How do I pack a backpack to prevent injury to my back and keep it comfortable while hiking?
The key to keeping your back happy is to drive as much pack weight to your hips as possible. A side note on weight is that the lighter your pack overall, the happier your back.
A lot of the packing order depends on your particular pack, but in general, the bottom of a pack is below your hips. Therefore, it is best to put something big and light in the bottom. A fleece is one idea, or your sleeping bag (if it's down, might be less great if synthetic due to the amount of crushing that will happen).
Now that we have the level of stuff above your hips, heavy things go next, right against your back. I like to put my food bag on one side and the tent on the other. Down the middle, cooking gear, maps, books, etc.
If there is room left away from your back, stuff your sleeping pad and random clothes.
On the top all this stuff, put whatever light items you have left (i.e. repair kits, first aid kit, rain jacket).
The key to this idea is that your heavy things are silo-like, i.e. tightly packed stuff sacks. That way their weight will be driven to your hips, and anything stacked on them will also drive weight to your hips. The "looser" your packing job, the less efficiently this will happen.
Well, this can somewhat depend on the type of backpack you have and the length of the trip you're planning to take (so how much you will be carrying), but there are a few general principles that apply to almost all situations:
From the bottom up:
One option that is super useful when you're travelling in a group is to have different packs for different purposes rather than each person carrying their own stuff. For example we have a "tent pack" and a "kitchen pack". The advantages include:
If you're in a group of 2 or more, consider it. Also, if you don't live together and didn't pack together, the pause before setting off during which you reorganize everything into categories is a fantastic way to check that you've all brought the right stuff.
As mentioned in other answers, it will depend on the type of your backpack. You can for example pack like this:
First you unbuckle all straps of your backpack, and lay it on the ground. Next to it you spread your ground sheet or shelter half, fold your sleeping bag or blanket on top of it, so it will be about as wide as the central part of your backpack, and put your extra clothes, food for cooking in the evening and morning, and anything that you will not need during the day, like so:
Then you fold the top and bottom parts of the sheet over your sleeping bag or blanket,and roll everything up tightly. Place the roll on the central part of the bag (if the roll is too large, you have too much stuff. Get rid of some of it), like so:
Fold the bottom flap up over the roll, fold the side flaps over the roll as well, thread the side straps through the middle strip on the bottom flap, and buckle them to the other side strap. Then fold the top flap with a detachable compartment down, and buckle the long bottom strap to it.
Place items that you will need on the trail, but don't want to keep in your pockets (map, snacks, emergency kit, rain poncho, ...) into the top detachable compartment. Strap your pot, canteen, hatchet, knife etc to the outside of the pack with extra straps, and you are ready to go. A nice example of the finished product can be found here.
Assuming that you have the right kind of a backpack according to your requirements.
First, you need to separate things that you need frequently and things you'll need less often. The way I camp/trek and plan things, I am okay to pack everything all over again in the morning.
Generally, it is best suited to pack lighter items in the bottom of the pack and heavier stuff toward the top, the idea is to keep heavier stuff closer to your back and not on bum. This keeps your center of gravity relatively high. Center of gravity plays a very important role in balancing your body when in motion. Higher Center of gravity tends to make it easy to haul the backpack easily while your performance with balance is hampered. Women naturally have a lower center of gravity, so the women I know and trek with, they pack heavier stuff at the bottom, that further increases their stability.
Remember, The lower your center of gravity is , the easier it is to keep yourself balanced, pack feels heavier. The higher your center of gravity is, the easier it is to haul the pack but chances are more to dwell/tip off or go off-balance.
So, order of packing:
Here's some advice from REI's page "Tips for How to Pack a Backpack":
OK, so here's a completely different take on this.
I'm an enthusiastic customer of Aarn Packs - a specialist New Zealand company. They are one of the few manufacturers to explore load carrying from the ground up, in conjunction with a university department of ergonomics.
The radical answer to improving weight distribution in a pack is to move some of the load to the front with a bodypack rather than a backpack.
This means that, depending on strap settings, up to 100% of the weight can be channelled vertically to the hips. The centre of gravity moves forwards so the wearer can maintain a fully upright posture, spinal load is reduced, balance is better, shoulder and back pain are virtually eliminated, and you have easy access to the front pockets on the move.
You pack your heavy items and water in the front pockets, so they counterbalance your clothing, sleeping back etc in the main pack. When you get it right, your centre of gravity (green spot) stays central:
Combined with additional innovations in the harness system that add stability and freedom of movement, this is a strikingly effective alternative to conventional packs.
It does get a little getting used to, and putting the pack on is slightly more hassle. But you have a surprising unobstructed view of your feet, and the payoff in terms of comfort and energy saved is well worth it.
Here's what it looks like in practice. Notice the more natural posture of the Aarn wearer compared to the guy with the external frame:
No commercial interest here - just a happy user. Small companies with the courage to innovate deserve support, I feel.