Threshold is a moving boundary
Distance changes with the trigger, location, weather, surprise, and what happened earlier that day. A dog may work calmly across a wide park and struggle at a greater distance on a narrow sidewalk.
Measure from the first quiet change, not from the first explosion. A fixed stare, closed mouth, forward weight shift, lowered body, or sudden refusal of food can show that the setup is already becoming difficult.
Find a starting point without testing the limit
Choose an open location with an exit and begin far enough away that the dog can explore normally. Let the dog notice the trigger briefly. If the dog can disengage and recover, note the approximate distance and end before several repetitions build pressure.
Don’t walk closer until a reaction proves you were too near. The useful session happens below that point. If the other dog or person moves unpredictably, leave instead of trying to preserve the exercise.
Use landmarks instead of pretending the distance is exact. A driveway width or a row of parked cars is easier to repeat on the next walk than an estimate made during a tense moment.
Track response and recovery
Record the location, trigger type, approximate distance, earliest body change, and time needed to return to normal movement. These observations are more useful than a single label such as reactive.
Eating is one clue, not a complete test. Some excited dogs eat while highly aroused, and some calm dogs are not food motivated. Look for several signs together, including the ability to move away without a struggle.
Adjust the next walk
Add distance after a hard encounter and choose a quieter route. Trigger stacking can make the next reaction happen sooner. A short decompression outing may be more useful than another training pass.
Use the broader dog to dog leash reactivity guide for the training plan. If you are unsure whether the dog wants approach or escape, review frustration versus fear.
Know when distance isn’t enough
Repeated snapping, redirected biting, or a handler who can’t safely maintain control makes self guided practice inappropriate. Avoid the trigger and seek qualified help. Don’t reduce distance to collect better notes or video.
A veterinarian should assess sudden new reactivity, especially with altered movement, touch sensitivity, confusion, or other behavior changes. Pain and health changes can reduce a dog’s ability to cope.