Muscle is THE Organ For Longevity

When thinking about your health and longevity, the amount of information can be overwhelming about what you need to do. We need to start somewhere, but where? While focusing on one particular organ or system is a little narrow-minded, I do think it is important for you to understand that muscle is the most important organ in your body for maintaining health and improving longevity. If you can build and maintain healthy muscle, a lot of other things will fall into place. In this article I want to discuss the role of muscle tissue, its importance for performance, health, and longevity, how to assess the quality and quantity of your muscle tissue, and what you can do to build and maintain it. 

Structure and Function of Skeletal Muscle 

When discussing muscle tissue in this article, I am talking strictly of skeletal muscle. There are two other types of muscle, cardiac and smooth, but they have different roles. Before discussing the function of skeletal muscle, I want to give you a basic understanding on the structure of skeletal muscle. 

Structure

The basic structure of a muscle consists of muscle fibers, muscle fascicles, and the skeletal muscle itself. Groups of muscle fibers are part of a muscle fascicle, and groups of muscle fascicles make up the skeletal muscle. Each fiber, fascicle, and skeletal muscle is surrounded by a layer of connective tissue that eventually becomes the tendon that attaches muscle to bone. When the muscle contracts, it pulls on the tendon and creates movement at the bone it is attached to. 

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Function

Muscle is a unique tissue that not only plays a role in our movement, but it is also the largest organ in the body. It secretes chemicals that communicate and affect other tissues like adipose, liver, lung, pancreas, bones, brain, and even muscle itself. The chemicals are called myokines which are secreted from muscle fibers. This is somewhat new information and not something I learned until recently. Originally, muscle was thought to be a tissue that only receives messages from the nervous system to contract and create movement. This is true, but does not speak to the complete function of skeletal muscle tissue.  

It is also unique by the fact that we can control its movement and our lifestyle factors can influence that way it looks and functions. You can control exactly how you want it to contract and even how it looks. If we want to lose fat, this is generally a systematic process and we have very little control of exactly where we lost that fat. This is not true with muscle, however. If we want to develop larger biceps we can target that muscle directly through strength training to improve its size and function. Muscle stands out in regards to voluntary control as we do not exert nearly the same amount of control over other organ systems.

Muscle and Its Role in Performance, Metabolic Health, and Longevity

Performance

When I speak of performance, I am not strictly speaking of athletic performance. For 99% of us, athletic performance is strictly for recreation. Performing as a human, however, is something all of us have to do. Performing may look different from person to person but it will involve activities of daily living, work, recreation, household duties, and more. Literally anything that requires us to move can be considered performance.

When it comes to human and athletic performance, muscle is at the foundation for allowing our body to perform the way we want to. If you want to dunk a basketball, drive the golf ball 300 yards, or bend over to pick up your children or grandchildren, muscle is going to dictate how well you do that. No matter what the task is, muscle determines how you interact with your environment and how well you are able to complete the task at hand. 

Metabolic Health

Not only does developing muscle tissue determine how you move and perform, but it plays a vital role in your metabolic health. Like I said earlier, muscle is not a tissue that just creates movement but also an organ that sends and receives chemical signals from other systems in the body. One of those is the endocrine system which functions (among other things) to regulate metabolism. 

Muscle’s role with the endocrine system is to limit excess glucose in the bloodstream by acting as a “glucose sink”. Skeletal muscle is essential for glucose clearance and responsible for up to 80% of glucose uptake after a meal. This is mediated by insulin, which is released by the pancreas when your body senses a rise in glucose levels. 

In a healthy system, glucose enters the body through food or beverage as carbohydrate and is broken down to be spread throughout the body via blood. Your body senses this rise of glucose and signals the pancreas to secrete insulin which stimulates the absorption of glucose into muscle tissue. This is important for both short-term performance and long-term health. In the short-term, the ability of the muscle tissue to absorb glucose provides it with energy to contract. Athletes are up to 25% more effective at disposing glucose into the muscle than non-athletes, presumably due to healthier and a larger quantity of muscle tissue.

