Longevity & Telomere Length - Endurance Training More Important Than Weights?
Ponce de Leon spent his life searching for the fountain of youth, a mythical body reservoir that offered the gift of youth to anyone who drank or bathed in its waters. Yet, despite his best efforts, the 16th-century explorer never achieved his goal of finding the fountain.
Some 500 years later, man’s quest for life extension and immortality hasn’t faded. If anything, the drive to increase our natural lifespan is greater than ever, in no small part thanks to the “biohacking” craze that’s enveloped the populace as of late.
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And while we look for all sorts of hacks, magic foods, pills, potions, and eating protocols to extend our time on earth, as it turns out the fountain of youth, may have been right under our noses all along in the form of exercise.
Recent studies have noted that we might be able to slow one form of aging -- the kind that occurs within your cells. 
To begin our discussion of how exercise helps combat the effects of aging, let’s start by reviewing the aging process itself.
An Overview of Aging
Whenever we’re presented with the question of “how old are you?”, after replying with some smart-aleck remark, we typically inform the inquisitor of age in relation to how long we’ve been alive.
And, for most people, this will satisfy their curiosity, before they delve into another line of invasive questioning.
But, that’s not the only type of aging that there is. In fact, researchers have established two types of aging: 
- Chronological aging -- the physical amount of time you have been alive (i.e. the amount of time that has passed from your birth to the present)
- Biological aging -- aging that occurs as you a result of accumulate damage to various cells in the body.
Basically, biological age takes into account more factors than just what day you happened to be born.
The discrepancy between the two types of aging is why someone who has lived “a hard life” can look significantly older than they chronologically are, such as the middle-aged rock star who more resembles your great grandpa than a 50-something-year-old.
As you’re probably aware, biohackers, “gurus”, and even the scientific community have become enthralled with slowing the effects of aging in recent years as more and more people seek methods to extend their natural lifespan.
However, while your favorite biohacker may have found “the trick” to extending the lifespan, in all honesty, the scientific community is actually divided on whether or not life extension with these “hacks” and fixes is even possible.
Animal research has shown that various drugs, treatments, diets, genetic manipulations, and phytochemicals may help combat biological aging, thereby increasing the health, wellness, and lifespan of animals. [3,4,5]
However, the same can’t be said of human research.
Factors that affect an individual’s biological age are multifactorial and include:
- Lifestyle (physically active, sedentary, etc.)
- Current and previous illness and disease
- Oxidative stress (as well as your body’s ability to combat it)
- Telomere shortening
The culmination of damage induced by these varying factors leads to the development of pathological conditions and, ultimately, our death.
Further complicating the matter is how much each factor contributes to aging, and which has more of a significant impact.
For instance, does our chronological age have more of an effect than our diet?
Does glycation age us quicker than shortening of telomeres?
Perhaps there’s more variation between individuals based on their way of living, meaning that one cause of aging may have a greater impact in one person than it does in another based on how they have lived their years on earth.
All of this serves to drive home the point that there is still much to be learned regarding aging, as well as how we can best “defend” ourselves from it. Previous attempts to extend the lifespan by mega-dosing antioxidants and vitamins has been proved unsuccessful thus far. 
So, where does that leave us?
Is it possible to naturally extend the human lifespan without getting some type of biological implant, gathering the Infinity Stones, or making a bargain with the Grim Reaper?
Maybe... just... maybe.
As we mentioned above one of the most important markers of biological aging, as well as one that has received increasing interest among researchers, revolves around an intriguing structure known as the telomere.
What Are Telomeres?
Telomeres are protein “endcaps” of our chromosomes, and they’ve been closely linked to our biological age as well as cellular dysfunction.
Every time a cell replicates, telomeres become shorter. Eventually, this shortening leads to senescence which is the inability of a cell to continue replicating.
This shortening of telomeres is due to two primary mechanisms:
- Oxidative stress, and
- End replication problem (the inability of DNA’s inherent replication mechanism to read and copy the ends of linear chromosomes) 
There are also several other things researchers have noted that can lead to a reduction in telomere length.
Factors such as sleep, genetic mutations, exercise (or, rather, lack thereof), and even depression are a link to shortened telomeres, and subsequently aging. But there are even more things to consider such as the circumstances in which you grow up.
For example, one study found that children who lost their fathers had significantly shorter telomeres than children who had not lost their dad. 
Additionally, a 2017 systematic review noted a link between childhoods filled with adverse circumstances (poverty, violence, etc) and shorter telomeres. 
While these findings are certainly intriguing (alarming), it should be noted that researchers are still trying to decipher whether the length of telomeres is a cause of aging, or merely a sign or marker of aging.
Still, taking steps to limit or counteract the various factors that contribute to aging (poor diet, psychological stress, emotional stress, etc), should lead to healthier aging. 
And, as it turns out, researchers have discovered that we may actually be able to combat aging at the cellular level (preventing telomere shortening) through exercise.
