Fitness Friday: Challenge Your Body Without Weights

Below are five ways to challenge your body without weights:
100s
Take the simple exercises like push ups, crunches, lunges, etc. and do as many reps as you can. This would build your endurance and help you perfect every move to its basic. This will help you later when you do add weight to your workout and it is great it you are simply trying to maintain your muscle mass.
Flex & Hold
Right after a set of an exercise flex that muscle as hard as you can and hold it for 10 seconds. This gives more definition to your muscle. You could also reverse the order, flex for 10 seconds right before doing the set.
Zero Rest Time
Trying going non-stop until muscle failure without counting reps. This technique is intense but helps you grow in your fitness style.
Make Your Own Weights
Add books, large water bottle or a heavy box lying around. Be creative and add resistance to your movement. Keep your body guessing and your mind entertained.
One Limb At A Time
Make every exercise challenging; just try doing it on one limb. One-legged squats, one-leg balance bicep curls, one-arm push-ups, etc. The balancing will help your build the core muscles along with the muscle you are working on.

P.S. NEW ANTHEM!