Adenosine Tri-Phosphate (ATP): The Fuel Source of Your Muscles
Q: I’ve heard about ATP. Can you explain what it is and its purpose?
A: When fueling our bodies, we often think of the carbohydrates, proteins, and fats we are ingesting. Different dieting techniques call for more, or less, of certain food types. In the end, successful digestion yields energy through various metabolic pathways. In skeletal muscle, they produce Adenosine Tri-Phosphate (ATP).
Skeletal muscle uses energy pathways for both long term, aerobic activities and short term, anaerobic activities. Aerobic activity utilizes oxygen, thus using the energy cascades known as the “Krebs Cycle,” “Electron Transport Chain,” and “Beta Oxidation.” These cascades prefer carbohydrates as their energy sources, however fats and protein can be used secondarily. The next time you are walking or running for distance, and feel your breathing pattern increase, know you are using these pathways.
Anaerobic activity uses different energy systems. These include the “Phosphagen Cycle” and “Anaerobic Glycolysis.” Anaerobic activities, like sprinting and weight training, require instant energy. To accomplish this, glucose and Creatine Phosphate are stored in your muscles. Very rapidly, glucose is converted to Pyruvate, while producing ATP, and Nicotinamide Adenine Dinucleotide (NAD+). Creatine Phosphate readily releases its phosphate for immediate utilization. So the next time you run up a few stairs, and feel the burn in your quadriceps, know that you just used these pathways.
At rest, Adenosine Di-Phosphate (ADP) levels are high. When energy is needed, these cascades begin to manufacture ATP. This is important because ATP is what causes the muscle unit to relax.
The functional unit of a muscle fiber is called a sarcomere. Within the sarcomere are contractile filaments called actin and myosin. Actin and myosin are interwoven between each other, like the fingers of your hands sliding in between each other. The myosin filaments have many appendages, called myosin heads that reach out and attach themselves to the surrounding actin filaments. Together, like oars in an old Viking boat stroking together, the myosin heads “heave” the actin filaments forward, in essence sliding them over themselves. In order to increase the strength of a contraction, the myosin heads must release, reset themselves to their original positions, re-attach, then “heave” again. This is achieved through ATP. When the power stroke has occurred, ATP causes the myosin head to disassociate and return to its original position. The ATP is then cleaved and the myosin head can re-attach itself.
Consider this. If ATP is not available, what would happen? The myosin head would attach and heave, but would not be able to release itself. The unit stays contracted. Sounds like... rigor mortis? When we stop breathing and metabolizing glucose, we run out of ATP, hence rigor mortis sets in.
What happens when we train? Through aerobic training, we increase the efficiency in how we utilize oxygen. The better we use it, the better we burn our energy sources. The better the energy sources burn, the more efficiently our bodies can yield and utilize ATP. Anaerobically, we store glucose and creatine phosphate more efficiently, so when we need it, BAM! There it is.
There are many products on the market, promising fat loss, higher energy outputs, and strength increases. These products claim to be “pre-cursors” of any and all of the discussed pathways. The only supplement shown to benefit short duration anaerobic exercise is Creatine Monohydrate. Specifically in the realms of serious weight lifting and body building, 70% of those who use it gain moderate strength increases and lean muscle mass. Unfortunately, these benefits do not apply to walking or running. Taking this supplement to make you walk or run better will not yield positive results.
A healthy diet of clean carbohydrates, proteins, and fats coupled with smart training are the keys to physiologic improvement.
• How much protein/day? Simply, size of a deck of cards, whatever the source.
• Don’t be carbo-phobic. Be carbo-finicky.
• Avoid saturated fats and seek essential fatty acids in foods.
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“Rest” days from training are just that. Allow for adequate recovery.
I personally suggest the following supplements to all my patients.
• A multi-vitamin to fill in any nutritional gaps in one’s diet.
• 1,000 to 4,000 milligrams of vitamin C for adequate recovery of soft tissues.
• Omega 3 supplementation that yields three grams of EPA/DHA. Omegas 3s have an anti-inflammatory effect on the body.
So what to think of all this mumbo jumbo? A simple understanding will help you conceptualize what you are accomplishing during your training. Lucky for us, if we eat, train, and rest smartly our bodies will do the rest for us. Keep on trekking!
— Greg Lekas
This Issue’s Expert
Greg Lekas, DC, is a chiropractic physician, nationally certified athletic trainer, and strength and conditioning specialist who works with patients of all athletic levels and abilities. He can be reached at greg@clearh2o.org.
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