You’re garage door likely has torsion or extension springs. Torsion springs are mounted to a metal rod that runs parallel to the door, directly above the door opening. Extension springs are long, light-weight, and run perpendicular to the door, above the horizontal portions of the door tracks.
As garage door springs age they lose their resiliency causing doors to feel heavier without their support. This “extra” weight will also cause strain on electric door openers as they attempt to lift the door.
In addition to causing the door opener to work harder (this may be audibly noticeable) worn springs can break suddenly and cause the door to slam shut. Garage door springs cannot be repaired but they can be replaced.
With new springs, your garage doors should require relatively little force to lift into an open position.
DO NOT disconnect the opener from the door if the springs break while the door is open. If the door is not connected to the opener, it may come crashing down under its full weight. AVOID leaving the door open to prevent someone from unknowingly attempting to shut the unsupported door.