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22. 3. 2012.

Potassium (K)

Potassium is the most represented cation in the cell. Concentration of this element is 40 times bigger in cell than in intercellular space. Maintaining of stabile potassium concentration is important for numerous physiological functions, among which are following: neural impulses transmission, membrane potential maintaining, muscular contractions, keeping normal blood pressure, and heart work.
90-100% of intaked potassium is absorbed in intestines, and then goes to circulation. Potassium is excreted from the body, the biggest part, through urine(when its excretion is connected to natrium and chormone aldosteron), and the small part through feces/sweat.
During repeated muscle contractions, potassium leaves muscle cells. During muscular work, due to electrochemical processes that are done on cell membrane of muscular fiber, permeability of same is changed, which causes frequent flux of potassium and natrium. Potassium concentration in plasma and interstitial space is elevated above basal during training. Potassium concentration in sweat is equal or even overcomes potassium concentration in plasma, so loss of calcium through sweat from intercellular fluid is bigger than natrium loss with sweat.
Potassium loss is 5-18 mEq at competitive activities. During 2 hours of training in warm surround, on intensity 50% VO2 max, loss through sweat equals 12 mEq. On lower temperatures loss is around 11,5 mEq.
Potassium also enters or leaves muscle cell along with glycogen. So, glycogen degradation during muscle work leads to release and potassium exit from muscle fiber.
Some authors think that potassium is lost when it comes to muscle cells damage – mechanical stress, but for now there are no valid proves for this axioma.
After training potassium is lost heavily through urine.
At long term training continous excretion of potassium from muscle cells to extracellular space is presence. Potassium level in plasma is in these conditions kept on same high level, so deficit that is seen is exposed in intracellular space.
It is thought that potassium needs can be increased after training. Than there is rapid entering of potassium into cells, what especially contributes glucose entrance and fast glycogen resinthesis. So potassium level in plasma rapidly drops after training end, but it is soon returned to normal or lower levels.
Some research works say that potassium deficit can be made when diarrhea and puking are followed with lower diet intake of this mineral. Fatique and weakness that are developed than negatively influent to physical performance.

Potassium intake

Recommended daily amount(RDA) is 2-6mg per day. Amount of 3,5 g is recommended only to the ones that are exposed to hard physical work and big sweat. By intake of some groceries: some fruit(banana, orange), vegetables(potato) and meat huge amount of potassium can be provided – 8-11g per day.

Potassium amount in groceries that are often used for compensation of potassium after the exercise
Potassium mg/portion
Potassium mg/100g(amount)
840/ 1 big(210g)
380/1 big
530/ 240g; 3,2% fat
370/ 2/3 cup
Orange, juice
475/ 240g
420/ 210g
450/ medium size
450/ 1 medium size
Pineapple, juice
330/ 240g
230/ 180g
300/ 1 cup
230/ 3 spoons
90/ 360g
Sport drinks
55/ 240g
30/ 240g
30/ 240g
0/ 360g can
450-500g of sweat contains 80-100mg of potassium. During 2-3h of hard work 300-800 mg K+. Generally, potassium intake along with food is given advantage compared to commercial stuff.

It is thought that drinks intake provided to the athletes can compensate potassium loss with sweat(after hard competition) when drink contains 5-15 mEq/l of potassium and when rehydration is 75-100%.
A lot of commercial drinks, made for athletes, contain potassium in amount of 2,5-5 mEq/l. Specific advantage of potassium intaked in these fluids, according to sport achievement, is not determined till now.

“Athletes’ nutrition”, Marina Djordjevic Nikic

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