Electroneutrality

When I last spoke about muscle fatigue, I was following the course of ion transfer through anaerobic energy production in skeletal muscle. The result of this net free proton counting was that glycogen earned a net proton loss and glucose a net 0. However, given the current understanding that muscle fatigue is in part caused by a build up of positive ions (acidosis), there must be a sort of blockage somewhere within the glycolysis/fermentation system where alkalizing lactate production cannot parallel proton accumulation from glycolysis. The system is thus dependent on the efficacy of lactate production and ion recycling to delay fatigue, and when lactate production gets overrun by the proton accumulation in glycolysis, then we might say that an acidic environment develops within the muscle and decays the energy production system (exactly how acidosis contributes to muscle fatigue will have to be discussed later). So if we can preserve and heighten lactate production, we might stall muscular fatigue.

Now, what makes the above described approach slightly erroneous is this concept of electroneutrality. Electroneutrality is a state where in a solution where many positive and negative electrolytes exist, the electrolytes will arrange so that the solution as a whole is neutral. Water is a prime example of just such a neutralizing solution, and this is significant because water is the main constituent of cytosol and cytosol is where anaerobic respiration (glycolysis and fermentation) takes place. Any free ion released in the cytosol (really, anywhere in the body) is quickly reincorporated into water molecules to neutralize the charge. The water molecule, H2O, can dissociate into H+ and HO-. The dissociation constant K(w) is very low, and so the concentration of H+ and HO- in water is also very low. Too, H+ and HO- exist only fleetingly before they are reconstituted as H2O or the ionized version of water, H3O+. Therefore, the idea that there is somehow an “accumulation” of protons (H+) piling up in the cell like a dirt mound is inaccurate when we talk about chemical reactions in an electrolytic solution (i.e. in the body). Instead, just as the ions are incorporated with other water molecules minimizing the “strength” of the H+ pile, we can spread the pile of dirt around a plot of land and minimize the height of the accumulating dirt.

Lindinger et al. 2005 critiques Robergs et al. 2004 for the latter’s “proton counting” method of assessing the net ionization produced during glycolysis and fermentation. Lindinger reminds us that we cannot neglect that these reactions take place in the cellular matrix of water, and that any resultant charge (ion) is subject to the balancing effect of constituent aqueous electrolytes. The dissociation and re-association of ions happens so fast that it might as well be considered instantaneous. Also, in keeping with the conservation of mass and energy, we must recognize this statement from Lindinger’s paper:

“…becausethe concentration of water is so large, and that of H⁺ so low,water effectively provides an infinite supply of protons, asrequired for any biochemical reaction that may require a proton,and similarly, protons evolving from biochemical reactions mayreassociate with HO^–.”

 

In other words, water gives and receives protons and electrons needed for chemical reactions throughout the body, so we do not necessarily create or deplete these ions.

Here is my final interpretation of this review:

The process of anaerobic respiration unquestionably emits and absorbs (for lack of a better word- or perhaps “reconstitutes”) positive ions (H+). The cytosol (read “water”) recombines free H+ as it becomes available from glycolysis, instantaneously, while simultaneously emits H+ for the fermentation of pyruvate to lactate. Therefore, we are not following one individual H+ ion through the entire anaerobic process from start to finish. We are only watching the over all balance of exchange of electrolytes between molecules. However, it seems that we must recognize that the cellular matrix can build a weak potential as more H2O molecules acquire H+ and become H3O+ if the production of lactate can’t keep up with production of H+ from glycolysis. While no particular current exists within the cell due to a pile of H+ ions lying around, the overall cell is weakly and homogeneously ionized. This interpretation must ignore the blood flow to and from the cell, as that adds a whole new layer of current exchange and constituent turnover.

This is where the chronic acidic or alkaline status of the body I believe becomes vital. While we provide our bodies with fuel, the types of foods we eat lend themselves to changes in our overall pH level. Fruits and vegetables are net alkalizing, meats acid producing, and carbs/fat neutral. While eating meat, we need to balance with fruits and vegetables. If instead meat is combined with a neutral product such as bread, we become more acidic. When a net alkaline state is ideal (you can think of the polarization that nerve cells work hard to maintain), then it’s easy to see how adjusting one’s diet to offer more alkaline foods and balance may benefit muscle activity, lower chronic fatigue, and may even delay the onset of acute muscular fatigue while working at anaerobic capacity.