There are two types of muscle fibers, fast-twitch and slow-twitch or TypeII and TypeI. Within the TypeII class there are fast-oxidative-glycolytic TypeIIa and fast-glycolytic TypeIIb fibers. Contrary to what some people believe, both exert the same amount of force, it is simply the rate at which they do so that varies.

TypeIIb fibers, as their name implies, are primarily anaerobic by nature possessing larger stores of glycogen and the enzymes necessary for anaerobic respiration, meaning they operate without oxygen. Adding to their architecture they have few mitochondria, the primary structure that is utilized for aerobic respiration. TypeIIa fibers on the other hand possess the enzymes necessary for anaerobic respiration and glycogen stores, along with oxidative enzymes and more mitochondria. Think of them as a hybrid fast-twitch slow-twitch fiber that can still exert maximum force as fast as the fast-glycolytic fibers. This characteristic of the TypeIIa fibers means they will out endure their TypeIIb counterpart.

Sprinters rely on these fast-twitch muscles to explode with every foot strike, batters to engage their shoulders and forearms instantaneously and basketball players to explode with their quadriceps calves and hamstrings into the air for a rebound or to slam it. So what is the deal with slow-twitch fibers.

Slow-twitch or TypeI fibers are what keep a marathon runner going, or a triathlete on his feet. They sacrifice contractile speed for long term endurance by having a complex network of capillaries and vast quantities of mitochondria within their structure to facilitate aerobic respiration, which will always out endure the utilization of glycogen stores which deplete quickly (more on glycogen utilization later). The capillaries that entangle these fibers ensure a steady supply of nutrients to the mitochondria, the same way a steady flow of fuel will keep your vehicle going. Which type of muscle fiber do I want then? Well unfortunately you do not have much say in the matter.

Your genetics determines your muscle fiber composition for the most part. It has been shown though that after years of training, and yes I do mean years, TypeIIb fibers can transition to TypeIIa fibers. Actually biopsies of some elite athletes show that after many years of training, they possess almost no TypeIIb fibers, meaning there is hope for creating a more elite YOU. Dedication to your training regimen is what is going to decide how successful this recruitment is. Stick to the explosive movements, your clean press, power cleans, jump squats and high pulls. Or on your normal exercises such as bench, uses intervals like 3-2-1. What this means is that when you are bringing the weight down to your chest take three seconds, so slow controlled movement, then hold for two seconds and explode up. There will be a detailed article on Explosive Strength regimens here soon.

Still confused? Think of it this way, birds legs, take a thigh for example are darker slow twitch fibers. They stand around and walk all day so they need these muscles to last. Their wings, are white meat, fast-twitch, ready to get them airborne if farmer john comes around looking for dinner. With a proper routine, you too can train to be explosive, increasing your overall athleticism dramatically. Jumping higher, running faster, and being able to be quicker in all movements just gives you an edge that pure bulk does not. So examine your routine, mix it up every so often and train to be explosive. Plyometrics are a great way to train explosive movements, refer to the playlist here for great plyometric exercises.

Until next time.

For our purposes, fitness is the epitome of health. Now this might seem bizarre or incorrect, but a properly executed fitness regimen will provide excellent health benefits. Merely exercising and dieting by no means produce fitness though. For example, someone who runs everyday but is on a high carbohydrate, low fat and medium protein intake  diet is at risk of developing atherosclerotic disease, among a slew of other things. Fitness then is a compound measurement of many key areas.

Being fit should be understood as a function of the following:

• triglyceride levels
• body fat
• muscle mass
• flexibility, blood pressure
• cholesterol levels
• lung capacity
• bone density
• mental health

Thus, one’s fitness level is a combined measurement that represents total body health, not merely an expression of athletic ability. Physical competence incorporates other skills and areas which may associate more closely with most people’s general understanding of  what fitness is but physical competence does not correlate with being in an overall state of physical fitness.

Closing this out, it is key to realize that if one strives for and achieves increasingly healthy and fit levels of all of the previously mentioned 8 areas of fitness, then one’s body chemistry will indeed change. This change precipitates a healthier, less disease prone life. It is for this reason that we strive to achieve high levels of fitness.

Future posts will focus specifically on each of these 8 areas and how to approach each in a total fitness regimen.