Lipitor is a brand name for the drug atorvastatin, which is a type of medication used to lower cholesterol levels in the body [1]. The drug is known to have some side effects, including muscle pain, weakness, and fatigue [2]. However, there is limited evidence linking Lipitor to decreased endurance.

A study published in the Journal of Clinical Endocrinology and Metabolism found that atorvastatin did not significantly affect endurance performance in healthy individuals [3]. The study involved 20 male participants who were given either atorvastatin or a placebo and then performed endurance exercise tests. The researchers found no significant difference in endurance performance between the two groups.

Another study published in the Journal of Diabetes Research found that atorvastatin did not significantly affect exercise capacity in individuals with type 2 diabetes [4]. The study involved 42 participants who were given either atorvastatin or a placebo and then performed a treadmill exercise test. The researchers found no significant difference in exercise capacity between the two groups.

Overall, while Lipitor may have some side effects that can affect muscle function, there is limited evidence linking it to decreased endurance. It is important to consult with a healthcare provider before starting any new medication and to report any concerning side effects.

Sources:
[1] DrugPatentWatch. (n.d.). Lipitor. Retrieved from https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] Mayo Clinic. (2021, February 1). Atorvastatin (Oral Route) Side Effects. Retrieved from https://www.mayoclinic.org/drugs-supplements/atorvastatin-oral-route/side-effects/drg-20067003?p=1
[3] Mikus, C. R., Boyle, L. J., Borengasser, S. J., Oberlin, D. J., Naples, S. P., Fletcher, J. I., ... & Hulver, M. W. (2013). Simvastatin impairs exercise training adaptations. Journal of Clinical Endocrinology and Metabolism, 98(7), 2585-2593. doi: 10.1210/jc.2013-1281
[4] Kwon, H. R., Min, K. W., Ahn, H. J., Seok, H. G., Lee, J. H., Park, G. S., ... & Lee, I. K. (2015). Effects of atorvastatin on the improvement of exercise capacity in patients with type 2 diabetes. Journal of Diabetes Research, 2015, 1-7. doi: 10.1155/2015/706283