When I ve used my arms the last couple of days for work, I can only lift my arms afterwards with a great deal of stiffness and pain. I used a manual post hole digger yesterday and did a moderate amount of work (less than I would normally do) and about 1/2 later I found it difficult to lift my arms. Less stiff today, but after doing some physical work like lifting moderate weight and using a hammer, the same stiffness. It s unusual.