This boasts guest vocals from the Plain White T's Tom Higginson.
Simpson told MTV News about this song, whose subject matter is relationship trouble: "It's a song that kind of relates to the last album, but it grew with the new record. And every girl has gone through that situation. You put your foot in your mouth and you go, 'Wait, why did I do that?' We're on our phones writing and texting too much!"
Higginson was recruited for this song after hanging out with Simpson when the Plain White T's toured with her fiancée's band, Fall Out Boy. He told Rolling Stone: "After the tour ended, I got a text from Pete [Wentz] that said 'Ashlee wants you to sing on her album.' I was like 'Hell yeah, man' and I tried to bribe him by asking if he could have Brendon [Urie, of Panic at the Disco] sing on our next record because I'm a huge Panic fan."
"Kickstart My Heart" is about all the ways Motley Crue gets their blood flowing without drugs. It was inspired by their bass player Nikki Sixx, who claimed he had to be revived with a shot of adrenaline to the heart after an overdose.