# Constraints Option with Flat-Bottom Position Restraints in mdp file **URL:** \ **Category:** User discussions\ **Tags:** mdp-parameters\ **Created:** [January 18, 2025, 10:56am UTC](https://gromacs.bioexcel.eu/t/constraints-option-with-flat-bottom-position-restraints-in-mdp-file/11070 "2025-01-18T10:56:42Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![fatemeh](https://avatars.discourse-cdn.com/v4/letter/f/9de053/32.png) [@fatemeh](https://gromacs.bioexcel.eu/u/fatemeh)\ **Post date:** [January 18, 2025, 10:56am UTC](https://gromacs.bioexcel.eu/t/constraints-option-with-flat-bottom-position-restraints-in-mdp-file/11070/1 "2025-01-18T10:56:42Z")
GROMACS version: Hello, I have a question regarding the `constraints` option in the `.mdp` file. When using flat-bottom position restraints in MD simulations with the AMBER force field, is it necessary to set `constraints = all-bonds`, or can I use `constraints = h-bonds` instead? Thank you in advance for your assistance! Best regards, ---
**Author:** ![jalemkul](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/jalemkul/32/18_2.png) [@jalemkul](https://gromacs.bioexcel.eu/u/jalemkul)\ **Post date:** [January 20, 2025, 4:47am UTC](https://gromacs.bioexcel.eu/t/constraints-option-with-flat-bottom-position-restraints-in-mdp-file/11070/2 "2025-01-20T04:47:46Z")
Use the constraint convention that the force field was parametrized to use. For AMBER, that is `constraints = h-bonds`. If you constrain bonds inappropriately, you can imbalance the subtle vibrational forces of the model. ---
**Author:** ![fatemeh](https://avatars.discourse-cdn.com/v4/letter/f/9de053/32.png) [@fatemeh](https://gromacs.bioexcel.eu/u/fatemeh)\ **Post date:** [January 20, 2025, 2:34pm UTC](https://gromacs.bioexcel.eu/t/constraints-option-with-flat-bottom-position-restraints-in-mdp-file/11070/3 "2025-01-20T14:34:44Z")
thank you so much