Segmental ECW Ratio

• A calculated value: extracellular water of the segment (L) ÷ total water of the segment (L).
• Both inputs are derived from impedance measured in that segment at several frequencies; low frequencies reflect mainly extracellular water, high frequencies also capture water inside cells.
• The manufacturer does not publish the conversion from impedance to a volume of water, so the value cannot be independently verified.
• On the result sheet the ratio is charted for all five segments, so it is visible at a glance which segment deviates.
• The manual publishes no separate numeric thresholds for individual segments. It applies the same logic as for the whole-body ratio, whose recommended range is 0.360 to 0.390.

• Compare the five segments with each other first. The ratios are mutually comparable, because they do not depend on segment size.
• The recommended range the manual works with for the whole-body ratio is 0.360 to 0.390; the evaluation sheet additionally distinguishes bands below 0.390, 0.390 to 0.400 and above 0.400. The manual gives no separate numeric thresholds for individual segments.
• A raised ratio in a segment with high water is, according to the manual, the situation in which lean mass in that segment is likely overstated.
• Read a deviation in one segment differently from a deviation in all five. The first points attention to what happened to that area, the second more to overall water balance and to measurement conditions. In neither case does the number establish a cause.
• The manual explicitly notes that a raised ratio also appears in people without any particular diagnosis: it names lean women, older adults and people with a high proportion of fat, in whom it reflects a relative increase in extracellular water for nutritional reasons or where muscle is lacking.

• Compare only measurements with the same preparation. In segments of the lower body the influence of time of day and posture is strongest.
• A difference of a few thousandths between two measurements sits within ordinary variation. What matters is the direction across several measurements.
• When the ratio rises in one segment and not the others, watch whether the difference holds. A one-off shift after one-sided loading or after prolonged standing is not information about a long-term state.
• The manufacturer Comparison Result Sheet shows the change in ECW Ratio between the current and previous measurement for the whole body and for each segment separately.
• A sustained rise across all segments alongside falling lean mass is a different situation from a one-off swing and is worth discussing with a professional who knows your context.

General principles: how to read change between measurements →

• The whole-body ECW Ratio – places the segmental picture in overall context and has a published recommended range.
• Segmental body water – the pair the manual explicitly flags: high water plus a raised ratio means a risk of overstated lean mass.
• Segmental lean mass – the value whose reliability this ratio assesses.
• Segmental intracellular and extracellular water in litres – show which compartment moved.
• Segmental phase angle – another segmentally measured quantity derived from the electrical properties of tissue.
• Body cell mass – the whole-body indicator the manual recommends where fat free mass is distorted by excess extracellular water.

• A raised ratio in a segment is not a diagnosis of oedema. The manual uses the term oedema to describe a physiological state, not as an output of the device. Oedema is assessed by examination, not by a single bioimpedance number.
• A raised ratio does not establish kidney disease. The manual does note that patients with impaired kidney function tend to have a higher ratio, but it also names ordinary situations without any diagnosis in which the ratio is likewise raised.
• A higher ratio does not mean more water in the segment. It means only a different division of the water that is there.
• A difference between sides is not automatically a problem. Judge it as a trend and alongside segmental lean mass.
• Segmental ratios do not add up to the whole-body one. The whole-body value is calculated from total volumes, not as an average of five segments.

• Time of day — the manual notes that water shifts towards the lower half of the body during the day.
• Posture before the measurement; the manual recommends standing for at least 5 minutes, because standing lets gravity draw blood into the lower limbs.
• Training, prolonged standing or sitting, and one-sided loading of a single limb.
• Food, drink and higher salt intake before the measurement; the manual recommends measuring fasted.
• Sauna, showering and room temperature outside the recommended 20 to 25 °C.
• Menstruation, during which body water fluctuates.
• The quality of electrode contact and correct position: arms must not touch the trunk and thighs must not touch each other.

• Use the segmental chart as a companion to the whole-body value, not instead of it. Read the whole-body ratio first, then look at whether the deviation is even.
• Look up the ratio for every segment with high water. This is the procedure the manual itself recommends because of overstated lean mass.
• When all segments are raised and muscle mass is falling at the same time, address muscle mass, dietary protein and strength training first.
• Follow a difference between sides over time. A one-off swing after exertion or a long day on your feet carries no meaning.
• Visible swelling of one limb, pain, redness or sudden enlargement belongs with a doctor regardless of what the ratio shows.

• It does not diagnose oedema, inflammation, kidney disease, or venous or lymphatic problems.
• It does not establish the cause of a difference between segments or between sides.
• The manual gives no numeric thresholds for individual segments; the published range concerns the whole-body ratio.
• It cannot say whether the ratio shifted through a gain in extracellular water or a loss of water inside the cells — both components in litres are needed for that.
• The equation converting impedance into a volume of water is not public, so the value cannot be independently verified.