• Muddy Shoes: Better That Way

    This time last year I wrote a blog about the brain benefits of regular exercise. I mentioned the idea that taking your exercise off-piste, i.e. avoiding any hard pavement or tarmac surfaces, is not just easier on the body (joints, ligaments, bones etc), but actually better for your brain. I’m going to expand on this theme here.

    If you’re jogging round the park and stick to the paths, you’re going to cross paths with many people also out exercising. Sticking to the grass, ideally by going right round the perimeter of your biggest nearby park, is likely to mean not having to come into close contact with other people who might be breathing Covid-19, flu or the common cold into the air you’re breathing. So there’s one good reason to exercise off the beaten track right there. You’ll be doing your civic duty in terms of reducing the spread of various diseases.

    By now you’re probably aware of the huge brain benefits of taking regular moderate to intense levels of cardiovascular exercise – in other words giving your heart / blood vessels plenty of work to do and getting out of breath to stretch those lung tissues. The better your heart functions, the more effectively it pumps blood to the brain. The better your lungs function, the more oxygen is added and waste gases removed as that blood passes through the brain.

    Exercise every other day and both these systems adapt to the high levels of activity so that, little-by-little, day-by-day, week-by-week, they slowly-but-surely become stronger and better coordinated when working together. That’s a reason to keep as active as possible because that way you’ll live longer and enjoy a better functioning brain. Exercise day. Rest day. Exercise day. Rest day. This kind of rhythm keeps brains happy. Not to mention the mood boosting impact of the adrenaline and endocannabinoids that are released into your bloodstream to help you keep going.

    Put exercise together with being outside and off-piste, THEN you have something even better: vestibular and cognitive training; to improve your kinaesthetic and information-handling intelligences, respectively. This is why I do a 6-10km run around Richmond Park at least once a month and have done for many years. It’s partly just the joy of being outdoors in all seasons. Usually I really feel the cold deep in my bones. I’m always the one wrapped up in more layers than anyone else; from autumn to spring. But when you’re out running you generate so much heat you always feel nice and toasty as you pick your way up hills, through woods, along the water’s edge and, in particular, after the killer climb towards the end.

    Note the puddles in the background on the right – a very slippery affair: Southwark Park 2021

    The fresh air clears out your lung holes, the exercise-triggered hormones make you feel high as a kite and the up-and-down bouncing motion even compacts all the food in your gut (helping whatever is in there to sit more comfortably; in my experience anyway). It’s almost as if our bodies were designed to do precisely that. Through millennia of careful natural selection, evolution expertly crafted our bodies and internal organs to have the capacity to run down much larger and stronger prehistorical animals. These animals were usually faster than us in a sprint, but jogging after them for hours and hours as a groups was thought to enable our ancestors to keep up until they ran out of puff making it easy to stick them with a spear. Jogging might seem a bit dull, but our bodies are very well adapted to it.

    When I say “vestibular training” – this isn’t a term you’ll find elsewhere. I use it to describe the type of workout that pushes the brain systems devoted to balance and coordination of body movements particularly hard. To picture what the vestibular system does it can be helpful to imagine yourself being thrown around on a roller-coaster. When your head (and body) fly though space on track weaving through space in three dimensions, a pair of special sensory structures inside the inner ear detect acceleration in the forwards <-> backwards and upwards <-> downwards directions. The sensory device that picks up acceleration in the upwards <-> downwards direction is called the saccule and for the forward <-> backward direction we have the utricle; both of which are a bit like a seed rattling around in a hair-lined pea pod inside your inner ear. They’re constantly broadcasting to the rest of the brain whether you are stationary or accelerating in one direction or another.

    The saccule and utricle get much more of a workout when running across open plains, meadows, hills, woods or even just muddy tracks. When there’s no path to follow, leaping across puddles and picking your way across a wooded inclines causes a lot of up and down movements as you dart around trying to make sure each footfall strikes a firm surface. When running on flat smooth surfaces, on the other hand, the information these sensory systems send to the rest of the brain is very basic, simple and straight-forward – too predictable to offer much of a challenge for the brain to integrate with the other sensory information. In other words, what I’m proposing is that our vestibular system thrives on being adventurous.

