Most musicians know of the woes of winter- cold fingers, numbness, a hunched spine to shield the wind, and an inability to keep warm. Aside from wearing warmer clothes, what else can you do to improve circulation, and what is actually happening in your blood vessels?
In cold weather, your circulatory system pulls blood away from your appendages to keep your torso and organs warm and supplied with blood. Thus, your hands and feet get cold first. While the heart is a primary mover of oxygenated blood to the body, your skeletal muscle movements also assist in this process, especially given the dense network of tiny capillaries in the body. In Katy Bowman's book, "Move Your DNA," she talks about how the musculoskeletal system is essential for getting blood from the arteries to the capillaries, something that few people talk about in health and circulation wellness.
"The mechanical stimulation of a muscle working causes the smooth muscle wall of the arterioles to relax and open...causing a drop in pressure that pulls blood from the arteries to the capillaries...In reality, working muscles pull your blood to the tissues that need it...Within a sedentary culture, the heart becomes the sole mover of blood." (Move Your DNA, page 58-read it!)
You know this because when you don't move, you have poor circulation, and when you move more (not just exercise), you improve blood blow and deliver oxygen to tissues. It's not just about your heart! With this in mind, moving more (not just exercising), but changing the frequency of sitting and static positions, and taking movement breaks can help improve overall circulation, which makes sense.
In the end, cold weather is only one of many contributors of poor circulation, which include peripheral artery disease, diabetes, and Raynaud's disease. With peripheral artery disease, the blood vessels and arteries narrow, and can eventually fill with plaque, which will reduce blood flow and can lead to tingling and numbness as well as eventual tissue damage and long term circulatory/cardiovascular issues. Diabetes can severely affect circulation and awareness of the body, and many people have neuropathy as well as poor circulation. Raynaud's disease is a circulatory disease which causes the arteries in the hands and feet to narrow, which therefore moves less blood through the body. Some people only experience Raynaud's disease in parts of the hand or fingers, rather than as a whole, and others develop symptoms as a young adult. It is essentially idiopathic (without a clear cause) and there aren't helpful cures for it as a whole.
So what can you do to improve circulation?
First thing, move more before playing- take the stairs before practicing, do some mobilizing movements, or even jumping jacks on a cold day. When we stay in a static playing position for a long time or play in cold circumstances, it is essential to keep blood flowing to the hands and feet and overall movement can help that. Secondly, everyone knows that cigarette smoking isn't great for the lungs and overall health, but nicotine is a vasoconstrictor, meaning that it narrows the blood vessels, which in turn diminishes circulation and blood flow. Lastly, other vasoconstrictors include caffeine, pseudoephedrine, and nasal decongestants. What that means is that you don't necessarily want to drink caffeine all day long on a chilly day, but instead switch to herbal teas, hot water with lemon, and other warming drinks. In both Chinese medicine and ayurveda, there is an emphasis on warming foods such as foods flavored with ginger, cinnamon, and cardamom, as well as cooked foods specific to the season of winter and fall, such as sweet potatoes, squash, pumpkin, etc. (This is a wildly simplified explanation of ayurvedic principles regarding warming foods.) On a simple practical level, I love the handwarmers that you can buy at drugstores that are single use, although I wish there was a more eco friendly option. (There are reusable ones you can microwave or dunk in hot water, but you can't bring a microwave to an audition or performance!) I'm also a big fan of wearing wrist warmers in cold climates, at least until you feel warmed up. You can also DIY a set of wrist warmers with a pair of socks if you don't feel the need to buy a pair.
Keep warm in these cold winter months and keep moving!