Levels of this primary sex hormone in men naturally starts to decline with age, and the loss could result in negative effects and drive some patients to try therapy to replenish their testosterone artificially.
The study did say that heavy exercisers may tend to get too exhausted after prolonged workouts, or may experience a drop in testosterone, which could explain the lower libido.
The new study reveals that rigorous workouts can lower libido in men.
A team of University of North Carolina researchers began work on the new study after noticing that there indeed weren't too many papers exploring the relationship between different levels of exercise and the male libido.
To find out how strenuous workout could affect male sex drive, Hackney and colleagues developed an online survey including almost 1,100 male participants who reported about their sex lives and exercise routines through three separate detailed questionnaires.
Clear patterns arose, such as men with light to moderate exercise were far more likely to disclose moderate to high libidos than those whose exercise routines were intense or prolonged.
"Fertility specialists will often ask a woman about whether and how much she exercise", said lead researcher Dr Anthony Hackney, a professor of exercise physiology and nutrition at UNC. A final set of questions delved on their general health and medical history.
Men taking part in the survey were volunteers who classed themselves as current or former endurance athletes - runners and cyclists. Those with the longest and most strenuous workouts were far more likely to be in the group where the sex drive was lowest.
The study involved grouping the respondents based on their answers, dividing them based on libido and workout intensity. Everybody was interviewed about their sexual appetite, classifying them regarding the low, medium and high libido. The results indicated that exposure to increased levels of intense training was strongly associated with decreased levels of libido.
This led scientists to believe that there might be a "tipping point" when it comes to working out, which is where men become too exhausted or no longer interested in having sex.
The findings were discussed in the journal Medicine & Science in Sports & Exercise.