Yes, biking for long periods of time (5 hours or more/week) may be associated with poor sperm motility and low sperm count amongst men [1
]. In comparison to sedentary males, regular male cyclists have a lower percent of sperm, and studies have shown that even after a 30-day recovery period, male cyclists experience decreased motility, volume, and concentration of sperm [2
Lower sperm count in males might be due to hormonal changes from exercise, leading to lower sperm production and testosterone. It also may be related to male cyclists placing high amounts of weight and pressure on their perineal area (an important structure that supports the pelvic floor), which disrupts the blood flow to the testis [3
]. Since the testis makes testosterone and testosterone is needed to produce sperm, there appears to be a direct correlation between biking and sperm production.