Excess post-exercise oxygen consumption
EPOC ( engl: excess postexercise oxygen consumption, German: More oxygen uptake after work or Nachbrennwert ) is a term used in sports physiology and releases the oxygen uptake more about the rest need ourselves after exercise to. It is characteristic for this increased respiration.
Physiological background
After beginning a physical load, the cardiovascular and respiratory systems only fits delayed on the increased oxygen demand and reached after a few minutes a steady state. There is therefore an oxygen deficit. When measuring nachgeatmeten O2 shows, however, that the amount is larger than the actual deficit in most cases. In the body, so run during and after exercise from processes that involve additional oxygen demand.
EPOC does not correspond, as assumed earlier, the initial oxygen deficit, but is rather an indication of the stress on the body and the resulting necessary regeneration. The height of the EPOC is dependent on exercise duration and intensity. In addition to increased oxygen uptake can be increased energy consumption of the body to determine which is characterized mainly by the burning of fat.
The decrease in O2 uptake curve after the stress shows a nearly exponential. We can distinguish three phases during which run among other various processes for the restoration of homeostasis:
- Replenishment of high-energy storage ( synthesis of ATP and creatine phosphate)
- Replenishment of O2 stores ( hemoglobin, myoglobin )
- Increased oxygen demand of the body tissue due to increased body temperature and increased catecholamines ( increased adrenaline caused an increase in oxidative processes )
- Increased activity of the heart muscle and respiratory muscle properties with a corresponding increased oxygen demand
- Increased production of the thyroid hormone thyroxine
- Gluconeogenesis from lactate
- Increased muscle tone
- Cellular regeneration processes
- Stimulation energy ready stellender mechanisms (eg respiratory chain )
A total of approximately 26 l O2 are nachgeatmet within 12 hours. Increased oxygen uptake is observed up to 38 hours after exposure. The stress intensity plays for the oxygen uptake more a lesser role than the loading duration. The effect of EPOC occurs in both aerobic and anaerobic performances at, with an anaerobic stress in higher EPOC values leads as an aerobic load for the same work done.
Importance
Trained point after a loading a faster decrease of the oxygen uptake than untrained, which indicates a greater ability to recover. In addition, there is a strong correlation between the intensity of a load and the strength and duration of EPOC. This value can therefore be used for performance diagnostics, eg to examine the current endurance ability or training to check the individual stress of a load, and thus to avoid under - or over-training.
As in the phase after a load, the energy consumption is increased and the demand is met in part by burning fat, the EPOC is of importance in training programs for weight loss.
Determination of the EPOC
Direct measurement
The direct value of the EPOC is measured by cardiopulmonary exercise testing, ie, by the study of respiratory gases during exercise with an ergometer. The surface is subtracted under the oxygen consumption in the rest of the area under the oxygen consumption by the load. The value is typically expressed in ml / kg.
Indirect calculation
It is possible to calculate the EPOC value indirectly from the heart rate. The advantage of this method is the relatively low overhead because only a heart rate monitor is needed with the evaluation software. In addition, the EPOC during any stage of the load can be calculated and thus represents the current strain of the athletes.
Oxygen debt
Earlier it was with oxygen debt (O2 debt) denotes the volume of oxygen that must be additionally absorbed by the body after the end of a load to compensate for the O2 deficit after mild dynamic work. The term oxygen debt is no longer used today because the nachgeatmete amount of oxygen is usually greater than the oxygen deficit.
Oxygen debt is only to be used if it is the rephosphorylation of creatine to creatine phosphate and thus for the recovery of high-energy phosphates.