Increasing women’s testosterone level boosts running capacity, new study finds

In the first study of its kind, a new European research has found that higher testosterone levels in females have a significant effect on a woman’s ability to run for longer.

Carried out at Karolinska University Hospital and Swedish School of Sports and Health Sciences, Stockholm, Sweden, the new study looked at 48 physically active and healthy 18- to 35-year-old women and randomly split them into two groups.

One group applied 10 milligrams of testosterone cream to the outer thigh each day for 10 weeks, while the other 10 milligrams of an inactive (placebo) substance.

The women’s hormone levels and body composition—percentage of body fat and lean muscle mass—were measured at the beginning and end of the 10 weeks.

To test how the testosterone cream affects aerobic performance, the researchers measured how long the women could run on a treadmill before reaching the point of exhaustion, and to test the effect on anaerobic performance, which requires short bursts of energy, the women were asked to complete exercises such as squat jumps and standing vertical jumps.

The findings, published in the British Journal of Sports Medicine, showed that the women who used the testosterone cream experienced a rise in their levels of the hormone, with average circulating levels of testosterone increasing from 0.9 nanomoles/liter of blood to 4.3 nanomoles/l among these women.


Perhaps unsurprisingly, the women who took the inactive cream experienced no increase in testosterone levels.

The women who applied the testosterone cream also experienced a significant boost to their capacity to run for longer, with the team finding that running time to exhaustion increased significantly by 21.17 seconds (8.5%) in this group, compared with the women who took the inactive substance.

The testosterone group also experienced increases in muscle mass and leanness, though their body weight did not change.

However, there were no significant changes on any of the anaerobic performance measures, or any significant changes in weight.

It is already known that testosterone levels can impact sports performance. The researchers note that male athletes have, in general, an advantage of 10-15% in comparison with female athletes, which is most likely due to men having, on average, more than 15 times higher circulating testosterone than women.


There has been much discussion recently about whether women with levels of testosterone high enough to fall into the male range, as a result of rare inborn conditions, should be allowed to compete against women with normal levels of the hormone, although evidence is limited on the effect of testosterone on female performance.

However, the International Association of Athletics Federations has said that female athletes with high levels of the hormone must lower their testosterone levels to below 5 nanomoles/liter of blood to be eligible to compete at international level in middle distance races (400 meters to 1 mile), which has been widely criticized and legally challenged.

“Our results are therefore of great importance for the ongoing discussion of whether it is fair to allow athletes with naturally high testosterone to compete in the female category without reducing their hormonal concentration to the female range,” conclude the researchers. IB /ra

source: technology.inquirer.net

More evidence that insomnia increases the risk of heart disease, stroke

New European research has found more evidence that suffering from insomnia could increase an individual’s risk of coronary artery disease, heart failure and stroke.

In the first-of-its-kind study, researchers at Karolinska Institutet in Stockholm, Sweden looked at data gathered from around 1.3 million people taking part in four major studies.

The researchers assessed whether there is a genetic association between insomnia and major cardiovascular diseases, including coronary artery disease, heart failure, atrial fibrillation and stroke. They used a technique called Mendelian randomization, which involves studying genetic variants to see if certain factors are associated with a higher or lower risk of disease.

As Mendelian randomization gives more reliable results if an association is found it is more likely to suggest a direct relationship.


The findings, published in the American Heart Association’s journal Circulation, showed that genetic variants for insomnia were associated with a significantly higher chance of experiencing coronary artery disease, heart failure, and ischemic stroke, particularly large artery stroke. However, no association was found for atrial fibrillation.

Although previous research has already found an association between insomnia and an increased risk of developing heart disease and stroke, this evidence is based on observational studies that are unable to determine whether insomnia is a cause of the increased risk of disease or if it is just associated with the conditions.


Dr. Susanna Larsson, the study’s lead author, commented that “It is important to identify the underlying reason for insomnia and treat it. Sleep is a behavior that can be changed by new habits and stress management.”

However, the team also noted that a limitation of the study is that the findings show a genetic variant link to insomnia and not whether participants actually had insomnia.

According to the researchers, insomnia affects up to 30% of the general population. Experts are becoming increasingly concerned about what they call a growing “sleep loss epidemic” with sleep deprivation now linked to a variety of health problems including weight gain, cancer and depression. HM

source: technology.inquirer.net