In regards to long-term health, the ability of muscles to dispose of glucose helps prevent insulin resistance, which can ultimately lead to metabolic syndrome and Type 2 Diabetes. When you become insulin resistant, your body stops reacting to insulin which limits the amount of glucose uptake into your muscle tissues. This causes elevated glucose levels in the bloodstream leading to Type 2 Diabetes. Developing metabolic disease, insulin resistance, and/or Type 2 Diabetes increases your risk for just about every disease out there including cancer, cardiovascular disease, stroke, and Alzheimer’s disease.

Excess consumption certainly plays a role in developing diabetes, but you can be a slim individual who still develops diabetes or metabolic syndrome. The problem there is that you are under-muscled and do not have enough muscle tissue to absorb glucose. In either case, having ample amounts of quality muscle will help keep you metabolically healthy. 

Longevity

I briefly spoke to muscle’s role in maintaining long-term health when discussing muscle’s involvement in preserving metabolic health, but I want to go even further into how having sufficient amounts of quality muscle tissue supports long-term health. This section will discuss what we primarily think of when talking about the function of muscle: movement. 

Muscle makes you move and movement is life. Whether it’s swimming, biking, rowing, throwing, kicking, or running away from zombies, muscle is the driving force behind creating all of those movements. Even when it comes to endurance exercise, muscle is instrumental in your ability to perform. Your VO2 max and cardiorespiratory fitness are associated with long-term health, but without quality muscle you won’t be able to perform those movements well for a long time. 

You can also think of muscle as protective armor to your bones and joints. One of the leading risks of injury as you age is falling. This is a SIGNIFICANT event that will usually alter the course of your life for the worse. Falls are the leading cause of accidental deaths for individuals 65 and older. Healthy and strong muscles can prevent these falls by maintaining the ability to react and catch yourself before you hit the ground. Having quality muscle will also improve the health and strength of your bones so if you do fall you will be more resilient to injury. 

I have seen first hand how having healthy muscle tissue can protect you from seriously injuring yourself if you fall. One year, my family took a family vacation to Jamaica. We were out on the pool deck where the staff had just rinsed down the walkways to clean them off. My dad rounded a corner too quickly and his feet slipped out from under him and landed directly on his shoulder. He hit the pavement HARD. This was in 2018 so my dad would have been 55 years old at the time. Fortunately he didn’t have any injuries. He has done some sort of strength training religiously 2-3x per week since college. Because of that he had the “armor” he needed to come away from that fall unscathed. As a PT, I have seen plenty of people who experienced the same event but came away with a torn rotator cuff or proximal humerus fracture which both most likely require surgery. Because he had been resistance training for so long, he had enough strength in his muscle and bones to prevent a catastrophic injury.  

How to Build Quality Muscle

Building quality muscle comes down to two things: consistent and progressive resistance training and nutrition. Because there are many nuances to resistance training, I want to discuss foundational principles to building muscle in this article. The nutrition aspect to building muscle is a little more straightforward so I will be able to cover that in more detail.

Resistance Training

Resistance training involves moving against or holding an external load. There are countless modalities to accomplish this: free weights, kettlebells, resistance bands, and machines just to name a few. I consider myself exercise agnostic, meaning I do not care what type of resistance training you do. I just want to present the principles so you can choose the exercises that you enjoy and can perform safely so you can be consistent with a routine. 

The first thing you’ll want to decide is how many days per week you want to dedicate to resistance training. You’ll need to do at least two days a week. You can certainly do more but two is the absolute minimum. I would also recommend at least one day off in between strength days to allow for recovery. This doesn’t mean complete rest, but it does mean choosing something that is not resistance training. 

Next, you need to structure your workouts. In order for your training to be effective, you need to perform 10-12 working sets per week for each muscle or muscle group. Your working sets should be 8-12 reps with the last two reps making you feel fatigued. You don’t need to train until failure, but you do need to fatigue the muscles a little bit. 

This may seem like a lot, but if you are doing a lot of compound movements you will be hitting multiple muscle groups with each exercise. A helpful way to improve your efficiency in the gym is to use supersets. Basically, you do an exercise for one muscle group and then another exercise for a different muscle group. You cycle between the two and then move to the next superset. (Click this link to download workout templates for 2, 3, or 4 days a week of training).  

Nutrition

When it comes to building muscle through nutrition, there is really only one thing you need to focus on: dietary protein. In order to stimulate muscle protein synthesis, you need protein to allow that to happen. We can’t produce it within our body so we have to get it from our diet. 

