When muscles are engaged in any kind of work, they demand an increased blood flow, or circulation, with its cargo of oxygen and other nutrients. Increased circulation is important for two reasons. First, it provides the muscles with the fuel it requires. Second, the flowing blood picks up and Removes the larger-than-normal amount of waste that is being produced.
If the work assigned to the muscles continues for some time, the inflow of blood into the muscle and its subsequent outflow strike a happy balance, which is what we want.
A feature of this balance is a slight enlargement of the working muscle. However, if the muscles are worked at nearly maximum intensity, as in, for example, a heavy barbell exercise, such as the bench press, curl, over head press, and if the repetitions are executed consecutively, the engorgement of the muscle produces congestion in its interior, thereby swelling the arm to a degree that is often astonishing. The process by which the arm has become engorged is called pumping.
A pumped upper arm may gain a full half inch over its normal size when pumped to that extent, an arm will feel very heavy, which is not surprising, since its actual weight has temporarily been increased. It will also feel stiff, since its flexibility will be temporarily reduced. In most cases, the degree of muscularity will be reduced. The muscles will look much larger and will be much larger, but will appear less defined than they normally do. In a few cases, particularly in a bodybuilder with an extreme degree of muscularity, a pumped muscle may actually appear more defined. In most forms of work, the effects of pumping usually occur without being noticed. For example, few people are aware that their lower legs are usually a half-inch larger at night than they are early in the morning. Their calves increase in size during the day as a result of pumping.
During the night, when calves are at rest, their circulation requirements are reduced greatly, and their size is decreased.
As far as pumping is concerned, weight training exercises are similar to any other kind of exercise. The number of repetitions performed and the relative intensity of effort are the only significant factors. In most exercise, movements are discontinued before any great degree of pumping is produced. For this reason, many new athletes feel that weight-training exercises are somehow different.
When they become involved in weight training, they notice the effects of pumping for the first time. Many new trainees are convinced that they are already becoming “muscle bound,” as a result of their initial work- out. In reality, muscular pumping is an indication that worthwhile efforts are being expended. If no noticeable degree of pumping is produced, then an exercise is doing little to build muscular size and strength. Although a notice- able degree of pumping becomes evident during any really productive exercise, it does not follow that an extreme Degree of pumping is a sign of doing proper exercise. Actually, it is possible to produce an extreme amount of pump from exercises that do nothing to build either size or strength. Light movements performed in sets of very high repetitions, especially if the movements are restricted in range, will produce muscular pumping without building size or strength. On the other hand, several sets of 8 to 12 repetitions of a heavy full-range movement will produce the same degree of pumping, and they will also induce maximum growth stimulation.
With an upper arm measurement of 16 inches prior to workout, a bodybuilder, strongman, power lifter, etc. can probably pump his arm to a measurement of 161/2 inches during a hard routine. But if it is 1 to 2 hours later, his arm will be somewhat smaller, probably about 15 7/8 inches. Measured 24 hours later, his arm will be back to its normal measurement of 16 inches, or slightly larger, if growth resulted from the work out. Accurate measurements of various body parts will show that they vary in size during an average day, even when you are not training. For example, your upper arms are slightly larger than normal when you first get out of bed in the morning and slightly smaller for an hour or so after you eat a large meal. Temperature will also affect your measurements, your arms being a bit smaller on cold days and larger on hot days. Measurements for record-keeping purposes always should be taken under precisely identical conditions. In practice, this is difficult.
For that reason, pumped measurements are useful because conditions are usually the same at the end of each workout. Furthermore, as long as your program remains unchanged, your pumped measurements will give an advance indication of your future development. If your upper arm normally pumps one half inch during a workout, and then abruptly shows a gain of three-quarters of an inch as a result of one session of the same type of workout, your arm is ready to grow during the next 48 hours. The ability to pump a muscle to a particular size usually precedes the actual growth of that muscle to the same size as its earlier pumped-up measurement. Saying it another way, if you pump your muscle until it is larger than normal, at the end of a regular workout, you can be assured that your muscle has the solid capacity to increase in size and strength until it is as large as when it was first pumped it up to its new dimension.
And there you have it, a bit of a different look at the “pump”