I usually get e-mails from people who are starting to train who find at the end of a rigorous workout that their vertical is slightly lower the next day.
This is actually normal.
It's part of the cycle of breaking down and building up muscles.
When you engage in a physical training program, not only are you fatiguing the muscle but you are also creating micro-tears within the muscle.
While these tears do weaken the muscle temporarily, but if you give yourself a proper recovery phase and eat nutritious foods within 24-72 hours (on average), your muscles will actually be stronger! The recovery time it takes to recover can vary from person to person, even up to seven days! I emphasize proper recovery and nutrition because this is when the actual muscle building happens.
If you don't give yourself a proper recovery period, you will break your muscles down over and over again without a proper build-up of additional power.
It is absolutely crucial to have a recovery phase.
Having an exaggerated recovery phase is better than risking injury.
How do you find out if you need recovery? The most effective way to find out is by monitoring your own performance.
If you are constantly getting stronger in the gym and performing at higher levels, then your recover is accurate.
If you are not as strong or motivated and you are not performing to your liking, then you need to take a closer look at your recovery.
This is also why I stress the importance of monitoring your vertical training on a daily basis.