Boxers or briefs: which is better?
IT'S a debate that has waged for decades - boxers or briefs? Now science has determined which form of underwear is better for men in the testicular sense, following a landmark study by Harvard University.
Fertility specialists have long been sceptical of what impact, if any, the type of jocks a bloke wears has on his fertility.
But the new research - the largest of its kind conducted - found that the loose and free-flowing boxer shorts are linked to a higher sperm count and better quality of swimmers.
Over a seven-year period, Harvard TH Chan School of Public Health in the US recruited the male partners of couples who were seeking infertility treatments.
Among the 656 men probed, 53 per cent usually wore boxer shorts and were found to have a statistically significant 25 per cent higher sperm concentration.
Their total sperm count was also 17 per cent higher, with 33 per cent more swimming sperm in a single ejaculation.
Those who wore briefs, small and tight undies, or jocks that finish just above the knee, had a dramatically lower sperm count that could reduce their chances of fathering a child.
"Since men can modify the type of underwear they choose to wear, these results may be useful to improve men's testicular function," says Dr Lidia Mínguez-Alarcón, who led the research.
Other factors might affect scrotal heat, such as the type of trousers - especially skinny jeans - and certain underwear fabrics, she said.
The study comes on the back of research released last year, which found sperm counts in men from Australia, North America and Europe have plummeted by almost 60 per cent in the past four decades.
Such a major decline in a short period of time suggests the way modern western societies live is making it harder for men to become fathers, Hebrew University of Jerusalem said.
It determined that the average annual fall in sperm concentration in men in those regions was a whopping 1.4 per cent.
"The results are quite shocking," epidemiologist Hagai Levine, who led that study, said.
"Given the importance of sperm counts for male fertility and human health, this study is an urgent wake-up call for researchers and health authorities around the world to investigate the causes of the sharp ongoing drop in sperm count, with the goal of prevention."
The Royal Australian College of General Practitioners said male infertility can be caused by a wide range of physiological conditions, including anatomical or genetic abnormalities, systemic or neurological diseases, infections and trauma.
"But in 30 to 40 per cent of male infertility cases, no cause is identified," it said.