Question 595: 1. To stay healthy is it alright to participate in a college class where women and men are exercising together, playing a sport (i.e. basketball, soccer, volleyball) ? All the Fitness Centers in College are male/female mixed and expensive, you have to travel very far to participate with other Muslim brothers to exercise in a halal way, and cannot afford equipment of your own. What should you do to prevent disease, laziness, and lethargy in this case.
Answer 595: Firstly, these sports you named are not necessary for a person to exercise. Secondly, in order that you want to stay healthy and prevent disease and laziness you can do other sports like walking. But, if those females participated in such sports have at least observed Islamic hijab in some cases and you are also completely sure that you don’t engage in a forbidden act and this doesn’t harms your beliefs and commitment to the faith (which is what normally happens) nor entails any harãm act you would be allowed to participate in such sports.
According to Sayyid Sistani (ha), one must refrain from going to such places where people go about half-naked is if it entails a harãm act. Based on obligatory precaution, one must refrain from going to such places, even if it does not entail a harãm act like looking with lust and the like.
 . For more information, please refer to: The official website of the office of Sayyid Sistani (ha), Youth’s issues » General Rules.