I take Celexa (it's actually a spin-off of the Lexapro molecule) for migraine prevention and it doesn't interfere with training.
That said, if you just started on Lexapro and/or this is your first experience with this type of a drug, expect to feel weird for a few weeks and stay in touch with your doctor as you experience various side-effects. We all metabolize these things differently. Getting to the right therapeutic dose of Celexa was, for me, rather uncomfortable. I was lethargic, then unable to get to sleep, then a bit jumpy. Once we found the correct dosage, however, everything fell into place and I feel great. The keys to success are 1.) not making any sudden changes in your dosing schedule (e.g. just deciding to stop or doubling your dose) and 2.) keeping your doctor fully informed about how you are feeling, even if it's before your next appointment.
Hope this helps a little. Good luck!