I'm starting the gym up again after a four years to try and get back into shape. I'm mainly only interested in using the treadmill. Before I used to just see how fast/far I could run in 30 minutes - my best was 4.7km. Is this any good? I'm not going to build muscle, but mainly to burn fat and to just become generally healthier by giving my body a workout. I want to focus mainly on the running. Should I time myself to increase my distance (e.g. to run further in 30 minutes every time I visit) or run a set distance each visit and try to reduce my time? Would 5k be a good place to start? I bought these trainers and they fit but when I lean forward I feel the front stretching slightly (at my big toe). Do trainers become a bit more slack with wear? Any obvious pieces of advice that you'd recommend before I begin?