Krebs Cycle Defined
The Krebs Cycle also known as Tricarboxylic Acid (TCA) or Citric Acid Cycle is a process occurring as part of aerobic respiration in the production of energy in the form of ATP (discussed in another article). Although slower in ATP production than our anaerobic (without oxygen) energy production systems in our body, it provides a lot more energy or ATP. In fact, because the Krebs cycle uses both carbohydrates in the form of glucose and fats in the form of triglycerides, it can produce 38 ATP per glucose molecule and on average 463 ATP per triglyceride molecule.1 This is compared to the measly 2 ATP produced via our first anaerobic phosphagen system. However, during quite explosive exercise, because we have insufficient oxygen, the anaerobic systems are utilised first to replenish our energy faster. If this is all going over your head a little, let's simplify things. Picture the Krebs cycle as a nuclear power plant, where workers (intermediates) are using raw materials (water, enzymes, etc) and changing them around to produce energy (ATP) and waste (carbon dioxide) and other products. Other types of nuclear material can also be used (fats and proteins) to create this energy.
Krebs’ Cycle, Training & Supplementation
As the Krebs’ Cycle is a critical component in producing large amounts of cellular energy, the use of the cycle is important to ensuring that you have sufficient energy over longer workouts and workouts which are more aerobically based. Because there are so many steps in the process which use so many intermediates, there has been great interest in the use of TCA cycle intermediates (TCAIs) and helping to increase the effectiveness of this cycle thereby benefitting athletes and bodybuilders. It has been suggested that TCAI supplementation may promote aerobic energy production by increasing the rate of oxidative ATP production during exercise, and the rate of creatine phosphate recovery after exercise.2 Another popular TCAI used in supplements is alpha-ketoglutarate (AKG), usually marketed as L-arginine AKG. Though there is inconclusive evidence to prove that this supplement is effective, one study3 has shown that the inclusion of arginine-based supplements may act as an ergogenic (performance-enhancing) aid, thus increasing the muscle fatigue threshold. However, it is important to note that arginine is not involved in the Kreb's Cycle.
Krebs' Cycle & Bodybuilding
The Kreb's Cycle is the most important energy production system in everyday life. It is the main energy producer at rest and for low-moderate intensity exercise and for longer durations of exercise. Increasing its efficiency in producing more energy may help you as the bodybuilder get more out of the gym by ensuring your muscles fatigue less and more slowly.1Essentials of Strength Training and Conditioning 3rd Ed. National Strength and Conditioning Association. Baechle TR and Earle EW. 2008 p. 29-31
2 Bendahan, D et al, 'Citrulline/malate promotes aerobic energy production in human exercising muscle' (2002) 36(4) British journal of sports medicine 282
3 Camic, CL et al, 'Effects of arginine-based supplements on the physical working capacity at the fatigue threshold' (2010) 24(5) The Journal of Strength & Conditioning Research 1306