スマホを置いて、顔を上げよう。メールやSNSのやりすぎは首を痛める原因になる。
ニューヨークの脊椎外科医、ケネス・ハンスラージ氏による最新の研究によると、スマホを見るために頭を前方に60度傾けたとき、首には約27キログラムの力がかかっているという。同氏の研究は「Surgical Technology International」の第25巻で発表されたばかりだ。
手に持ったスマホを見るために、うつむく方向へ首を曲げていくと、首に加わる力はどんどん大きくなっていく。次に示すハンスラージ氏作成のイラストは、それをわかりやすく示している。
傾きが15度のときは12.2kg、30度のときは18kg、60度のときは27kgの重さがかかる。
ハンスラージ氏は、コンピュータ支援設計（CAD）を使って脊椎のモデルを作り、脊椎にかかる力を計算しながら、頭部を0度から15度、30度、45度、60度まで曲げてみた。「これは頭の傾きぐあいに応じて首にかかるストレスを、かなり精密に算出したものです」と、ハンスラージ氏はハフポストUS版の電話インタビューで述べた。
「この計算は、首を前方へ傾けることだけを考慮したものです」とハンスラージ氏は指摘する。つまり、首を前方へ曲げながら同時に左右どちらかに傾けると、また違うことが起きる可能性があるというのだ。
では、首を痛めないためには、どうすればよいのだろうか？
「スマートフォンのようなデバイスを利用するのは結構ですが、頭の空間的な位置には、特に注意を払うことをおすすめします。スマートデバイスを使っているときは、頭をなるべく垂直に近い状態に保つことを心がけるとよいでしょう」と同氏はアドバイスする（研究には、適切な姿勢は「耳が肩の位置にあり、肩甲骨が少し引っ込められた姿勢」だと書かれている）。
また、ハンスラージ氏は、脊椎に関連したもうひとつのよくある問題についても指摘している。一日中デスクワークで、椅子に座りっぱなしでいることから生じる肩こりや腰痛だ。
コンピュータの画面を見ながら日々をすごすオフィスワーカーにも、首や腰の痛みを緩和するためにできることはいくつかある。たとえば、ストレッチングを欠かさないこと、こまめに休憩をとって少し歩くこと、そして首をまっすぐにしたまま画面を見られるようにモニターの位置を工夫することだ。
この記事はハフポストUS版に掲載されたものを翻訳しました。
[日本語版：水書健司/ガリレオ]
姿勢を悪くしてしまう習慣
Carrying Your Purse(01 of20)
\"Women\'s purses tend to be oversized and filled to capacity, and that puts a lot of weight on one shoulder,\" says massage therapist Danielle Chow-Leong. \"This tends to make us round our shoulders, which shortens our pectoral muscles and puts more stress on our upper back and neck muscles. Pectoral muscles rarely hurt, but compensatory muscles become hypertonic (tight), may spasm or even give off a burning sensation.\"\nHow to fix it: Wear a knapsack instead of a large purse on one shoulder, Chow-Leong suggests, or a crossbody bag (which tends to be smaller, giving you less room to stuff heavy things into it). If you want to keep carrying your purse, change up the side you wear it on for half the day.
Sitting With Your Wallet In Your Pocket(02 of20)
\"Sitting with your wallet in your back pocket can cause increased compression to gluteal and piriformis (butt) muscles,\" says Chow-Leong. \"The increased height on one side causes a shift in the pelvis if sitting is prolonged. This can also cause increased shortening of other muscles surrounding the hip. Blood supply and nerve supply can be compromised, which may cause numbness and tingling down the affected limb.\"\nHow to fix it: Remember to take your wallet out and put it on the table when you\'re at work or at a restaurant.
Sleeping On Your Stomach(03 of20)
\"Sleeping on the stomach causes a hyperlordic (arched) curve in the back, and depending on which side your neck is turned to, shortening of those neck muscles as well,\" explains Chow-Leong. \"It will cause shortening of the psoas (the muscle between your trunk and your legs), quads and lower back muscles, which will increase the tone to these muscles as well.\"\nHow to fix it: \"The best position to sleep in is the one we suggest for pregnant women,\" she continues. \"This means sleeping on your side, with a pillow under the head that maintains a 90-degree angle to the shoulder, like when you\'re standing. Keep a pillow between your knees and hug one in front as well so as to not roll backwards while sleeping.\"
Washing The Dishes(04 of20)
\"When washing dishes, most people do not stand firmly on the ground with their weight evenly distributed. Most tend to put all weight on one leg and just brace with the other,\" says Chow-Leong. This, like sleeping on your stomach, can cause increased pressure on one hip and even on one knee. \"Anytime there\'s instability, one side is always overworked and eventually wears down faster than the other side.\"\nHow to fix it: Pay attention to how you\'re standing when you\'re doing something for a prolonged time, like dishwashing. \"Make sure you stand evenly on both feet and face the sink to decrease the amount of unnecessary rotation that occurs,\" she says.
