That indicates a biomecanical problem. Your arms aren't designed to provide power and that's what happens when you use them too muchNow I wish I could find a way to get rid of the pain between my shoulder blades that I get while tripping.
I use a tump for my wood canvas canoe - portaging with paddles, life jacket, dog pad and fish poles attached to the canoe. I also use a tump to port my wannigan with my bed roll on top. I find I can travel longer even as my kit gets heavier with the use of a tump. I do have to practice and "build up" to heavier weights before a trip. I also find I get "trail broke" a little faster using a tump over using my shoulders. All this said, I have never seen anyone else using a tump on any of my trips.
I will have to see if I have any pics of my kit - likely nothing very helpful. However, I have not tumped for lots of years, so I am careful to take a few weeks of working out to get my body prepared for the trip.
I also train my dog in obedience and canoe/timber manners, so we train together. I may start out with 2 driveway laps, with my wannigan and about 10 pounds in it, with my dog tetheard to my waist. My driveway is about 1/8th mile - one way with a slight grade. The dog and I practice walking the load. In time I put about 20 pounds in the Wannigan and walk up to 3 laps, the dog still attached to me has his pack on with about 3 pounds of water for weight.
After I can master that without breathing to hard or any significant fatigue - I move up to walking about a half mile field romp with my dog - practicing recall, sit stay ... hide and seek, then put on my wannigan loaded and my bed roll ( 18 pounds with blanket, and axe ) about 50 pounds give or take and nightly ( after work) walk 4 laps on my driveway no stopping, my dog using his packs with 6 pounds of water ( 3 pounds per side ), attached to me with his 6 foot leash. Last year I knew he was ready when we kicked up a deer at the edge of the driveway no more than 15 feet away. The deer exploded back in the timber, my dog (leashed to me) wanted to give chase in the worst way, but I yelled NO - SIT! He sat and looked a t me, then at the bounding deer, then back to me. With 50 pounds on my head, if he suddenly ran that could have been ugly. He received a hearty good boy and pat on the head. We continued our laps up and down the lane confidence growing.
My canoe with the gear in it after a 7 day trip last year was 72 pounds. My wannigan with bedroll attached at the end of the trip was I think 47 pounds and my canvas pack was 44. I use the shoulder straps as well as the attached tump on it as well if it is a long port. If it is manageable I tump the canoe with the pack on my shoulders and double port only. Usually I triple port as most of them seem to be longer, 2/3 of a mile or more.
If I this is not really too clear, jsut PM me. I do not always express myself well when typing.