Many of us grow up with the belief we'll be able to have kids when we're ready. We assume we're fertile and won't have trouble starting a family, but in reality, many couples trying to conceive experience fertility issues. Now, researchers at Urmia University in Iran suggest six months of exercise can improve low sperm quality and count — a leading cause of male infertility.

"Our results show that doing exercise can be a simple, cheap and effective strategy for improving sperm quality in sedentary men," said Behzad Hajizadeh Maleki, lead author of the study, in a statement.

One in three couples struggle to get pregnant due to poor semen quality, according to the researchers. In-vitro fertilization (IVF) is the only treatment available for couples unable to conceive naturally. However, poor semen quality could potentially increase the risk of miscarriage, birth defects, and the development of childhood cancer.

Read More: Smoking Pot Burns Out Sperm Count For Men By A Third, Harming Fertility

Sperm quality can sometimes, but not always, be improved with lifestyle changes or medications. Currently, men seeking to improve their fertility are advised to combine healthy eating with regular exercise, while giving up smoking and reducing alcohol intake. However, the link between exercise and sperm quality has been proven.

In the recent study, published in the journal Reproduction, Maleki and his research team looked into whether exercise duration and intensity influences sperm quality. A total of 261 healthy men between 25 and 40 were assigned to one of four groups, including moderate intensity continuous training (MICT), high intensity continuous training (HICT), high intensity interval training (HIIT), or a control group that did not exercise. MICT and HICT exercises comprised of running on a treadmill for half an hour and one hour for three to four days per week respectively. HIIT included short one-minute bursts of sprinting on a treadmill, followed by a one minute recovery period, repeating between ten to fifteen times. These routines were followed for six months.

Semen samples were collected before, during, and after the different exercise routines to analyze the men's semen volume, sperm count. morphology, motility, levels of inflammatory markers, and their response to oxidative stress.

Read More: Soda Decreases Male Sperm Count And Increases Female Mortality Rate, Study Finds

The findings revealed men in all exercise groups had improved sperm quality across all measures compared to the samples from the control group. Those in the MICT exercise program had 8.3 percent more semen volume; 12.4 percent higher sperm motility; 17.1 percent improved sperm cell shape/morphology; 14.1 percent more concentrated sperm; and 21.8 percent more sperm cells on average. However, the researchers noted sperm count, shape, and concentration dropped back towards pre-training levels after a week of no exercise; sperm motility decreased 30 days afterwards.

The study authors acknowledged losing weight more likely contributed to improving sperm quality. Previous research has found couples in which the man is overweight or obese, and the woman is of normal weight, take longer to conceive than couples with no weight problems. The researchers suspect too much body fat may be linked with changes in reproductive hormone levels, including testosterone in men.

However, in the current study, researchers emphasize MICT, or moderate intensity continuous training, had the most significant effect for men because this workout reduces the gonad's exposure to inflammatory agents and oxidative stress.

Read More: Male Fertility 101: 7 Little-Known Facts About Sperm For Men's Health

A similar 2013 study found exercise does offer protective effects when it comes to sperm quality. Men who weightlift often showed increased testosterone levels, and improved insulin sensitivity, and therefore, higher sperm count. These have both been linked to higher sperm concentrations.

Maleki and his colleagues caution sperm count isn't the only reason some men can't have children. Male infertility problems are complex, and may not always be resolvable with lifestyle changes.

One thing we can all agree on — a healthy diet and regular exercise doesn’t harm anyone.

Source: Maleki B et al. Just 6 months of frequent exercise improves men's sperm quality. Reproduction . 2016.