    Another part of the vestibular sensory system are the semi-circular canals (superior, posterior and lateral canals; see below). These three semi-circular fluid filled tubes are responsible for monitoring rotations of the head (and, by attachment) the body. These are the three types of rotation, each of them dealing with in terms of common head gestures: Nodding to say “yes” – that’s “pitch” rotation. Shaking your head to say “no” – that’s “yaw” rotation. (If you’re Greek, please reverse that ;-)) If you try to touch your ear to each shoulder in alternating fashion – that’s “roll” rotation. These semi-circular canals are also in the inner ear and broadcast any changes in the signal they detect to the rest of the brain too.

    The inner ear

    What does the brain do with all the info on acceleration and rotation (from saccule, utricle and semi-circular canals) as you pick your way around a puddle on the slippery canal tow path? One important role for it is as feedback on how well the brain is steering your movements. If you don’t find firm footing, and slip, the saccule / utricle will detect the unexpected changes in acceleration, and if your body has twisted in the slip this will be detected by the semi-circular canals, so the cerebellum (at the back of the head) has the information it needs to instruct various leg muscles to contract in the right order to catch our fall, in the blink of an eye. This is exceedingly good brain training. And you don’t get the same bang for your buck if you’re just doing laps of the local athletics track.

    Cerebellum (in red) hanging off the back and underside of the cortex

    This approach is not without its jeopardy. Rolled or sprained ankles can happen if you lose concentration and take you’re eye off the uneven terrain. But take it slow and easy on the more treacherous stretches and you can get away with it; even in middle age. And then there are the added challenges posed by man’s best friend.

    In any London park (and I’m sure it’s the same all over the UK) every time you step from tarmac to grass you run the risk of stepping in dog shit. Unpleasant yes, but every cloud has a silver lining. I’ve found it’s possible to harness the power of disgust to push yourself harder in terms of increasing focus and concentration. Recall how disgusting it is to realise you’ve stepped on a turd by getting a whiff of that foul stench and feelings of repulsion that come with the knowledge that you’re now bringing it with you, can be used as an incentive to become a full-on dog poo ninja.

    It may sound ridiculous, but constantly keeping a keen eye on precisely where you put each foot fall is really taxing on a variety of sensorimotor and cognitive abilities. In other words, not only do you get really good at dodging the doo doo, but you end up with abilities that are helpful in everyday life even when you’re not exercising. The kind of far transfer I’m talking about stems from the fact that doo doo dodging requires a high level of vigilance, stretching the brain pathways of attentional control to their limit, placing greater time pressure on the brain to think quickly the faster you go. You have to be ready to change direction and veer off from your chosen foothold at the drop of a hat. The concept of poo dodging might not be pleasant, but I’m convinced it speeds up your reaction times, improves your running gait and ultimately leads to a more nimble running style.

    Running on the flat encourages a very uniform gait. It becomes a matter of developing muscle density, stride cadence and boring things like that. Running on all terrains requires you to develop the brain capacities of a mountain goat: sure-footed even on uneven slopes scattered with slippery scree. The brain has to work out how to deal with all sorts of unexpected obstacles that you often don’t notice until you are right on top of them: branches to hop over, tree trunks to swerve around, streams to fjord, fern-filled valleys to scramble up and down. A richer, undulating terrain provides a greater challenge for the various brain regions receiving the vestibular sensory information to sink its proverbial teeth into.

    And then there’s the evidence – outlined in a previous blog – indicating that being outside in mother nature doing any kind of recreational activity for 2-5 hours per week has a demonstrable impact on happiness and well-being. What are you waiting for? Slip on that thermal underwear, a tracksuit and a pair of old trainers you don’t mind running through puddles in and get out there!

    In addition to these monthly brain blogs I also tweet the occasional bit of excellent brain science that I stumble on via Twitter (@drjacklewis).

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