Kicking butts: forget for a moment all that stuff about cancer—that's tomorrow. Smoking can screw up your workout today!

Smokers live up to 10 years less than nonsmokers and are more susceptible to emphysema, bronchitis, strokes, heart disease and multiple cancers. But that's then and this is now, and, goes the flawed thinking, why worry about the future when you're young and fit?

Because tobacco may be cheating you out of the muscle gains you rightfully deserve.

"The immediate effect smoking can have on your exercise efforts can be just as disastrous as its future consequences for your health," says Scott Swartzwelder, Ph.D., a clinical professor of medical psychology at Duke University and co-author of Pumped: Straight Facts for Athletes About Drugs, Supplements and Training.

You don't have to be a die-hard smoker to limit your athletic potential. If you puff occasionally, use chewing tobacco, live in an urban environment, or find yourself the victim of secondhand smoke from time to time, you're still susceptible to the following hazards related to nicotine and cigarette smoke:

* Less muscle gain

Inhaling carbon monoxide, either from pollution or cigarettes, deprives every muscle in your body of energy-rich oxygen. The less oxygen your muscles have to draw from, the less effective they are at contracting, which can inhibit how much weight they can lift.

"By [making you unable] to push a muscle through its full anaerobic threshold, smoking essentially forces you to use less weight than your muscles can truly handle," says Swartzwelder. "If you're working with muscles that are working inefficiently, you'll have a harder time breaking them down enough to stimulate the most muscle growth."

* Slower muscle gain

Smoking often delays the healing of fractures, cuts and wounds--and therefore impacts the fundamental mechanics of resistance training.

"When you lift weights to build muscle, you're creating microscopic tears throughout the tissue that need time to repair," says Ed Morand, master trainer for New York Sports Clubs/Town Sports International. "It typically takes your muscles between 48 and 72 hours to heal properly."

Proper rest lets your muscles adapt so they're stronger for your next workout, but smoking can interfere with the recovery stage, causing muscles to take even longer to repair themselves and thus slowing down your gains.

* Impaired strength

The muscles you're proud to flex are only as powerful as the bones tucked beneath them. Osteoporosis may sound like the last thing any youngish male needs to worry about, but, according to the American Academy of Orthopaedic Surgeons, all regular smokers experience a decrease in bone mineral.

For serious exercisers, weaker bones may not be able to handle all the stress that weightlifting incurs. This "increases your odds of being susceptible to a fracture," says Swartzwelder, which could translate into spending more time at home sidelined by an injury and less time getting the job done.

* Hindered performance

Nicotine decreases blood flow to all the tissues in the body. Because of this, tobacco users have a higher incidence of nerve problems, which can severely affect athletes who need to be fast and responsive. Although it may help you concentrate, nicotine--just like carbon monoxide-inhibits how quickly a muscle can contract.

That goes for chewers as well as smokers. "There's a whole subculture of athletes who use smokeless tobacco because they think it enhances their reaction times," says Swartzwelder. "But slower contractions mean a slower response from your muscles to move your body wherever it needs to be on the playing field."

* Nutritional ruin

If you think your carefully designed nutrition plan can stand up to the Marlboro man, think again. "Tobacco increases the volume of free radicals in the bloodstream," says Keith Ayoob, R.D., director of nutrition at the Rose F. Kennedy Center at Albert Einstein College of Medicine in New York City. "These electron-deficient molecules wander throughout your system looking to steal electrons from whatever they come in contact with." The extra proteins, amino acids and carbohydrates you've been eating to build yourself up get broken down and left essentially useless by these scavengers.

Tobacco also puts a crimp in your campaign against blood fats. "Carbon monoxide from cigarette smoke increases the amount of cholesterol that finds its way into your arteries, causing the same risks of stiffness and rupture of the arterial walls that a high-cholesterol diet can," says Ayoob.

* Less action

Perhaps it was the broad delts and tight glutes that made her overlook your foul breath, yellowed fingers, and the fact that you had to take her to Burger King because you spend up to $2,550 a year for your daily pack of Camels.

But no amount of muscle you've built will impress her if your love muscle can't perform.

"Studies have shown that smoking just a few cigarettes can affect how much blood flows through the penile arteries," says Swartzwelder. Indeed, male smokers are roughly twice as likely as nonsmokers to suffer from impotence. If you've got fatherhood on the agenda, tobacco also reduces the chances of your sperm successfully reaching their objective.