Where you get your protein from is your choice. It doesn’t matter (to an extent) where you get your protein, but what IS important is the amount of protein you are getting per day. You need to consume 1.6 - 2.2 grams per kilogram of desired body weight per day. Let’s say your goal is to weigh 100 kg (220 lb). You would need to consume 160 - 220 grams of protein per day. 

This is hard. I have to be very conscious about what I eat in order to get to that daily goal. There was a time where I had trouble gaining muscle but I couldn’t figure out why. I was training but I wasn’t getting the results I wanted. For starters, I didn’t know how much protein I actually needed per day. Once I knew the number I needed I started to track my protein intake and learned that I was not eating nearly enough. Once I learned how much I needed and started tracking my intake, I was getting the results I wanted. 

Protein isn’t the only macronutrient you get from our diet. You also consume fats and carbohydrates which also can play a role in muscle growth. Protein is the priority, but you can’t ignore fat and carbohydrates. For carbohydrates, you want to consume 3 - 7 g/kg/day. For fats you want to consume 1 g/kg/day.

Supplementation 

Besides dietary protein, there are supplements that you can take to help improve muscle growth. What I’m about to present is certainly not an exhaustive list, but I want to give you supplements that are safe, effective, affordable, and have research to back their use.

Creatine

Creatine is a nitrogenous organic acid involved in energy transfer in the form of phosphocreatine and then excreted by the kidneys in the form of creatinine. The bulk of creatine is stored in muscle tissue. Creatine is found in food from meat sources but is also produced in the kidney and liver. 

There is ample research to support creatine’s role in improving training, performance, and lean mass gains. Supplementation increases intramuscular creatine concentrations which improve adaptations to intense exercise. It also boosts the expression of proteins and growth factors that support muscle remodeling and rebuilding. It also helps with glycogen uptake in the muscle, which we discussed the importance of earlier. There is also research to support its role in enhancing recovery, injury prevention, thermoregulation, and neuroprotection. 

To supplement with creatine, anywhere between 5-15 grams per day has been shown to be beneficial. The amount you take will depend on your size and activity level. I recommend starting with 5 grams per day to make sure you can tolerate it. I have found for me that 10 grams upsets my stomach but if I keep it between 5-7 grams then I am okay. 

Protein Shakes

If you have a hard time meeting your daily protein requirements strictly from your diet, a supplemental protein shake is a great way to boost your daily intake. There are numerous types of protein shake available ranging from whey protein to pea protein. I prefer whey protein powder as it has higher leucine content which is essential for muscle protein synthesis. The choice is entirely up to you, though.

When choosing a supplemental protein shake or powder, look for one that has at least 3 grams of leucine or 10 grams of essential amino acids. You also want to purchase one that has at least 20 grams of protein per serving. I usually mix my whey protein powder with milk which adds more protein to the shake. I also add creatine that way I get both creatine and protein in one drink. 

Caffeine

Caffeine doesn’t have quite as much support in its role in improving muscle hypertrophy as creatine and protein supplementation, but it has been shown to be beneficial. Research shows the most gains are seen at 5-6 mg/kg per day, but this is at the upper limit of tolerable ranges for most people. 

People also respond to caffeine differently so if you are new to caffeine make sure you start at a lower dose (2 mg/kg) and work your way up. You also want to consider the timing of your caffeine consumption and the fact that caffeine is found in other drinks besides coffee. 

Try to limit caffeine consumption to the morning as it can stay in your system and affect your sleep later that day. Many pre workout drinks contain caffeine so try not to drink them before an afternoon workout. 

To help you understand how much caffeine to consume in a day, I will use myself as an example. I weigh ~175 pounds which is ~80 kg. A typical 8 oz cup of coffee contains 95 mg of caffeine. I drink about 24 oz of coffee each morning which is 285 mg of caffeine. That puts me at 3.5 mg/kg each day. 24 oz is about as much coffee as I can tolerate before I get anxious and jittery. I also limit my caffeine intake to strictly in the morning so it doesn’t affect my sleep. You don’t have to follow my exact routine but you can use it as a guideline to help you use caffeine more effectively. 

Assessing Muscle Quality and Quantity

By now you might be wondering how do I know if I have enough muscle? There are several ways to measure muscle quality and quantity: body mass index (BMI), DEXA scan, functional movement testing, strength testing. 

