I agree with you too that generally it is important to work through a fast as most of the time we have no choice. Every fast i have ever done, i have had to work through it. The only "however" here has to do with heavy lifting.
By all means Mikka can give it a shot, but in my personal experience, lifting 50 pound bags of cement for 8 hours a day wouldn't work out (would it for you?). This is why i presented an alternative possibility.