Can Gymnasium become a power plant?

We have all seen today's world economy is depended highly upon resources, especially energy resources. Much of the world political conflict are around the competition of natural resources. The development of green technology to generate energy power thus becomes the top priority in most countries' development agenda. It is a recent news about a young kid designed a man-powered washing machine. So my idea came from two parts of recent technology development:

First is about collecting the man power. It is an exciting field, but actually nothing new. In the Netherlands, most bikes have a dynamo to generate enough power to light up for bikes, both front and back light. It is just a little dynamo touching the inside surface of the rolling front wheel. You can control whether to let it work or not just by moving it towards or away from the wheel. So it is easy to let it work when it is dark. So this power is generated and used immediately. It is not saved for other uses.

Recently, similar dynamos are designed to attach to human body's move. US and Canadian scientists have built a novel device - a bionic dynamo that effortlessly harvests energy from human movements. It can generate enough energy to power a mobile phone for 30 minutes from one minute of walking. The basic idea is similar to the design of the hybrid car. When you walk, the part of your stride that is before your foot hit the ground, there is power used for braking to slow your steps down. That part can be collected.

The second part of my idea is about selling electricity back to the grid. It seems that in UK it is already a possibility if you can generate more electricity than you needs. When you have a wind mill or solar panel that is possible to generate more than your own needs, you can set up a meter and monitor how much you refill back to the grid. The energy company will pay you back for the amount you created.

So my idea is about collecting and selling electricity back to the grid. Isn't the gymnasium the great place for this invention? There is not need, maybe, to collect individual muscle power. But all those treadmills are the most powerful collector of man-power. There must be a way to collect them. The gym can be operated together as a generator for the national grid. Currently all these energy were wasted if not making all those treadmills worn out. The amount of money it generated might be quite enough to cover the operation cost. It might be necessary to attach a meter to calculate how much power you produce, rather than how much calories you burned. If you produce a certain amount of power, you can use the gym for free. Isn't this great? People would feel like to going to gym because they are also contributing to the society, and it is free!

Let me know if you think this is a great idea. Also let me know if you want to start to explore it. I haven't done enough calculation to prove it really economic feasible. It is just an exciting idea in my mind recently.

The image is from here.