RE: Maximum Heart Rate
Your maximal heart rate is the highest number of times your heart can beat in a minute of exercising at volitional exhaustion. Maximum heart rate is a genetically determined "random" variable so your heart rate is individual to you. You should therefore take this value with a pinch of salt; The accepted error in the age-predicted formula is ± 10-12 bpm, so your heart rate could be as high as 209bpm.
But this is only an estimate and the only real way of getting an persons maximal heart rate is through clinical testing. If your comfortable working at that heart rate then you'll be fine (unless you have a heart condition), use a scale from 1-10, 1 being very very light work and 10 being very very heavy. Then see where you rate with your associated heart rate (10 should be maximal). Do this with a exercise perfessional and not on your own as you'll be working maximally.
p.s. it may have been the xenadrine!