First, you need to know how an erection happens.

A man's ability to become erect depends upon several different organ groups to function in a chain reaction. First, the stimuli is visual which triggers a hormonal release from a particular region of the brain. This hormone then causes blood to pool into the penis filling the tissue and engorging it.

The penile tissue involved in this filling or pooling of blood is the Corpora Cavernosa. Small openings in the corpora cavernosa fill with blood leading to firmness and erectness of the tissue. Erectile tissue contains a specialized arrangement of arteries, shunts, and venous sinusoids within a matrix of connective tissue and smooth muscle, forming a highly structured criss-crossing of interconnected fibers and spaces that are tensed as the cylinder expands during erection. This tissue will respond to a very specific stress placed upon it causing the cavern dimensions to increase, thus enabling more blood to store and your size to increase.

Techniques like urut batin or other natureal penis enlargement or erection enhancement exercises attempt to use massage to manually encourage blood flow ot the penis, remove blood stasis (pools of blood that block capillaries from delivery their fresh blood supply) and expand or lengthen penile tissues (corpora cavernosa, suspensory ligaments, etc), somewhat like stretching a muscle. Technically, the penis does not contain any muscles per se, but...

How natural penis enlargement happens

The corpora cavernosa in the penis is similar in construction to the pore cells in marine life called sponges. Repeatedly stretching the absorptive pore cells in a live sponge will cause the cells to expand and heal in the expanded state, adapting to the minute tearing of the cellular walls, thereby making the pore cells larger and more capable of absorbing more water and nutrients.

The corpora cavernosa inside our penis is a live tissue which responds much in the manner of a sponge; therefore, continuous stretching and healing should cause the distensible blood spaces to increase their ability to absorb more blood, as a sponge does with water, and thereby increase actual size of the erectile tissue.

At the same time, stretching of the suspensory ligaments (tissues that basically attach your penis to your body) result in elongation of the ligaments which are somewhat elastic in nature. This perhaps lengthens the penis but more importantly, it can change the position of your penis, from one where up to 25% of its length is hidden inside your body, to one where more of it is on show. Between the marginal real lengthening and the visibile lengthening, the results can be quite impressive, with 1" to 2" of additional length visible.

Do natural penis enlargement exercises really work?

Natural penis enlargement techniques have become increasing popular in America and around the world. "Jelqing" is also the most common term for a number of natural penis enlargement exercises.

In the late 1970's comprehensive research was carried out in the United Kingdom by Dr. Brian Richards. The results were published in the British Journal of Sexual Medicine Magazine. The study showed positive results for 87% of the test group. (Some reported an increase in penis length of up to 1.4 inches as well as in penis girth of up to 1 inch.)