How much weight could a human lift? This is a difficult question to answer because there are too many variables, but possibly three or four tons.
There are many ways of lifting weight and there are different records for each method. The heaviest weight ever lifted by a human is purported to be 2,844 kg, which is very close to three tons. This was lifted by a strongman called Paul Anderson in the 1960s. However, this record was never verified and is currently not listed as the world record. The current heaviest weight ever lifted was a Canadian called Gregg Ernst. In 1993, he lifted two cars and their drivers, a combined weight of 2,422 kg. He used a lift technique called a backlift, which is where the competitor goes down on their hands and knees with the weight across their back. They use all of their muscles to lift the weight a little bit off the ground. There are many other weightlifting records. The heaviest deadlift is held by Hafpor Bjornsson. He lifted 501 kg. If you watch the video on YouTube (I’ll put a link in the sources), he doesn’t seem to have that much trouble. Some of the world’s strongest man challenges involve lifting weights that are over 250 kg onto platforms. So what would a theoretical limit to how much a human can lift be?
One reason that Hafpor Bjornsson can lift so much is because of his size. Generally, the larger someone is, the more muscle mass and the larger bones they have. However, there must be a weight that even his body could not move. When Bjornsson lifts that 501 kg, he needs to rely on his bone density, his muscles, his ligaments, his tendons, and the strength of his blood vessels.
The first thing when lifting a heavy weight is the support our skeletons give us, and bone is an incredibly strong material. Bone is not a solid material. It has a honeycomb structure which makes it lighter and flexible. Our bodies need our bones to be strong, but they also need to be light enough that we can move them. This tradeoff has given us the bones that we have, and they are incredibly strong, but maybe not as strong as they would be if they were solid. One cubic inch (16 cm3) can support 8,600 kgs before it is crushed. This is a small section of bone, though, and it gets weaker as it gets longer because there are more places where it can fail, but let’s take that 8.5 tons as an upper limit to what a human could support. Bearing in mind that to get that upper limit all of the bones would have to be aligned along their strongest axis.
The next problem is that we are not made of solid bone. We have joints that need to move, and these are all weak points where a heavy weight can make our bodies fail. Joints are made up of tendons, ligaments, and cartilage. How much weight can they support? Tendons are very strong, and they are able to store mechanical energy, a little like springs. Strong tendons are what enable kangaroos to hop as fast as they do. Tendons are made of bundles of collagen fibers, and they are very strong, but they obviously have an upper limit. It obviously differs depending on the size of the tendon, but it takes about 1,400 kg to tear a tendon. There might be a way of positioning the joint to protect the tendon and increase that weight. Ligaments are also a problem because they can tear and come off the bone. Muscles can also rip and shear as well. It might be possible to protect all of these things with a suit, but the maximum limit is still going to be way below that 8.5 tons that our bones could support.
And then we have our blood vessels. When you do strenuous exercise, your blood pressure increases because your muscles need more energy and oxygen, which the heart has to supply at a faster rate. When you are weightlifting, you are using your muscles at close to their limit and the heartrate has to increase significantly. Alongside this, people lifting enormous weights will usually hold their breath and then exhale forcefully. This is called the Valsalva maneuver. It gives the lifter more tension in their body and more strength, but it also dramatically increases the pressure inside the body. This can cause small blood vessels to burst. You might have seen weightlifters getting nosebleeds or bloodshot eyes. If a human was trying to hold up a weight of several tons, their circulatory system would not take it.
The last problem we have to overcome is our brain. Our brains are not stupid, and their job is to keep us as safe as possible. You can lift more weight than you think you can, and you can run faster and further than you think you can. We can see this because when people have to lift more, such as when a car gets stuck on a child, they lift the weights, tearing muscles in the process. Our brains act like a speed limiter on a sports car to keep us within a safe margin. If someone was going to try to lift several tons, they would need to work out how to take their brain out of the equation. One method some weightlifters use is ammonia. The ammonia clears the brain, numbs the pain receptors, and allows the lifter to bypass their limiter. Still, even with all of these things, a human is not going to lift more than a few tons. If we start to grow bigger, then that would be a different story. The African Bush Elephant, for example, can carry 10 tons. And this is what I learned today.
Photo by Vido Boskovic: https://www.pexels.com/photo/man-in-blue-tank-top-carrying-a-barbell-5759751/
Sources
http://www.samson-power.com/ASL/anderson.html
https://www.facebook.com/watch/?v=578100602906238
https://www.theworldsstrongestman.com/world-records
https://medilexinc.com/a-spoonful-of-medicine-blog/bone-strength