A new study aims to show that exercise can be a beneficial treatment for patients.
If the research proves successful, exercise training could be introduced as a new NHS treatment for prostate cancer.
Half of the participants will carry out two-and-a-half hours of aerobic exercise every week for 12 months - initially with the support of a qualified trainer and then with free access to local gyms.
The other half will be given information about the benefits of exercise for cancer patients but will have no supervised sessions.
The men will then be monitored to see if the cancer spreads.
If this smaller study proves successful, researchers hope to lead a full-scale trial looking at whether regular exercise can help keep prostate cancer from spreading to other parts of the body.
Dr Liam Bourke, lead author of the study and principal research fellow at Sheffield Hallam University, said: "Evidence suggests that men who are physically active after a prostate cancer diagnosis have better cancer survival than men who aren’t active.
"It’s not clear yet how this works, but it might be that exercise affects the way some genes regulate cancer cell growth and DNA repair."
He added: "The clinical academic team in Sheffield have been working hard for eight years to develop the intervention that is being tested in this exciting study. It builds on what we already know and is the first step towards finding out whether exercise could be an effective and practical NHS treatment for localised prostate cancer.
"If we show it works and is feasible, it could be a real leap forward and good news for cancer patients."
David Curtis, 68, is one of the study's participants. He was diagnosed with early prostate cancer in March 2014 and has been exercising as part of the PANTERA study for several weeks.
"I was never someone to go to the gym, even though I’ve always been active, but now I go to the gym twice a week and do lots of walking," he explained.
"Since starting on the study, I’ve started to lose weight and my PSA level has come down which is a really positive indicator."
PSA is produced by both normal and cancerous prostate cells, and a high PSA level in the blood can signal cancer.
Throughout the study, researchers will look at the effect that regular exercise has on the body, including on PSA levels, and will also gather information about how well it runs, to prepare for a full-scale trial.
Professor Malcolm Mason, Cancer Research UK’s prostate cancer expert, said: "Taking exercise is good for all of us, whether or not we have cancer – but this interesting study could help discover whether it’s particularly helpful and a viable, additional treatment for some prostate cancer patients.
"Focusing on patients whose disease is under active surveillance, rather than being treated in other ways, provides a fantastic opportunity to monitor the effects of exercise on prostate cancer - and could even shed light on its potential as a supplemental therapy for other types of cancer."