What nobody has countedEmerging evidence
No study counts neck pain on treadmills. In a review of running injuries in 9,864 runners, 79% of injuries were at or below the knee, and injuries of uncertain site or to the upper body made up 3.7%; the neck isn't counted on its own. No lab study has measured head angle or neck muscle work on a treadmill, or the neck and upper back muscles during running; the nearest data are from walking on the ground. Neck pain itself is common: 30% to 50% of adults have it in a year, a guideline says.
So this map is built from lab studies of phones, screens and head posture, studies of handrails, phones and falls on treadmills, studies of the conditions, and NHS, NHS inform, National Institute for Health and Care Excellence (NICE) and professional body pages, and it says so. That most neck pain on the treadmill comes from a long session holding the head in one position, often looking down, is our reading: the data come from walking on the ground and seated screen use.
Sources 1, 2, 3
What looking down does to the neckEmerging evidence
Walking while reading or texting on a phone, 26 adults held the head about 29 to 32 degrees forward, against about 0 looking ahead; in 28 young adults it was 31 degrees browsing one-handed and 38.5 degrees texting with both hands; and in 60 young adults neck bend was about 32 degrees walking with a phone. The further the neck bends, the more load on it and the harder the muscles at the back of it work, in 32 young adults texting while standing, and within about 15 degrees of upright that work stayed low in 44 phone users. A model of seated tablet use put the demand on the neck muscles at 3 to 5 times that of a level head, lowest with the tablet propped high, and a review of 12 lab studies found phone use raised neck and shoulder muscle activity.
In office studies, a screen 40 degrees below eye level raised activity in 6 of 10 neck, shoulder and back muscles against one 15 degrees below, in 12 workers; in another study of 10, the upper trapezius didn't differ but comfort was best with the high screen. Many treadmill consoles and phone ledges sit below eye level, so watching them means looking down (our reading). These are short lab studies of load and comfort, not of injury.
Sources 2, 4, 5, 6, 7, 8, 9, 10, 11
Does the posture cause the pain?Mixed evidence
Not on its own, as far as studies can tell. In 7,092 young Swedish adults followed for 5 years, texting didn't predict new neck pain, though it went with existing neck or upper back pain lasting; in 150 young adults, texting posture wasn't linked to neck pain. Adults with neck pain had slightly more forward head posture than those without in 15 one-off studies, and teenagers didn't; in 26 studies one posture angle differed by about 3 degrees and two others not at all.
Surveys find heavy phone use goes with neck pain (more than twice the odds in 7 studies of 10,715 people), and neck and upper back complaints are the commonest among phone users, but those studies can't show cause. NHS inform says neck problems are rarely caused by serious disease or damage, and the Chartered Society of Physiotherapy (CSP) advises regular breaks from fixed positions. So the fair summary is mixed: a long, unbroken spell in one position, and how often you do it, seem to matter more than the angle.
Sources 12, 13, 14, 15, 16, 17, 18, 19
The rails, the phone and the moving beltEmerging evidence
Gripping the rails makes the work easier: at the top stage in 10 adults, oxygen use was 26.1 with free arms, 23.9 resting the hands and 20.6 gripping, and heart rate 142, 137 and 121 beats a minute; even light support lowered the work in 15 women on a stepping treadmill, and holding on inflated estimated fitness by 22.4% in 35 students. No study has measured the neck or shoulder muscles while holding the rails, so that gripping hunches the shoulders is our reading, not a measured fact.
Texting or talking dropped self-chosen treadmill speed from 3.1 to 2.8 miles an hour in 44 students, every phone task changed gait on a treadmill in 36 active adults, walking with a phone slowed 27 adults and widened their steps, and across 25 studies texting consistently changed how people walked. In US emergency departments, treadmills caused 66% of an estimated 70,302 home exercise machine injuries in 2007 to 2011, and treadmill head injuries rose by more than 1,000% over 18 years; neither study links injuries to phones or looking down.
Sources 20, 21, 22, 23, 24, 25, 26, 27, 28
How the causes are told apartEmerging evidence
An ache at the back of the neck that builds through the session and eases when you look up is usually the position. Tight tops of the shoulders are usually the upper trapezius and its neighbours; an ache between the shoulder blades is usually the upper back muscles. A pressing headache on both sides is usually a tension headache, which the NHS says isn't a sign of an underlying condition; a one-sided headache from the back of the head with neck pain can come from the neck, which needs more than a sore neck to diagnose.
A throbbing headache brought on by hard effort may be a primary exercise headache: about 1 in 8 of 1,838 adults had had one, and it is commoner in hot weather and at altitude. The headache classification says the first one must be checked for a bleed on the brain and problems with the blood vessels, and NICE lists a headache triggered by exercise among those to assess. A sudden, extremely painful headache is a 999 call: the NHS says a bleed on the brain may be more likely when straining, such as lifting something heavy.
Neck, jaw, shoulder or arm pain that comes on with effort and eases within minutes of rest can be angina, whose attacks usually last less than 10 minutes; in 88 published cases of headache caused by the heart, effort brought it on or made it worse in 56%, and in 21 it was the only symptom. Pain, pins and needles or numbness down one arm is usually a trapped nerve: 83 people per 100,000 a year, peaking at 50 to 54, and preceded by exertion or injury in only 15%. Clumsy hands, numbness in both arms or trouble walking can be pressure on the spinal cord. A stiff neck with a fever or dislike of light can be meningitis.
Sources 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39
When a scan helps, and how it usually goesStrong evidence
Not for ordinary neck pain: in 1,211 people without neck symptoms, magnetic resonance imaging (MRI) scans showed bulging discs in 87.6%, including about three quarters of people in their 20s. NHS inform says X-rays and MRI scans are usually not needed to diagnose a trapped nerve in the neck, and a guideline asks clinicians to follow established rules on scans. Tests matter for a first exercise headache, signs of pressure on the spinal cord, a trapped nerve that isn't improving and a significant fall.
The NHS says most neck pain only lasts a few weeks, and NHS inform says new neck problems should begin to settle within 8 weeks. In 7 studies of new neck pain, pain fell from 64 to 35 out of 100 by 6.5 weeks but was 42 at a year, and half to three quarters of people report neck pain again 1 to 5 years later. A trapped nerve usually starts to improve within 12 weeks, with big gains within 4 to 6 months, and 90% had no or only mild symptoms at follow-up in a population study. No one can promise a date, which is why the plan keeps strength work going.
Sources 40, 41, 3, 31, 42, 18, 43, 44, 45, 36
