Sure someone will have suggested something like this before but just in case, whilst reviewing my latest exercise routine plans i thought i will add a weekly review to see how much i really achieved in the last week. So...
i set up a task "exercise review"
repeats every Sunday
then modified all my tasks already in exercise list to include a time in minutes value, not in the estimate field but in the name
for example Yoga class at gym , Cycle to and from work 
Then i created the following saved search:
Searched for: list:exercise and status:completed and completedWithin:"1 week of today"
and i can look at that every Sunday - it can either be in my list of lists or as a URL on the exercise review task itself - and i can see how much time i spent exercising this last week
Works, though beware, it can be very sobering if you didn't achieve all you that much :(
i take that as motivation to do more the coming week :)
Posted at 8:57pm on February 26, 2012