Usually ordinary back pain or a strained muscleStrong evidence
The NHS says a common cause of back pain is an injury like a pulled muscle, and that back pain usually improves within a few weeks but can last longer or keep coming back. NHS inform lists doing more activity than you normally would among the things that bring it on.
In 17 winters of US emergency department data, about 11,500 people a year were treated for snow shovelling injuries and emergencies, about 4 in every 100,000 people. A third had hurt the lower back, most injuries were soft tissue strains, and 5.8% needed a hospital stay. US orthopaedic surgeons name sprains and strains of the back and shoulders as the commonest snow clearing injuries. Emergency figures miss everyone who stayed at home, so ordinary sore backs are far commoner than this, and serious injury far rarer: one Swiss university hospital found 21 shovelling admissions in 13 winters, among about 350,000 emergency cases.
Sources 1, 2, 3, 4, 5
What sets it off: heavy scoops, throwing and twistingEmerging evidence
US orthopaedic surgeons say that holding a shovelful of snow with your arms outstretched puts too much weight on your spine, and that you shouldn't throw snow over your shoulder or to the side. In a lab study, the load on the low back rose with how far the upper body bent forward.
In 999 people with a new episode of low back pain, each compared with themselves over the 4 days before it began, short-lived triggers raised the odds: heavy loads, awkward postures, moderate or vigorous activity, tiredness and being distracted during a task (from about 2.7 to 25 times the odds). These are relative, short-term risks, not a sign of damage, and people seldom recognised tiredness, distraction or a load held away from the body. In 416 people with back pain followed for a year, more hours of lifting and bending raised the odds of a flare a little but didn't predict being worse a year later. A long session of heavy, wet snow piles these triggers together; that is our reading, not a measured finding.
Shovelling also keeps you bent forward: in 10 men clearing snow, the trunk bent about 49 degrees with a straight shaft. After 20 minutes of full bending, 47 volunteers' lower backs stayed looser for some minutes, and the authors suggest standing and walking before a demanding lift.
Sources 4, 6, 7, 8, 9, 10, 11, 12
Shovelling is a workout, not a choreStrong evidence
The Compendium of Physical Activities rates shovelling snow by hand at 5.3 METs (metabolic equivalents, multiples of the energy you use at rest) at moderate effort and 7.5 at vigorous effort, against 3.0 for vacuuming. The NHS counts heavy gardening, such as digging and shovelling, as muscle strengthening. Like any workout, it needs building up to.
Sources 13, 14, 15
The first big fall, and why it isn't the cold on your musclesEmerging evidence
No study has measured a first-snowfall peak in back pain. US orthopaedic surgeons say snow removal can be especially dangerous if you don't exercise regularly, and the Heart and Stroke Foundation of Canada says a longer warm-up is needed in cold weather.
Cold itself didn't trigger back pain: temperature, humidity, air pressure, wind and rain had no link with new back pain in 993 people, and a reanalysis of 981 agreed. So the likely culprit is a big, unfamiliar load done fast after weeks of less activity (our reading), not the cold on your muscles.
Sources 4, 16, 17, 18
The heart: hard work, and a small rise in heart attacks after heavy snowEmerging evidence
Shovelling heavy snow is hard work for the heart. In 10 unfit men aged about 32, heart rate reached 86% of maximum after 2 minutes and 97% after 10, and blood pressure went slightly higher than at the peak of a treadmill test; the fitter the man, the lower his relative heart rate. When men shovelled at their own pace, including men with heart disease that caused no symptoms, it took about three quarters of their peak heart rate: hard, but within the range used for aerobic training.
Heart attacks rise a little after heavy snow, mainly in men. In Quebec, in 128,073 hospital admissions and 68,155 deaths from heart attacks over 33 winters, men had 16% higher odds of admission and 34% higher odds of death the day after 20 cm of snow, while women showed no clear rise. Because such days are rare, fewer than 1 in 100 of those heart attack admissions came the day after 20 cm or more of snow. A British Columbia study found a similar, borderline rise, a Calgary study found none, and in subarctic Tromsø the weather made little difference except in people over 65.
