resistance training exercise

How can changes in movement increase the difficulty of a resistance training exercise?

This question is phrased in a broad manner but I will answer as I think you mean. The stricter you can make a particular movement become, the more difficult it will become and resultantly you will use less overall weight. This simply means that your targeted muscles are doing more of the appropriate workload and you are using less body momentum to cheat the weight up. For instance I admit to sometimes letting my ego get the best of me and I do standing alternate dumbell curls with 75 lbs for 6 reps. If I sit down and attempt the same exercise, I have basically eliminated all cheating from the movement and would now be unable to perfporm this same feat. I have to lower the weight by 10 lbs per dumbell. Another example would be dumbell side laterals. If I really started rocking and swinging the weight I can handle 45 lb dumbells, but with strict form 30′s are a chore. Generally speaking you should aim to maximize your strict form as a beginner.