So for the new study, which was published this month in Medicine & Science in Sports & Exercise, researchers at the University of North Carolina in Chapel Hill decided to ask active men about their sex lives. 
 
 They began by developing a questionnaire based on earlier psychological research into men’s sexual behavior that asked, for instance, how often they thought about and engaged in sex. The scientists also created a separate questionnaire with detailed queries about exercise habits, including how often and intensely the men worked out each week. 
 
 A final set of questions asked about general health and medical histories. 
 
 Then the researchers contacted running, cycling and triathlon training groups, university athletic departments, and publications targeted at endurance athletes and asked them to alert members and readers to the questionnaires, which were available online. 
 
 Almost 1,100 physically active adult men completed all of the questions. Most were experienced athletes who had participated for years in training and competitions. 
 
 The scientists used their responses to stratify the men based on both the extent and intensity of their workouts. They wound up with groups whose weekly exercise was short, moderately lengthy or quite prolonged, and separately whose weekly exercise was light, moderate or extremely intense. 
 
 It was possible, of course, for someone to be in the top or bottom of both of these categories, meaning that their workouts were both long and intense or light and short. But the scientists wanted to examine each of those aspects of a workout separately, so did not track such overlaps. 
 
 Newsletter Sign Up Continue reading the main story Please verify you're not a robot by clicking the box. Invalid email address. Please re-enter. You must select a newsletter to subscribe to. Sign Up You agree to receive occasional updates and special offers for The New York Times's products and services. Thank you for subscribing. An error has occurred. Please try again later. View all New York Times newsletters. 
 
 They also categorized the men according to their answers about their sex lives, creating groups with relatively high, moderate or low libidos. 
 
 Finally, they compared the men’s exercise habits to their reported interest and engagement in sex. 
 
 And there were clear patterns. The men whose exercise routines were moderate or light in intensity or duration were far more likely to report moderate or high libidos than were the men whose workouts were especially prolonged or intense, even after the researchers controlled for age. (Older men tend to report less interest in sex, although not by much.) 
 
 Advertisement Continue reading the main story 
 
 In effect, strenuous exercise “was associated with lower libido,” says Anthony Hackney, a professor of exercise physiology and nutrition at the University of North Carolina who led the study. 
 
 Of course, this was a small sample of men who voluntarily chose to complete a personally intrusive survey. It is impossible to know whether they were truthful or representative of the rest of their gender. 
 
 This type of study also cannot tell us whether too much exercise actually causes low libido, only that the two are linked. 
 
 And it did not examine why strenuous exercise might dampen libidos. 
 
 But Dr. Hackney speculates that both physical fatigue and lower testosterone levels after exhausting exercise likely play a role. 
 
 He and his colleagues hope to soon mount experiments that directly track exercise, hormone levels and libidos to learn more about their interactions. They also aim to learn more about whether the intensity of the workouts or duration has the greater impact on male sex drive. 
 
 Perhaps most important, he hopes eventually to pin down at what point exercise might start to lower some men’s libidos. Both moderate and light physical activity were associated in this study with relatively high libidos, he points out. “But there does seem be a potential tipping point,” after which more exercise may blunt desire. 
 
 The necessary studies likely will require years and many cooperative men to complete. In the meantime, he suggests that if someone is worried about whether his training is affecting his sex life, he might try exercising a little less, to see if his libido changes. 
 
 This advice could be especially important for couples trying to conceive, he says. “Fertility specialists will often ask a woman about whether and how much she exercises,” he says. “Based on our data, we think they should also be asking the man.” 

 Low sex drive? Try exercising less, study says 
 
 Intense exercise might give you a lean physique, but it could potentially slow down your sex drive, suggests a new study published this month by researchers at UNC Chapel Hill. 
 
 Previous studies have typically measured hormone levels in men, data which is easy to measure quantitatively. These scientists, however, put down their probes and asked men to talk about sex. 
 
