With lazy summer days behind us, school and work are back in full force. Both bring nerve-wracking presentations, pitches and interviews. Could changing your body language help give you the confidence to nail them?In short: yes. We already know that body language can give away how you’re feeling about yourself: Confident people fill more space, stretching and opening their bodies to maximum capacity, while those who are unsure or uncomfortable shrink with hunched shoulders and folded arms. But, there might be more to those poses than you think. According to researchers at Columbia University and Harvard University, you may be able to feel more powerful simply by imitating a confident pose. And, those feelings may come from physiological changes that occur when you shift your body language.MORE: Discover Happiness In Your Own BodyThe basic idea isn’t new: researchers have long known that mimicking some facial expressions and body language can change how you feel. Forcing a smile can increase the feeling of enjoyment, for example, and hunched shoulders can make you feel sad. But, the Columbia and Harvard team is the first to apply the idea to power poses and confidence.The research may be especially important for women. According to the researchers, the work was partially inspired by the fact some of their graduate students were outspoken in class, while others did not participate. Those in the latter group had hunched, closed body language. And, they were more likely to be women.Confident posesHarvard Business School social psychologist Amy Cuddy, who presented the research this summer at the TEDGlobal conference in Edinburgh, Scotland, and colleagues have tested this idea with respect to powerful body language, and the findings are intriguing. In tests so far, research subjects who hold open, expansive poses associated with power and dominance for two minutes reveal a physiological change that impacts how they feel and act.MORE: When Body Language Backfires After spending one minute sitting with their with feet on a desk, arms folded wide behind the head like an executive in a board meeting, and then another minute standing with opened arms leaning aggressively on the desk, the test subjects have shown a surge of testosterone, a hormone associated with dominance and risk tolerance, and a decrease in cortisol, the stress hormone (compared to those hormones levels pre-test). They are also more likely to take risks in gambling-style test games, and report that they feel “more powerful” and “in charge.”QUIZ: Measure Your Body Image and HappinessIn contrast, test subjects who hold two low-power poses for a minute each, including sitting in a chair with their hands clasped in their lap and standing with legs crossed and arms folded, are typically more risk-adverse and less likely to report feelings of power.It’s not just youPower posing doesn’t just impact self-perception, behavior or physiology. Others notice the change, too. Cuddy’s research shows that when the high- and low-power body language test subjects give a speech after holding their respective poses, those who struck the more powerful poses receive higher evaluations.Of course, this doesn’t mean you should throw your feet up on your professor’s desk during office hours or lean aggressively across the table during a meeting. But, it does mean that you can do similar poses beforehand. In research so far, the effects of the two-minute power posing last at least 17 minutes. Try making yourself as big as possible for a couple of minutes in a private space before your potentially anxiety-inducing performance. Then, during it, sit or stand with confidence: shoulders back and relaxed, and use a clear, strong speaking voice.Keep “faking” the pre-presentation power poses until you naturally feel confident leading meetings or speaking up in class without them. Or, fake it till you make it.MORE: Dress For Your Body TypeCuddy’s TEDGlobal talk isn’t yet available online, but check out her PopTech talk from 2011, this brief Time interview, or her original journal article for more on her body language research. And, start practicing those Wonder Woman poses for a successful semester or post-vacation meeting pitch.