Isotonic

For Isotonic muscle exercise, see Isometric exercise and Weight training.

Isotonic literally translates to equal solution. The term is used in several domains.

Cell biology

An isotonic cellular environment occurs when an equal solute concentration exists inside and outside the cell. Water molecules flow in and out at an equal rate by osmosis, causing the cell size to stay the same. It will not lose or gain any solutes. Plant cells in an isotonic environment are flaccid, and they will wither. The equilibrium of water movement is unable to provide plant cells with internal pressure for structural support, and therefore plants prefer to live in a hypotonic environment. In this situation, the concentration of solutes inside plant cells is higher than outside, and the plants use active transport to transport solutes in. This also ensures the concentration of water will be higher outside plant cells than inside.

Bio-chemistry

An isotonic solution has an equal amount of dissolved solute in it compared to the things around it. Typically in humans and most other mammals, the isotonic solution is 0.9 weight percent (9 g/L) salt in aqueous solution, this is also known as saline, which is generally administered via an intra-venous drip. It is a medium between hypotonic and hypertonic solutions. Red blood cells normally exist in a 0.9 percent salt solution (saline) with the same concentration of salt in the outside solution.

Athletics

This term is also used in relation to a sports drink with balanced mineralised levels mimicing the osmolality of blood. This property is claimed by their advertising campaign to increase physical endurance. The limited (6 rowers) scientific study they quote however attributes the 10% increase in endurance over water to the higher carbohydrate content. ^*

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Cell biology

Bio-chemistry

Athletics

See also