It's hard to avoid hearing about green issues these days. What with them wanting to build wind farms next to your city instead of coal-fired generators, worrying about illegal dumping polluting the water table, or warning about climate change, today is all about being kind to the environment. We see this in moves to make the vehicles we drive more efficient and suggestions the public transport system should be upgraded. At a personal level, we are encouraged to save energy, dispose of our rubbish responsibly and ride a bicycle. . .

Now there's an exciting idea. Of course, everyone would think you weird if you were to start walking. No one ever walks anywhere. But get on a green machine - no fossil fuels and no air pollution - you're making a cool statement about who you are and that you care about the planet. A group recently worked out that if everyone who lived within five miles of their place of work decided to ride rather than get in a vehicle for just one day every week, this would prevent five million tons of pollution every year. Now that would really make you feel good, wouldn't it? You did it as a kid around the neighborhood. Living out in the countryside, the bike was probably the only way of getting around.

As an adult, riding a bike is not only good for the environment, it's good for you too. You get your body and, most importantly, your heart fit, increasing your strength and stamina while burning calories. There's nothing else that can get you where you want to go and help you lose weight at the same time. There are also psychological benefits. The evidence shows the more you exercise, the more you release stress. It's having fun and releasing endorphins to make a rewarding package.

But, for all you save on gas bills and lose those pounds, there's a potential downside. Those shaped seats you get to sit on can compress the blood vessels and the nerve endings in your groin. The vital bit between your penis and the anus is called the perineum. If you find yourself getting a little numb or you have a tingling sensation of the wrong type, you should change the seat. If you don't, this can slowly build up damage in the blood vessels, reduce the level of pleasure in sex, produce erectile dysfunction and cause you pain. Believe us when we say you are not expected to sacrifice your manhood to save the planet. So consult an expert on the shape, size and tilt of bicycle seats. You need something that supports rather than compresses when you push down and back along the line of the seat.

This is important. If you fail to take action, the damage to your perineum can become serious and the erectile dysfunction permanent. Even the power of Viagra will not be sufficient to force the blood vessels to dilate in this critical part of the body. So, do not continue to ride if you get warning symptoms of numbness. Allow your body to recover. Fit a different seat and, with Viagra's help, you should be back in the saddle again in a few days.