Backpacks for dogs

I keep hearing about staffies wearing backpacks to give them more of a workout on a walk, but I don't know much about it. What's the deal? Are they human backpacks that have adjustable straps and they've just been shorterned for dogs, or are they a different shape?

How do you train a dog to wear one?

Is 20 months too young to start, or is Gizmo good to go?

Will the other dogs tease him, resulting in Gizmo coming home from the park crying because they've been mean?

http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2060353.m570.l1313.TR0.TRC0.H0.Xdog+back+packs.TRS0&_nkw=dog+back+packs&_sacat=0

nope they are actually made for dogs, my boy has one, started with nothing and over a few months built it up so now he carries his own water, extra dog bags, treat and two weight sand bags (human ankle weights) but for just short walks he just has the sand weights, calms him down lovely when he is wearing it and tires quicker. starting your boy with nothing and building it up, you wont have more than two small waters in his back pack for a couple of months so if you start now by the time he's 2 years he'll be able to carry some water without a problem and then slowly increase the weight.

Thank you, that's super helpful. He'll be able to carry water just in time for summer.
Hopefully he'll like it.

theres a pouch either side for the backpack disribute the weight evenly it'll work well for gizmo http://www.amazon.co.uk/Petown-BackPack-Harness-Release-Carriers/dp/B00M4RVXJO/ref=sr_1_3?ie=UTF8&qid=1456269799&sr=8-3&keywords=backpack+dog+medium get this yin off amazon unfortunately i cannae recommend yin but disribute the weight evenly and he should be ok.

18 months is the minimum age but really best to wait for 2 years so they are fully developed and won't cause health issues later on. Backpacks are great just work up slow and don't go over 20% of their bodyweight