A man died after collapsing at an organised outdoor boot camp-style fitness session in Leeds.
The man, thought to be in his fifties, was taking part in the British Military Fitness (BMF) programme at Roundhay Park on Saturday morning.
He collapsed having suffered a suspected heart attack and was taken to hospital, but his death was confirmed a short time later.
A BMF spokeswoman confirmed that an incident had happened but declined to provide any further comment at this stage.
BMF was founded in 1999 as an alternative form of group fitness training to gyms, with motivation provided by military trained instructors.
There are now more than 400 classes in more than 145 locations across the UK, including Roundhay, Horsforth Hall Park, Springhead Park in Rothwell and Wellington Place in Leeds city centre.
Participants have to fill in and sign a health questionnaire before taking part.