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Agreed! What follows is in addition, not in contradiction. The complexity of human musculoskeletal coordination is astonishing. Particularly in sport, but als

Agreed! What follows is in addition, not in contradiction. The complexity of human musculoskeletal coordination is astonishing. Particularly in sport, but also in daily life. Consider: how many ways are there to raise a cup to your mouth? Basically: infinite. And yet you do it without a care, almost reflexively, barely paying attention. In sub-second sporting tasks, the role of the conscious brain is likely to be zero, but the role of anything above the brain stem is also often unclear. The spine - home to reflex action - doesn't have the processing power to determine how to return a tennis serve, yet this sort of action is far quicker than any deliberate, calculated, conscious action. When I last spent any time reading around the subject, the literature was full of stuff like how the central nervous system updates its expectations based on feedback when trying to achieve a goal; and hints about how musculoskeletal movement might involve "orchestration" of composable units of coordination. It's a fascinating area of research. Overlaps with robotics and ML are obvious, although I suspect those approaches are "inventing" rather than "discovering". Nothing inherently wrong with that, of course.

Teever 4y ago
I don't think that returning a tennis serve is a literal reflex as you're claiming. From my understanding a reflexive move requires some sort of stimulus, and there's no way that your spine can have stimulus of an incoming tennis ball unless the eyes and therefore the brain are involved.
- austinjp 4y ago
  My post isn't clear, in that case. I'm not claiming it's a literal reflex :) A top-flight tennis player is responding extremely quickly, and extremely accurately. Deliberate, planned action is not happening. It's something else. It's not a spinal reflex, it's something that involves parts of the brain to very rapidly 'orchestrate' a highly complex musculoskeletal dance. The raw processing necessary to coordinate that dance cannot (in my understanding) be achieved by familiar neurological pathways -- observing, planning, deciding, coordinating. The planning and deciding aspects are bypassed. Only a tiny fraction of the observing aspect is used, such as the moment the other player strikes the ball (because the ball then moves too fast to react to). Some form of prediction happens. Then a number of 'movement primitives' seem to be selected and orchestrated. Ideally, the whole system is tweaked in real-time based on feedback (visual, proprioceptive) regarding whether the goal was achieved -- i.e. did you return the serve well. It's wild. It's also possible I'm mis-remembering and mis-interpreting some of this stuff :) Good place to start reading: https://pubmed.ncbi.nlm.nih.gov/?term=%22motor+primitives%22+human+sport https://pubmed.ncbi.nlm.nih.gov/?term=%22motor+primitives%22...

Teever 4y ago

I don't think that returning a tennis serve is a literal reflex as you're claiming. From my understanding a reflexive move requires some sort of stimulus, and there's no way that your spine can have stimulus of an incoming tennis ball unless the eyes and therefore the brain are involved.

austinjp 4y ago
My post isn't clear, in that case. I'm not claiming it's a literal reflex :) A top-flight tennis player is responding extremely quickly, and extremely accurately. Deliberate, planned action is not happening. It's something else. It's not a spinal reflex, it's something that involves parts of the brain to very rapidly 'orchestrate' a highly complex musculoskeletal dance. The raw processing necessary to coordinate that dance cannot (in my understanding) be achieved by familiar neurological pathways -- observing, planning, deciding, coordinating. The planning and deciding aspects are bypassed. Only a tiny fraction of the observing aspect is used, such as the moment the other player strikes the ball (because the ball then moves too fast to react to). Some form of prediction happens. Then a number of 'movement primitives' seem to be selected and orchestrated. Ideally, the whole system is tweaked in real-time based on feedback (visual, proprioceptive) regarding whether the goal was achieved -- i.e. did you return the serve well. It's wild. It's also possible I'm mis-remembering and mis-interpreting some of this stuff :) Good place to start reading: https://pubmed.ncbi.nlm.nih.gov/?term=%22motor+primitives%22+human+sport https://pubmed.ncbi.nlm.nih.gov/?term=%22motor+primitives%22...