Article: If you’re backpacking for a week or more, get a backpack that’s at least 70 liters (18.5 gallons). If you’ll only be backpacking for a few nights, a pack in the 30-50 liter (8-13 gallons) range will work. The longer your trip, the more you’ll be packing. It’s important that you get a larger backpack if you’ll be gone for an extended period of time.  Some backpacks are measured in cubic inches. As a rule of thumb, daypacks will mostly be under 2,500 cubic inches, while weekend packs are somewhere in the 2,500-4,000 cubic inch (40 to 65 liter) range.  For week long trips, you will need around 4,000-6,000 cubic inches (65-95 liters) of space. Before you go backpack shopping, measure your hip size and the length of your torso. Look at the tag or product details for any backpack you're considering to find out what fit you should get based on these measurements. Some backpacks are sold in small, medium, and large sizes that correspond with different hip sizes and torso lengths.  To find your torso length, measure from the bottom of your neck to the top of your hips.  Measure your hip size by wrapping a tape measure around your hips, a little above where you wear your belts. Internal-frame backpacks have a built-in frame that will help you keep your balance on uneven trails. They also help distribute the weight in your pack to your hips, making them easier to carry. Frameless backpacks are lighter than internal-frame packs because they don’t have a frame weighing them down. Choose a frameless bag if you’re concerned about your pack being too heavy to carry. Frameless bags are usually cheaper than more advanced backpacking packs, making them a great option if you're on a budget. Some backpacks are more advanced than others. The features you’ll need depend on the length of your trip and where you’ll be backpacking. Some common features to consider are:  A mesh back panel. If you know it’s going to be hot during your trip, get a bag with a mesh back panel to prevent your back from overheating.  Extra padding. A backpack with extra padding on the straps and hip belts will help prevent you from getting sore during your trip.  A rain cover. If you’re worried about it raining during your trip, look for a backpack that comes with a rain cover. You can cover your backpack with the waterproof rain cover to keep the contents of your pack dry. You don't want your bag to tear or get soaked in the rain during your trip. Look for a bag made out of nylon, polyester, or a blend of the two. Ask a friend or family member if you can use their backpack for your trip if you can't afford a brand new one. You can also purchase a discounted used backpack online through websites like eBay and Craigslist. Try to find one that's the appropriate size and fit for you. Check that all the zippers on the backpack work and that there aren't any holes. You don't want to use a damaged backpack or your things could get lost or ruined.
Question: What is a summary of what this article is about?
Choose a backpack size based on the length of your upcoming trip. Get a backpack with the right fit. Get an internal-frame backpack for extra stability. Go with a frameless backpack if you want something light. Look for a backpack with the right features for your trip. Find a backpack made out of a durable, water-resistant material. Borrow or buy a used backpack if you're on a budget.

The diaphragm is a muscle that sits like an upside-down bowl just beneath your ribs, contracting and relaxing to move air through your lungs. Deep "belly breathing" that visibly moves your abdomen in and out helps strengthen this muscle and improve your endurance. If your belly stays flat and your chest pumps up and down, you're taking shallow "chest breaths," and will fatigue sooner. This will help ensure that you are getting enough oxygen to your body, and is the best way to prevent muscle and lung fatigue.  It also helps increase endurance by getting proper oxygen circulation to your muscles. Your mouth is wider than your nostrils, allowing you to take deeper breaths of air. Allow air to enter through both your mouth and your nose. Most experienced runners coordinate their breath with their steps, such as the popular "inhale for three steps, exhale for two" (or simply "3–2"). This helps you breathe more consistently. You may also be forced to switch to a different pattern (such as "2–1") at higher speeds, which helps you keep track of the intensity of your run. There are several popular alternatives to these patterns, such as "2-2" or "2-3." Experiment with different breathing patterns to find the right one for you. You should be able to form full sentences while running without huffing and puffing.
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One-sentence summary --
Breathe with your diaphragm. Take longer breaths. Keep your mouth open. Find a breathing pattern. Use the "talk test" to determine if you are breathing enough.