You cannot play at your full capacity without a proper warmup. If you sit down and start playing something complex you will play it poorly. Your fingers will not reach the required positions in time or fret the notes effectively; your picados will stutter and tone suffer. Doing a bad job is the least serious of the problems brought on by playing with cold hands. Your fingers will hurt. And if your push ahead and try to work your way through the pain, it will get worse. Even if you manage to warm up after a while, the pain and the unpleasant feeling from hearing yourself slaughter the piece will stay for the rest of your practice. By the time you are warmed up, you will have wasted precious time trying to play the piece without paying attention to your tone or timing. Therefore you will not benefit from this activity in terms of progress.
There are cables inside your hands that connect the muscles to the bones. These cables are called "tendons." Tendons transmit the contractions of the muscles to the bones. Playing guitar is a predominantly tendon activity, more significantly in the left hand because it involves lots of pushing. Every time you fret a note you are putting some weight on a particular tendon. Tendons slide back and forth inside tendon sheaths. Imagine a metal wire snugly placed within a plastic pipe… Whenever you move your fingers, the tendons will rub on the insides of the sheaths that hold them. So, it is extremely important to get this narrow tendon passage "lubricated" without causing small tears and abrasions due to friction. And how is this done? Through a proper warm up. When your hands are cold, the tendons are dry and they will rub against the sheaths causing tiny tears especially when you perform stretches. If you insist on playing difficult stuff with no proper lubrication you may generate so much damage that the scar tissue on the tendons and the sheaths will prevent you from moving your fingers, it will hurt like hell and you'll end up with the much dreaded "tendonitis." How do I know all this? Because it happened to me. Preparing for an album recording, I practised very complex stuff without proper warmup and then I had to stop playing for 6 months. Once you get tendonitis, you cannot get rid of it completely. It will flare up every time you force your hands or play a long gig, etc.
The only way to lubricate your tendons and prepare them for heavy-duty playing is warmup. When you pick up your guitar for practice, start playing passages that require almost no effort. I always begin by slowly placing my fingers on the frets, hammering a few notes, doing some legatos and slides. Gradually increase the force you put on the fretboard. Do not do any stretches at the beginning. Ease yourself into difficult positions. It takes me about half an hour to start playing pieces properly at half speed. Only at the end of an hour do I manage to use my full technique.
The following video is a brief sample of my left hand warmup routine:
There are cables inside your hands that connect the muscles to the bones. These cables are called "tendons." Tendons transmit the contractions of the muscles to the bones. Playing guitar is a predominantly tendon activity, more significantly in the left hand because it involves lots of pushing. Every time you fret a note you are putting some weight on a particular tendon. Tendons slide back and forth inside tendon sheaths. Imagine a metal wire snugly placed within a plastic pipe… Whenever you move your fingers, the tendons will rub on the insides of the sheaths that hold them. So, it is extremely important to get this narrow tendon passage "lubricated" without causing small tears and abrasions due to friction. And how is this done? Through a proper warm up. When your hands are cold, the tendons are dry and they will rub against the sheaths causing tiny tears especially when you perform stretches. If you insist on playing difficult stuff with no proper lubrication you may generate so much damage that the scar tissue on the tendons and the sheaths will prevent you from moving your fingers, it will hurt like hell and you'll end up with the much dreaded "tendonitis." How do I know all this? Because it happened to me. Preparing for an album recording, I practised very complex stuff without proper warmup and then I had to stop playing for 6 months. Once you get tendonitis, you cannot get rid of it completely. It will flare up every time you force your hands or play a long gig, etc.
The only way to lubricate your tendons and prepare them for heavy-duty playing is warmup. When you pick up your guitar for practice, start playing passages that require almost no effort. I always begin by slowly placing my fingers on the frets, hammering a few notes, doing some legatos and slides. Gradually increase the force you put on the fretboard. Do not do any stretches at the beginning. Ease yourself into difficult positions. It takes me about half an hour to start playing pieces properly at half speed. Only at the end of an hour do I manage to use my full technique.
The following video is a brief sample of my left hand warmup routine: