Two words, static holds!! if someone said to me, your only allowed to train one way, for me it would be with static holds / max contraction training. When i get don training with my trainer i'll be returning to using them exclusively.
Reason - The fully contracted position (or the position of maximum motor arm) is the one position where all the available muscle fibers can be brought into play, that being true, the question can be asked, where is the merit of moving into or out of the one position? All it represents is a diminishing in muscle fiber recruitment.
Muscle fibers are recruited solely by the amount of weight they are made to contract against, this being the case, a full range of motion restricts you to using a much lighter weight than what you can maximally contract against.
Another benefit to training this way is that it minimizing wear and tear on the joints and connective tissues - as your not having to move through positions of disadvantaged leverage that a full range of motion has you do. This type of training is ideal for someone such as yourself who is exposed to a lot of wear and tear in your job.
Max Contraction Video - http://www.youtube.com/watch?v=ekJtCzRnD7E
You do require two ingredient's though, a strong training partner to help you into the contracted position and machines with big weight stacks....
If you don't have access to the above, then i'd recommend something like pre-exhaustion, that is, an isolation movement for a given muscle group trained to failure, immediately followed by a compound movement trained to failure. You wont be able to use as much resistance on the compound movement after first pre-exhausted that given bodypart, however that wont matter, the main thing is you go to failure.
My trainer John Martini (current overall Mr N.I) has used this technique with amazing results over the last 2 years, he pre-exhaust's everything. He explained to me that using compounds first is more strength oriented, he went on to say its a low stress high intensity technique that is over time less stressful of the joints and connective tissues.
Anyway, hope this helps, if ya need me to elaborate more on anything just let me know:)