Heart emergencies are a small share of shovelling emergencies but nearly all the deaths: 6.7% of the US emergency visits, including every death the study counted. Those affected are mostly men and people who rarely exercise and have high blood pressure, high cholesterol, diabetes or a smoking habit, or earlier heart disease or a stent; in Detroit, 33 of 36 sudden heart deaths during snow removal were in men. But after a New York blizzard most people with shovelling-related heart attack or angina had no known heart disease, and a quarter of women's heart attack or angina visits were linked with shovelling. For most people the risk on any one day is very small.
Sources 19, 20, 21, 22, 23, 24, 25, 26, 3, 27, 28, 29, 30, 31
Why the effort matters, and how being active protects youStrong evidence
Heavy exertion is a short-lived trigger for heart attacks, mainly in people who rarely exercise. In 1,228 people after a heart attack, heavy exertion raised the risk in the following hour about 6 times overall, but far more in people who exercised less than once a week than in those who exercised 5 or more times a week; a German study found the same pattern, and across 52 countries physical activity in the hour before roughly doubled the odds. Regular activity is protective.
Shovelling is mostly arm work, and arm work raises heart rate more than leg work for the same effort. The American Heart Association adds that straining to lift heavy loads makes people hold their breath, which causes big increases in heart rate and blood pressure. Cold adds to it: in 20 people with stable coronary heart disease, arm exercise at minus 15 C raised the heart's workload by about a fifth against the same work indoors, cold air brings angina on sooner, and in England and Wales each 1 degree C fall in daily temperature went with a 2% higher risk of a heart attack over the next 4 weeks. In Finland, snow shovelling was one of the three commonest activities at the time of exercise-related sudden cardiac deaths.
Sources 32, 33, 34, 35, 36, 37, 38, 39, 40
Slips on ice, roofs and snow blowersStrong evidence
After an ice storm in Indianapolis, back injury was the commonest injury from falls on ice (19.3% of 327 injuries), and fractures were mostly of the ankle, wrist and hip, rising with age. In Cardiff, fractures rose almost 3 times on days of snow and ice in 1981, wrist and forearm fractures about 7 times, and 2.2 times 33 years later. In Sweden, slipping on ice or snow caused 9% of all adult fractures, 1.4% of them in the spine. In Norway, fall fractures in people aged 65 to 79 were about 40% more common from October to March, and in the US a third of older people's winter falls outdoors were weather related, nearly all slips on ice or snow. Working-age adults fall too, most often in the morning, and in older adults freezing rain raised falls more than snowstorms did.
The most serious back injuries tied to snow clearing come from falls: in New York State and Helsinki, people who fell from roofs while clearing snow broke the spine and limbs, and Helsinki's were nearly all men. Snow blowers move the risk rather than remove it: they cause hand injuries in the chute, and almost all snow blower deaths in US emergency data were from the heart. With osteoporosis, the Royal Osteoporosis Society suggests trying to avoid going out in bad weather, especially when it is icy or snowy.
Sources 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52
When a scan mattersStrong evidence
Not for back pain after shovelling. The National Institute for Health and Care Excellence (NICE) says don't routinely offer imaging outside specialist care for low back pain, with or without sciatica. A scan matters for the warning signs: an emergency magnetic resonance imaging (MRI) scan for suspected cauda equina syndrome, an X-ray after a fall on ice with a possible fracture, and in specialist care when the result would change treatment. Chest pain needs an electrocardiogram (ECG) and blood tests in hospital, not a back scan.
Sources 53, 54
How it usually goesStrong evidence
In 47 groups of people with low back pain, average pain in new back pain fell from 56 out of 100 to 26 within 6 weeks, then more slowly; an earlier review found a fall from 52 to 23. NHS inform says the biggest change usually comes in the first couple of weeks, and most problems improve within 6 weeks.
Back pain often comes back: within a year of recovering, 69% had another episode in one cohort. That is common, not a sign of damage, and it is why the plan keeps going through the winter. No one can promise a date.
Sources 55, 56, 2, 10, 57
