As with most profound physiological processes, the pump results from the complex interplay of a number of related functions. In bodybuilding terms, the required stimulus for an effective pump is, of course, proper weight training. As bodybuilders, they train with weights for the sole purpose of stimulating muscle growth, and the pump indicates we are heading in the right direction as far as this aim is concerned.
To achieve maximum muscular growth a pump (scientific name, hyperemia) is essential, and the only way this can be achieved is to train correctly with the right energy intake, to allow sufficient blood flow to the working muscles. Working muscles need blood to supply them with oxygen and nutrients, and remove waste products (namely, lactic acid and carbon dioxide).When a muscle is trained, blood flow is diverted from many other bodily processes, to supply this muscle with what it needs to perform maximally. The blood first needs to become oxygenated (which is done through gaseous exchange in the alveoli of the lungs) before it is pumped to the working muscles, where it is pooled, thus resulting in the tight feeling we call the pump. It is thought that during training, a muscle can receive up to four times the amount of blood it would ordinarily get. Why exactly do the muscles need all this blood? As mentioned, the muscles require sufficient oxygen and nutrients to continue the sustained contracting that results in a pump. Over time, the pump will also create a greater number of capillaries (tiny blood vessels), which will, in turn, provide the muscles with more nutrients and oxygen and allow for larger pumps and more growth in the long term.
How is the pump achieved?
As mentioned, a number of interrelated factors are required for a muscle to pump with blood. The first of these serves a protective function. When we begin training, the nervous and endocrine systems signal the heart to pump more blood. This blood, made available through an increase in cardiac output and blood pressure, pools in its intended muscle, thereby helping to create the pump.
The fight or flight survival mechanism underlies this process, because the muscles are preparing for vigorous work. Whenever we engage in any form of vigorous activity, blood is diverted from unessential bodily processes (such as the urinary or digestive systems), to be used by muscles relevant to the task at hand.
A muscle that does not receive adequate oxygen will fail to continue contracting over a longer term, thereby limiting the intensity of an exercise, which, in turn, stifles the muscles efforts to pump up sufficiently. Lactic acid (a by product of high intensity work) will also congregate in the muscle, causing it to fall short in terms of energy expenditure.Blood that is supplied to the muscle under conditions of maximal work will help to flush this lactic acid out, thereby assisting the pump. The pump is also achieved when hormones and signaling factors such as nitric oxide (NO), released in response to the acidity caused by high lactic acid levels, cause local capillaries in the muscle to dilate, thereby allowing more blood to flow into the muscle. Blood that is supplied to the muscle under conditions of maximal work will help to flush this lactic acid out, thereby assisting the pump. The pump is also achieved when hormones and signaling factors such as nitric oxide (NO), released in response to the acidity caused by high lactic acid levels, cause local capillaries in the muscle to dilate, thereby allowing more blood to flow into the muscle.