Pelvic floor exercises have long been recommended for women - now researchers say they could help men too.
The exercises could have the same effects as Viagra
The exercises were found to help men with erectile dysfunction as much as taking in Viagra.
The researchers say the findings mean men have an alternative to drug therapy.
For around 50 years, women have been advised to perform pelvic floor exercises to strengthen their muscles for childbirth.
The pelvic floor is a "hammock" of muscles which support the bowel and bladder.
It really is use it or lose it
Dr Grace Dorey, University of the West of England
Pelvic floor, or Kegel, exercises involve clenching the muscles you would use to prevent yourself urinating.
This latest research indicates it is also important for men to maintain the muscle tone and function of their pelvic floor muscles with the exercises.
The team from the University of the West of England in Bristol studied 55 men with an average age of 59 who had experienced erectile dysfunction for at least six months.
The men, all patients at the Somerset Nuffield Hospital, Taunton, Somerset, were given five weekly sessions of pelvic floor exercises and assessed at three and six months, and asked to practise the exercises daily at home.
It was found 40% of the men regained normal erectile function - some of who had severe erectile dysfunction, and another 35% showed some improvement.
Two thirds of the men had said they also had problems with urination. These improved significantly after they began the exercises.
Dr Grace Dorey, a specialist continence physiotherapist who carried out the research, told BBC News Online: "The exercises were found to be equally as effective as taking Viagra.
"Pelvic floor exercises improve function in a physical way, in a more natural way.
"Men should be doing preventative exercise. It really is use it or lose it."
She said men should be exercising their pelvic floor exercises from puberty onwards.
A spokesperson for the Impotence Association said: "The value and effectiveness of pelvic floor exercises should not be underestimated when considering the management of sexual problems such as impotence and premature ejaculation.
"The exercises are thought to strengthen the muscles that surround the penis and improve the blood supply in the pelvis, which is an important factor in relation to erectile dysfunction."
The Impotence Association helpline number is 0208 767 7791.