As some of us have experienced, extending our arms straight while doing “arm raise” makes the exercise harder comparing to having our elbow bent. Also, if you extend your arm above your head while doing crunches, you will need to use more abdominal strength to get yourself up from the ground. The reason behind this phenomenon is based on the “levers of the musculoskeletal system”. To make the lever theory simple, as you extend the distance of the outside force (a dumbbell) from your pivot point (shoulder), your must exert more force to lift the weight or keep it parallel to the ground. Also, when you extend your arm out when doing crunches, gravity pulls your hands down at further distance away from your pivot point, hip flexors; therefore you will need to use larger force to crunch up. In conclusion, if you need to make your exercises more intense, extend the weight further from the pivot point will help you do more work.

Some exercises for you to experiment:

1. arms front raise
2. arms  lateral raise
3. basic crunches
4. hip abduction
5. hip adduction
6. bicep curls with different angle at elbow, the pivot point