A Dennis team will visit agencies including MediaCom, Manning Gottlieb OMD, Vizeum and UM London from Tuesday 2 July, setting agency staff a three-minute exercise challenge.
The man and woman from each agency who complete the most press-ups, sit-ups and burpees within the three minutes, will be invited to the event's grand final this summer.
A leaderboard will be displayed on Mensfitness.co.uk from 2 July so agency staff can see where they are in the rankings, and the overall male and female winners will receive prizes including a sports bike, personal trainer session and sports holiday.
The competition marks the official launch of Mensfitness.co.uk, which soft-launched earlier this month. It has been redesigned to ease navigation, and now offers more than 10,000 articles on training and diet, as well as interviews with sport and movie stars.
An online shop has also been added, stocking more than 2,000 products including fitness equipment and sports nutrition supplements.
Russell Blackman, the group publisher of Men's Fitness, said: "The appetite for Men's Fitness content has never been stronger and it's increasingly clear that our readers' needs are evolving in the way they want to consume our content.
"Traffic to Mensfitness.co.uk has increased significantly and steadily over the past couple of years and we have continued to respond to our readers by launching this new and improved site, which provides consistently exceptional advice from the world's leading authorities on training and nutrition."