Just like how an investor of money will put their savings into inflation proof funds like stocks, gold or other means, we also need a way to invest our internal energy after gathering it in the Lower energy center.
So to put it simply.
Step 1 - Cultivate lower energy center to gather and gain internal energy.
Step 2 - Invest or flow this into your root and legs to build up a foundation.
Anatomically the location's that we're speaking of is from around the hip to the feet. This includes your butt muscles, genitals, anus, tailbone and all of the components of the legs.
The word "root" in context of the body is a more polite way of saying "anus" which can be thought of as the bodies roots or foundation as kinetically it all emanates from here and grounds tension and force back here.
Hence a weak root means you're unable to ground much force or in simple terms, you can't tense and apply much muscular and other pressure because it hurts your body, not because you lack the neuromuscular power(mental strength).
It can also relate to bone health, bowel health, sexual power like erection or vaginal strength, ejaculatory power as well as general stamina and endurance.
Another way to look at it is that the anus is the middle section, the tailbone is the back and the perineum and its muscle (kegel muscle) which is location behind the testicles and in front of the anus for men and inside the vagina for women is the front section.
This is what we commonly think of as "The pelvic floor".
Training
Internal training for this area is performed by training the perineal, anal and sexual muscles.
So you'll want to focus from the tailbone region to the head of the penis for men or the clitoris for women. This whole area is full of internal muscles which can be exercised.
To do that, warm up by gently tensing it in a pulsing manner. You might want to count or do about 2 per in and out breath.
Then tense a bit more, performing it every out breath. Relax and open the pelvic floor during the in breath.
As you warm up more and more you'll be able to feel deeper within this space and have more of a physical grasp or grip over it.
Increase the strength and length of time that you perform this exercise after every set.
You can do about 50-100 reps per set and work up and down like a pyramid going from quick and weak to slow/strong then back to quick and weak.
Really, how you do it is up to you though. Just make sure to know your body and not harm anything.
As a side note this muscular area can be used to halt ejaculation in men. Usually the arse area is pulled in or tensed lightly. Hence strengthing this area aids in premature ejaculation.
Next are physical external exercises.
Anything that exercises the butt, legs and genitals is good for strengthening the root area.
Sex, walking, running, squats, leg press, calf raises, jumping, step techniques, dashes, glute raises, glute tensing, cycling or my favorite - horse stance are all great ways to exercise your legs and arse.
I find the main factors of leg training is pure muscle and circulation training which intends to improve muscular strength and blood flow.
Next is leg control. Taichi, martial arts and leg movement patterns are good for this.
And finally is improving your "mind muscle connection" that can be improved from standing stances, taichi and meditations.
To end our training section we have spiritual meditations. In my view the most interesting.
Similar to the past Lower energy center meditations this one requires you to have a firm grasp and a decently cultivated LEC.
Start by focusing on the Lower energy center which is under your belly. If you focus too high up then your belly inflates, too low and your energy goes cold.
Meditate on this area until your mind is settled and you feel enough density to work with.
Then while your focus in anchored at the LEC, stretch it out to your root region.
One way to do this is feel the lower back, then go inward, then feel the butt region and go inward while holding each area in your mental inner sense.
If this is done correctly then the butt and genital region will relax a little and fill with energy.
Next step is to flow this energy through your hips and into the legs, down to your feet.
This helps to increase your legs blood flow and aids greatly with standing meditations or stance.
That's the end of this meditation. I recommend holding it for 10-20 minutes.
Herbs and minerals is the last section.
Anything which aids stamina without having an overly heating or stimulating effect is good for the root. Usually cold, anti inflammatory herbs are used or those which aid bone health.
Horsetail is one example, ashwaganda, pickley lettuce, wild lettuce and common salt can be used.
*Disclaimer* This is not medical advice. I am not a medical practitioner.