The Biology of Climbing

            Climbing, as I’m sure many of you know, is a very intense sport that puts an extreme amount of strain on your body.  Tendon and ligament injuries are common amongst climbers that render themselves useless for months at a time.  This following sequence of articles are going to focus on the biology of climbing; things you can do to keep yourself on the rock instead of on the couch.

How your body makes the energy that keeps you climbing

            In all living cells, energy is temporarily packaged within a remarkable chemical compound called adenosine triphosphate (ATP), which holds a readily available energy for very short periods of time.  We may think of ATP as the energy currency of the cell.  When you work to earn money, you might say that your energy is symbolically stored in the money you earn.  The energy the cell requires for immediate use is temporarily stored in ATP, which is like cash.  When you earn extra money, you might deposit some in the bank; similarly, a cell might deposit energy in the chemical bonds of lipids (fats), starch, of glycogen.  Moreover, just as you dare not make less money than you spend, so too the cell must avoid energy bankruptcy, which would mean its death.  Finally, just as you do not keep what you make very long, so too the cell continuously spends its ATP, which must be replaced immediately.  

            Humans use a form of cellular respiration requiring oxygen which is called aerobic respiration.  During aerobic respiration, nutrients are catabolized to carbon dioxide and water.  The cells of your body use this method to obtain energy from glucose.  Glucose is transformed from many different chemicals in the foods you eat.  Certain foods contain more glucose than others, which yield more energy.  But that doesn’t mean you should eat these foods only, as other low energy foods contain many nutrients your body needs to build muscle, bone, and cells.  The following formula shows this process:

C₆H₁₂0₆ + 6O₂ + 6H₂O ® 6CO₂ + 12H₂O + Energy (as ATP)

(For you anti-chemistry people) Glucose + oxygen + water gives you carbon dioxide + more water + energy to pull down hard.

Aerobic respiration has four stages:

1. Glycolysis: A six-carbon glucose molecule is converted to two, three-carbon molecules of pyruvate, and ATP and NADH are formed.
2. Formation of acetyl coenzyme A: Each pyruvate enters a mitochondrion (a tiny body inside of a cell that makes energy) and is oxidized to a two-carbon group that combines with coenzyme A, forming acetyl coenzyme A.  NADH is produced and carbon dioxide is released as a waste product.
3. The citric acid cycle: The acetate group of acetyl coenzyme A combines with a four-carbon molecule to form a six-carbon molecule.  In the course of cycle, citrate is recycled to oxaloacetate and carbon dioxide is released as a waste product.  Energy is captured as ATO and then reduced as high energy compounds NADH and FADH₂.
4. The electron transport chain and chemiosmosis: The electrons removed from glucose during the preceding staged are transferred from NADH and FADH₂ to a chain of electron acceptor compounds.  As the electrons are passed from one electron acceptor to another, some of their energy is used to pimp hydrogen ions (protons) across the inner mitochondrial membrane, forming a proton gradient.  In a process known as chemiosmosis, the energy of this proton gradient is used to produce ATP.

It’s the simplest way I could explain; this is how your body moves, lives, functions.  Any cell in your body goes through this process if it wants to do its job correctly.  At any one time there are trillions of molecules of ATP being used up.  Yes, that is trillion, with this many zeros; 000,000,000,000,000.  And that is the basics of how your body has the energy to move.

            Now, with the normal process I just told you about, each reaction produces about 34-38 ATP molecules.  This is the normal rate of production of ATP, and is what you would like.  There are circumstances though when your cells need more oxygen then the body can supply.  And as I stated earlier, normal cellular respiration requires oxygen to carry out the production of ATP.  When this begins to happen the cells immediately switch over to a process that doesn’t need oxygen to produce ATP and you notice a burning in the muscles, and might feel a little “off.”  This is a lactic acid build up from an emergency production of ATP called fermentation.  And this is a very inefficient process.  Each time it goes through the motions, it only creates 4 ATP molecules.  But, in return for these measly 4 ATP molecules, it releases a toxin into the body in either the form of lactate or alcohol.  Humans can only go on like this for a few minutes before the cells just stop functioning.  This is why sprinters can’t sprint for minutes at a time.  The cells are not capable of producing the needed ATP to function, and therefore cease all normal activities.

Resources

Biology, 5th edition, Solomon, Berg, Martin

Principles of Anatomy and Physiology, 6th edition, Tortota, Anahnostakos

Physical Examination and Health Assessment, Jarvis