The second law of motion will impact them because of unbalanced force. As for a fitness activity that a overweight person could do...long as the things they are moving are bigger than them it could have an impact, speed walking.
Answer: Is there any type of fitness activity that a significantly overweight person could do where Newton's second law of motion would not be a factor? a.As long as the things they are moving are bigger than them it could have an impact, speed walking.