Louis-Alexis Gratton |
A Brief Overview of Strength Physiology
Maximal strength development is pretty straightforward. Most people know that to get stronger, you need to gain muscle and lift heavy weights, and that is really the gist of it. However, for those of you interested in the physiological underpinnings of strength training, or, to put it more simply, in understanding what are the changes happening within our body that make us stronger when we lift weights, we’ll offer a brief overview here. Note that this article is intended to be used as a quick reference guide in regards to the mechanisms of strength development, as we won’t get into a detailed analysis, which would make for quite a lengthy discussion.
Strength adaptations can be regrouped in two categories: morphological adaptations and neurological adaptations. Morphological adaptations relate to structural changes in the body, while neurological adaptations are related to increased efficiency of the neuromuscular system. Both are important, but neurological adaptations slightly more so, as they are the main reason why, for example, a 200lbs powerlifter might be able to lift more than a 250lbs bodybuilder.
When we’re talking about the morphological adaptations to strength training, our main point of focus is the development of myofibrillar hypertrophy, also known as ‘functional’ hypertrophy because of the increases in contractile components within the muscle – as opposed to sarcoplasmic hypertrophy, an increase in the volume of muscle cell fluid, a phenomenon common amongst bodybuilding athletes using higher rep ranges, for example. The more myofibrillar hypertrophy there is, the more force potential a muscle possesses, because of the added mass that can now be used directly by the nervous system to move weights.
Changes in the muscle architecture and related structures is another important morphological adaptation. Pennation angle (the angle formed between the direction of the muscle fibers and the general direction of the muscle itself) as well as collagen alignment in connective tissues, for example, will gradually be modified specifically according to the movements performed, underlining yet again the importance of frequently training the precise exercises in which you wish to get stronger.
Increases in bone density and connective tissue hypertrophy are also impactful morphological adaptations for the body to be able to move heavy weights safely and efficiently.
Neurological adaptations to strength training are a bit more complex. They are related to the motor unit, comprised of a motor neuron and the muscle fibers it innervates. One of the most important adaptation regards recruitment. During a muscle action, motor units are either activated or not, that is, either they contract the fibers or they don’t. There is no partial activation. For more force to be generated, more motor units must be recruited. Hence, the ability to recruit a maximal amount of motor units is a desirable adaptation that happens with strength training.
The frequency of the nerve impulses delivered by the motor neuron to the muscle fibers as an activation signal is another important factor, which we commonly call rate coding. The higher the rate at which it is delivered, the higher the tension produced. Strength training has been shown to improve frequency of the repeated activation, allowing muscles to generate higher forces. Improvements in the synchronization of the activation of motor units also happen in reaction to strength training. Motor units usually work relatively asynchronously to produce movement. There is evidence that strength training has a synchronisation effect on the activation of motor units so as to elicit maximal tension during a muscle contraction.
An indirect but important neurological adaptation regards the inhibition of the Golgi Tendon Organ, a sensory organ that monitors the change in tension at the juncture of muscles and tendons. Its role is to limit force production in a muscle to prevent injury when excessive tension is perceived. Strength training reduces the sensitivity of the GTO so that more force can be generated before the activation of this protective reflex.
Finally, improvements in intermuscular coordination is a crucial factor in the ability to produce force. This relates to the skill of coordinating co-contraction of agonist muscles and relaxation of antagonist muscles during a movement.
While morphological adaptations increase the potential of the human body to produce force, neurological adaptations are the key to develop maximal strength. They explain why more muscle mass alone doesn’t necessarily guarantee higher strength levels and how strength athletes who are confined within the boundaries of weight categories can continue to gain strength throughout their career without changes in bodyweight.
Adaptations of this type are better produced through the use of multi-joints barbell exercises and a lower rep range (one to six is a good general guideline), as well as a conscious effort to lift with maximal intent no matter the weight on the bar. For more information on how to get stronger for powerlifting through the use of those principles, we invite you to take a look at our article on powerlifting periodization.
We hope that this short synthesis has given you a clearer understanding of the physiology of strength. Most textbooks dedicated to the development of strength as well as general human physiology volumes will give you a much more detailed explanation of the principles seen above, and we strongly encourage you to seek them out if you wish to further your understanding of strength training physiology.