 The researchers began by distributing a questionnaire to 1,100 physically active men that asked them how often they engaged in and thought about sex. A separate questionnaire probed participants' exercise habits. 
 
 Upon crunching the numbers, the scientists concluded that participants with the lowest and mid-range training intensities were more likely to have a high/normal libido. The researchers also found that participants who trained for shorter and mid-range durations had greater odds of a high/normal libido score than those who exercised for a long period of time. 
 
 The sample of men voluntarily elected to complete the survey, so the study hardly represents all men. Additionally, the data does not confirm that excessive exercise causes low libido, only that the two are linked. 
 
 Anthony Hackney, who led the study, told the New York Times that physical fatigue and lower testosterone levels associated with exercise likely account for dampened libidos. 
 
 Hackney's research stands out as one of the few studies that looks at men's exercise and its far-reaching impacts. Past studies have tended to look at hormonal imbalances in women. 
 
 This latest study hopes to add men to the conversation. 
 
 "Fertility specialists will often ask a woman about whether and how much she exercises," Hackney told the New York Times. "Based on our data, we think they should also be asking the man." 
 
 Read Michelle Robertson’s latest stories and send her news tips at mrobertson@sfchronicle.com. 

 PURPOSE: 
 
 This article aimed to study the associations between aspects of endurance exercise training and sexual libido in healthy men using a cross-sectional online survey study design. 
 
 METHODS: 
 
 A developed online survey questionnaire was used. The questionnaire was based on preexisting validated questionnaires and was used to assess elements of physical characteristics, exercise training habits, and libido of participants (n = 1077). Three evidence-based categories were created for the primary outcome of total libido score and low, normal, and high-response category sets. The high and normal categories were combined to form a high/normal score group, and the low category formed a low score group. Odds ratio (OR) values were calculated to examine group categorization. 
 
 RESULTS: 
 
 Age, training intensity, and training duration of participants had significant (P < 0.02) univariate relationships, with libido scores, and were thus included in the multivariate model. In the multivariate model, training intensity (P < 0.0001) and duration (P < 0.002) components were the most significantly associated with libido group designation (high/normal vs low). Participants with the lowest (OR = 6.9, 95% confidence interval [CI] = 2.6-17.9) and mid-range training intensities (OR = 2.8, 95% CI = 1.4-5.3) had greater odds of high/normal libido state than those with the highest training intensity. Participants with the shorter (OR = 4.1, 95% CI = 1.6-10.0) and mid-range training durations (OR = 2.5, 95% CI = 1.3-4.8) at their current intensity also had greater odds of high/normal libido score than those with a greatest duration. 
 
 CONCLUSION: 
 
 Exposure to higher levels of chronic intense and greater durations of endurance training on a regular basis is significantly associated with a decreased libido scores in men. Clinicians who treat male patients for sexual disorders and/or council couples on infertility issues should consider the degree of endurance exercise training a man is performing as a potential complicating factor.
– All right guys, if you're working on a beer belly and wish you hit the pavement more, fear not: at least your libido might be stronger than the guy who spends hours at the gym every day. Noting a distinct lack of data on the relationship between exercise and sex drive in men, researchers at the University of North Carolina dug into the subject, and their findings may not please devoted gym rats. They report in the journal Medicine & Science in Sports & Exercise that light and moderate exercise is associated with higher libido, while strenuous exercise is associated with lower libido. The results were drawn from detailed questionairres about the men's exercise habits and sex lives, reports SF Gate. It turns out that men who regularly engage in workouts that are particularly long or intense might not have enough reserve energy or even testosterone to want to, well, sweat between the sheets. The New York Times reports that the small sample size is only of men who volunteered to fill out a highly personal questionnaire, and that it's impossible to determine whether their answers were honest or representative of a larger population of men, but the researchers hope to follow up with research that also tracks hormone levels and perhaps even sorts out just how long or strenuous exercise must be to reach a "tipping point" that then affects sexual desire. (Maybe a little light therapy would help.)