A study published in Human Reproduction (2014;29(11):2575-82) reported that higher levels of moderate to vigorous physical activity were associated with higher sperm concentrations among couples going through fertility treatments. Men in the highest category of outdoor activity (>1.5 hrs/wk) and weight lifting (>2 hrs/wk) had 42% and 25% higher sperm concentrations than men who did not exercise.
Men who bicycled more than 1.5 hours per week had 34% lower sperm concentration compared with men who did not bicycle. These investigators speculated whether their finding was due to mechanical trauma caused by compression of the scrotum on the bicycle seat. One also wonders whether this could be further complicated by the penchant of many bicyclists to don spandex.
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