Men who train vigorously on bicycles have low sperm quality verging on infertility, LiveScience reports. A recent study of Spanish triathletes found that those who rode more than 180 miles a week saw the percentage of healthy sperm drop from a group average of 10% to 4%. “We found a statistically adverse correlation between sperm morphology and the volume of cycling training undertaken per week,” the lead researcher says.
“Moreover,” the researcher says ominously, “normal physiological homeostasis—the body’s ability to regulate its own environment—may become irreversibly altered, therefore resulting in complex anomalies.” The researchers surmise that the heat and vigor of the exercise, coupled with “repeated mechanical trauma to the testicles,” are responsible. Casual riders need not worry—only the extreme cases have been linked to low count and irreparable damage.