ADD, I have learned the things that 'stove' you up in our age bracket is when you perform a new task and use a set of muscles you don't use in your regular activity. Plus, when you rent a jackhammer or cement mixer, etc. you naturally go at it relentlessly. I used an industrial size, backpack leaf blower that I wore for about 5 hours. I had back spasms for 6 months.
Let me guess. You are putting your donut shop in a retail space that was not a food place previously and are trenching for plumbing and maybe power. Was there an existing class I exhaust hood or do you have to put one in? Are you working with a restaurant equipment company or just buying used stuff?