Bioelectrical Impedance Analysis (BIA) Monitor

What is it?

It is a battery powered, non-invasive assessment tool for body composition (What the body is made up of).

How does it work?

The monitor uses four electrodes, two of which are placed on the hand and wrist and the other two on the superior foot and ankle. Once subject data has been input to the device i.e. gender, height, weight, activity level, and waist and hip circumference, the test is completed taking all of 4 seconds. During these 4 seconds an undetectable current is passed through the body and depending on the resistance in encounters (high resistance – high fat percentage; low resistance – low fat percentage) it will determine the following:

• Fat mass and percentage

• Lean body mass and percentage,

• Total body water

• Estimated basal metabolic rate

• Estimated average daily energy requirement

Electrical conduction through the tissues depends on the water and electrolyte content. Because the fat free mass contains almost all body water, conductivity is much greater than compared to fat mass, equaling less impedance. Due to the lack of fluids within the fat mass, impedance is greater and so the current travels slower. This difference in current flow reflects the amount of fat in those tissues.

How accurate is it?

It has its pros and cons like any other assessment tool but as long as certain subject preparations are completed the BIA method is seen to be as accurate as any other body composition method.

Most studies conclude that BIA works well in healthy subjects however accuracy decreases at the extremes of body weight i.e. BMI >34 and BMI <16.

A subject’s hydration plays a huge role in BIA. Altered hydration will affect the impedance the current encounters during the test. Therefore, it is crucial subjects maintain an as close to normal state of hydrations as possible. This means members should prepare by abstaining from eating or drinking 4-5 hours prior to test, from exercising 12 hours prior to the test, and from consuming caffeine or alcohol (diuretics) 24 hours prior.

Other significantly altered hydration states which may decrease test accuracy include:

• Large volume IVs

• Diuretic therapy

• Edema

• Kidney, liver and cardiac disease

• Status post major surgery

• Pregnancy.

Why choose BIA over the skin fold method?

The BIA method provides a quick, much less invasive choice when looking to assess your body composition.  It does not require the subject to expose any body areas other than the back of the wrist and hand and superior portion of the foot to get its results. This can be extremely comforting for an individual subconscious of the way they look.

At the touch of a button this BIA monitor will provide the assessor with data regarding fat and lean mass percentage and weight, body water percentage and amount (L), and an estimation of basal metabolic rate (the amount of energy you body consumes at rest to maintain normal body function) and daily average energy requirement. This is more data than that of which can be retrieved through our current skin fold assessment, with less effort and more accuracy.

Riki Dallas | Recreation Manager| This e-mail address is being protected from spambots. You need JavaScript enabled to view it. | p: 03 2182989 | a: 77 Tay Street, Invercargill