What is heavy?-Friday April 21st, 2017

After figuring out that it requires less energy, and is safe for your back to perform a stoop lift for a light load, the next logical question is what is heavy? And how long will it take for your lower back to fatigue? This will be different for every person. Originally, I envisioned taking the formula from Garg's method and deriving it, like a maximization problem in calculus. Unfortunately, the formulas from Garg's method are straight lines so calculus doesn't make sense to use. In fact, the stoop lift will always require less energy than the squat lift, but there are weights where the load can only be lifted by performing a squat lift. A second way to determine when a lift is too taxing is by monitoring physiological signs while the subject performs the lift. This is also difficult to do because it requires certain facilities, it is time consuming, and ultimately the results only apply to one person. To avoid this bulky one result process, Snook's Liberty Mutual psychophysical tables were developed. These tables are used in the field of ergonomics to help determine when a job is too physiological demanding to perform. This table is helpful to employers, but it certainly doesn't help the everyday person. So how can you apply this information to everyday life? Well most likely, you don't need a table to tell you when something is heavy. The difficulty lies in knowing your back will fatigue faster than your quads. Take moving boxes for example. For the most part moving boxes aren't too heavy. If you only had to move one box, you could get away with performing the stoop lift to move that box inside. But continuing to use the stoop lift to move 30 or 40 boxes will tire your back well before you can even start to unpack! By starting from box one with the squat lift(which will feel awkward, and is all too easy to forget), you can save your back a lot of discomfort.  

Muscles-Monday April 10th, 2017

I would be remiss to not talk about the actual sport of weightlifting during my project. As you can see in this clip, weightlifters use the squat lift while competing. This may seem to contradict my last post where I showed that the stoop lift takes less energy to lift the same box to the same height. So why don't weightlifters use the easier lift? Well, frankly, if they tried, the bar would never get off the ground! The squat lift takes more energy because it uses the quadriceps in your legs. This big muscle group takes more energy to activate, but is more powerful because
of this. Your quad muscles run along the front of your thigh. You can flex these muscles by extending your leg forward with a locked ankle and you should be able to feel that muscle from just above your knee to almost all the way to your hip. These muscles are used during walking and running. The quadriceps also help to stabilize the knee and knee cap. This is a muscle thats important to work out at the gym and stretch before exercising.  Your lower back, on the other hand, doesn't have a major muscle group supporting it. Have you ever been able to flex your lower back? Upper back you can flex by trying to pinch your shoulder blades together, but there isn't really enough muscle mass to flex your lower back. Most people, that aren't doctors, haven't even heard of the muscles in your lower back that are responsible for this lift. Muscles like the Erector Spinae Muscle. The muscles that are there are important for stability, but they aren't muscles that you would train at the gym. What this means is, these muscles are perfect for picking up your keys, wallet, or phone after you drop them. Maybe you can get away with picking up a light suitcase, but anything heavier is likely to strain your lower back. This is why it is common to hear people say to lift with your knees not your back. This is difficult for people, because why use extra energy when you don't have to? After reflecting on this in my own life, I realize that I will even use my bicep muscles to alleviate stress on my back during a stoop lift, rather than doing a squat lift.