Ergo-log just posted a cool little study demonstrating some pretty significant performance enhancement benefits from inhaling the essential oils of either citrus sinensis (orange tree) or mentha spicate (spearmint) before exercising. Go take a look.
The participants in the study ended up running a 1500m distance 12-15% faster than without the essential oil boost. That's one heck of a boost.
Although the researchers don't know exactly how this works, the suspicion is that volatile compounds in the oils enhance lung function (as determined by forced expiratory volume). Given the design of the study - no controls, small number of participants - the reliability of the results is still open to question, as is unfortunately the case with most research of this nature (there's not much money in it!).
However the use of smelling salts and aromatic compounds in sports from fighting and boxing to powerlifting has a pretty decent historical record of efficacy. So there's a good case for believing this may work whether it's doing so directly by enhancing lung function, or indirectly by arousing consciousness and/or adrenaline.
And although this was only tested in a cardiovascular activity, if it works the way the researchers reckon, the chances are it would also be pretty effective for weightlifters hoping to push out a few more reps or a new max and against acute lactic acid build-up.
Here's a link to the full (free) paper itself: