Wow! A cable controlled back hoe! Those were getting rare when I was a kid 50+ years ago! I'll bet they are a bear to keep in clutches!
Your arm strength is not supposed to hold any powered work being done. If it does, the clutches aren't adjusted correctly. It's all about leverage. The "clutches" look like and operate like oversize automotive brake shoes. Hand levers move the clutch shoes to engage the drums to provide working force, be it swing, travel, hoist, pull, or crowd. The hand levers have adequate leverage to fairly easily engage/disengage the clutch shoes past the over-center locking cams which hold the shoes tight to the drums doing the work. Success totally depends on the tightness of the shoes and the locking cams. (but no smart operator will ever remove their hand from the lever doing work, regardless)
The only thing that gets strenuous are the cable drum brakes, which are band-type brakes operated by a pair of foot pedals. Your thighs can get very tired by afternoon. Leg pressure/strength is required to keep the cables from slacking and to control the drop of the load, the stick, the crowd... and on a backhoe, the boom. It depends on your attachment up front. Basically, you're mostly riding the brakes all day with constantly-varying foot pressure depending on what motion is going on. Your legs control the spool-out of cable from the drums, and it's your legs that are holding the load (and also the boom on a backhoe) in the air.
You are basically running two big winches. It takes coordination and be of a certain mindset to run cable machines. When your legs get tired to where you're nicking the top of dumptruck tailgates as you spool out the dipper, it's time to go home ! Been there, done that. Many many hours in these machines. Until 2008 we had three 10B's , three 22B's , and a couple Lorain's. Nowadays have only one operational 22B and a parts machine