Electricity through Gymnasiums

I started going to gym around 2 weeks back, which is pretty cool. It has everything including power backup but I am particularly intrigued by those self-powered machines. They get powered on after someone starts doing exercises on for few seconds. They convert mechanical energy to electricity and these machines gave me this idea…

Most of the power generation converts mechanical energy to electric energy, if we could harness the mechanical energy wasted during exercises then some energy problems of India could be solved. I am not talking about them at large scale, though the solution is very much scalable.
For example, my own gymnasium must be consuming around a hundred units of power daily, with 5 AC to run and 3 high power amplified speakers, not to speak of the electricity consumed by light bulbs and treadmills. The cross-trainers and the bicycles we work on are self powered, cycle them once or twice and the display on them comes to life. I am sure the display consumes far less power than is generated at the time of exercising, if that extra power could be fed into a system for charging batteries and that power could be used when batteries are charged fully then a considerable amount could be saved on electricity and hence greenhouse emission.

Talking about electricity, in my housing society there are 300 flats, on an average one person per two household goes to gym which makes for around 150 persons. Each of them burn around 1000 calories per day which comes to around 150,000 calories which is 150,000 X 4.184= 627,600 joules (1 calorie = 4.184 joules) and 627,600 joules = 627,600/3,600,000 units of electricity = 0.174 units of electricity. This amount may look like too little but here is how to look at it, we have a power backup through a 0.5MW generator which translates to 0.138 units of power generation, get the picture now? We are talking of considerably higher power generation for free and all that while people improve their health!
If my own society had gym, which was free for its society members, which could harness this power, we would never need that generator! And the picture gets even better; because the gym will be free more people will join the facility which means more power generation. It does mean using humans as rats on wheels, but who cares, people will do it willingly.
Is anyone listening?!!