“More human” requires effort…
Until you get it right. 
And then “more human” effort…
Until you can’t get it wrong!

If you want to be good,
You really don’t have a lot of choices,
Because it takes what it takes,
You have to do what you have to do.”
-Nick Saban

and… “it’s in your DNA.”

The instructions “… to do what you have to do” until you can’t get it wrong… is in your DNA.

Muscle use for athletic performance involves a wide range of genes that fall into two categories: ‘athletic’- and ‘energetic'-genes that influence the use of your muscle fibers.

Athletic’-genes influence your muscle fiber type such as…

Athletic’-genes

Muscle Structure and Fiber Composition

No one is ever 100% slow-twitch or fast-twitch. In general, muscle fiber type falls along a sliding scale from 15% slow-twitch/85% fast-twitch to 50% slow-twitch/50% fast-twitch to 85% slow-twitch/15% fast-twitch, with most athletes at 50%/50%.

Muscle fiber composition varies across muscle groups throughout the body. For example, stabilizer muscles such as the abdominal muscles and the soleus muscles in your lower leg (calf muscles) are primarily composed of slow-twitch muscle fibers because they work all day long. On the other hand, phasic/power muscles (also known as dynamic “GO” muscles) such as the glutes, quads, lats, pecs, biceps, and triceps are primarily fast-twitch.

Your muscle fiber type is essentially set in stone with slight adjustments known as hybrid adaptation, as muscles contain hybrid fibers that adapt to endurance or speed demands by acting more oxidative (endurance) or more glycolytic (speed) based on training demands without completely changing their core fiber composition.

For example, biceps are roughly 60% fast-twitch while triceps are closer to 70%. And, depending on whether you train with heavy loads or explosive power, both muscle groups can convert highly fatigable Type IIx fibers into more useful, fatigue-resistant Type IIa to become more fast-twitch dynamic “GO” fibers.

Some atheltic’-genes include… ACTN3, MSTN, and TTN genes

The ACTN3 gene directs the production of alpha-actinin-3 protein found in fast-twitch muscle fibers that supports more speed and more power (with proper training). 

The MSTN gene controls the production of the myostatin protein that acts as a natural brake to limit excessive skeletal muscle growth. 

(Side note: While anabolic steroids do not alter the core DNA sequence of the MSTN gene, they can suppress its downstream signaling activity. The resulting change in gene expression removes the natural braking system, allowing unnatural muscle growth.)

(Unnatural muscle growth is not good for you.)

The TTN gene codes for the titin structural protein (the largest protein in the body), which provides passive elasticity and structural integrity, or spring-like action, as muscles contract and relax. (Proper training will influence the TTN gene expression to increase muscle use and efficiency. 

The IL-15RA gene encodes the alpha receptor for interleukin-15, a signaling protein that regulates skeletal muscle development, lean mass gains from exercise, and the reduction of body fat. Variations in this gene influence how the body manages muscle volume and overall fat distribution. In other words, as you lose weight, you get stronger.

Myth: Strength is associated with muscle mass.
Human Truth: Bigger muscles do not equate to bigger strength.

While elite sprinters have up to 70-80% fast-twitch fibers and elite endurance athletes have up to 70-80% slow-twitch muscle fibers, muscle fiber composition is the least variable factor when it comes to athletic performance from one sprinter to the next or from one endurance athlete to the next. The real influence that distinguishes a sprinter from the next sprinter or an endurance athlete from the next endurance athlete is their genetic code for what’s “…in their DNA,” which determines how the muscles use energy, oxygen, hormones, recovery, and detox. (To include efficient mechanics and proper training modules.)

Energetic’-genes

Energy Metabolism, Oxygen Use, Hormonal Response, Recovery, Detox

The real difference from one athlete to the next athlete for what’s “… in your DNA” involves the use of energy, oxygen, hormones, recovery efforts, and the detox process. A few of these genes include…

Energy Metabolism

• ACE gene: Influences the renin-angiotensin system, affecting blood pressure, cardiovascular efficiency, and skeletal muscle response during endurance or power tasks.

• PPARGC1A (PGC-1α) gene: Regulates mitochondrial biogenesis, helping turn on genes that improve aerobic capacity and energy production in slow-twitch fibers.

• AMPD1 gene: Manages nucleotide metabolism inside skeletal muscle, impacting how quickly muscles process energy and manage fatigue during high exertion.

• AMPK gene: This fuel-gauge gene triggers pathways that produce more ATP, burning more glucose and fat reserves. It also saves energy by stopping non-essential tasks that consume ATP, such as making proteins, fats, and cholesterol.

• MCT1 gene: Controls lactate transport proteins, dictating how efficiently muscle cells clear out lactic acid buildup during intense anaerobic efforts.

Oxygen Use

• VEGFA gene: Promotes the growth of new blood vessels (angiogenesis), which delivers more oxygen to active muscle tissues.

• HIF1A: Acts as a master switch that senses low oxygen levels and triggers responses to boost oxygen delivery and red blood cell production.

Hormonal Response and Recovery

• ADRB2 gene: Encodes beta-2 adrenergic receptors, altering how muscle tissue responds to adrenaline to mobilize energy during exertion.

• VDR gene: Controls vitamin D hormone receptors, which regulate cellular processes involved in muscle tissue repair, contraction, and overall strength development.

• IL6 gene: Produces interleukin-6, an important signaling protein (myokine) released by contracting muscles to direct tissue healing and the inflammation response post-exercise.

Detox Process

• CYP genes: Convert fat-soluble toxins into a more reactive, water-soluble form.

• GST gene: Attach glutathione to reactive intermediate toxins so the body can safely discharge them from the body.

• COMT gene: Helps clear neurotransmitters (dopamine, adrenaline) and estrogen metabolites via methylation.

• UGT gene: Add glucuronic acid to hormones, bilirubin, and dietary compounds for easy elimination.

These are just 19 of the 135 genes that greatly influence muscle use
for proper athletic performance.

Muscle Use… to do what you have to do…

‘Athletic’-genes + ‘Energy’-genes = Proper Muscle Use

The human body comprises more than 600 muscles, supported by various muscle fibers across multiple muscle groups and three energy systems, enabling athletic training within 5 to 7 training zones. (While typical training programs use zones 1-5, other variations may include zones 1-7 or training descriptions that include… capacity training and utilization training.) 

Training Zones:
Zone 1 -Recovery <55%
Zone 2 -Base/Endurance Training 55-70%
Zone 3 -Tempo Training 70%-85% 
Zone 4 -Lactate Threshold 80-90%
Zone 5 -VO2 max 90-100+%
Zone 6 -Anaerobic Capacity/Power Training 100% ++ 
Zone 7 -Neuromuscular Max Effort 100% +++ (breathing your own blood)

And the most desperate training zone…
Zone 8 - Overtraining (beating a dead horse) STAY AWAY from zone 8!

Energy Systems:
Oxidative System (aerobic with oxygen)
Glycolytic System (anaerobic without oxygen) 
Phosphagen System (explosive burst of energy)