Stop and get medical help
If you get chest pain or pressure, feel faint or dizzy, are unusually breathless, or your heart races or beats irregularly during exercise, as our plans advise.
Call 999 (911 in the US)
For chest pain that comes on suddenly and doesn't go away, feels tight or like squeezing, spreads to your arms, neck, jaw, stomach or back, or comes with sweating, feeling sick, light-headedness or breathlessness; severe difficulty breathing; someone who faints while exercising; palpitations that don't go away, or come with chest pain, shortness of breath or feeling faint; or a headache that starts suddenly and is extremely painful, especially while lifting or straining, or comes with numbness or weakness, difficulty speaking or loss of vision. The NHS says a bleed on the brain may be more likely when lifting something heavy. Don't drive yourself to A&E.
Sources 51, 52, 53, 54, 55
Back pain with chest pain, or sudden severe pain
Call 999 or go to A&E: back pain with chest pain, or back pain that started after a serious accident, such as a car crash.
Call 999: sudden, severe pain in the tummy or back, which can come with breathlessness, pale or grey skin, or collapse. It can be a burst abdominal aortic aneurysm, most common in men aged 65 or over and in people who smoke or used to smoke.
Sources 56, 52
Back pain with numbness or bladder changes
Call 999 or go to A&E: loss of feeling or numbness around the genitals or bottom, new trouble peeing or controlling your bladder or bowels, changes in genital sensation during sex or problems with erections or orgasm, or pain, tingling, weakness or numbness in both legs. These are signs of cauda equina syndrome, which needs treating in hospital urgently. Don't drive yourself.
See a GP if pain spreading down a leg hasn't improved after a few weeks of home treatment, is getting worse or stops your normal activities. Sciatica on both sides, or weakness or numbness in both legs that's severe or getting worse, is a 999 call or a trip to A&E.
Sources 56, 57
Same day
Same day: you have or have had cancer, and new back pain that is severe and doesn't let up, is getting steadily worse, is worse at night and disturbs your sleep, is worse when you cough, sneeze or strain, or comes with tenderness over the spine. Contact your cancer team or GP urgently. With cancer, new weakness, difficulty walking, numbness or bladder or bowel problems are an emergency.
Same day (GP or NHS 111): back pain and you feel hot, cold, shivery or generally unwell, or severe pain that starts suddenly or is getting worse quickly.
See a GP
Pain at the top of the back, between the shoulders, rather than in the lower back.
Unexplained back pain with muscle spasms, loss of height, or a curved spine or change in posture: a possible osteoporotic spinal fracture, more likely with older age or long-term steroid tablets.
Back pain that hasn't improved after a few weeks of looking after it at home, stops you doing day-to-day activities, worries you, or you're struggling to cope.
Pain that doesn't improve with rest or is worse at night, or pain that is worse when you sneeze, cough or poo.
Unexplained weight loss, or a lump, swelling or change in the shape of your back.
Source 56
Neck and arm symptoms
Call 999 or go to A&E: new problems walking, loss of bladder or bowel control, or a sudden loss of coordination, such as difficulty doing up buttons. These can be signs of pressure on the spinal cord.
Same day (urgent GP appointment or NHS 111): severe neck pain that starts suddenly or gets worse quickly; heaviness or weakness in the arms or legs; pins and needles in an arm along with neck or arm pain; or pain between the shoulder blades.
Same day: clumsiness in your hands, or numbness, pins and needles or weakness in one or both arms, that is getting worse; problems with balance or walking since the neck pain started; or neck pain with a severe headache.
Source 58
A trapped nerve in the neck
Arm weakness or numbness that keeps getting worse, severe pain that painkillers and rest do not touch, or an unexplained fever.
No improvement after 6 weeks of exercise, or arm symptoms still there beyond 6 to 12 weeks.
During neck moves
Dizziness, light-headedness or tingling into an arm during the neck moves are stop signs, not sensations to push through.
During any session
Stop straight away if you feel any pain or become unwell, the NHS says, and contact 111 if your symptoms worry you or don't go away.
Pain you'd call mild to moderate, no more than about 5 out of 10, that settles within an hour or so, with your back no worse the next morning, is acceptable; if it is worse, do less next time (fewer reps, a smaller range, a lighter load), not nothing. Stop or shrink any movement that sends pain, pins and needles or numbness further down your leg. That's our back pain guides' rule.
Source 59
Ask for an urgent GP appointment or call NHS 111
Ask for an urgent GP appointment or get help from NHS 111 for a headache that's triggered or made worse by coughing, sneezing, bending down or exercising. In the US, contact your doctor or urgent care.
Check first
Speak to your GP first if you haven't exercised for some time or have medical conditions or concerns, as the NHS advises. Get advice before heavy lifting or hard straining work if your blood pressure is uncontrolled, or you have heart disease or chest pain when you're active, a pacemaker or defibrillator, diabetic eye disease, glaucoma, a hernia, recent eye or tummy surgery, or you're pregnant, as our breathing guide lists. After a recent shoulder dislocation or shoulder surgery, follow our shoulder dislocation guide or your surgical team first.
Speak to a GP first if you haven't exercised for some time, or if you have a medical condition or concerns. Get advice first, too, if you have a health problem, an injury or symptoms, have recently had a heart attack or an operation, or are pregnant or have recently given birth.
Source 60
A heart condition or high blood pressure
If you have a heart condition, follow your cardiac team's advice on how hard to work, and stop for the warning signs above. People with long-term conditions may wish to ask their specialist before starting. With uncontrolled high blood pressure, avoid straining against a held breath; the high blood pressure guide has more.