There was a thread about listening to music when exercising during sefira http://www.theyeshivaworld.com/coffeeroom/topic/listening-to-non-live-music-on-sefira#post-370591
Also Halachically speaking by R’ Moshe Dovid Lebovitz also talks about this. I’ll copy and paste it, but if you want you can see it also by googling Halachically Speaking and going to the archives It’s Volume 5 Issue 9.
Without Intent
Many cases of listening to music are not because one wishes to enjoy the music. For example, one who is exercising and wishes to listen to music to make the exercising better is permitted to do so since his intent is not to enjoy the music.
Harav Yisroel Belsky Shlita, see Shiurei Halacha (Harav Felder Shlita) page 26.