The following might be best in a separate thread but it certainly applies to “dynamic pumping”…
It is important to remember that there are at least 3 approaches to pumping and to short cycle (dynamic) pumping that affects the amount of vacuum in the cylinder during the “Hold” part of the cycle. I will explain the concepts with examples using a manual pump even though many guys use electric pumps.
Pump & Stop: Pumping to 5” Hg and stop pumping. As the penis expands in the cylinder the vacuum will decrease and eventually stabilize at a level less than 5” Hg. This type of cycle is similar to when guys pump up then disconnect the pump from the cylinder for mobility and long hold times. The length of time to stabilize and final level of vacuum seems to vary depending on erection status.
Pump at constant vacuum: Pumping to 5” Hg and continuing to pump a little as the penis expands to keep the gauge at 5” Hg for a certain time. The penis is exposed to 5” Hg vacuum all the time even as the penis expands in the cylinder. This method will produce the most edema if time and vacuum exceed the threshold of the tissue - in other words, with enough vacuum and time fluid will be pulled into the skin thereby forming a blister.
Pump with controlled leak: Pumping to 5” Hg, stop pumping, then gradually decreasing the vacuum with a controlled leak (valve) thereby lessening the exposure of the penis to vacuum. This approach subjects the penis to spikes in vacuum but only for a short time and is the method that the Mr. Fantastic pump system uses.
Short cycle (dynamic) pumping can use any of these 3 methods by simply cycling to lower vacuum (or none) instead of “pump and hold.”
When guys report the their results it’s important know exactly what they are doing in terms of pumping technique. I also think there are many variables such as erection status (“pumping hard vs soft”) that affect results. The “pump with controlled leak” technique has the most variables of all.