Muscle Geek: Issue One

How Do Muscles Work and How to Improve Muscular Contractions

If you haven’t been inside an anatomy lab or taken a biochemistry course in awhile, it might be time to dust out some of those cobwebs. Having a deeper understanding of how muscles work incrementally increases you ability to utilize and improve them.

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What is the Structure of Muscles?

Let’s go from large to small. First, humans have 640 skeletal muscles (these are the ones that create movement you use to run, jump, lift, and eat chips while reading this). These muscles are all striated, and unlike smooth muscles (those of the digestive system) you have to think about using them to elicit a contraction. Muscles connect to the skeleton via tendons and when they contract, the move the bones in different directions (like a bicep curl, moving the distal ends of the radius and ulna toward the top of the humerus). Because muscles use so much energy (calories) to complete these contractions, they are supplied with their own respective nerves, veins, and arteries.

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In a high school anatomy class I took, my instructor, Ms. Scott placed dozens of uncooked spaghetti noodles together and wrapped them in plastic wrap, calling it a fascile. She repeated this, and then wrapped all of the individual bundles of spaghetti noodles together, creating at last, the muscle. This is a good representation of a muscle that indicates how many layers upon layers we take for granted it takes to build a muscle.

Looking at the diagram above, you can see that each “spaghetti noodle” is bundled together in small groups, and then those bundles are combined into one big cross-section; making the muscle.

Myofibrils are parallel fibers that run the length of a muscle (in our representation, these are the spaghetti noodles). Myofibrils are surrounded by mitochondria, a smooth connective tissue (the plastic wrap) called the sarcolemma, and finally, nuclei (because they are cells after all).

Now imagine dozens of these sarcolemma-covered myofibrils all packed together and you’ve got a muscle organ. To provide additional support to the muscle body, there are three different connective tissues that (1) wrap around the entirety of the muscle body (epimysium), (2) wrap around the fasciles (perimysium), and (3) wrap around the individual muscle fibers (the endomysium).

How Do Muscles Move?

In biochemistry we learn that “a change in protein shape equals a change in function.” Myofibrils (the spaghetti noodles) are divided up into smaller sections called sarcomeres, which are divided by something called a z-line. So the segments are zig-zagged due the structuring of two proteins called actin and myosin. Picture actin like the shape of a golf club, and myosin a thick straight filament. Actin really wants to bind (outstretch the clubhead and reach forward, pulling itself closer to the myosin) to the thick myosin filaments, which shortens the sarcomere, increasing the thickness as these two filaments overlap. This is the reason your biceps brachii muscle gets bigger and the muscle belly size increases when you flex it, the sarcomeres shorten, pulling your forearm toward your shoulder.

Image Courtesy of Britannica.com

On the myosin are two other proteins called troponin and tropomyosin. When you tell your muscle to move, the nerve supplying the muscle generates what is called an action potential, which is a weak electronic stimulus that travels down the length of the nerve, through the sarcoplasm (into the sarcoplasmic reticulum), flooding the area between the actin heads and the myosin filaments with calcium and adenosine triphosphate (ATP).

Image Courtesy of ucl.ac.uk

Troponin binds to the calcium, changing the shape of the troponin as well, leaving areas on the myosin filament where actin can grab onto it, using ATP. Once the actin head is binded to the myosin, it drops the ATP (which has been converted to adenosine diphosphate +phosphate) and picks up a new ATP molecule, detaching and reattaching over and over throughout the movement. Tons of actin heads do this, shortening the sarcomere over and over, and eliciting a contraction.

Image Courtesy of ucl.ac.uk

How You Can Improve Your Muscular Contraction?

Aside from good nutrition, utilizing something called the ‘mind-muscle connection’ can increase the number of muscle fibers that do the work. When you think about what you are doing, rather than checking out the girl with the nice legs on the stairclimber across the gym, you are increasing the amount of muscle fibers doing the work, leading to a bigger contraction, more weight being lifted, and a better quality lift. Warm-up sets that help prepare your muscles and your mind can also assist in this.

Some supplements, including creatine can help to nourish muscular contraction. To ward of metabolic fatigue, you want to continue producing as much ATP as possible for good contractions (so that the actin heads can continue binding with the myosin, unbinding, and rebinding over and over and over again).

Before suggesting that creatine is the only thing you need, keep in mind that there are three pathways your body takes to produce energy, and creatine supplements only the ATP-PC pathway; though, without it, one scientist discovered that the actin heads are not able to unbind from the myosin and produce a weak state of contraction, almost like rigor mortis (For more information regarding this interesting phenomenon, see: Brody, T. Nutritional Biochemistry. Academic Press, San Diego, California. 1994.)

You can also train to increase the speed at which muscle contract by training what are termed as fast-twitch fibers (that’s it’s own subject be covered) by implementing training movements such as Olympic lifting, jumping, and plyometrics.

Questions? Comments? How to Contact Us?

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