Exercise More to Age Less
The link between physical activity and attenuation of telomere shortening in humans dates back to 2010, when a study by Puterman et al. observed that “vigorous physical activity appears to protect those experiencing high stress by buffering its relationship with TL (telomere length).” 
Since that time both animal and human research have continued to strengthen the relationship between increased levels of physical activity and telomere length. Studies in elite athletes and “masters” athletes observed longer telomere lengths than their age-matched non-exercising counterparts. [10,11]
A 2017 study analyzed the data of 5,823 adults who participated in the Center for Disease Control's National Health and Nutrition Examination Survey.  Researchers chose this databank as it is one of the few data pools that includes telomere lengths individuals participating in the survey.
Additionally, the index also includes data for 60 different physical activities the participants might have partaken in over a 30-day timeframe. Researchers used this to estimate individuals levels of exercise.
What they found backed up the findings of previous work -- sedentary folks had the shortest telomeres.
More specifically, sedentary people had 140 base pairs of DNA less at the end of their telomeres than ones who were “highly active.” FYI, to be considered “highly active” men had to jog at least 40 minutes per day, five days per week and women had to jog at least 30 minutes per day, five times per week.
Interestingly, the study found no significant difference in telomere length between those who performed low to moderate amounts of physical activity and the sedentary individuals. And to top it off, it was noted that highly active individuals have a biological aging advantage of seven years (meaning they’re “seven years younger at a cellular level) than moderately active folks, and nine years “younger” (biologically) than sedentary individuals. 
Given this information, it may spur legislators to overhaul the guidelines on the “bare minimum” of exercise and physical activity needed to promote health and wellness.
At the time of this 2017 study, the scientific community still was in the shadows as to the exact mechanism by which exercise preserves telomere length. They suspect it may be tied to oxidative stress and inflammation, but are unsure. This is largely due to the fact that studies until now have been largely based on finding associations and links.
Most recently, a study published in the January 2019 issue of the European Heart Journal, showed that both endurance and interval training exercises reversed the shortening of telomeres.
124 middle-aged, non-smoking, healthy, previously inactive adults, participated in the randomized control trial. Subjects were randomized into one of four groups and told to maintain their lifestyle and diet for the next SIX MONTHS. The four groups an individual could be randomized into included:
- Aerobic endurance training
- High-intensity interval training (HIIT)
For the duration of the study, the control group participated in no exercise program as they were instructed to maintain their current lifestyle and diet. All other groups performed their training sessions three times per week for 26 weeks.
The aerobic endurance training consisted of 45 minutes of walking or running at 60% heart rate reserve.
Participants in the interval training group performed the “4 × 4 method.” which consisted of four high-intensity sprints with a warm-up and a cool-down.
Individuals in the resistance training group performed circuit training using eight machine-based exercises:
- Back extension
- Seated row
- Seated leg curl
- Seated leg extension
- Seated chest press
- Leg press
Additionally, resistance training subjects also had their 20-rep max checked every 6 weeks so that their training weights could be adjusted to ensure progressive overload.
The study showed that 6 months of aerobic endurance training or high-intensity interval training increased telomerase activity two-fold. However, researchers measured no significant change in telomerase activity in the control group or the resistance exercise group.
Researchers aren’t exactly sure why aerobic and high-intensity interval training benefitted telomere length but not resistance-training, but they do theorize:
“Endurance training and RT induce a number of differential haemodynamic, metabolic, and/or neurohumoral responses, both acute and chronic.4,39,40 Precise comparisons between endurance and a resistance exercise protocols are scarce. Our intra-individual comparisons of heart rate during acute AET, intensive IT, and resistance exercise (Supplementary material online, Figure S8) showed that the mean and the maximum heart rate are higher in the endurance training modalities. This may suggest that, compared with resistance exercise, endurance training may induce a higher rate of (laminar) vascular shear stress, which may, e.g. via NO, potentially contribute to the observed cellular effects.17 Endothelial NO synthase and telomerase activity have shown to be linked in a signalling pathway mediating exercise-induced vascular protection.” 
Essentially, the researchers think that the aerobic and high-intensity training stress the cardiovascular system more than this study’s resistance training protocol did, which may have downstream effects on telomere length via interplay with nitric oxide.
The researchers admit that this study does not mean resistance-training is unimportant for health and longevity, as the amount of muscle mass an individual has is one of the biggest markers of longevity. 
What they do suggest is that resistance-training is not a complete replacement for endurance-type exercise (cardio).
This begs the question though, if the study’s participants had done a type of metabolic resistance training, or some other style of higher intensity resistance-training that sufficiently elevated their heart rate and stressed their cardiovascular system, would they then have observed improvements in telomere length with resistance training?
Suffice it to say that more randomized control trials are still needed in the area of exercise and its effects on telomere length to say with certainty what is the best form of exercise for longevity.
But we can be fairly certain of one thing -- more activity is better.
Therefore, it’s likely best to incorporate a mix of both resistance training, aerobic endurance training, and high-intensity interval training if you’re looking to maximize health, longevity, and the length of your telomeres.
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