" Studies on volunteers have shown that cycling in a standing position does not alter penile blood supply , " says mr nargund .
纳甘德先生说：根据志愿者参与的研究，表明站着骑车不会改变阴经的血液循环。
Early epidemiological studies , however , reported that postcoital douching was no more effective than " rhythm " or " penile withdrawal " methods , which are unreliable .
The change was prompted by scientific evidence that suggests circumcision can reduce the risk of urinary tract infections in infants and cut the risk of penile cancer and sexually transmitted diseases , including hiv and the human papillomavirus or hpv , which causes cervical and other cancers .
