Let’s look at how all this effects your measurements. Let’s say you have an upper arm measurement of 16 inches before you perform a workout. If you are training hard enough, your arm will probably pump to about 16 1/2 inches during your workout. But, if you measure your arm two hours later – measured accurately – your arm will probably be smaller than it  was before your workout, maybe about 15 7/8 inches. If you measured your arm “cold” (not pumped) twenty-four hours later, your arm would be back to it’s normal measurement of 16 inches – or slightly larger – if you managed to gain muscle fast.

What’s the point of all this? Well, accurate measurements of various body parts will clearly prove that measurements vary considerably during the course of an average day – even when you are not training. For example, your upper arms are slightly larger than normal when you get straight out of bed first thing in the morning – and slightly smaller for an hour or more after you have eaten a large meal. Temperature, of course, will also dramatically effect your measurements – your arms are usually a bit smaller on cold days, and larger on hot ones.

Therefore – for any sort of accuracy – you should try and take your measurements under the same conditions. Unfortunately, in practice, that is a very difficult thing to do. And it is for that reason alone, that pumped measurements are of such importance. When you measure a particular body part when pumped, the conditions will almost always be the same, at the end of each workout.

Also, as long as your training program remains the same, your pumped measurements will give you a definite indication of future muscle growth. For example, if your upper arm normally pumps only one-half an inch during your workout, and then shows an increase of three-quarters of an inch as a result of performing exactly the same workout, then this is a very clear sign that your arm will grow during the next forty-eight to seventy-two hours.

In other words, the ability to pump a muscle to a particular size, demonstrates the potential growth of that same muscle. The bigger the difference in your pumped measurement from workout to workout, the greater the muscle growth. Period.