Need to get a solid diet and don't worry so much about improving specific body parts. Work on your whole body and start with working out 3 days per week performing:
Pull ups, push ups, sit ups/crunches or other ab exercise, and squats. For the pull ups if you can't do one do partial reps and negatives. If you can get a friend or someone as a spotter they can hold your legs and help you develop enough strength to do full reps. The most important exercise by far at your age is pull ups. For squats start off using no weight or just the bar to get proper technique down and gradually add weight. Just stay consistent and you will notice results. You should also get a solid diet. Oh and don't forget to stretch!
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Bodybuilding: The science of hacking the human body.
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i will try that
