I recently wrote an article on upside down yoga poses such a Viparina Karani and headstands and how they help with drainage of the lymph and how this aid to recovery. If you would like to read this please check out link below
There are various upside down poses and one of the most important poses is the headstand. Yogi's called the headstand the king of all yoga poses due to the physical and mental health benefits it provided. Headstands are also used by Shaolin Monks and they are known for meditating in this position for long durations.
I think this is not just a great way to stimulate your lymph flow, blood circulation for recovery but also a great way to strengthen the neck. For grapplers such as Judo, Brazilian Juijitsu, Sambo players the last thing you want is someone to be cracking on your neck during a BJJ or nogi class and injuring your neck. I have heard of this happening many times and it is a scary situation. Nowadays, with help of youtube the white belt students are learning all sorts of guillotines and neck cranks and they try them out at their BJJ class. Hopefully the instructor is alert and can prevent some of these guys applying the technique incorrectly. This of course applies to all students. It is very important the instructors can guide their students during these types of techniques/maneuvers/applications. With this being said, I think strengthening the neck is very important to prevent injury.
Wrestlers are also very prone to neck injuries during suplex throws. Wrestlers already have quite a few neck drills built in their warms ups since they know the importance of this but different exercises such as this can be be beneficial.
This can be done for recovery and for neck strengthening. I recommend consulting your doctor before doing this type of exercises since they can be dangerous if not performed right. This type of stands improve circulation to the brain which can aid athletes with greater focus. Being focused on the goals, strategies, medals after all is something it's worth it's weight in golds for atletes.
Working on a soft surface like an ab mat can help. Sand is also another surface that might be good. All of these exercises in this article should be done under a professional's guidance.
If you have not seen my article about training on sand, please check link below: