Biomechanics

(<2023-Apr-04> epistemic status: 4:1 confident)

The internet fitness culture has been echoing the meme "fix your APT" (anterior pelvic tilt). Somehow, someone got the idea that you get APT from sitting in chairs. That never happens! Longtime chair sitters, unless they have good sitting habits (which no one in the West has), will get a habit of posterior pelvic tilt, not APT! Watch people sitting in an airport or cafe sometime, it should convince you. Some people may be lucky enough to show APT despite chair-sitting a lot, but the chair-sitting didn't cause it, being born caused it.

Anterior pelvic tilt (APT) is good, and not the same thing as excessive lordosis: lumbar sway, a swayed lower back. That is to say, the pelvis should be tilted, but the lower back should not be in much of a sway: that combination is the human neutral, see Esther Gokhale's book for picture proof from ancient statues and traditional cultures. The word "neutral pelvis" is a lie.

There is a time and place for taking steps to "fix" the APT, and that's when you're fixing lordosis in the process.

Esther Gokhale talks about the "lumbo-sacral arch". There should be an arch in your back at the very bottom (i.e. not in the low back, that's too high). The disk between your last nontrivial vertebrae, called L5–S1 (lumbar 5–sacral 1), is wedge-shaped. That means an arch there is the neutral position. Trying to undo this arch causes uneven pressure on this disk, and we all know what that means.

If you like, you can think of it this way: your butt should stick out. That is to say, your back should be straight, but your butt should stick out. Seem impossible?

It's a personal journey to get to know your spine so you can ensure that it gets neither lordotic nor kyphotic when e.g. you bend down to pick up objects. I can't give a flyby summary here, only recommend books like Gokhale's 8 Steps to a Pain-Free Back.

(<2023-Apr-04> epistemic status: 2:1 confident)

Many myopics (near-sighted people) may have 'pseudomyopia', which is when your eyes do not have an inherent flaw but have adapted to reading at close distances, such as computer monitors, and the muscles have changed their 'resting length'.

A technique called print-pushing is the way to untrain pseudomyopia. It is a habit to have for life even after you reach perfect vision, so long as books and screens fill our lives.

Here's the jargon. You have three reading distances:

• D₁ is the maximum distance at which the letters are still perfectly clear and effortless to read.
• D₂ is almost the same as D₁, but it is "the distance at which letters start to blur", an useful distinction as you'll see shortly.
• D₃ is the maximum distance at which you can read at all, and letters are very blurry. This is far from D₁ and D₂.

The first mistake made by people wanting to train away their myopia is to read at D₃. Actually this might do nothing, much like failing to lift a weight that's too heavy. Read at D₂, which is also a lot more sustainable, as it is only a little uncomfortable, and you can get into the habit of always reading near this distance.

During any reading session, the points of D₁ and D₂ are always moving, even on a timescale of minutes (you're an organic machine, what do you know). So the essential habit is to first find D₁, then try to "push out" to D₂, and to always be pushing out to D₂ in case it has moved since a few minutes ago – testing your limit, so to speak.

If your vision is already pretty good, you may have to hold your book or screen impractically far away to reach D₂, and the solution is to get yourself a pair of… reading glasses. They have plus lenses, not minus lenses, the opposite of what you'd normally use for myopia. They will move D₁ and D₂ closer to you, and the workout is all the same for your eyes.

In this world of computer monitors, I guess it'd make sense to teach our children to use reading glasses before they develop myopia.

My lumbar spine hurts when I do ab workouts. That should not happen.

One explanation is that the hip flexors (iliopsoas) are pulling on the spine. They always do, nothing wrong with that, but the abs are supposed to counteract that force so that the force is expressed elsewhere. This is a reaching analogy, but imagine your core as a full tub of toothpaste. When the cap is off, pressing on it causes it to deform. The abs are like the cap. They prevent the spine from deforming.

Most ab workouts involve the hip flexors to a degree. What should happen in e.g. a leg-raise is that they help you flex the hip while the abs counteract the hip flexors' effect on the spine – so that the spine becomes the fixed point towards which the legs get pulled, rather than them both moving closer to each other.

This does not cancel out any of the hip flexors' work, merely shifts the phenomenal effect of the force being exerted by them (i.e. where you see the result of their contraction). And if it seems like it's a waste of calories that one muscle activates purely for counteracting another, that's pretty much all the core muscles do. It's necessary because you don't have any bones in your abdomen – they are a substitute for bones.

Under this theory, my lumbar spine hurts because either I'm not activating my abs enough, or I am but they're that much weaker than my hip flexors.

To make the abs catch up in strength and restore a balance, target the abs in a safe way. If nothing else, you will learn to contract them fully and to notice when they are failing so you can cease the "ab" workout before your back starts hurting.

Try lying down and contracting only your abs and see what results (may be very little movement). Think of bringing your ribcage towards your pelvis, or of pancaking some object under your low back. Maybe do this for isometric sets (i.e. hold for time)?

