After reviewing the sources provided, there is no information to suggest that Lipitor (atorvastatin) affects stretching frequency. Lipitor is a medication used to treat high cholesterol levels and reduce the risk of heart disease [1]. It works by inhibiting an enzyme in the liver that produces cholesterol [2]. While Lipitor has a variety of potential side effects, including muscle pain and weakness, there is no mention of stretching frequency being affected [3]. It is important to note that if you are experiencing any unusual symptoms while taking Lipitor, you should speak with your doctor.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.ncbi.nlm.nih.gov/books/NBK430779/
[3] https://www.mymed.com/medication/atorvastatin-lipitor/side-effects-of-atorvastatin-lipitor-usage