How do Muscles Work

Muscles are a beautifully complex and elegant organ that do a lot more for us than simple locomotion. Unfortunately, any system can and does fail

How do Muscles Work?

A message from the brain requesting a muscle to contract is actually a nerve signal being delivered along a series of wires (neurons) directly to the targeted muscle cell surface. These signals cause both muscle movement (on and off) and set the length of the muscle, creating an enduring tightening of the muscle (muscle tone) which sets our posture. Upon arrival at the cell surface, the nerve message causes the release of calcium from its storage sites within the muscle cell. When the free calcium within the cell reaches a critical level, the muscle cell will contract. Contraction is actually a sliding mechanism whereby two sets of protein rods slide across each other, shortening the overall length of the two sets of rods. Relaxation occurs by default when the signal to contract stops. When this happens, the free calcium is actively pumped back into the storage containers (sarcoplasmic reticulum) by calcium pumps found in the cell.  With magnesium dominant again, the protein rods slide apart. The muscle relaxes and blood flow resumes. Trillions of these proteins, all working together under the direction of the brain, produce the wonder of movement. Watch the Olympics or a nature program to fully grasp the genius of muscle and body design. 

How did magnesium get into the story? Magnesium (Mg++) is nature’s antidote for calcium (Ca++). These two minerals oppose each other, creating an on-off switch. Understanding the full complexity of this mechanism can be overwhelming – at the same time, it can be very simple.

How do Muscles Malfunction?

If the muscle cell has too much free calcium it will lock up. That is how rigor mortis (translation from Latin: contraction of death) is brought about. After death, when blood flow has stopped, but before the muscles proteins break down, energy and oxygen depletion causes the calcium pumps to stop working. Calcium floods the cell, the protein rods lock up and the muscle becomes rigid. Within a day or so, the calcium/protein bonds break up and the muscles become unlocked again – into the coffin you go!

All cells deprived of oxygen and nutrients die through the same calcium poisoning mechanism. We stay alive by keeping calcium under control and safely stored in the containers supplied in each cell! The race against the clock in a “Code Blue” situation when the heart stops beating is really a race to get the calcium pumps up and running again.

In living muscle cells, the balance between calcium and magnesium is critical for optimal muscle function. Too much calcium, a calcium pump failure, or too little magnesium can result in the same rigor or latched state that occurs after death. The actin and myosin protein rods get pulled tight by the over-abundant or un-opposed free calcium.

When the OFF Switch Fails. What is a Trigger Point? 

 While in the latched state the muscle is pulled tight. This can affect the whole muscle. Usually only a portion of the muscle is involved and is termed a trigger point. Trigger points are so named because they trigger a very painful response when contracted, stretched, compressed or injected. Contracted muscle does not in itself cause pain. It is the lack of blood flow brought about by compressing the blood vessels running through that segment of muscle that causes hydrogen ions (acid) to build up. In response, the acid receptors in the muscle start to send pain signals to the spinal cord and brain – just as they were intended to do. 

Time to Recap!

In summary then, there are two common ways to interrupt blood flow to muscle; either by compression or contraction. Since we need to be alerted to impending muscle death following prolonged blood flow shutdown, we are gifted with a powerful and effective sensing mechanism that alerts us to the cessation of blood flow. Unfortunately, in some instances where the on-off switch in the muscle malfunctions, we are not able to simply change position or stretch and allow blood to start flowing again.  

Muscles require energy to “switch off”. Therefore, they can be left in the “on” position in situations where calcium is left overwhelming the magnesium off switch.

I believe that adequate blood flow to well-functioning muscle cells with sufficient energy production to keep the calcium pumps functioning and enough Mg++ to counter-balance the Ca++ are essential to prevent muscles locking in the latched state. This is known as muscle conditioning. That is what exercise does and why it is so important.