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.
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Back pain with leg or bladder symptoms
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.
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A hernia
See a GP if you think you have a hernia, a bulge or lump that may get bigger when you strain and smaller when you lie down. Get help from NHS 111 if you have a hernia and pain in or around it, a bloated tummy, you feel or are sick, you're vomiting blood or your vomit looks like coffee grounds, you're constipated, you have a high temperature or feel hot, cold or shivery, or you've suddenly become confused. Call 999 or go to A&E for a femoral hernia (a small lump at the top of your thigh, in your groin) with very bad tummy pain, sickness, being unable to fart or poo, a high temperature or sudden confusion.
The knee
Go to A&E (accident and emergency) if you've injured your knee and it has changed shape, it becomes very swollen very quickly, you felt a pop or snap, you can see bone sticking out, or it's bleeding heavily. Don't drive yourself: ask someone to take you, or call 999 if the pain means you can't move your leg to get there.
Get advice from NHS 111 now: the knee locks, gives way or clicks painfully. Painless clicking is normal.
A pop or tearing feeling at the front of the knee after a fall, a jump, a landing or a heavy squat, then you can't straighten the knee or lift the straight leg, there's a dent above or below the kneecap, or the kneecap sits higher or lower than on the other side. Go to A&E or an urgent treatment centre, or get help from NHS 111, as our knee pain when squatting guide explains. In the US, go to urgent care or the emergency department.
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The hip
Call 999 or go to A&E for severe hip pain after a fall or injury, if you can't walk or put weight on your leg, or for tingling or loss of feeling in your hip or leg after an injury. Ask for an urgent GP appointment or get help from NHS 111 for severe hip pain that started suddenly without a fall, a hip that's swollen and feels hot, skin around it that has changed colour, or hip pain with feeling generally unwell and a high temperature.
After an injury
After an injury, if you heard a crack, the limb has changed shape or is pointing at an odd angle, it is numb, tingling or has pins and needles, or the skin has turned blue or grey or feels cold.
If a stretch brings on a sudden sharp pain, a snap or a pop, and it's very painful or getting worse, there's a lot of swelling or bruising, or it hurts to walk or stand on the leg. In the US, contact your doctor or urgent care.
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A nerve or the joint, not a muscle
Burning, tingling, numbness or pins and needles down an arm or leg while stretching usually means a nerve is under tension, so ease off to a position without it. A pinch at the front of the hip or ankle at the end of a stretch is the joint, so work below it. See a GP or physiotherapist if either keeps happening (our suggestion).
A pinch at the front of the hip or ankle is the joint, not a stretch: stay just short of it, and see a GP or physiotherapist if it keeps happening (our suggestion).
Very flexible joints
See a GP if you think you or your child have joint hypermobility syndrome, for example joints that keep dislocating, ongoing joint or muscle pain and stiffness, frequent sprains, tiredness even after rest, poor balance or thin, stretchy skin. A GP may check your Beighton score, arrange tests to rule out other conditions and refer you to a physiotherapist.
Slowly and with control, in the middle of your range, stopping short of locking your knees or elbows or hanging at the end of a joint's range. If a joint feels about to slip, stop or make the movement smaller (our editorial rule, the same as in our shoulder dislocation guide).
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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 from 0 to 2 out of 10 is fine, and up to 5 is acceptable if your knee is back to its usual level by the next morning; for tendon pain just below or above the kneecap, keep it to 3 or less. Sharp, catching or giving-way pain, or new swelling, means stop. That's our knee guides' rule.
During the exercise, pain up to about 5 out of 10 is acceptable. It should settle within an hour or so, and your hip should be no worse that night or the next morning. If it is, do less next time (fewer repetitions, a smaller range, a lighter load), not nothing.
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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.
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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.