Gardening(05 of20)
\"The typical gardening position causes increased stress on knees, which creates an exaggerated arch in the back, The excessive plantar flexion of the ankles when kneeling is also hard on the feet,\" says Chow-Leong. But that\'s just the start of it. When most people garden, they tend to have all plants and tools resting on the dominant side of their bodies. Therefore, they\'re constantly rotating to one side. As well, people often slump when gardening instead of keeping their backs straight, which can round the shoulder and put more pressure on the neck and upper back muscles. \"Without very strong abdominal muscles to compensate for the hyperlordotic curve in lower back,\" says Chow-Leong, \"one will inevitably have low back pain and or soreness the next day.\"\nHow to fix it: This can be avoided by kneeling only minimally, using both hands to grab plants and tools and making sure you stand up at regular intervals to give the body a break. \"Drink lots of water to avoid dehydration as well,\" advises Chow-Leong, \"because dehydration can also contribute to muscles cramping.\"
Carrying Children(06 of20)
\"People tend to carry their children with their dominant arm, and this causes repetitive stress on that one side,\" says Chow-Leong. \"Those dominant arm, neck and back muscles are constantly hypertonic and may spasm, or even shorten and cut off nerve or blood supply to the end of the limb, which may cause numbness and tingling.\" Putting a child on your hip, meanwhile, will cause the same imbalance to that hip and possibly more stress to that knee joint as well. \nHow to fix it: Rotate the arm and hip with which you carry your child, or use a baby carrier, where the child rides on your back or in front of your chest.
Sitting Cross Legged(07 of20)
Why is this polite stance so terrible for you? \"This posture can cause an impingement of blood and nerve supply (numbness and tingling) to the leg that is pinned underneath,\" explains Chow-Leong. \"This also causes the weight to be shifted to one hip, which could then shift the alignment of that hip. This will also cause all the gluteal muscles on the under leg to shorten and possibly spasm due to the added weight.\"\nHow to fix it: Sit on both ischial tuberosities (bum cheeks), says Chow-Leong, and cross only at your ankles.
Wearing High Heels(08 of20)
Those shoes may look great, but as we well know, they can cause all sorts of problems for our bodies. \"Wearing heels causes a hyperlordotic curve in the low back, which can result in tight low back, gluteal and quadricep, and calf muscles,\" says Chow-Leong. \"Stress to the knees could also cause pain, depending on one\'s history of knee pain, as well as pain in the arches, depending of the height of the heel.\" Meanwhile, if the shoes are too tight or worn for too long, the compression of muscles, bones and tendons in the feet can also be painful or make feet sore. \nHow to fix it: Wear heels for a shorter duration, or opt for a smaller heel. \"Keep in mind that wearing flat shoes is not necessarily better as they often don\'t supply enough support for the arches,\" she says. \"A good peppermint soak is always good for the feet regardless of whether in heels or not.\"
Squinting At Your Phone(09 of20)
\"Most people who squint do it with a head forward posture which causes increased stress to the upper back and neck muscles,\" says Chow-Leong. \"This posture will tend to round your shoulders and cause mid and upper back muscles to overwork. The squinting itself will cause increased tone to your face muscles, which, combined with increased tone to neck muscles can easily contribute to tension headaches.\"\nHow to fix it: Try to notice when you\'re squinting and keep your head back instead of straining it forward — that goes for looking at all screens. Taking breaks can also be helpful, notes Chow-Leong.
(10 of20)
この後は、姿勢を良くする効果をもたらすストレッチを紹介
The Mountain (11 of20)
HOW TO: Starting in a standing position, place your palms facing outwards and stretch your arms. This pose helps your body stand tall and strong. (credit:Ingrid Knight-Cohee)
Spinal Extension (12 of20)
HOW TO: Lying on your stomach with your hands by your shoulders, gently press your hands into the floor, while elevating the chest and arching the spine. Hold this pose for three breaths before lowering. Repeat 10 times (credit:Ingrid Knight-Cohee)
Plank (13 of20)
HOW TO: Elevate your body into a “table top” position, resting on your forearms and toes. You can modify this pose by lowering knees to the floor. Hold for 30 seconds and repeat three times. (credit:Ingrid Knight-Cohee)
Hamstring (Seated) (14 of20)
HOW TO: In a chair or on a stability ball, extend one leg forward to stretch. Keeping the spine extended, lean forward with your chest toward the toes of the extended leg. Hold for 30 seconds and switch legs. (credit:Ingrid Knight-Cohee)
Hamstring (Floor)(15 of20)
HOW TO: Lying on your back, extend one leg towards the ceiling, while keeping the other one straight on the floor (modify with a bent knee). Hold for 30 seconds and switch legs. (credit:Ingrid Knight-Cohee)
Chest Stretch (16 of20)
HOW TO: Standing or seated, clasp both hands behind your back and extend the arms as you open your chest forward. You should feel a stretch in both in your arms and chest. Hold this position for 30 seconds. (credit:Ingrid Knight-Cohee)
Cat/Cow (17 of20)
HOW TO: Kneeling on all fours, gently round your back into a cat pose and extend the spine inwards for a cow stretch. Repeat 10 times. (credit:Ingrid Knight-Cohee)
Child's Pose(18 of20)
HOW TO: In a kneeling position, sit on your heels, separate the knees and fold forward, resting your forehead on the floor. Hold this pose for 30 seconds. (credit:Ingrid Knight-Cohee)
Low Back Twist (19 of20)
HOW TO: Lying on your back, pull one knee towards the chest. Gently carry the bent knee over to opposite side, and turn your head in the opposite direction. Try to keep your entire back in contact with floor. Hold for 30 second and switch sides. (credit:Ingrid Knight-Cohee)
Superman (20 of20)
HOW TO: Starting on your left knee, extend your left arm, while stretching out your right leg behind you. Here, you will feel the stretch in both your arms and legs. (credit:Ingrid Knight-Cohee)
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