/3’s based on comparison to those in their age range.
For the three models in the table, Model 1 is age adjusted only, Model 2 is adjusted for age and other confounding variables like smoking, alcohol, BMI, medical conditions and family history. Model 3 takes into account the confounding variables of Model 2 and then additionally rules out contribution from Fitness by taking that measured variable into account.
Just looking at the data corrected for age, we see that the weakest third is the reference range with a hazard ratio of 1. We see that there are statistically significant reductions in risk of all cause mortality, cardiovascular disease and cancer in the middle third and strongest strength groups. All cause mortality is statistically significantly reduced in all three models. When looking at cardiovascular disease mortality, examining the contribution of other confounding variables lessens the trend in death reduction and it becomes statistically insignificant, further worsened when corresponding cardio respiratory fitness is examined as a contributing factor to their reduction in mortality. But note that the effect of improved strength on cancer mortality remains statistically significant, across all three models and the slight trend towards less affect with regards to Resistance training in Models 2 and 3 is diminished. Strength clearly seems to be tied to a reduction in cancer risk, and it is likely somehow promoted by the actual muscle mass itself, in my opinion.
Some additional information provided by the BMJ study is contained in the graphic representations above. On the left side top graph we see all cause mortality, and the trend for strength to statistically reduce death in an age adjusted analysis persisted and was quite linear across the three strength groups, when examining people in the ideal BMI range. Looking at people with a body mass index greater than 25, we see there is some loss of protection going from the middle third strength group to the upper third strength group, and I would have to assume that that is due at least in part to the negative affects of obesity, likely present in the stronger population to a higher degree. Heavy people tend to have better maintenance of strength. To some extent this could also be attributable to the overtraining scenarios identified in previous meta-analysis.
Cancer mortality in the graph below that appears to follow the same trend, with a clear linear affect in those at ideal body weight, and a diminished reduction in cancer risk in the strongest group compared to the middle group, though here we see they are closer to equal, recognizing that it is likely cardiovascular mortality influencing the worsening of all cause mortality the most. And if previous thoughts are correct, Obesity definitely drives cancer.
Moving to the graphs on the right side, where we are looking at all cause mortality based on age greater than or less than 60 years. The effects of mortality become more pronounced in this graph as the likelihood of mortality increases with advancing age. This is seen in all cause and cancer analysis.
The purpose of this very long read and all of the graphic representation provided along with the explanation is to hopefully create motivation in you, to understand that you simply must do resistance training. It is foolish to not lift weights or do some sort of strenuous muscular activity that involves allworking body parts at least 1 to 2 times per week. I hope that I have accomplished my goal of motivation!
Thank you, Dr. Bob
