1) Demand too much of 2) Load beyond the limit 3) Strain 4) Strain excessively 5) Too much strain 6) Work too hard 1) Overextend 2) Overload 
• (v. i.) To strain one`s self to excess. • (v. t.) To stretch or strain too much; as to overstrain one`s nerves.
O`ver·strain' intransitive verb [ imperfect & past participle Overstrained ; present participle & verbal noun Overstraining .] To strain one's self to excess. Dryden. 
[n] - too much strain 2. [v] - strain excessively 3. [v] - overstrain oneself
The condition of a structural material which has been stressed past the yield point. Materials can be annealed - given a form of heat treatment - to remove the effects of overstrain.
noun too much strain