Close to 400 people have signed up to take part in Naomi House Hospice’s Foam Fest event on Southsea Common on April 23.
Participants dodge, dive, and climb their way through a 3k course of inflatable obstacles and foam cannons.
Places cost £20 and runners are asked to raise a minimum of £50 in sponsorship.
Keith Wilson, marketing manager at Naomi House & Jacksplace said: ‘This is one of the most unique and popular events on the Naomi House calendar, and we are delighted to be returning to the incredibly supportive city of Portsmouth.
‘The reaction to Foam Fest has been huge and I would urge anybody hoping to take part to secure their place soon.’
The 3k run is open to over-14s only.
To secure your place visit naomihouse.org.uk.