Why Does Exercise Cause Botox to Wear Off Faster?

I have had several anecdotal cases of Botox wearing off sooner than expected in patients that perform excessive, vigorous exercise. One example that comes to mind is an aerobics instructor and her mother. I injected both of them the same day with the same vial: 50units to each patient. The aerobics instructor's Botox started losing significant effect in 6 weeks, but her mom's Botox-effect lasted the expected duration.

Fortunately this has not been a common occurrence, and I'm not sure why it may occur.

There is no viable evidence to suggest that Botox wears off faster in patients who lead a more active
lifestyle. As with any other procedure, however, it is advisable that a recovering patient allow 6 hours
healing time before resuming physical training. There have been no scientific studies proving that
exercise deteriorates Botox treatments.

I am not certain if this is a widely held belief but it does appear that the botulinum effect does dissipate faster in areas of increased muscle activity such as around the eyelid muscles.