The "no sex before a game" theory for athletes is TOTAL BS ... so says former NFL superstar Ottis Anderson -- who tells TMZ Sports, he wasn't exactly celibate back when he won Super Bowl MVP.
The St. Louis Cardinals all-time leading rusher was being herded around NYC today ... when we asked him if abstaining from sex before games actually gives you a noticeable testosterone boost.
Ottis -- who also played for the NY Giants -- tells us he thinks it's a complete myth that dumb people are buying into ... and encouraged athletes to bang away.
Check out the clip -- Anderson's a living legend ... and hilarious.
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