I’m going to level with you. I like idioms. Apologies in advance if you don’t share my idiomatic enthusiasm. I have to level with you about something else:
There is far too much level in your life.
In fact, there’s an excellent chance that on any given day, the only input your body receives from the ground is “flat and level”. You get out of bed, maybe walk downstairs, and to the kitchen. Out to the car (perhaps in the flat and level garage?), you park and head to work, school, the library, grocery store. It’s all flat and level. You head over to the gym–flat and level. You can see where I’m going with this, ya?
I’m making an assumption here, actually. If you’re wearing shoes as you go about your flat and level day, the input your body receives isn’t flat and level. Your shoes probably, almost certainly, have a heel on them, and because of this, the input your body receives on flat and level down is actually “downhill”. That’s a topic of another post, maybe, but I do have to elaborate a little… Have you ever gone on a hike up a big hill? You may be familiar with the feeling of getting achy knees on the descent. Most of us don’t walk (downhill or otherwise) in a way that is overly friendly for our knees (another future post! they’re piling up!), and guess what… Walking “downhill” in shoes is no different. The amount of “downhill” you’re walking in shoes may be subtle but that just means that it takes a lot longer for the achy knees to show up.
Our species, Homo sapiens, evolved 200,000 years ago1.
These ‘early’ humans spent a large amount of their day foraging and hunting for food (read: moving over the land). Approximately 188,000 years later, about 12,000 years ago, humans began to develop the ability to grow food and change surroundings. They (we?) began breeding animals, and farming, and villages turned into towns and cities. With the growth of cities came the organization of paths into roads. Early ‘paving’ was with stones (not so flat OR level), but the Champs-Elysée was paved with asphalt on a concrete base in 1824 and it caught on. This isn’t a blog about the specifics or history of pavement/asphalt, but let’s, for the sake of argument, say that flat and level (i.e. not cobblestone) roads and sidewalks have been around for two hundred years. Humans have certainly been walking on engineered hard surfaces for a lot longer (those crafty Romans!), but it’s quite recent that hard walking surfaces became flat and level as well. Saying it another way,
Homo sapiens walked for 199,800 years on varied, mostly uneven terrain, before it all got flat and level.
Now, we, as humans are adaptable, there’s no doubt. But our bodies evolved with our environment, and flat and level ALL OF THE TIME was not a part of that until 200 years ago. Our bodies evolved to require the input of varied terrain in order to work optimally. Varied terrain is not optional for optimal physical function. We do, however, live at a time where it is so hard to get variety underfoot that you have to actually go out of your way. And maybe feel a bit guilty (confession: I often walk beside the sidewalk, and not ON it. On the boulevard side if possible. And not, obviously if the homeowner has recently spread new grass seed. I’m not a monster.).
Here’s the good news!
Our (highly adaptable, remember?) bodies appreciate ANY amount of variety you can give them. ANY input that is not “flat and level” is different than flat and level input. Which is a ridiculous sentence to be sure, but I also like idioms so it makes sense to me. Somehow.
Really though. Walk beside the sidewalk (join 
me, please! Power in numbers!). Step on the root/rock/lego(!) instead of around it. Take the ramp instead of the stairs. Walk on the ruts. Step on the cracks. Get creative. Keep a small rock under your desk for foot mobility work on company time. Take a step off the path and walk along a fallen tree. Hike in the forest and step on all the roots. Replace some of your pavers with river rock and walk on that instead. Put a rock mat in your kitchen. Use river rock tiles in your shower. Get step-on-ables (rocks, tape up a rolled towel, stick, tacks (just checking)) and leave them in a row in a hallway you have to use every day. It is a bit of work, folks, because society is flat out not making this easy for you… but try your level best to buck the level trend.
You’ve got this.