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. The American Heart Association says these need immediate medical evaluation.
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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; arm pain that comes on suddenly with pressure, heaviness or squeezing across your chest; severe difficulty breathing, or a chest that feels tight or heavy; 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. The NHS says a bleed on the brain may be more likely when lifting something heavy. Don't drive yourself to A&E.
Sources 49, 50, 51, 52, 53, 54, 55, 56
A headache with effort
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.
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Your shoulder
Ask for an urgent GP appointment or get help from NHS 111 for sudden or very bad shoulder pain; not being able to move your arm; a shoulder or arm that has changed shape or is badly swollen; pins and needles that don't go away; or pain that started after an injury or accident, like a fall. In the US, contact your doctor or urgent care. See a GP if shoulder pain is getting worse or hasn't improved after 2 weeks. While your shoulder is sore, the NHS says not to make up your own strenuous exercises or use heavy gym equipment.
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Your neck and arms
See a GP if neck pain comes with other symptoms, like pins and needles or a cold arm, as the NHS says. NHS inform advises an urgent GP appointment for clumsiness in your hands, or numbness, pins and needles or weakness that's getting worse in one or both arms.
Stop if your fingers tingle or go numb: that's a nerve, not a tired muscle, as our grip strength guide says.
Sources 40, 57
Your upper back
See a GP if back pain is coming from the top of your back, between your shoulders, as the NHS advises. With osteoporosis, a new or worsening hunch, lost height or sudden upper-back pain can mean a spinal fracture: see a GP (our kyphosis guide).
Sources 58, 59
Before you start
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 hard or straining work if your blood pressure is uncontrolled (140/90 or higher at a clinic, or 135/85 at home), 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.
With controlled high blood pressure, the American Heart Association considers low- to moderate-intensity strength training with proper breathing safe. Breathe out as you lift, as our breathing guide advises.
With a pacemaker or defibrillator, the American Heart Association asks you to check with your doctor before upper-body strength training, because repeated arm movements can damage or dislodge the leads.
Sources 60, 61, 48