Although he has three children Homer Simpson’s lifestyle isn’t good for his fertility.
As Dr David Walsh, medical director at the Sims IVF Clinic in Dublin, points out, the renowned TV character drinks excessively, is overweight and consumes copious amounts of fatty foods such as doughnuts. However, Walsh maintains that Homer has got one thing right.
“He does a lot of things wrong but he doesn’t cycle a bike,” he says. Spending hours in the saddle is one of the few otherwise healthy endeavours that negatively impacts on a man’s fertility.
The ideal temperature for sperm production is about 34.5 degrees Celsius, which is just below body temperature (37 degrees). The best quality sperm will be produced when kept away from the body, something which cycling prohibits.
"When you're on a bicycle, you're in lycra shorts, you're wearing very tight underwear, your testicles are brought up under your crotch and then you sit on a hard thing," says Dr Louis Keith, a male fertility expert and professor emeritus of gynaecology and obstetrics at Northwestern University in Chicago. "This is not good for testicular health."
Sperm quality
Keith adds that spending eight hours a day on a bicycle saddle seven days a week "has got to have an adverse effect on your sperm quality".
Research of competitive cyclists has also linked the sport to poor semen quality.
One study in South Africa concluded “that endurance cycling appears to be associated with a significant alteration in sperm morphology (for example, its shape)”.
Similarly, researchers at several universities in Spain and Brazil found that cycling more than 300km a week is "detrimental to sperm morphology".
Sperm samples
The sperm samples, which were taken from 15 triathletes, also showed that those who cycled the most had the lowest percentage of "morphologically normal sperm".
However, it’s not just professionals or even serious amateurs who can be affected. A Boston University survey of 2,200 men attending fertility clinics found that those who cycled for five hours or more a week to be associated with low sperm counts and poor sperm motility (ie its ability to move).
Walsh says the severity of the infertility is “dose related” and that the more a man cycles, the more likely his sperm quality is to be affected. The problem is also a lot more common in Ireland than many people think, especially given the sport’s increased popularity in recent years.
Cycling Ireland, the national governing body for the sport on the island of Ireland, notes that its members increased by 43 per cent in 2010 and 21 per cent in 2011.
There has also been an increase in non-competitive and recreational cyclists. Between 2006 and 2011 the number of people commuting to work by bicycle increased by almost 10 per cent, according to census figures compiled by the Central Statistics Office.
“We see it a lot,” says Walsh, adding that it is “certainly” an issue for a significant amount of men cycling.
Significant issue
Dr Simon Thornton, consultant in reproductive medicine at the Beacon Care fertility clinic, agrees.
“With the big increase in cycling [throughout Ireland] that we’re seeing, it’s actually quite a significant issue,” he says. “We’re certainly seeing more and more of it. If you’ve got a young male coming along [to the clinic], it’s one of the first questions we ask.”
Taxi and long-distance lorry drivers are also affected by similar symptoms, he says.
The good news for male cycling aficionados is that infertility induced by the sport usually isn’t permanent.
“If they cut back on cycling, sperm quality improves,” says Thornton. “If it’s just cycling and a heat effect, it’s normally reversible.”
Simply reducing the amount of miles in the saddle, or stopping altogether, will improve sperm quality for the vast majority of cases, according to Walsh.
“It should improve but it takes the guts of three months or 80 days,” he says, adding that this was the approximate length of the sperm life cycle.
Staying healthy on your bike
Medical officer with Cycling Ireland Dr Conor McGrane says the three most important things for anyone getting into cycling – aside from wearing a helmet – are:
1. To get a bike that fits you properly.
2. Get a good quality pair of cycling shorts.
3. Increase the training load gradually.
For commuter cyclists he says it's vital for them to make sure they are "visible or seen properly" and never try to undertake a vehicle, especially a large one.
"Seventy per cent of cycling deaths are caused by people undertaking buses and HGVs," says McGrane. "It's a fairly consistent figure in all the major cities."
He also notes that injuries from falling off a bike is a serious issue. Falls lead to bruising and "road rash" – general skin abrasion caused by sliding on roads or pavements – and he advises people to "clean [such an injury] out, cover it for a few days and then leave it open to the air".
More serious falls can result in broken bones, particularly collar bones, which McGrane says account for about "90 per cent" of the breaks he has come across in cyclists.
Saddle rash and saddle sores which are "often caused by ingrowing hair or blocked hair follicles" are other regularly occurring injuries, as is chaffing which McGrane says tends to be caused by clothes.
"It's more common if you don't have a good quality pair of cycling shorts or a poor quality saddle," he says. "It's linked to how long you spend on the bike . . . almost directly. For a commuter cyclist it wouldn't be an an issue."
Chaffed skin could be treated by "staying off the bike for a while" or by applying antibiotic or cortisone-based creams to the affected area.
Nerve compression caused by sitting on a saddle for extended periods of time can also cause temporary erectile dysfunction for men.
"You can sort it out by getting a better saddle," says McGrane. "It's not that common – you'd have to do an awful lot of cycling and it's always reversible."
Pains and strains in the neck, knee and hip, as well as in the heels and groins, are also common injuries for people who "rapidly" increase the amount of cycling they do.
"It is just because [their] muscles haven't had time to adjust to it," McGrane says . Cycling an inappropriately sized bike can also cause such pain.
He says that commuters should seek advice from vendors about getting a bike that is properly sized to their body while serious amateurs would benefit from getting a professional bike-fit done.
In spite of the associated risks, McGrane maintains that the "health benefits of cycling far outweigh the problems".
"[People who cycle] tend to be a lot healthier. They live longer, stay more active for longer and tend to be happier as well."
