Shewhobikes -- core strengthening is absolutely wonderful for cycling. Like your leg muscles -- your core -- full abdominals and back area -- benefit from strengthening. Besides your legs, they are the key muscles that strengthen your body's stability. Cycling is very dependent upon your core having the strength to control and maneuver the bike, and if you road bike especially, your back and lower back can take a beating if you are not building the muscles around it to their optimal levels. This is what core strengthening does for you. You also gain a great deal of flexibility that cycling can sometimes take away -- whenever you do a sport like cycling over and over, your muscles become somewhat tightened into those positions, and yoga and pilates esp I have found have allowed me to counter that by loosening up that tightness I get in my back, hips, etc.
Pilates is probably the optimal way to build your core (look for classes at your gym or good DVDs I like are Mari Winsor, Stotts Technique). The other way, and also very beneficial you can even do at home is done with a ball (those large ones you fill with air). There are several core exercises you can do for torso and back -- several of the balls you can buy come with some, or you can pickup an issue of Women's Health mag, Self, Shape...they all have routines in there on the ball. Yoga moves that focus on your core can also be used. Added benefits -- recent studies are showing that yoga is an aid in easing post cardio exercise muscle pain -- additionally it relieves lactic acid build-up pain. Yoga is preventative -- these studies showed results with people doing yoga 2-3 times per week.
Also check out some sites that provide info and some floor and ball exercises:
www.ultracycling.com
www.yogajournal.com/practice/196.cfm
www.hubbub.com/DailYoga/30MinuteYoga.htm
http://www.active.com/story.cfm?stor...TOKEN=44930982
http://www.ginmiller.com/gmf04/artinfo/bestabsSB2.htm
http://www.shopnbc.com/pom2k.aspx?ca...laytype=2&ft=0
Good luck, I have never had a better back since I started core strengthening!!