Remember that the abs connect the ribs and pelvis, nothing else. Focus on getting these parts close together.

A trick that weakens the hip flexors for a while is to stretch them. Stretching a muscle weakens it by 30% for like the next half hour, I heard. To do this, get in a lunge position and tense your butt and you should feel a stretch deep in the thighs: that's the iliopsoas muscles.

You can also prevent them from working by using opposing muscle groups as in a Janda sit-up. Perhaps also good is the inverse boat pose / locust pose – so you're laying on your stomach and lifting the rest of the body off the ground – or the thoracic bridge.

Ab workouts that don't flex the hips should be relatively good, but even a plank makes my back hurt after a while, so I guess it is important to focus on feeling your abs contract the whole time and to give up when they can't go on rather shuffle the load to other muscles to keep the plank going. When the plank starts to become unstable, that's it.

Tip: If planks bore you, do wrist circles during, and count those instead of seconds.

The thesis in the "barefoot running" community is that the feet affect the whole body.

1. Katy Bowman claims it's impossible to have good posture when your shoes have heel support.
2. The muscles of the arch are meant to be active when you're walking, so arch support is bad because it lets them slack off. It may result in pooling of blood/lymph in the feet (<2022-Jan-22> 1:1 confident), progress flatfootedness (<2022-Jan-22> 2:1 confident), and what-not.

These observations beg the question of why we are using shoes in the first place?

• Warmth
• Protection from roundworms
  • Not existed in the West for a few decades, but maybe starting to be an issue again
• Protection from sharp objects
  • Broken glass: it's less sharp than you think, there's less of it than you think, and plexiglass (what they often use at public installations like bus stops} is not sharp at all. Besides, if you don't worry about going to the beach barefoot, it would be inconsistent to start worrying about it away from the beach. Beaches have glass too.
  • Something that may genuinely cut you is metal: tin-can lids or half-buried pieces of car chassis. Get a tetanus shot.
  • Empty syringes (an issue in ghettos) – however, these pierce through shoes anyway. Barefoot or not, syringes may pierce you if you drag our feet along the ground and hit it at exactly the wrong angle. In fact, going barefoot may reduce this risk since you're more aware of the ground.

You can get all these benefits without drawbacks if you design a shoe correctly. Thus barefoot/minimalist shoes. Here the adjective "minimalist" means absence of design antifeatures like arch support, not necessarily that they use little material.

ASIDE: it's hard to google for true barefoot blogs nowadays, due to all the "barefoot shoes" people use. Horrible name. You may have better success googling for "unshod".

A related thing is the negative-drop shoe – hard to find, but some think it may be therapeutic. Maybe it would make good posture difficult for the same reason positive-drop shoes do, but it would have good effects on the calf muscle length, which are too short in most people.

If you believe in negative-drop, you could also sleep in night splints and wake up with stretched-out calves that way. Then walk around in regular zero-drop minimalist shoes.

Tip: You can DIY night splints if you have a pair of old ski boots. Saw open the top of the toebox to prevent bunions (but keep the sole). Though your partner may not approve.

This is a more interesting topic than it may seem: why stretch?

It seems we love to oversimplify the body, we think of it as an inert piece of taffy that needs only be stretched out to work properly.

But that doesn't make any sense. There's nothing in muscle tissue that would cause them to be tight after disuse, like a tin of beard wax that becomes rock-hard when left out in the cold. Muscles and tendons don't work that way. They are always at 37 degrees Celsius, blood-filled, and capable in principle of being stretched out far past the greatest range of motion you've ever seen from them: if you've ever lifted the limb of a person or pet who just passed away, you know what I mean. So why do they feel so tight while we're alive? It's the brain stopping them. (<2022-Jan-22>: 20:1 confident) There's nothing tight in the tissue itself!

Reading Katy Bowman gave me plausible descriptions of the actual effects of stretching and the reasons to do it.

In short, you should never stretch hard, but you should stretch often. The idea is to open up a bigger Range of Motion (RoM) than the limbic(?) brain is usually inclined to allow. This is also why it's so effective to relax when stretching rather than apply a lot of force: it's all about coaxing the brain into thinking this muscle length is okay and will not lead to danger of tearing.

This is also why injury risk increases after stretching: of course there's a greater risk of damage when you put the muscle under a heavy load beyond the normal RoM. This is countered by giving yourself experience using that muscle at that RoM, and building muscle fibers that can handle it. It's also why you can see such significant improvements in flexibility if you work out the muscle at the widened RoM rather than just stretch and call it done: the limbic brain is okay with the increased flexibility as a new default, when the strength is there. This is basically the reason you'd stretch often, not because change happens when you stretch, but because change happens when you use those muscles as you go about your day. (<2022-Jan-22>: 10:1 confident) An implication is that it's pointless to stretch just before bed, but stretching in the morning may pay off.

• Pronation/supination
• Adduction/abduction
• Flexion/extension

• Esther Gokhale
• Katy Bowman

• Fitness