Why Fit Matters: Your Dog’s Harness Should Work With Their Body

Choosing a harness often starts with a fairly simple question: Will it fit my dog?

But there is another question worth asking.

How will my dog move while wearing it?

Dogs walk, run, climb, play and occasionally launch themselves after something they absolutely did not need to chase. Their equipment needs to stay secure while allowing their bodies to move as naturally and comfortably as possible.

That is where harness design and proper fit become important.

Dogs Were Designed to Move

A dog’s front legs aren’t simply hanging from the body. The shoulders, upper limbs and surrounding muscles all work together as the dog moves forward.

Muscles around the shoulder and upper forelimb, including the deltoid, triceps, supraspinatus and biceps, contribute to that movement.

That’s why we pay attention to where the straps of a harness actually sit.

A strap positioned horizontally across the front of the shoulders may interfere with the dog’s natural forward movement. A harness sitting too close behind the elbow can create another problem: repeated rubbing against the sensitive skin of the armpit.

Neither is something we want from equipment a dog may wear every day.

Not Every Harness Works the Same Way

There are countless harness designs available, and some are intentionally designed to help reduce pulling by limiting or redirecting a dog’s forward movement.

That can be useful in certain situations. But control shouldn’t be the only consideration when choosing equipment.

We believe owners should also consider where the harness sits, whether the shoulders can move freely, whether anything is rubbing behind the legs, and whether the dog can comfortably walk with a natural stride.

There isn’t one piece of equipment that’s perfect for every dog. Body shape, behaviour, activity and the person at the other end of the leash all matter.

Watch the Armpits

This is one of the simplest things you can check at home.

Look at where the rear chest strap sits behind your dog’s front legs. If it’s tucked directly into the armpit, movement can cause repeated friction and chafing.

It may also contribute to another problem with some harness designs: the great canine disappearing act.

Some dogs become remarkably good at backing out of a harness. Once they discover they can bring an elbow underneath a loosely positioned rear strap, what was supposed to be safety equipment can suddenly be lying on the sidewalk while your dog is heading in the opposite direction.

For medium and larger dogs, we generally look for approximately three to four finger widths behind the elbow. For smaller dogs, approximately two to three finger widths is a useful starting point.

The individual dog’s proportions still matter, which is why those numbers should be treated as fitting guidance rather than an absolute rule.

Why We Designed the Fluid Motion Harness

These considerations are a large part of why the JettaJacks Fluid Motion Harness looks the way it does.

The Y-shaped front is intended to avoid placing a horizontal strap directly across the front of the shoulders. The adjustment points allow the harness to be positioned around the individual dog’s body rather than expecting every dog of a particular weight to have exactly the same proportions.

The rear chest strap is designed to sit back from the elbow, helping reduce rubbing while providing a more secure position around the rib cage.

It isn’t about adding features simply so we can say there are more features.

The design starts with the dog underneath the harness.

Four Things to Check When Fitting a Harness

Once you’ve chosen a harness, the fitting matters just as much as the design.

First, look at the front connection. On a Y-style harness, the lower point of the Y should sit around the upper sternum rather than riding high into the throat.

Next, look behind the front legs. There should be enough clearance that the straps aren’t continually rubbing against the dog’s armpits.

From above, the harness should sit centred along the dog’s back rather than continually twisting toward one side.

Finally, check the tension. The harness should be secure without squeezing the dog. You should be able to comfortably slide a finger beneath the straps without having to force it through.

Then do something people sometimes forget: Let the dog walk.

Watch from the front, side and behind. Look at the shoulders. Watch the stride. Check whether the harness stays where you positioned it.

A harness can look perfect while a dog is standing still and behave completely differently once that dog starts moving.

The Best Harness Is the One That Fits Your Dog

There is no piece of dog equipment we would recommend simply because it happens to be ours.

Different dogs have different bodies, behaviours and needs. What works beautifully for one may not be the right solution for another.

What matters is understanding what you’re putting on your dog and paying attention to how your dog responds to it.

Because good equipment shouldn’t ask your dog to accommodate its design.

The design should accommodate the dog.