Kalle is correct that hydraulics are not very energy efficient, which is one reason automobiles are changing to electric-assisted steering. We have one test facility that applies hydraulic loads to 10 Hz. When tuning the Delta controller we could only work 10 minutes at a time and/or lower the pressure. If not, the oil got so hot you could smell the paint melting on the cylinders. That was even with the cylinders stationary, just the normal balance flow thru the servo-valves. I didn't see a cooler in the system which has a large pump and motor (designed decades ago).
Not all mechanical testers use hydraulics. I think some for lower forces like fabric tension testers have electric positioners. However, if you need large loads and fast cycling, hydraulics is best for a general-purpose testing machine. If you have a dedicated test, with defined loads and frequencies, that will be used for years, one might design a more efficient loading system using something like a rotating unbalanced weight or spring-mass with electromagnetic drive. There likely are such dedicated testers in high-volume qualification testing like automotive suspensions and tires.
My experience with mechanical testing is limited. One memory is visiting a local test shop in GA to inquire about environmental testing. I saw a test where they repeatedly dropped a large sand-bag on a folding chair using a pnuematic cylinder, running for weeks. It was to get data for a lawsuit, which the tech said was a big part of their business. He didn't relate the weight of the injured party.
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