Factors influencing hydrogen ion concentration in muscle after intense exercise.

Intense exercise raises hydrogen ion levels in muscles, causing a drop in pH that reduces muscle performance.

During intense exercise, the balance of charged particles in blood plasma stays stable even as lactate increases, because sodium, potassium, and calcium ions rise at the same time and counteract lactate's acidifying effect, showing that blood and muscle cells regulate acidity through different mechanisms.

During 30 seconds of maximum cycling, lactate builds up in the quadriceps muscle to 47 mmol/L, and this increase explains most of the drop in the muscle's strong ion difference from 154 to 106 mmol/L, resulting in intracellular acidosis.

After intense exercise, the balance of charged ions inside cells stays altered even as lactate levels drop, because lactate remains elevated and potassium levels fall, showing that potassium changes directly affect cellular acid-base regulation.

During intense exercise, carbon dioxide levels in the femoral vein rise to 106 Torr and return to normal within 9.5 minutes, contributing briefly to blood acidity after exercise. Lactate levels remain high longer than carbon dioxide.

After intense exercise, the amount of potassium inside muscle cells drops from 142 mmol/L to between 123 and 128 mmol/L and remains lowered for at least 9.5 minutes as potassium moves out of the cells.