Today I'm going NERD LEVEL on blocking. This is an interesting detail I found that can make or break your blocking. I can't explain the why, so I'm calling on all anatomy/physiology experts out there to come up with an answer, and leave it in the comments section.
When using Guard Principle (one-in-one-out), we know that we have to bring one hand back when the other goes out. This is relevant to both striking, and blocking. What I find fascinating, is that the lead arm actually goes dead when the rear arm fires. After years of doing this, and countless number of punches coming at my head, I noticed this 'lag', and dull response time, and paid close attention to it.
If you have expertise in this field, and can provide a thoughtful, educated reason for it, I'd love to hear it. Please leave it in the comments section below so we can all benefit from it.
Now, on to the important part - not getting hit! Follow the principle shown when you're firing punches, or blocks, and this problem goes away. We do not need a partner to fix this. Practice the Guard Principle while performing shadow boxing, bag work, and 3-level blocking and you can train your hand to respond as needed.