In practice, of course, walking—with or without a pack—does take effort. With each step, your center of mass rises and falls in an arc, like an upside-down pendulum. Back in 2002, Donelan and his colleagues showed that much of the energy you burn while walking comes from the transition from one pendulum swing to the next: negative work by the knee joint to brake as your foot lands, then positive work by the ankle to push off again.
So when you strap a pack on, the actual cost of supporting the pack against gravity isn’t a big deal. Instead, it’s decelerating and then reaccelerating it with each step that costs energy—which is why some researchers are pursuing ideas like suspended packs that counteract some of this up-and-down motion. That can offer big savings on level ground; once you start climbing a hill, though, then you can’t avoid spending energy to hoist the pack against gravity.
Of course, energy cost isn’t the only consideration in backpack design. Pigman, who is now working on a Ph.D. in biomechanics at the University of Delaware, has further data coming out soon on force transmission to various parts of the body. Hip straps are supposed to redistribute force from the shoulder muscles to the much larger muscles around the hips, which should improve comfort and fatigue resistance, even if you burn the same amount of energy overall. They also reduce the risk of “rucksack palsy” resulting from compressed nerves under the shoulder strap.
Where is the most efficient place to position a load? Believe it or not, it’s on your head. Women in Kenya and other East African countries, researchers reported in the 1980s, carry up to 20 percent of their body weight either balanced on their heads or supported by a strap around their foreheads (like porters in Nepal sometimes use) without expending any extra energy. The problem, as a review in Military Medicine points out, is that it takes too long to learn how to do this.
https://www.outsideonline.com/2251986/s ... nsiteshare
Where do you see the future/evolution of backpacks? Thur-hikers carrying some sort of rucksacks on their heads?