Start off any exercise program gently
Each week should include: short run; longer run; press-up, sit-up, pull-up circuit; rest.
Every week add a little bit to each of the exercises
Don't train if you don't feel well
Stop if you feel any pain in your joints (but burning lungs is ok, in fact it's encouraged)
But most importantly, don't listen to the advice of random guys like me on the internet. Ask a PTI at your unit.
yeah, run like her old man just walked in through the front door as you where just getting to your vinegar stroke thrice weekly and you'll be super D duper in no time, just dont actually get caught by her old man......
Fitness is well overated. Why run to a battle and you'll never be fast enough to dodge a bullet! Get in the unit bar, invest in some bezzering and let the PSIs shag you mum, sister and girlfriend (cat/dog too if you're going RSignals).