Why We Studied Load Distribution While Developing ABUBA4

A dog carrier backpack does not make weight disappear. Good load-carrying design changes where and how that weight is supported.

While developing ABUBA4, our dog carrier backpack, we wanted to understand three things: what a hip belt actually changes, why load position matters, and how shoulder strap design affects pressure. So we read research on backpack biomechanics and ergonomics.

We did not use that research to say ABUBA has been scientifically proven. None of these studies tested ABUBA, or any dog carrier. We used them to better understand the design problems we were already seeing.

The Question That Started With ABUBA4

Earlier ABUBA models were simpler. As we worked on a carrier for longer outings and larger dogs, shoulder concentration became a bigger design issue.

The question changed. It was no longer "Can we carry the dog?" It became "How should that load be supported?"

That question sits behind several ABUBA4 features: a fixed wide hip belt, a close-body fit, top strap balance and thicker shoulder padding. Before we get to them, here is what we read.

What We Read, and What It Showed

All four studies below are about human backpacks. None involve dogs or dog carriers.

Chest and hip belts and shoulder pressure

Dai and colleagues studied 28 healthy male participants carrying backpacks at four load levels, up to 30% of body weight, with chest and hip belts either fastened or unfastened. Under those conditions, using the belts reduced high-pressure regions around the lateral clavicle and the medial trapezius. The effect was weaker at the highest load tested.

The study tested chest and hip belts together, so it can't tell us what a hip belt does on its own. What we took from it: belts can change how pressure is spread across the shoulders, and that benefit has limits as loads get heavy.

Hip belt use and strap adjustment

Mackie and colleagues used a simulator to test school load carriage configurations. Backpack weight had the greatest effect on shoulder strap tension and shoulder pressure. Hip-belt use and shoulder-strap adjustment also had substantial effects.

This reinforced something we already believed. A carrying system shouldn't be understood as one isolated feature.

Shoulder strap width

Golriz and colleagues tested straps from 5 to 8 cm wide with a 20 kg load on a manikin. Under those conditions, pressure at the shoulder-backpack interface decreased as strap width increased. Load placement also mattered, and the two interacted.

We are careful with this one. Strap width and padding thickness are not the same variable, so this study does not prove that ABUBA4's thicker padding reduces pressure. What it did was remind us why contact area and strap structure deserve attention when the load is heavy.

Load position

Daffin and colleagues placed a fixed load, 5% of body weight, at three horizontal distances behind the wearer: 0, 0.20 and 0.40 meters. They measured postural stability while participants stood with their eyes closed on a force platform. Stability changed the most when the load was furthest from the body.

Our interpretation is that it is worth keeping the carrier, and the dog, close to the wearer instead of letting the load hang unnecessarily far behind the body. The study did not test dogs or ABUBA.

What the Research Did and Didn't Tell Us

It helped us understand that:

  • hip belts can influence how pressure is distributed across the shoulders
  • shoulder strap configuration matters
  • load position matters
  • fit is part of the carrying system

It did not:

  • test ABUBA4
  • test dog carrier backpacks
  • validate a fixed load-transfer percentage for ABUBA
  • show that ABUBA prevents pain or injury

How It Shaped ABUBA4

These are the four design decisions where the reading and our own fitting experience met.

Wide fixed hip belt. It is designed so the pelvis can take part in supporting some of the carrying load.

Close-body fit. It is designed to keep the carrier closer to the wearer. Getting that right depends on choosing the right size, which is why we ask owners to measure carefully. Our ABUBA Size Guide explains how.

Top strap balance. Adjusting the straps, including the top strap, helps fine-tune how the carrier sits forward and back against your body.

Thicker shoulder padding. ABUBA4 uses padding approximately twice as thick as ABUBA3 and LITE2. It is intended to give more cushioning in heavier carrying situations.

The Dog Back Support Cover is also part of the ABUBA4 support structure. We don't claim that these human backpack studies prove anything about its effect.

What We Can't Claim Yet, and What We Want to Measure Next

During development, we have used approximately 70% as an internal description and design target for the load-distribution effect we are aiming for. An internal design target is not the same as instrumented product data. So we currently explain the mechanism, and we do not present 70% as a verified ABUBA performance result. That distinction is intentional.

The next step is measurement. These are goals, not completed tests. We would like to look at:

  • shoulder strap force
  • hip belt force
  • load transfer ratio
  • different dog weights
  • different wearer body types
  • different strap-adjustment conditions

ABUBA4 was not designed by copying a paper. The research helped us understand what we were already observing during product development and fitting.

The design question remains a practical one. How can we support a dog's weight more effectively when carrying becomes necessary? That question continues to shape how we develop ABUBA. You can find more of how we explain our products in Learn.

Sources

  • Dai Y, Li J, Cui W, Li J. Coupled effect of load weights and belt use on male shoulder pressure redistribution. Ergonomics. DOI: 10.1080/00140139.2024.2328357 · PMID 38495011
  • Mackie HW, Stevenson JM, Reid SA, Legg SJ. The effect of simulated school load carriage configurations on shoulder strap tension forces and shoulder interface pressure. Applied Ergonomics. 2005. DOI: 10.1016/j.apergo.2004.10.007 · PMID 15694074
  • Golriz S, Hebert JJ, Foreman KB, Walker BF. The effect of shoulder strap width and load placement on shoulder-backpack interface pressure. Work. 2017. DOI: 10.3233/WOR-172651 · PMID 29254136
  • Daffin L, Innes S, Stuelcken M. Changing the horizontal position of a fixed backpack load: The effect on postural stability in young adults. Work. 2023. DOI: 10.3233/WOR-230044 · PMID 37182859

Continue exploring:

Back to blog