Walking is usually easy because your brain is getting constant information from the nerves in your legs about where they are in space and what they’re touching, and when it has that information it can basically run walking on autopilot. When your legs fall asleep, what’s actually happened is that your nerves have been under pressure for long enough that they temporarily stop sending those signals back to your brain. When you try to walk, your brain isn’t getting any of that normal feedback from your legs for a while, so it’s basically flying blind without knowing where the legs are.
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