Approach to energy metabolism

Muscle contraction, as well as many other cellular functions, takes place thanks to the energy released by the breakdown of the phosphoanhydride bond that combines the phosphorus α to the phosphorus ß in the ATP molecule:

ATP + H2O = ADP + H + + P + Energy available

The muscle cell has limited ATP reserves (2.5 g / kg of muscle, for a total of about 50g). These reservations are sufficient only for maximal works lasting about one second. However, our body has energy systems that allow it to continually re-synthesize ATP.

THE MECHANISMS OF ATP RESINATION:

The mechanisms for ATP resynthesis are 3 and 4 factors must be considered for each:

POWER: maximum amount of energy produced per unit of time
CAPACITY: total amount of energy produced by the system
LATENCY. time required to obtain maximum power
RESTAURANT: time required for reconstitution of the system

ANAEROBIC METABOLISM ALACTACID:

In muscle, as in other cells, there is an important reserve of active phosphoric groups called phosphocreatine or creatine phosphate (CP) or phosphagene. Creatine phosphate is formed in resting muscle by associating an inorganic phosphate molecule with a creatine molecule. When the body immediately needs large amounts of energy phosphocreatine donates its phosphate group to the ADP according to the following reaction:

PC + ADP = C + ATP

In the anaerobic alattacid mechanism the oxygen does not intervene and it is to this characteristic that the adjective "anaerobic" is owed. Also the production of lactic acid is absent and this is why the term anaerobic is placed alongside the adjective "alattacido"

The anaerobic alactacid system has a very short latency, high power and extremely low capacity. In fact, phosphocreatine reserves are quickly depleted (about 4-5 seconds). However, these reserves vary from subject to subject and increase with training

During intense and short-lived muscular activity, the decrease in developed strength is directly linked to the depletion of the phosphocreatine muscle reserves. The centometrists know that in the last few meters they are inexorably dropping their top speed.

ATP and phosphocreatine stored in the muscles are used simultaneously during short and intense efforts. Overall they give an energy autonomy of 4-8 seconds

System features:

Power: High (60-100 Kcal / min)

Capacity: Very low (5-10 Kcal)

Latency: Minimum (PC degrades as soon as the concentration of ATP drops)

Refreshment: Rapid (at the end of the effort or at the decrease of intensity, most of the creatine is refosphorilated to CP in about 10 "); this system of resynthesis is important in activities that require strength and speed (jumping, short and fast running, training force with short series and high load)

ANATHERIC METABOLISM LACTACID:

Even this energy system does not use oxygen. In the cytoplasm of the cells the muscular glucose is transformed into lactic acid through a series of 10 reactions catalyzed by enzymes. The end result is the release of energy that is used for ATP resynthesis

ADP + P + Glucose = ATP + Lactate

Since the pyruvate in the presence of O2 participates in the production of ATP, glycolysis is also the first phase of the aerobic degradation of carbohydrates. The availability of O2 in the cell determines the extent of aerobic and anaerobic metabolic processes.

Glycolysis becomes anaerobic if: oxygen is scarce in mitochondria to accept the hydrogenions produced by the Krebs cycle

If the glycolytic flow is too rapid, or if the hydrogen flow is greater than the possibility of transport from the cytoplasm into the intramitochondrial site for phosphorylation (excessive intensity of exercise and therefore ATP required)

If they are present in the isoforms of LDH muscles that favor the conversion of pyruvate to lactate typical of fast fibers.

System features:

Power: Less than the previous one (50 Kcal / min)

Capacity: Much greater than the previous one (up to 40 Kcal)

Latency: 15-30 seconds (if the exercise is immediately very intense it intervenes at the end of the alactacid system)

Refreshment: Subordinate to the elimination of lactic acid with glucose resynthesis, with energy supplied by oxidative processes (payment of the o2 lactic debt); this system of resynthesis is important in intense activities lasting between 15 "and 2 '(eg run from 200 to 800m, track tracking, etc.).

AEROBIC METABOLISM

In rest conditions or moderate exercise, ATP resynthesis is guaranteed by aerobic metabolism. This energy system allows the complete oxidation of the two main fuels: carbohydrates and lipids in the presence of oxygen which acts as an oxidizer.

Aerobic metabolism occurs mainly within the mitochondria except for some "preparatory" phases.

System yield:

1 mol of palmitate (fatty acid) 129 ATP

1 mol of glucose (sugar) 39 ATP

in fact fatty acids contain more hydrogen atoms than sugars and consequently more energy for ATP resynthesis; however, they are poorer in oxygen and therefore have a lower energy yield (with the same amount of oxygen consumed).

The mixture of fatty acids and glucose changes with the intensity of exercise:

at low intensity fatty acids are more involved

increasing the effort increases glucose cleavage instead (see: Energy metabolism in muscular work)

Power: slightly lower than the previous ones (20 Kcal / min) Variable depending on the subjects' O2 consumption

Capacity: High (up to 2000 Kcal) Depends on glycogen and lipid reserves especially l The duration of use depends on exercise intensity and training level l At low intensities the usage time is practically unlimited, at high intensities the presence of glycogen

Latency: greater than the previous ones: 2-3 '

Refreshment: Very long (36-48 hours)

SUMMING UP: