The agency, based in Essex, won the account following a competitive pitch.
The women-only boot camps have also been designed by women. They give participants the chance to tone up and get fit and also offer advice on nutrition, coaching sessions and aftercare.
The training sessions are run by Marine physical training instructors.
Voice will handle media relations with a particular focus on lifestyle consumer titles. The agency will also handle guerrilla marketing, exhibition, sponsorship and branding support.
Voice MD Nichola Cain will head up the account and report into the Ultimate Boot Camp directors Sam Watts and Rachel Davies.