I ride my bike to and from work every day (half an hour each way). I notice that the muscle content in my legs is increasing, but the fat is not disappearing. I am worried that all of the fat will eventually turn into muscle and I will be left with monstrous, manly legs. Is there any way of preventing this from happening?

First of all, fat does not "turn into muscle" or vice versa. By the time we reach adulthood, we have a finite number of fat cells and muscle fibers in our bodies. The fat cells just get bigger or smaller according to our food intake and energy output. Muscle fibers grow in response to the amount of work we make them do.

Now, cycling may make your legs a little more muscular (not that there's anything wrong with that), but fat loss is the key to keeping your legs from getting too big. The longer we exercise, the more calories we burn. You're getting a daily total of one hour of cycling, in 30-minute doses. Why not add a detour, on your trip to or from work, that adds another 15 minutes to some of your weekday rides? On weekends, try to cycle at least one day for at least an hour, for more continuous calorie burning. Of course, extending your rides makes you more fit, too.

Another strategy is to use a lower (smaller) gear, causing you to pedal faster in order to maintain the same pace. This is more efficient and fatigues your legs more slowly, which is why racing cyclists are always pedaling in the 80-100 rpm range. More pedal strokes per minute means each pedal stroke is easier, recruiting fewer muscle fibers.

It's the same principle you would employ when working out with weights. Performing fewer repetitions of an exercise with higher resistance builds strength and size more quickly than using less weight and doing more repetitions, which is better for tone and definition. You can see this reflected in the different leg development between cyclists who race on the track, turning big gears, and road cyclists who spin lower gears to get over mountains.

As long as we're on the subject of resistance, do some upper body weight training exercises. You'll increase your lean muscle mass, which will raise your resting metabolism, so that you'll burn more calories even at rest. You'll also balance your physique. The fat on your legs will disappear, and you'll be left with thighs of steel.

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