The Mechanics of Strength and Fitness (Part I)

This is a two-part article that first looks at the science and mechanics behind the terms 'Strength' and 'Fitness', and then explains a very important phenomenon, and that is why Strength is such an important attribute in everyone's lives. (Link to Part II is at the bottom of this article.)

As the common parkour saying goes, "Be Strong to be Useful".
But how many people are indeed Strong enough, let alone Useful? We're not just talking about parkour practitioners here, or even athletes from other sporting disciplines. We're looking at this from the perspective of the general, sedentary, desk-bound population. Yet the word 'Fitness' seems to be on everyone's mind, and people clamor to get from one new fad to the next, joining countless 'fitness' classes and activities, in the hopes they will get fit and in-shape, not understanding the crucial role Strength plays in their goal of getting fit, and how they are actually far from getting truly fit.

Strength is a very important attribute that humans cannot ever have enough of. But sadly, most humans are unaware of how to obtain it, and many are against obtaining it even after being shown how, but will still chase endlessly after that elusive yet enigmatic goal, Fitness.
Let me explain to you in this two-part article why exactly Strength is so important.

It all started with a huge debate I once had with my buddy, The Architect, over the definition of the term Fitness, and later on the utility of Strength. He was heavily into Crossfit at the time, and argued that Strength was not essential for most people (especially populations like housewives and desk-jockeys), and that Crossfit style training was more effective, because unlike Strength Training/Heavy Barbell Work which only made people strong which they didn't really need in their day-to-day activities, Crossfit made people 'Fit'. I asked him to define what he meant by Fit, and how exactly Crossfit made people Fit. He had no answer, but kept repeating that Crossfit made people Fit, and because Crossfit made people Fit, it was more useful for most people in their day to day lives, even asking why people need to be that strong in the first place. By saying this he raised a very interesting point, and this was the basis of my deciding to explore and explain the importance of Strength, and writing this article.

Let's just step back here for a moment, and review the definitions of the terms 'Fit', and 'Strong'.
What do we really mean, when we say 'Fit'? Is it the ability to torture oneself the most with the maximum exercise one can handle? Is it the ability to feel fatigued to the point of collapsing at the end of every training session? No! Fitness does not mean one can do any activity that one enjoys and that makes one exhausted. Fitness has a proper scientific basis. Many times, if properly done, any activity that aims to make you truly fit won't even exhaust you that much, because it is efficient at using the body's resources. At the same time, exhausting yourself through excessive exercise day in and day out poses a very harmful degenerative threat to the body, which we call over-training, which in turn leads to catabolism, or the break-down and loss of healthy muscle.
In the Exercise Science community, the accepted scientific definition of Fitness is that the term 'Fitness' doesn't mean anything in or by itself, but it comprises of five constituent elements - Strength, Cardio-respiratory Stamina, Flexibility, Muscular Endurance, and Body Composition - in that order. If you have all of these attributes in the correct order and the correct proportions, you are relatively Fit. You can always increase the proportion of each attribute you posses, and get Fitter. But at the same time, it is easy to train one or two attributes more than the others, and in the wrong order, and throw your proportions out of whack, which will not make you fitter, but will make you imbalanced.
So by that very definition of Fitness, unless somebody got Stronger, he was not getting correspondingly Fitter, because his proportions were still out of whack if he was solely developing the other attributes. Now even the Architect agreed that Crossfit doesn't really make people Stronger (according to him at least not in a very efficient manner, or to the levels that we hold as acceptable base Strength levels that should be displayed by every human being; but according to scientific facts of exercise science, Crossfit cannot make anyone stronger at all, period (more on it below)), but then he continued to state that Crossfit would make one Fitter. That in itself is a logical contradiction. But we'll come back to that later.

Now, defining Strength. Strength is the ability of your muscles to produce force. As simple as that. Strength is therefore, like Fitness, a very relative term. The more force your muscles can produce, the stronger those muscles are. In itself, Strength doesn't mean anything.
Let's look at why this is in a bit more detail.

We know from the laws of Biology that muscles are the link between two bones connected by a joint that Displace one bone relative to the other. That is, muscular movement causes displacement. We know from the laws of Physics, that in order to displace any object, you need Force. We also know from the laws of Physics and Inertia, that the greater the Mass of an object, the more the force that is required to displace it.
When you are just moving your own limbs relative to your body, the mass of your limbs is relatively a lot less, and hence do not require much force to displace them. When you use your limbs as a lever to displace the rest of your body, however, when you walk for instance, the force required to displace it increases, because the mass of your body is relatively greater.
Now, we also know that force equals mass into acceleration, so when you use your same limbs as the same lever to displace your same body, but you increase the rate of displacement relative to time, meaning you try to run, you are increasing the Acceleration keeping mass constant. Which means you need to increase the force applied to displace the same body. Or when you keep the mass of the body the same, but use your limbs to jump, still increasing acceleration (because now it has to counter the downward acting force of gravity), you still need to increase the force applied. If you want to run faster, or jump higher, you need to increase acceleration (mass will still remain constant, you can't really fluctuate your bodyweight in the middle of a run or jump), which means you will need to increase the amount of force applied even further.
Applying this concept a different way - When you interact with any external object, you are using your limbs as levers to apply force to that object in order to displace it. Once again, the more the mass of the object, the more inertia it has, and the more force required to displace it. And the faster you wish to displace it, again the more force required to accomplish it.

So this tells us that the magnitude of maximal force your muscles are capable of producing at any given point of time is the relative strength of those muscles at that given point of time. And in order to get Stronger, you need to increase the magnitude of maximal force those muscles are capable of producing.

