Hypoxia
In our body, there are three main energy systems responsible for ATP resynthesis, which is the universal energy source for all biochemical processes. These three energy systems are: 1) Phosphagen, 2) Glycolytic, and 3) Mitochondrial respiration. (1) In foreign literature, these are the names of the three primary systems. To facilitate understanding, let’s break them down.
Phosphagen (or Anaerobic Alactate):
This system uses creatine phosphate to produce energy and operates over a very short period of time, approximately the first 10 seconds after exercise begins. (2) The importance of this system lies in its rapid ATP regeneration compared to other systems. (3) This system is critical for athletes performing short-duration efforts, such as shot putters, 100-meter sprinters, and weightlifting athletes.
Glycolytic (or Anaerobic Lactate):
This system uses energy to regenerate ATP from blood glucose and muscle glycogen stores. (4) Similar to the anaerobic lactate system, peak ATP concentration is achieved within the first seconds of exercise, slightly later than the first system, around 30 seconds. ATP concentration gradually decreases and reaches a minimum after 2-3 minutes of intense exercise. (1) This system is actively trained in figure skaters, 400-800 meter runners, 500-meter rowers, etc.
Mitochondrial respiration (or Aerobic):
This system utilizes energy sources within the muscle (free fatty acids and glycogen) and outside the muscle (adipose tissue and food). (5) The aerobic energy system responds quickly to the demands of intense exercise but, due to its relatively low metabolic rate of ATP production, cannot meet energy demands at the beginning of exercise, regardless of its intensity or vigor. (1) This system is critical for endurance athletes.

Hypoxia
We will also examine the types of hypoxic techniques and their effects on energy systems. There are basic hypoxic training techniques: 1) “live high, train high” (LHTH), 2) “live high, train low” (LHTL), and 3) “live low, train high” (LLTH). (6) In addition to these basic techniques, there are variations of training within these protocols, such as ischemic preconditioning (IPC), blood flow restriction (BFR) exercise, low-intensity continuous hypoxic training (CHT), repeated sprint training in hypoxia (RSH), sprint interval training in hypoxia (SIH), and resistance training in hypoxia (RTH). (7) Each of these impacts energy systems differently.
A meta-analysis (Bonetti and Hopkins, 2009) reports that resting IHT can improve VO2max in amateur athletes. This method trains the aerobic energy system. Moreover, a later study (8) states that the IHT protocol significantly enhances the body’s aerobic capacity. Regarding IPC, several studies (9)(10) confirm that this type of passive hypoxic exposure helps improve aerobic adaptation by 1-5%. BFR is characterized by its use in both strength and aerobic exercises, so the energy system developed depends on the program followed. BFR with weights enhances explosive power and muscle strength, while BFR with aerobic exercises allows for better muscular adaptation in endurance sports. (11) RTH is an excellent hypoxic method for training anaerobic systems. (7) Meanwhile, RSH directly improves anaerobic system performance in sprint sports (12), enhancing athlete performance and quick recovery capacity by 1-5% under normoxia conditions. (13) Conducting general LHTL, LHTH, and LLTH protocols, a study (14) found that all these methods positively impacted athletes’ aerobic capacity to varying degrees.
In general, to train anaerobic energy systems, it is effective to use various active and passive hypoxic training techniques. To improve aerobic performance, it is best to focus on endurance training and long-term hypoxic adaptation. (15)
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