We often receive questions when people get two scans over a period of time and they see muscle differences and they think they have lost quite a lot of muscle.

One of the most common parameters that InBody users follow is the SMM – Skeletal Muscle Mass. It is shown in KG on the InBody results sheet, in the Muscle – Fat Analysis table, the Segmental Lean Analysis table and then also down the bottom left on the line graph. The graph and table is an excellent way for you to see, at a glance, how you’re progressing over the course of your scans.

What to look for when comparing scans

As you know, using an InBody Body Composition analyser is a precise way to measure body composition. We always try as much as we can to standardise the conditions when scanning but we have had people make comparisons between scans, for example before and after training where there has been some changes and they believe these changes represent muscle gain and/or muscle loss. To make a fair assessment, you need to look at the overall evaluation of the scan, particularly over time and test in as similar conditions as possible.

It’s not always lost muscle

We measure the skeletal muscle mass at InBody, but the first thing you need to know is what muscle is made up of; most of it is water.
To give you an example as to why there can often be a discrepancy between scans relating to muscle, we’ll use a 90kg male who goes to the gym and he has a fair amount of muscle on him.
When he trains in the gym, he gets what’s often referred to as a “pump”. A “pump”, by definition, is where more water/blood is pumping into the muscle. Arnold Schwarzenegger made the term “the pump” famous in the 1975 film Pumping Iron, where he charismatically described what he believed the pump felt like, but essentially it’s water and blood pumping into the muscle.
Now, let’s say this person “pumps up” in the gym. If you look at him it would appear that he has more muscle than when he started due to this “pump”.
It’s the same muscle but it’s just pumped up. Now, if you saw him an hour later, he wouldn’t look as pumped but you wouldn’t say that he lost muscle, because he still weighs the same. All he’s done is changed the intracellular and extracellular fluid ratio temporarily.

When doing an InBody scan, it will scan you in your current state. So if you scan after exercising, it will register the extra fluid in your muscle cells, and therefore register more muscle. If you were to scan him some hours after training, the scan would show normal muscle amounts compared to the artificial pumped muscle straight after training.

It is difficult to replicate those exact conditions when you next scan, so if you were to scan again, it is likely that you would have less fluid within the muscle cell, resulting in what appears to be “lost muscle” on paper.

Water ratios

There are more factors that you would need to look at to get the full picture, in particular the intra and extracellular water and the total water content. If someone was slightly dehydrated and did not have much hydration status then the muscle may register as a little bit lower, but it could be likely that they have not lost muscle.
Understandably, most people draw the automatic conclusion they could not have gained/lost that much muscle when they are only evaluating one parameter of the scan, so it is important to always look at the scan as a whole and checking the water related parameters.
As mentioned earlier, if a bodybuilder “pumped up” and deflated, you’re wouldn’t say he or she lost muscle, they just changed the ratio of water in the muscle.
When you get the scans and start comparing them, you may initially think “I’ve gained/lost muscle”, and that may actually be the case, but before you draw that conclusion (particularly when scans have only been done once or twice) you should still be evaluating the water ratio in the body, because that’s what muscles are – the water, so InBody measures the intra and extracellular water, that being muscle.

Evaluating change

Our advice is always to measure people over a period of time to create a standard for that person that you can precisely compare to, so instead of evaluating one or two scans, it may be 3 or 4 over a long period of time. This will help to create a baseline to compare to so you can then precisely and effectively evaluate their changes without being too quick to look at one parameter and question the changes without looking at the overall scan. It is vitally important to replicate to the best of your ability standardised testing conditions to ensure fair comparisons between scans.