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It's January, which means the gyms are full of exercisers resolving that 2011 will be the year they meet their fitness goals. In labs around the world, meanwhile, exercise scientists are resolving to settle some of the fitness questions that still dog us. Here are 10 confusing, contradictory, or just plain complicated areas of exercise science that will see significant progress in 2011:
1. Compression garments
Manufacturers claim the garments - everything from knee socks to full compression suits - offer a wide range of benefits, such as reduced muscle soreness, greater power and increased endurance.
WHAT WE KNOW Some studies have shown positive effects, but others have failed to reproduce these benefits. It's clear the garments do something, but it's not yet clear what.
WHAT WE'LL LEARN IN 2011 The biggest question is how much compression is needed and on what parts of the body.
2. Bone density
For older adults, weak bones are susceptible to breaks in a fall - one of the most serious threats to mobility and independence.
WHAT WE KNOW The long-standing belief that "weight-bearing" activity is the key to bone health has been superseded. Strong muscles are now thought to produce strong bones, and jarring activities like running also helps.
WHAT WE'LL LEARN IN 2011 It's still not clear why cyclists have abnormally low bone density, or how low-impact activities such as elliptical training stack up. New techniques to measure bone health will allow more accurate studies.
3. Muscle cramps
The painful spasm of a muscle cramp can bring a workout to a rapid halt.
WHAT WE KNOW The dominant theory says cramps are caused by electrolyte depletion through sweat. But recent studies suggest electrolytes have nothing to do with it, but a problem with neural signals to the affected muscle.
WHAT WE'LL LEARN IN 2011 Both sides will analyze data on cramping athletes at big sporting events such as marathons, but the most reliable answers will come from painful lab studies where cramps are electrically stimulated.
4. Marathon heart damage
Several recent studies have deployed blood tests, electrocardiograms and cardiac MRIs to detect heart damage in runners who've just completed a strenuous endurance challenge.
WHAT WE KNOW Marathoners' hearts definitely take a beating. But the most recent studies suggest the damage disappears in a week or two.
WHAT WE'LL LEARN IN 2011 Experts don't agree on whether this heart damage is significant or whether it's just a passing occurrence, so they'll use more detailed tests to see how long the effects last.
5. The perfect warm-up
Making sure your muscles are warm and supple before exercise has been shown to boost performance and reduce the risk of injury.
WHAT WE KNOW Traditional "static" stretching appears to have little effect on injuries and actually reduces your strength and endurance. Top athletes now rely on more active "dynamic" exercises to warm up.
WHAT WE'LL LEARN IN 2011 Researchers are experimenting with different dynamic routines to figure out which ones are best for which activities.
6. The placebo effect
If you believe a pill will help you, it probably will - and that makes it very difficult to reliably determine which supplements and drugs have a real effect.
WHAT WE KNOW Harvard scientists recently demonstrated that a sugar pill was just as effective as drugs for irritable bowel syndrome - even when the patients knew they were taking a placebo.
WHAT WE'LL LEARN IN 2011 Scientists are continuing to unravel the placebo effect's unexpected powers. As a result, we'll likely find that many popular sports supplements are nothing more than placebos. (Whether anyone will care is a separate question.)
7. Beet juice
In 2009, researchers at the University of Exeter announced that drinking beet juice for a few days allowed subjects to run about 15 per cent longer in treadmill tests.
WHAT WE KNOW A series of follow-up studies have confirmed the initial result, and shown that nitrates in beet juice are responsible for its endurance-boosting effect.
WHAT WE'LL LEARN IN 2011 Other labs will attempt to duplicate the Exeter results under different conditions. If they succeed, get ready for beet-flavoured Gatorade.
8. Antioxidants
Popping antioxidant pills like vitamins C and E is no longer standard practice among the health-conscious after several massive studies have failed to find any benefits.
WHAT WE KNOW A few studies now suggest antioxidants may actually block some of the benefits of exercise, such as heightened insulin sensitivity and increased mitochondria levels, as well as delaying muscle recovery after exercise.
WHAT WE'LL LEARN IN 2011 Vitamin studies have been famously contradictory over the years, so this debate won't be resolved quickly - but look for further studies.
9. Mental training
Researchers at Bangor University in Wales expect to complete an experiment in which they attempt to improve endurance in a cycling test by training their subjects' brains - an area called the anterior cingulate cortex, to be precise.
WHAT WE KNOW The researchers have shown mentally challenging tests that fatigue the anterior cingulate cortex reduce endurance. Now they're trying the opposite experiment.
WHAT WE'LL LEARN IN 2011 The idea that our physical limits are dictated by the brain rather than the muscles is the hottest debate in exercise science. Look for a flood of related studies.
10. Fuel during exercise
You don't need a sports drink to run 100 metres, but you do to run a marathon. The middle ground is more complicated.
WHAT WE KNOW Recent studies have found that for exercise lasting an hour or less, you get as much benefit from rinsing and spitting a sports drink as you do from drinking it - which means your muscles aren't actually low on fuel.
WHAT WE'LL LEARN IN 2011 Exercise lasting one to two hours, such as a typical soccer game, remains the big question. What combination of intensity and duration do you need to take in carbohydrate to maintain your performance?
Alex Hutchinson blogs about research on exercise and athletic performance at www.SweatScience.com.
Alex Hutchinson