First of all, you can try to communicate with the upstairs residents and explain that your fitness behavior has caused trouble to the downstairs residents. I hope they can pay attention to the exercise mode or reduce the exercise time. If the other party accepts communication and can make changes, then the problem is basically solved.
If communication doesn't work, then we can reflect this problem to the property management company or the greening management department and ask them to take appropriate measures to reduce noise. For example, you can install sound insulation equipment or adjust the exercise time of residents. At the same time, we can also complain to the relevant departments in order to seek more practical and effective solutions.
In a word, if the treadmill upstairs disturbs people seriously, we can't tolerate this situation, and we should take active measures to solve the problem and safeguard our legitimate rights and interests.