Hi,
You can warmup in the shower, although it is not the best option. If you resort to it, please make sure that you do not warmup your testicles as well. They are better kept at a temperature below that of your body’s.
Using a heating pad is a much better option.
You can also wrap a warm cloth around your shaft, or use a cut bottle of warm water.
warmup method: the Aladdin’s bottle
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Hot WrapsA hot wrap is an essential warm up for any PE exercise. Here are two methods, others may work just as well.
Warm water and washcloth. Take a washcloth and soak it in warm/hot (not scalding) water, wring some of it out and wrap it around your penis.
Sock full of rice. Take a sock, and put 1/2 to 1 cup of uncooked rice (straight out of the box) in it. Tie sock or sew it together. Place in microwave (time varies depending on how much rice you put in your sock and on your microwave). This is every bit as effective as the washcloth, and you don’t get wet.
You should take your hot wrap and apply it for 5-10 minutes minimum before doing exercises. This warm up will reduce the risk of injuries. It serves to increase the blood flow to your genitals, which will be beneficial when you actually start exercising. It also makes the skin and tissues more pliable, and easier to stretch.
It would be wise to include hot wraps at the end of your workout as well, and possibly at some point in the middle of your routine. You will find that bruising will occur much less frequently if you do so.
It does not matter in which order you do the stretches. Stretch in all five directions (upwards, downwards, to the left, to the right, and straight out), and hold the stretch for up to 20 to 30 seconds. Do not stretch too hard, just enough to feel tension on your shaft. And do not grip your glans (head of the penis), make sure your grip is about an inch below the ridge of your glans.
As for Kegels, the following threads will help you.
Kegel - the secret revealed
Locating the bc muscle