Energy conservation

I was thinking about energy shortage in the current situation. Also thinking fuels which are short term like petroleum etc. I understand we are using solar, tidal, wind and other non-conventional ways to generate power but not in high volume. What could be done at root levels to tackle power shortage.

We have learnt in our school days that energy can neither be created and not be destroyed, it can only be copnverted from one for to another. Having this as background, I had some wiered thinking few days back.

We have seen in recent past that people have become very health conscious and do a lot of exercise to excert energy and burn a lot of calories. This is energy expended and getting lost as heat or some kind of energy which can not be used in constructive manner. Is there a way to pouch these burnt calories into one of the useful forms?

What can be done:
1. Can we dynamos fixed under thread mills and cycles in gyms

2. Special mats which can sense step imapct and convert into electrical energy,  in pathways of parks where milliions of people walk every morning

3. Many more sensors and energy converters in fitness centers !

What you guys feel !!!!
Regards,
Karthik Sunil