Trying one of Jascha Heifetz’s warmups, with a slight alteration- apparently many of his students used this to stay agile and warmed up, regardless of how cold a venue was! Could be a good option if one finds oneself unable to warm up audibly before a performance.
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It involves the fingers 1) in a neutral, somewhat curled position, 2) retracting actively and swiftly, which engages the extensor muscles, 3) letting them rebound forwards into a soft fist, which somewhat engages the flexors. The fingers are, to the best that they can, quite close together. The original exercise involves an active pushing forwards- which is also really effective. A few minutes in, and the hand does feel preliminarily warmed up...! The hands strike a sweet spot between floppy, completely relaxed muscles and tightened muscles.
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Featuring a sneeze as well...
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