We hope you have adequately understood by now what Strength means in scientific terms. Now, let's wrap up this little Physics 101 lesson, and for the sake of consistency, talk about the other attributes of Fitness.

Cardio-respiratory Stamina, in very simple terms, is the ability of your heart to pump a given volume of blood (oxygen) in a given amount of time, especially during a period of physical exertion. The more oxygen your heart is able to supply to your body during a given amount of time, the more stamina you have. Or conversely, if your heart can continue pumping the same amount of blood (oxygen) for a sustained duration of time, once again the more stamina you have. Once again, Stamina is also a relative term, and does not mean anything in itself.

Flexibility is the ability of the human body to maintain full and complete range of motion around joints. This ability depends on the extensibility and elasticity of skeletal muscle. Flexibility is a large and complex topic in itself, and we won't go into the details here. If you wish to read up more on this topic and about the different types of flexibility, we recommend this excellent article.

Muscular Endurance is the ability of a given muscle to contract and produce force (usually the same amount of force) repeatedly over a sustained duration of time. The more duration of time you can sustain the repeated force production, the more muscle endurance you have.
And if you look at it objectively, most everything that is peddled in the world in the name of Fitness is nothing but Muscle-Endurance work, as it entails you doing hundreds of repetitions of the same thing, with negligible forces being produced in the movements. Maximal Force and Maximal Duration are inversely proportional. Which means you can never train for both at the same time. Which means if you keep repeatedly producing force in an action for a sustained duration, the magnitude of force being produced will be very less, and hence, no higher strength will be required to perform said movement, nor will it develop any higher strength.
Also, you may see the futility of solely learning to repeatedly produce less amounts of force for sustained durations, because it does not mimic most real-life actions a lot. You may need to pick up a heavy object off the floor once, walk with it a few feet, and then place it somewhere else. This will need your lifting muscles to produce force equivalent to the mass of the heavy object in order to lift it off the floor just once, but this force will be comparatively higher. But you're not likely to continue picking it up, putting it down, and repeating the process for tens or hundreds of repetitions at a stretch, are you?

Lastly we have Body Composition, which is, roughly speaking, the ratio of muscle-to-fat in your body. But since that doesn't pertain to our discussion, and it is mostly concerned with nutrition rather than exercise, we won't go into it in this article.

Now there's another important biological concept that you need to understand. All Tissues in the body respond and adapt to Stress. If you apply stress to a tissue in carefully measured doses, it will first degenerate from the immediate stress, then it will heal itself through proper diet, rest and recovery, and 'supercompensate', and come back a little better than it was before the stress was applied to it. This is the same of the tissues present in your muscles, which apply in Strength, Flexibility, and Endurance, or of the tissues present in your heart and cardiovascular system, which apply in Stamina, or any other kind of tissue in the body really, like skin, bones, internal organs, etc.
When you stress the muscle tissues by forcing them to apply force against a magnitude of mass which is equivalent to your muscles' maximal force output, it causes Stress on those tissues, which causes an adaptive response, which then cause the muscle tissues to recover and regenerate, and come back with the ability to produce an even slightly higher magnitude of maximal force than before. This is what makes you Stronger than before.
When you apply stress to your cardiovascular system by forcing it to pump a certain volume of blood (oxygen) during an intense activity, after it has been provided adequate rest and nutrition, the tissues in this system will regenerate with the ability to pump just a little bit more blood (oxygen) during the same intense activity than before. This improves your level of Stamina, and ensures you don't run out of breath as fast as you did the previous time you did the exact same magnitude of the activity.
When you stress the muscle tissues to continue producing force for a certain duration (let's say this is your maximum limit beyond which you achieve failure to produce any more force to sustain the activity), then after rest and recovery the muscle tissues will regenerate with the ability to sustain production of that force for a slightly longer duration than the previous point of failure. This is what increases your level of Endurance. (Training to failure is not the safest or most effective way of improving Muscular Endurance, but the actual approach to this training is beyond the scope of this article. The 'training to failure' bit has just been added to demonstrate an example of the adaptation of tissues to stress.)

The key thing to take away from here is that in order to get stronger, you always need to force the muscle tissues to respond to an increasing amount of stress, which means increasing the magnitude of the mass that provides resistance to your muscle tissues to produce force against. If the mass remains constant, you will remain at the same level of strength, and will never increase your strength.
This is the reason why proper Strength Training with barbells and a model based on constantly increasing resistance is the most optimal way to increase Strength, and why Crossfit will NEVER help anyone to increase their Strength, because all their models are based on sustaining physical activity for extended periods of time rather than increasing mass/resistance. Which is why Crossfit may be good for increasing Muscular Endurance and Cardiovascular Stamina, but never Strength. And for that reason, Crossfit will never make you really fit, because it neglects to address the prime component of Fitness, but over-develops Muscle-Endurance, which is the least important, and sometimes counter-productive component of Fitness, thereby causing an imbalance.

Yet sadly, the market is overflowing with tons of programs that claim to make you 'fit' merely by making you dance, or do Yoga, or kick-box, or lie on your belly on a giant ball and flap your arms; or, in many cases, even lift weights, but for a sustained duration. None of which contribute to true fitness, because they mostly focus on Muscle Endurance, or in some cases help build Flexibility or Cardio-respiratory Stamina. But none help build any Strength. And none focus on more than one (of the five) attribute of Fitness, therefore being very incomplete activities for building Fitness.

To read up further on why Strength is such an important attribute of Fitness and general athletic performance, read Part II of the article.