Do some exercises eg push ups,bench dips,crunches.sit ups etc. Do about 20-25 of about 3sets each. For weights you could use mineral water bottles or anything that allows you to have a good grip and most importantly to YOUR grip.
To build up stamina jog till about the 50m mark then walk back to your starting point and then jog to the 100m mark. Do this about 5times. As you find the distant easier increase it plus this time jog to the 100m and walk back then to the 150m mark and walk back..again about 5times. You can even start running instead of jogging as your stamina improves.
For the duration of this workout which you will see results in about 4 to 6weeks cut back on the coffee,ciggies and possibly anything fattening or too sugary if it's too hard..then at least reduce.
Try to have two full days of rest in the week even if you're tempted to do some exercise DON'T!
After your runs, go home and ice the area where the strains are felt. You could use a pack of frozen peas wrapped in a towel or an ice pack if you have one. Ice for about 2 to 3 minutes. Then having cool down,take a warm towel and soothe the area before shower.
It might be hard at first but in no time your body will adapt to this new routine and you'll find it a pleasure.
This is recommended to those in the beginners stage but works for everyone in general.
Try it....and in about 6weeks max...welcome to a brand new you!!
