Why some folks are strong, and how you can be like them

If you start reading this and get bored or confused…. Well just skip to the last paragraph. The rest is just me trying to explain the workings of the neuromuscular system in layman’s terms. I find it quite fascinating.

The human body is an amazing machine. The Lord, in His infinite creative majesty, has wired us in such a way that our bodies will respond and adapt to repetitive stress. One such stressor is resistance training, or simply lifting weights. Whether you are a first time gym goer, or an elite athlete, the goal of any weight lifter is the same: to get stronger. What you may have noticed though, is that some people are just naturally stronger than others. Strength, or the ability of muscles to produce tension and therefore torque around a specific joint, is a product of both hard work and genetics. There are three primary components that account for individual differences in muscular strength: neural efficiency, muscular size, and the distance of the force arm.

For a muscle to contract, an electrical signal must be sent from your brain via a motor neuron to a designated group of muscle fibers. This is called a motor unit. A motor unit is simply an α-motor neuron and all of the corresponding muscle fibers it innervates. The human body is extremely efficient, and therefore it only recruits as many motor units (muscle fibers) as are needed for a given task. For example, if you are going to lift a 5 pounds, your body will only recruit a few motor units, because it will only take that many muscle fibers to lift 5 pounds. It would be a waste of energy to recruit more muscle fibers to lift such a small weight. If, however, you are going to lift 200 pounds, recruiting only 10 motor units will not get the job done. To account for the increase in weight, your body will now recruit a higher number of motor units. The idea here is that as intensity increases, motor recruitment increases. This holds true for an activity such as running as well. To go on a easy jog does not require many motor units (and the ones it does activate are Type 1, but that’s a whole other story). Conversely, going on an all out sprint requires many motor units.

By engaging in high intensity exercises, the human body will adapt and be able to recruit more motor units. This is the primary reason that many sedentary people see large strength gains in the first 12 weeks of weight lifting regimen. Contrary to popular belief, it is not primarily due to your muscles growing, though that does happen. At first, the large gains that you will see from week to week, and even day to day, are due to your body’s increased neural efficiency. For example, lets say you wanted to lift 100 pounds, but you were not strong enough. After a week of training, all of a sudden you can lift it. This is most likely due to your central nervous system being able to send enough of an impulse to recruit the required amount of motor units for the given task. After consistent resistance training, your efficiency gains start to taper off, and you become about as neurally efficient as you will ever be. To continue to gain strength, your body must undergo another adaptation: muscular hypertrophy.

Muscular hypertrophy is simply an increase in the size of a muscle through an increase in size of its component cells. Strength is directly proportional to the cross sectional area of a muscle, therefore the more cross sectional area (the larger the muscle) the more strength. Muscular hypertrophy can be increased through strength training as well as through high intensity interval training (H.I.I.T.). Lower intensity, longer duration aerobic exercises such as jogging generally do not result in very effective tissue hypertrophy. This is why athletes that compete at short, high intensity events (like sprinters) are jacked- their muscles, because of the demands put on them, have adapted and undergone hypertrophy. This is also why athletes that don’t put these kind of demands on their muscles (like marathoners) are tiny- their muscles, in an effort to be more efficient, have not undergone hypertrophy and are therefore small. Like I said, the human body is amazing, and it will adapt to whatever you throw at it. Marathoners don’t want to carry around an extra 20 pounds of muscle for 26 miles, and sprinters need to exert maximal force in minimal time.


Now let’s say there are two individuals who both are equally neurally efficient, and both have the same size muscles. Is it possible for one to be stronger than the other? Well actually, yes, and its all thanks to levers.

Before I start, credit must be given where credit is due, so thanks goes to Dr. Ernie Kirkham, my professor at Texas A&M. His a brilliant man who shared with me the concept of muscular torque and outside resistance. A deeper understanding of this concept can be seen in his notes, found here: http://kirkham.tamu.edu/Muscle%20Torque%20-%20Outside%20Resistance.pdf


Ok, so here is how movement is produced. Your brain sends a signal to your muscle. The muscle, which is connected to a bone by a tendon, then contracts and begins to pull that on that bone. This occurs at joints, which is where a bone meets a bone. Therefore, strength is not linear, but rather angular. This means that when you lift something, the path of that object around the fulcrum (the joint) is not in a straight line- it is curved. This means that muscular strength is actually a measure of the torque that a muscle can exert around a joint. For those of you who don’t remember (or failed) high school physics, torque is just a force exerted (the "effort") multiplied by the distance of that force arm, or DFA (the distance from the green triangle to the red arrow). Therefore, by increasing either the force, or the distance, more torque can be produced. We have already discussed the way that your body can increase force (neural efficiency and hypertrophy). But what about increasing your DFA (just quit being lazy and go look at Kirkham’s notes. I promise it will all make more sense). Well, unfortunately that is something that the good Lord decides for you- there is no changing where the tendon inserts into the bone. Short DRAs (the distance from the downward blue arrow to the green triangle) and long DFAs are what account for the success of many powerlifters and strong fellows. Think about it- that’s why guys with (relatively) short arms tend to be strong. The torque opposing the muscle (DRA x Load) is not as high as someone with longer arms.

 Ok, so I realize that not everyone finds this as fascinating as I do. I hope you can have a deeper appreciation of the human body, and its vast complexity. To me, my study of the body has deepened my faith in the Lord, for how could we ever have simply evolved from some lower life form. No, I am confident that our creative creator knit us and wired us in an amazing way, and that ultimately we are manifestations of His power, splendor, and majesty.

“To the only God, our Savior, through Jesus Christ our Lord, be glory, majesty, dominion, and authority, before all time and now and forever. Amen” -Jude 1:25