To the investigators’ knowledge, this is the first study to identify a correlation between bicycle set-up, and neurological compromise in women cyclists. Our findings that handlebars positioned lower than the saddle result in increased perineal SP and decreased GS are consistent with our hypothesis. Low handlebars may cause riders to lean forward, thereby shifting more weight to the perineal region, instead of leaning back on their ischial tuberosities (IT), as would be expected in a more upright position.
Potter et al. examined SP in experienced male and female cyclists (n=22)
riding with their hands on the tops versus the drops of the handlebars [14
]. Compared to men, women had a greater change in maximum anterior pressure when switching from the tops to the drops. This is similar to riding with handlebars level to the saddle and lower than the saddle and supports the concept that higher pressures are placed on the genital structures when the hands are positioned below the saddle. While Potter et al. used only traditional saddles, we included both traditional and cut-out saddles. This suggests that low handlebars compromise neurological function for women riding nosed saddles. In evaluating male cyclists, Schrader et al. noted significant improvements in GS after reducing perineal SP using noseless saddles [11
]. Further studies are warranted to determine if noseless saddles provide a similar protective effect to the female pelvic floor.
Carpes et al. measured SP in an upright and forward position while participants (n=22)
were seated on traditional and cut-out saddles [18
]. The authors did not find any statistically significant associations between trunk position and total SP in female riders. Similarly, handlebar level, which affects trunk position, was not significantly associated with total SP in our study. However, we also evaluated pressures in the perineal region and found that low handlebars were significantly associated with increased perineal SP. Based on our findings and those of Potter et al., one would anticipate that a bicycle set-up, saddle design or a cyclist’s position that increases the forward angle of the pelvis, could result in similar increases in perineal pressure and decreased neurological function.
Bressel et al. assessed the influence of saddle design on pelvic angle and trunk angle in female cyclists (n
]. They found that partial cut-out saddles increase anterior pelvic tilt, regardless of the hand position on the tops or the drops of the handlebars. Thus, it is not surprising that riding on cut-out saddles was independently associated with higher perineal SP in our study. Interestingly, after adjusting for saddle type, mean perineal SP remained significantly higher for women who rode with their handlebars positioned lower than the saddle compared to those who rode with their handlebars level with the saddle. These findings suggest that handlebar height and saddle type may have a cumulative effect on perineal SP and pelvic floor trauma. Further research with larger studies is needed to fully elucidate these relationships.
It is compelling that regions in the mid perineum were most affected by the handlebar level. We posit that the right and left perineum sites and posterior vagina may be less affected due to their more posterior positioning near the ischial tuberosities and that the clitoris and urethra may be too cephalad to receive an impact. Similarly, we cannot explain why GS deficits were one-sided in the labia. One can hypothesize that riders have a dominant side to which they exert more pressure. This theory is supported by previous studies that have identified unilateral vulvar hypertrophy and lymphedema in competitive cyclists [4
]. Since decreases in left labial sensation was only significant on bivariate analysis, larger, dynamic studies are needed to identify spatial relationships of increased pressure points and compromised blood flow or altered neurotransmission to these areas during riding.
Interestingly, we previously showed that SP are not significantly associated with GS [13
]. It is possible that the handlebar position exerts an effect on GS through methods other than compression or that our method for recording pressure lacks sensitivity to detect the influence of pressure on neurological function. The small sample size may have precluded our ability to effectively evaluate these relationships. Still, it is important to note that simple changes to bicycle set-up may provide beneficial effects to pelvic floor integrity.
It was surprising to note that in the multivariable models, the strong positive associations between age and SP, and age and VT, diminished when handlebar positioning was included in the models. One can speculate that, as women age, they modify their riding styles to reduce untoward symptoms, given the disparity in handlebar positioning between younger and older women in our riders. Larger, longitudinal studies are warranted to determine the validity of this conjecture.
Overall, our results suggest that handlebars positioned below the saddle yield detrimental effects to the female pelvic floor. However, this conclusion contrasts the recommendations by Thompson et al., who reported that correct bike fit for the handlebars should be 1 to 2 inches lower than the saddle [19
]. While the authors did not state whether the recommended bicycle fit was geared toward the more serious cyclists or to recreational cyclists, a lower handlebar position enhances the aerodynamic posture of the rider. This exemplifies the ongoing struggle between selecting a more aerodynamic bicycle position for control and speed or a more ergonomic position to reduce neurovascular compromise [14
]. Our participants used their own bicycles that were set-up to their preferences and specifications. We believe that these conditions were more likely to yield results that are closer to real-world relationships between cyclists’ configurations and bicycle geometry. Additional research is needed to establish the best risk/benefit profile for women riders, in order to allow women to decide at what cost they will ride.
Our study, as well as several of the studies described above, may be limited by a selection bias as noted in the original study [12
]. Specifically, study participants who were uncomfortable with their body and women who do not suffer from neurological symptoms may not have been motivated to participate. In addition, most of the women were normal weight, more experienced cyclists. Therefore, our findings may not be generalizable to the less experienced, recreational, over or underweight cyclists. In addition, our sample size was small. While a power analysis was conducted for our original study, an additional power analysis was not performed for this secondary analysis [12
]. A larger sampling would allow us to assess whether the paucity of differences were due to a lack of power or a lack of association. Still, ours is the largest, published study addressing this very important women’s health issue and presents further evidence that female riders are susceptible to detrimental consequences to the pelvic floor. Our findings also emphasize the fact that enhanced knowledge about female specific bike fit is necessary. While all of the women in our study had normal sexual function, our group and others have identified an association between female sexual dysfunction and altered genital sensation [12
]. In addition, genital sensory stimulation has been shown to play a critical role in sexual arousal and the erectile response in men [21
]. Longitudinal studies with larger, more diverse groups of women cyclists are needed to further discern the role that different components of bicycle fit and accoutrements have on adverse cycling outcomes as well as to determine the long-term effects of increased saddle pressure and decreased genital sensation on sexual function in women.