Bioenergetics and metabolism during physical activity.

Power supply systems:

Metabolism is the totality of biochemical reactions of the organism mediated by biological catalysts or enzymes.

Depending on the magnitude of the stimulus: volume and intensity, the body can turn to different sources of energy for metabolic processes, during physical activity.

There are roughly three systems of provision of energy and ATP resynthesis:

1) System of the phosphagen system ATC-CP, called also historically anaerobic (although it is not strictly in the absence of oxygen) alactacid (although it is not strictly in the absence of lactate). Characterized by physical efforts of very high intensity and short duration.

2) The glucolítico, also called anaerobic lactacid system. Characterized by physical efforts of high intensity and intermediate duration, with production of lactate. Studies Nuclear magnetic resonance (NMR) oxygenation of human muscle Myoglobin in exercise showed that the levels of oxygen in muscles in exercise decreases with the charge, but even at maximum consumption of oxygen it is well above the mitochondrial needs. This rules out the hypothesis that the accumulation of lactate is due to a lack of oxygen. Due to the intensity of work, accumulation exceeds removal and produced the "shuttle" or exchange of lactate to other places where it can be reused, or oxidized.

(3) The oxidative aerobic system. Characterized by low intensity and long-term efforts.

Classically expressed the specific characteristics of each system as set forth in the following table, although most modern studies tend to relativize these aspects.

 

System/Caract	Sources	It take to intervene	Maximum intervention	Important intervention
Phosphorous	ATP - CP intracellular	Null	2 a5 sec	0 to15 sec.
Glucolítico	Glucose and glycogen	10 sec.	30 a40 sec.	30 sec to 2 min.
Oxidative	Carbohydrates, lipids and Prot.	1-3 min	2 a5 min.	2-3 min to hours.

 

System/Caract	Recovery	Limiting factors	Maximum power	Capacity	Examples
Phosphorous	50%: 45seg 100 ci95%:1.16 - 3 min	Exhaustion CP	90 kcal/min	Up to 30 sec.	Games, jumping, lanz.
Glucolítico	ENTR:60 - 90 min No Entr:120 - a180min	Metabolic acidosis	30 kcal/min	Up to 3-4 min	100 mts bigest. plain 400mts
Oxidative	Permanent	Agot.glucog. VO2.Dream	10 kcal/min	HS - days	Marathon, triathlon

Both the muscular contraction and the neuronal processes occur in a matter of milliseconds, therefore the energy process must occur in those units of time. Using NMR techniques with ³¹P (phosphate 31), for the measurement of metabolites phosphates with a time resolution of 1 millisecond (ms) with a 1 herz (Hz) stimulation, it was established that in this model, the glycogen decreases not oxidativamente in a matter of milliseconds to fill the pool of ATP/PC while it is resynthesizing oxidativamente in periods of ~ 1 second between contractions. A fraction of lactate is oxidized, between contractions to restore the PC and glycogen deposits. In the light of these new investigations, both glycogenolysis and muscle contraction is activated in milliseconds by action of the ca ++ (calcium), and glycogenolysis provides the necessary ATP during the milliseconds of contraction, for the filling of PC.

The use of fats as a substrate is only done in the realization of physical work in the oxidative system. Within this system, there are also numerous subsystems some of which use this fuel as prevalent. During a period of increased intensity occurs increasingly increased use of carbohydrates as a source of energy and the use of lipids is reduced. The degradation of glucose according to the speed of energy requirements can take a fast track (fast glycolytic) via the enzyme lactate dehydrogase (LDH), with conversion of Pyruvate to lactate and progressive accumulation of this; or a slow pathway (Glycolysis slow) via the enzyme pyruvate dehydrogenase, entering the mitochondria to pyruvic acid and starting the series of reactions of the Krebs cycle or the tricarboxylic acids (CATC), for utilization of oxygen to generate ATP