Balancing a Physical Education Class

I have a challenge balancing my fifty minute physical education class.  The difficult part for me is the lack of time.  I'll use these last couple of days as an example.  We start our class with 10-15 minutes dedicated to our fitness focus.  We then get the students together to explain their stations for their flag football unit.  In order to thoroughly explain those stations, and educate the students it takes at least 12-15 minutes.  Then the students must be divided in groups and get out to the fields that we play on.  Besides these tasks, there are always minutes that are lost during transitions.  By the time the students get out to their stations, they have about 6-10 minutes to actually work at the stations.  Of course the second day of stations is better, because we do not have to thoroughly explain the stations again.  Each segment of the class is essential and justified, I just wish each segment wasn't so rushed.