Dear Dan:
1. If I change the weight on an exercise, for example dumbell rear laterals, will the weight for a similar muscle group change. For instance, machine rear lats or cable rear lats?

2. I am having trouble with hammer curls due to tendonitis, which is gradually getting better. Should I continue doing the exercise, but with lower weights or discontinue until I don't have any pain ?

The only exercises that have "global" weight changing capabilities are those listed in the strength testing area (bench, chest press, squat, leg press, power clean etc). So, changing the dumbbell rear lateral weights will not change the weights of another exercise that works the similar muscle group.

When it comes to the dreaded tendonitis injury, it is usually best to continue doing the exercise but with much lower weights or at least a weight load that does not create pain when performing the exercise. Keeping the muscle groups supple and strong is a key factor in reducing the stress placed on the tendons and ligaments of the involved joint. But, with anything, it really depends on the severity of your injury and the advice of your doctor on whether or not you should continue exercising!