A Fixed-Length Leash
Although it’s tempting to walk your dog on the longest leash available, using an extendible leash can lead to problems. From a training perspective, flexible leashes encourage pulling because the dog always feels tension around his neck, which translates to “a tight leash means I get to go forward” mentality (and dogs should always walk on a loose leash). Plus, you and your dog aren’t really connected when he’s walking 15 feet in front of you – there’s no communication between dog and handler when there’s that much distance between them.
Extendable leashes also come with numerous safety concerns: the thin line can snap, the locking mechanism can jam and the leash can cause rope burns and other injuries to both dog and human. A fixed-length leash between four and six feet is more than enough room to roam, plus it’s safer for everyone.