Body Mass Index (BMI)

Your body mass index (BMI) is a quick and simple way to get a rough estimate of what your body fat percentage is. This is by no means perfect but it can get you in a ballpark range. There are many BMI calculators that will do the calculation for you. Remember, the percentage that you calculate is an estimate of your body fat percentage. The remaining weight is lean tissues that are not only muscle but bone and organs as well. If you already know your BMI, this chart below will help classify yourself based on your score.

DEXA Scan 

A Dual-Energy X-Ray Absorption (DEXA) scan uses low- and high-energy x-ray beams through the body and measures bone, lean mass, and fat mass status within the body. You lie on a table while an arm scans you for about twenty minutes and shows your body composition. 

DEXA scans are able to provide much more objective and accurate information regarding your body composition. They are very versatile as they are able to provide information about your bone health and lean mass status. A DEXA won’t give you an exact measurement of how much muscle you have in your body since it is assessing other lean tissues. It can give you an idea, however, if you are at risk of developing osteoporosis and/or sarcopenia. 

DEXA scans can cost between $150-$300 and you are exposed to very small amounts of radiation. It is the equivalent to one x-ray image or spending five hours outdoors. If you really want to get a more objective measurement of body composition, then the DEXA scan is the way to go. I don’t think it’s necessary for everyone, but it does provide valuable data. Despite the cost and radiation exposure, it can be worth getting an accurate body composition. 

Functional Movement Testing

The quantity of your muscle tissue is not the only important factor when it comes to determining if you have a healthy muscular system. The quality of your muscle tissue is important as well. For me, I like to assess the quality of your muscle through functional movement patterns and strength testing. 

The functional movement patterns I like to test include squat, forward bend, forward lunge, lateral lunge, single leg squat, overhead reach, and a push/pull movement for your arms. This assessment tells me HOW you move. If you have great muscle mass but your movement patterns are suspect, then you have things you can improve upon. 

Not only do I look at how you move, I want to know how you feel during that movement. Do you feel tight in your groin with a lateral lunge? That is something you can work on. Although strength is a huge component of the function of muscle, you also need to be able to move well through large ranges of motion aka mobility.

Another movement assessment that is a great test for strength and mobility is the stand-sit-rise test. This test involves you starting in a standing position, sitting down on the floor, and then returning to a standing position. You are scored based on how you are able to perform the movement. If you are able to do the entire movement under control without using your arms for assistance you receive a score of 10. You are docked one point for every extra point of contact that assists you in the movement. 

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Strength Testing

How strong you are also gives you a lot of information on the quality of your muscle tissue. Like I said before, it’s not only about being strong. You need to be mobile as well. But, strength is a great proxy to how your muscle functions and your overall health status. 

There are countless ways to test your strength. Traditionally, a one rep maximum (1RM) lift has been an objective way to assess your strength. This is a totally acceptable way but not appropriate for all populations. Your goals, activity level, and comfort with weightlifting will all determine what kind of strength testing to use. 

For testing general strength in the clinic I typically use grip strength. It is quick, objective, and gives you a lot of information into overall strength. Grip strength has been associated with walking speed, functional capacity, and future health outcomes. The stronger your grip strength, the healthier you and your muscular system are as a whole.

Your goals will also determine how to test your strength. Maybe you want to be able to dunk a basketball. If that’s the case, you will likely need to squat a deadlift a certain percentage greater than your body weight. 

For a more practical example, however, let’s say you are now forty years old and want to be able to pick up your grandkids when you are 75 years old. That means you will need to be able to squat down and pick up 25-35 pounds. You lose ~7% of your muscle mass per decade, although this can be mitigated through progressive resistance training. If you want to be able to pick up 35 pounds when you’re age 75 that means you need to be able to squat down and pick up 50-55 pounds at the age of forty. If you can, great! Keep working to lift more weight. If you can’t, that’s okay. Now you know what you need to do to get better. 

Your muscle tissue is an amazing organ. It is one of the few organs we have voluntary control over. It is the largest organ in the body and plays an integral role in performance, metabolic health, and longevity. Resistance training and proper nutrition are the two main avenues in building and maintaining a healthy amount of muscle tissue. If you want to live a long and healthy life, your top priority should be developing strong and mobile muscle tissue that will allow you to move efficiently and protect you against the diseases of aging.