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What is Bio-Electrical Impedance Analysis?

Bio-electrical impedance analysis (BIA) measures the impedance or opposition to flow of a small (500 mA) electric current passed through body fluids.

Impedance is also affected by the frequency at which the current is passed.

At a frequency of 5 kHz impedance of the fluids outside the cells (extra-cellular fluid or ECF) is high, while impedance through the cellular fluid (intra-cellular fluid or ICF) is low (because cell membranes act as imperfect capacitors).

At a frequency of 280 kHz, however, impedance to current flow through cells can be used to assess total fluid volume.

Prediction equations, determined by experimental research, correlate impedance measures to estimates of TFV (Total Fluid Volume), ECF volume, ICF volume, body mass, plasma volume (PV) and body fat mass.

BIA is safe, non-invasive and has been used on humans since the 1980s.

Principle of Multi-Frequency-BIA

Principle of Multi-Frequency-BIA


How Can BIA Help Me?

  • An aid to optimizing the care and performance of your horse.
  • Monitor hydration status before and after exercise.
  • Monitor hydration status during exercise:
    are your hydration strategies working to prevent or minimize dehydration?
  • Monitor hydration status during and after trailoring/air transport.
  • Monitor body mass, percent body fat, and plasma volume.

What is Hydration Status?

Hydration status refers to the water content of the horse.

Water is found in 2 main 'compartments':
   inside the cells (intra-cellular).
   outside the cells (extra-cellular).

Water can be lost and gained by either compartment. This loss or gain can occur at different rates in each compartment.

Normal hydration status is referred to as euhydration.

Loss of water is referred to as dehydration.

Re-gain of water is referred to as rehydration.

Why is Dehydration a Problem?

Water is almost always lost from the body with ions or electrolytes.

Water and ion loss occurs through sweating, urine, faeces and breathing.

Water and ion losses in excess of that regained through the gastro-intestinal system results in dehydration.

Dehydration is an imbalance in water and ion levels in the body.

Dehydration impairs the ability of cells and the body to function at optimum levels.

A loss of Body Water of only 1%, approx. up to 3 litres, will impair performance.

Dehydration can be prevented by administering water and ions to the horse to drink, such as quality oral rehydration solutions.

Horse Stalactites illustration

Why have a BIA unit for my horse?

  • To safely, rapidly and accurately quantify total body water and extra-cellular fluid volume.
  • To optimize rehydration strategies to maintain optimum performance.
  • To easily estimate body weight for feeding, medication and de-worming programs.

Research Results

The Equistat devices have been validated against 'gold standard' dilution techniques for measuring total body water, extra-cellular fluid volume, plasma volume and body mass.

Prediction equations were determined using data from 20 horses, ranging in weight from 430-560 kg.

Validation has been performed using additional horses.

Research Conclusions

The Equistat devices accurately estimates Total Fluid Volume, ECFV, PV and body weight in horses.

BIA technology appears to provide an excellent diagnostic tool for measuring hydration status of horses.

"Equistat® has been scientifically proven to be a rapid, non-invasive method to estimate your horse's hydration status and body mass. This reliable technology provides important, objective information that can be used to evaluate and improve the health and performance of horses."

Dr. Michael I. Lindinger, Ph.D.