But soon you're plagued by sore muscles and winter colds. You skip pre- and post-workout stretching because you don't have time. And you start to become annoyed by all the fitness articles lecturing you to drink water by the gallon.
Everyone offers conflicting advice, and who knows if any of it matters?
To allow you to zone out in peace during your workout, here are the answers to some basic fitness questions.
Should you stretch?
Years ago, in gym class, stretching served as an introduction to the activity du jour. These days, people are discouraged from stretching cold muscles. Doing a light warm-up such as jogging in place for a few minutes before stretching increases blood flow to the muscles so that they're more easily extended.
"If you put a rubber band in the freezer and then stretch it, it snaps," says Darren Dutto, assistant professor of kinesiology and health promotion at California State Polytechnic University, Pomona. "It's the same idea with muscles and connective tissue."
Stretching, which keeps the muscles and connective tissues supple, should be an integral part of a fitness routine. Dutto recommends that people do light stretching following their warm-up and save deep stretching for after the main activity.
You don't have to be an athlete concerned with performance to focus on flexibility. A regular stretching routine provides great benefits to people with sedentary jobs, improving back health and promoting good posture, Dutto says.
The deep stretches that are part of yoga also can boost emotional health, says Brenda Strong who runs Yoga Villa in North Hollywood.
"When you breathe and stretch, there's a sense of opening," Strong says. "Metaphorically, stretching makes you feel like you have space in your life."
How much water should you drink?
Athletes and people who work out intensely should be concerned about hydration. But the average American who gets light to moderate exercise doesn't need to obsess about it, says Bettye Nowlin, a registered dietitian and a spokeswoman for the American Dietetic Association.
Let's start with the mantra to drink eight glasses of water a day. Researchers from both the Institute of Medicine and Dartmouth University have found no scientific basis for the oft-cited rule.
The American Dietetic Association still recommends at least eight cups of water daily, but that amount includes other beverages and foods, including milk, orange juice, lettuce and yogurt. Even caffeinated beverages count toward daily water intake.
For people who participate in vigorous physical activity, the goal is to replace the amount of fluid lost through sweat. These people should consume two to three cups of fluid up to three hours before the workout. During the activity, they should drink 4 to 8 ounces every 15 to 20 minutes. After the workout, they should drink three cups of fluid for every pound of body weight lost, Nowlin says.
Water and sports drinks are the best choices. People tend to drink more when a beverage is flavored, which gives sports drinks an advantage, Nowlin says.
Sports drinks replenish sodium and potassium, which are lost through sweat. They also contain some carbohydrates, about 14 grams per 8-ounce serving, she says.
Should you exercise when you're sick?
There's nothing more disruptive to a fitness routine than getting sick. Still, show your fellow gym rats some holiday spirit and spare them from your germs.
During the first few days when you're most contagious, stick to solitary activities. Take the dog for a walk. Or stay home and do an exercise tape.
"It's not a good idea to go to the gym where you can infect other people," says Dr. Loretta Samaniego, director of the emergency department at Valley Presbyterian Hospital in Van Nuys.
Once you're past the infectious stage, listen to your body. If you have a cold, sometimes light exercise can make you feel better. lf you have a fever or feel lethargic, exercise isn't a good idea and could prolong the recovery, Samaniego says.
If you do exercise, drink plenty of fluids to avoid dehydration. The body depletes fluids at a higher rate when you're sick, she says.
Should you exercise sore muscles?
Muscle soreness happens to everyone and doesn't necessarily mean you're out of shape. Someone who runs regularly will be sore if she does a new activity that works the muscles a different way, like tennis.
Whether to exercise or rest depends on how sore the muscles are, says Dutto.
Soreness often sets in about 24 hours after the activity, and the inflammation peaks at the 48-hour mark. Taking an anti-inflammatory medication like ibuprofen can help. Soaking in warm water, massaging the muscles and applying balms, creams or ice also can provide relief, according to the American College of Sports Medicine.
If you can tolerate the aches and pains, engage in light exercise or light stretches. But don't push it. Muscle soreness can alter your form, which in turn increases the risk of injury, Dutto says.
"If you're very very sore, it's hard to exercise," he says. "If you do exercise when you're sore, you have to be careful to maintain good technique."
How much exercise is enough?
As if it wasn't hard enough to get in 30 minutes of exercise, the Institute of Medicine upped the ante and triggered a collective groan in 2002 with guidelines calling for one hour of daily physical activity.
This eclipsed the 30-minute goal touted by many other health organizations. Much hand-wringing ensued that the one-hour recommendation would further discourage the many sedentary Americans who get little if any exercise.
The difference between the two recommendations has to do with fitness goals, says Dr. Tim Church, medical director of the Dallas-based Cooper Institute. Thirty minutes is enough to gain cardiovascular health benefits. But to lose weight or maintain weight loss, people need to aim for one hour, he says.