Biomarkers Related to the Aging Process

As an individual ages, key biomarkers can be observed that contribute to the degradation and eventual demise of the organism. This degradation or dysfunction starts at an earlier age than overt symptoms are witnessed.  What biomarkers start to degrade first depends on the lifestyle and genetics of the individual.  Nevertheless, a vicious cycle generally will begin, with the various biomarkers and their dysfunction feeding off each other, hastening the organism’s decline.  In the following research, I have chosen three biomarkers that are intimately connected, and in the real world, are surely most common.

                                                                     

 

                                                                                          Sarcopenia

The word “sarcopenia” is derived from two Greek words: the prefix “sark” translates to meat; the suffix “penia” translates to loss. (Bellanti, 2021).   As an individual ages, less hormone secretion is occurring, such as decreased testosterone, growth hormone (GH), insulin-like growth factor (IGF-1), and estrogen. If a practice of strength training is not ongoing as one ages to mitigate this loss by stimulating protein synthesis, the potential for falls and injuries are very common.  In fact, by the time individuals are over the age of 80, up to 50% of those individuals suffer from sarcopenia (Bellanti, 2021). 

Essentially, 2 major things are happening during the process of sarcopenia: there is a loss in muscle quality first, followed by a loss in muscle quantity. 

1. In a loss in muscle quality, a loss in strength can be noticed due to key structural changes, such as a decrease in the number of nerve cells that signal muscles to move (a key factor), defective anabolic signaling of GH, a general decrease in the macronutrient (CHO, fat, and protein) uptake, and a replacement of muscle tissue with fat and fibrous tissue.
2. Then later, in loss of muscle quantity, there is a decrease in both the number and size of muscle fibers.

A byproduct of one’s strength is power, and that power loss or velocity when doing repetitive tasks quickly is lost first to a greater degree than strength.  Power needs an explosive anaerobic system for increased velocity (type II muscle fibers); unfortunately, there is a decrease in the number of working nerve cells that trigger that power, even in the early stages of sarcopenia.

But engaging in sensible practice of strength training regularly, focusing on movements that challenge mobility and functional strength that simulate to some degree activities of daily living (ADL), one can preserve strength, power and muscle mass.  At least twice weekly is the current recommendation, with a 48-hour recuperation between those workouts (CDC, 2023)

                                                                    

 

                                                                             Mitochondrial Dysfunction

So, strength and power are adversely affected, but what about aerobic endurance?  Unfortunately, the aerobic system (types I and IIa muscle fibers) is adversely affected as well due to dysfunctional mitochondria caused by the aging process.  This ultimately also leads to sarcopenia.  In the healthy human, there is a delicate balance between mitochondrial biogenesis that creates new mitochondria, and mitophagy, the selective destruction of old or damaged mitochondria.  However, physical inactivity in the aging individual causes greater mitochondrial mitophagy due to oxidative stress, thus upsetting the delicate homeostatic balance.

Yet even in the elderly, mitochondrial biogenesis can occur via the practice of regular aerobic activity, which activates key signaling pathways (A master regulator of mitochondrial biogenesis is called peroxisome proliferator-activated receptor gamma coactivator 1 alpha). (Bellanti, 2021).   This begins a cascade of reactions leading to the production of proteins needed to synthesize new mitochondria.  Aerobic activity that is at a conversational pace, but the individual is breaking a sweat (zone 2) seems to be the best intensity for mitochondrial biogenesis. (Marshall, 2024).  The current recommendation is getting at least 150 minutes of cardiovascular exercise per week (CDC, 2023).

                                                                              Diastolic Dysfunction

Through the natural process of aging, exacerbated primarily by long standing hypertension, as well as other co-morbidities, the Left Ventricle (LV) of the heart (the chamber that is responsible for delivering blood into systemic circulation) becomes stiff and less compliant.  Essentially, concentric remodeling (scar tissue) occurs in the myocardium, caused by a rise in collagen within the extracellular matrix (Aurigemma, 2006).  As a result, the preload, or amount of blood in the LV chamber prior to LV contraction or systole, is decreased.  As a result of less blood leaving heart into systemic circulation with each heart beat, there is a decreased stroke volume, which translates into a decreased cardiac output (SV x HR/min = CO).  A lower CO translates into a lower VO2max, or how much oxygen one’s working skeletal muscles can extract.  This is known as diastolic dysfunction (DD), and it adversely affects an individual’s VO2max potential.

                              

                                                                How can aerobic exercise mitigate DD?

Regular aerobic activity (not strength training) can reduce the stiffening of the heart muscle and thus improve the filling of the heart during diastole.  In fact, aerobic training for three to four months can significantly improve VO2max, decrease symptoms of shortness of breath with exertion, and improve quality of life measures (Fogoros, 2024).

                                                          What looks good on paper versus the real world

On paper, regular practice of strength training and aerobic activity as one ages can potentially postpone one’s demise for a decade or more.  In reality, not many individuals over the age of 65 are even close to practicing the minimum amount recommended to gain any benefit (CDC, 2023).  In fact, only 8.2% of older adults met the criteria for both aerobic and strength training activity (Kruger, 2007).  More recently (Pahor, 2014), this trend continues.  In the LIFE Study randomized clinical trial, after completing the structured exercise program for sedentary individuals, there was a one year follow up.  The physical activity group arm at this follow up had regressed to where the control group arm was regarding regular exercise, and the other arm of the study, the health education group, had at this point caught up to the physical activity group.

                                                                          How can retention be improved

What is the defining difference between people who continually exercise at a high level, despite orthopedic or other insults to their body, compared with more sedentary individuals?  The short answer is intrinsic motivation.  Individuals who exercise day after day, one decade after another are generally motivated by the enjoyment of running, biking, swimming, walking, playing a sport.  They may find personal growth through the process, as they feel stronger, healthier, more flexible, at ease.  They may find enjoyment in setting personal goals to attain.  They may find a sense of purpose or well-being from their chosen physical activity.  In contrast, with extrinsic motivation, individuals may want to improve solely physical appearance.  They may exercise for some reward, whether money, a vacation, a trophy. 

How can an individual become more intrinsically motivated?  I honestly do not have an answer.  As a strength and conditioning specialist, I can only guide and educate, and from that, motivate them in a way that is more sustainable.  Over the hundreds, perhaps thousands of individuals I have trained throughout my life, I have only worked with a small handful of individuals that were intrinsically motivated.  Those individuals will always exercise, whether I am in the picture or not, whether they are injured or recovering from injury or not.  I believe they appreciate my advice, guidance, creativity and intuition when working with them, but they could continue without me. 

One key element of their workout week that looks different, day in and day out from extrinsically motivated people, is their consistent desire to do other forms of physical activity on the days that I do not see them, for a more comprehensive exercise program.  After all, what I guide them through is but a drop in the bucket, and they realize that. 

Ben Barrett