CYCLING PERFORMANCE TIPS
The concept of concentration, or osmolarity, is an important one in understanding biologic
systems. The human body tries works maintain a specific concentration of dissolved
molecules (electrolytes, sugars, amino acids, etc.) in the fluid bathing the cells
(and in the fluid part of the blood or plasma). Adding the total number of molecules
(size is not significant, number of individual molecules is) and expressing that number
relative to the volume of fluid being analyzed, one gets the osmolarity. The higher the
osmolarity, the more concentrated the solution, and the higher its osmotic activity
Their are several ways that the body attempts to protect the osmolarity of the extracellular
- Free water (without particles) can move freely to equal the concentration. Water
flows from low osmolarity to high osmolarity at a rate directly proportional to the
difference (gradient) in osmolarity. Or in other words, body water will redistribute
itself so that under steady state conditions the osmolarity of all body fluid compartments
is identical and equal to total body extracellular osmolarity.
- When osmolarity is high, you are thirsty and will drink.
- The kidneys can either excrete free water (if overall osmolarity is low) or retain
free water as sodium, potassium, and other molecules are excreted in the urine (if overall
body osmolarity is high).
The body will also avoid rapidly absorbing too many particles (high osmolarity fluids)
and upsetting the concentration balance in the body (homeostasis) by slowing down
emptying of the stomach if high concentration fluids are ingested. This allows the
kidneys time to adjust and thus wide swings in the concentration of body fluids.
- osmolarity - the total concentration of solute particles in a specified volume of water
- isoosmotic = the osmolarity of two solutions is equal. No fluid shifts occur.
- isotonic = two solutions where there is no subsequent flow of water between them.
- hypoosmotic = the solution that is hypoosmotic has a lower osmolarity than the
solution to which it is being compared. A hypoosmotic solution has a tendency to gain water.
- hyperosmotic = the solution that is hyperosmotic has a higher osmolarity than the
solution to which it is being compared. A hyperosmotic solution has a tendency to lose water.
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