My lesson learned as a thru-hiker regarding a backpack: Get a great hipbelt which fits your body! You do not want slipping! The hipbelt must grip your hips.
Why? The vast majority of the weight of your pack must ride on your hips. The shoulder straps should simply stabilize the pack. Even if you have big muscular shoulders, weight on your shoulders will wear on your back or hurt your back. The hipbelt is the key to the benefit of any backpack for long distance hiking.
Honestly, this was a lesson first learned in Scouts, and further learned on the A.T. When trying on a backpack, insist on being given some weight to put in the pack. I was at a store last summer trying on a pack, but they did not have weights to put in the backpacks. I knew of weights since they were used at a great outdoor gear store I worked for years ago. They were like giant heavy bean bags. I nicely told a manager I needed weight in the pack to get a true feel. She went and found some weights I could put in there. I ended up buying that pack thanks to that special manager. Only with weight in the pack are you able to test the hipbelt and learn if it really is going to cling to your waist.
The hipbelt must be the correct circumference for your waist. Do not rely on the specifications you read on the Internet. Try it on! Can you tighten the belt enough so it firmly rides on your waist?
Second, you need to know your torso length, which is the distance between two of your bones in your spine. A person at a quality outdoor gear store will be qualified to measure this. Some packs are adjustable for a range of torso lengths. An adjustable pack is necessary for a growing teenager, and may be the best pack for you. Otherwise, the fit in the store is crucial. The torso length will determine the pack size you need, since the shoulder straps will be at the correct level. Torso length is crucial to make sure your shoulder straps are not too high or too low. You should be able to put two fingers under the shoulder strap. That is not where the weight should be.
I have an extremely small waist, whereas I have an 18 & ½ inch torso. If you barely have hips like me, or if you have larger hips, you may need to get creative. Do not be concerned about the color or the name brand of your pack. Get one that fits.
I am on my third backpack since my thru-hike in 1990. Even moreso than tents, you have a much better selection today. What did I use in 1990? You guessed it: My old backpack from my Scouting days, which is an external frame. I was a rare bird out on the A.T. even in 1990. Yet it worked, because the hipbelt was snug on my hips!! Would I do that today? No.
Bottom line: You want a pack which does not slid down your waist and put pressure on your shoulders. If the hipbelt fits you, and if the torso length is correct, you will be ready to triumph on the trail.
Hunter
