It is no secret that Shilajit has been used by athletes and other very physically active people across the world for quite some time now, and that is because of a few good reasons.
Ultimate Absorption of Minerals and Electolytes
One reason is because Shilajit's high mineral content greatly assists in replacing vital electrolytes, making it much easier to maintain stamina and endurance. Not properly replacing those electrolytes can lead to increased fatigue and even different deficiencies over time, so it's very important to not overlook this when having a generally physical lifestyle. Shilajit's fulvic acid content helps to deliver nutrients deep into and out of our cells, making issues like digestion no longer a problem as far as absorbing the minerals one needs. Minerals like iron, calcium, and magnesium can easily be absorbed, clearing up many of the issues that people have in relation to mineral deficiencies. 
Immense Energy Producer
Another way Shilajit benefits those who exercise, or those who just have very physically active lifestyles, is by greatly supporting the production of ATP(Adenosine Triphosphate), which is our bodies primary source of energy. Most supplements advertised for energy will temporarily give one a little boost, but very few actually work synergistically with the body to produce ATP, which one will never burn out from, but will rather have sufficient energy reserve levels built up, to then be used by our body as needed. In other words, Shilajit helps to build up our bodies true energy source, which helps to deeply nourish us and diminish symptoms related to fatigue and sluggishness.
Healthy Testosterone Levels
Testosterone is not only responsible for the development of male sexual organs, but is imperative in the development and growth of bone mass and muscle for both men and women, as well as maintaining brain function and energy. Aging is a factor that usually contributes to the decline of testosterone in men and women, and things like weight gain, hair loss, loss of libido, decrease in muscle and bone mass, and fatigue begin to occur. Shilajit helps to maintain healthy testosterone levels in both men and women, as studies suggest 
1. Das, Amitava, et al. “The Human Skeletal Muscle Transcriptome in Response to Oral Shilajit Supplementation.” Journal of Medicinal Food, vol. 19, no. 7, 2016, pp. 701–709., doi:10.1089/jmf.2016.0010
2. Pandit, S., et al. “Clinical Evaluation of Purified Shilajit on Testosterone Levels in Healthy Volunteers.” Andrologia, vol. 48, no. 5, 2015, pp. 570–575., doi:10.1111/and.12482.