You do not jelq your skin, the point of the jelq stroke is to move blood through the chambers inside your penis, as Workin_4_it described it before, imagine your penis is a tube with tubes inside of it, now the outer tube is your tunica and the inner tubes are the CC and CS chambers. When you jelq, blood expands those inner tubes as it increases the pressure your penis can withstand so slowly, over time there is more room for expansion thus growth.
You jelq over your skin, not the skin itself.
If you got weaker erection after jelqing, then maybe you did one or more of the following:
- Used a tight grip for jelqing.
- Stretched too hard.
- Jelqed at a high erection level.
- Too many reps.
- Jelqed or stretched the glans.
- Overtrained your PC muscle.
Take rest and do not do any of the above when you jelq next time.
