If we are "out of touch" from the ground, then we are full of stress and probably experience some illnesses. It is also logical to think that the basis of this study is from the fact that every thing 'emits' energy, and that getting close to nature like plants, body of water and earth..
Now that we live in technology and our lives revolve around gadgets, our mobile phones and computers, we receive a lot of unhealthy amounts of radiation. I am not so knowledgeable about the scientific terms, or what to call those, but what I am sure about is that we live in an unhealthy environment. We spend our days inside poorly ventilated offices or houses with not enough oxygen. That probably is the reason why we get sick very easily.
So try to get in touch with nature as often as you can. I will make this as my new goal. I want to live healthier, I want to really live..
If you can walk barefoot, the better.. of course in a park or somewhere where there is well, ground (not cement!). A walk in the beach is great too, you get to do 'earthing,' plus, you get the healthy benefits of negative ions from the sea breeze!