Stretched length across papers

Stretched flaccid length is taken by pulling the shaft to a point of resistance and measuring from bone to tip while holding that tension. That single word, resistance, is doing a lot of work, and it is the reason stretched-length figures move around between published studies more than erect figures do.

Tension is a judgement call, not a fixed force

An erect measurement does not depend on how the measurer holds anything - rigidity comes from the body, not from applied force, so there is comparatively little for a protocol to standardise beyond angle and landmark. A stretched measurement is different in kind: the number depends directly on how hard a hand pulls, and "pull until you feel resistance" is a description of a sensation, not a quantity. Two trained observers, both following the same written protocol in good faith, can apply noticeably different tension and still both believe they have found "the" resistance point, because the protocol never specified a force, only a feeling.

Some protocols add detail - pull until the tissue stops giving, or pull to the point just before the participant reports discomfort - but these still describe an endpoint by feel rather than by a measurable quantity like a fixed number of newtons applied through a spring-loaded device, which most clinical settings do not use.

What this predicts, directionally

Because tension is operator-dependent, a between-study comparison of stretched-length means should show more spread than a comparison of erect-length means, once other protocol differences are accounted for. This site will not attach a number to how much more, because the underlying test - the same protocol, the same men, different observers, force logged directly - is not something this site has a citation for. The direction is defensible from how the measurement is defined; the magnitude is not something to invent.

This is one specific instance of the wider pattern that published studies disagree with each other for protocol reasons before anatomy is involved - stretched length is simply the state where that general problem is sharpest, because it is the one state in the standard protocol set that depends on an applied force nobody measures directly.

Why clinics use it anyway

Given all that, it is worth asking why stretched length appears in the literature at all rather than being discarded as too operator-dependent. The answer is practical: stretched flaccid length correlates with erect length well enough to serve as a private, non-erect proxy in a clinical setting, which matters when obtaining or measuring an erection is not appropriate for the encounter. It is a useful measurement with a known weakness, not a discredited one - the weakness just needs to be carried alongside the number rather than forgotten.

The technique itself - how far to pull, what resistance is supposed to feel like, how to hold it while reading - is a separate, practical question with its own answer, worth reading if you are trying to take the measurement rather than trying to read a table of published means.

Reading a stretched-length figure in a paper

Two habits help. First, do not average a stretched-length mean from one study against a stretched-length mean from another as if the difference is informative about anatomy - check first whether the two papers describe their tension instruction in comparable terms, and most do not describe it in enough detail to compare at all. Second, treat a single study's stretched-length figure as more protocol-dependent than that same study's erect figure, even though both come from the same paper and the same measurer.

None of this is a property of a rating or a score. A judged verdict does not have a tension protocol to disagree about, and neither does an estimate read from a photograph - both vary for their own reasons, unrelated to how hard anyone pulled a shaft during a clinical visit. If a subjective figure is closer to what you actually want, a rating platform or a gallery of scored photos is answering a different question than any stretched-length table, and the two should not be read against each other as if they measure the same thing.