5 things your body might be telling you if you faint after exercise

Exercise has immense health benefits, but it should never cause you to faint afterwards, especially not on a regular occasion.

On Saturday night, Amy Dowden reportedly collapsed backstage on Saturday night after performing live on Strictly Come Dancing with her JLS partner, JB Gill.

It’s been reported that soon after the live show, Amy started to feel unwell and an ambulance was called to take her to a nearby hospital for checks.

The 34-year-old professional dancer has been battling breast cancer for almost two years, getting the all clear in February 2024 after chemotherapy and a mastectomy.

Lightheadedness after exercise is not uncommon, according to Peloton, but it definitely shouldn’t be how you feel after every workout, and it could be a sign that your body is fatigued and needs attention. Dr Frankie Jackson-Spence (@drfrankiejs) explains: "A simple faint is where there is temporary loss of consciousness that quickly resolves, usually due to reduced blood flow to the brain due to a drop in blood pressure. Some people feel dizzy, sick or light headed prior to passing out."

If it’s a one-off occurrence then Dr Jackson-Spence says it’s nothing to worry about long-term, but it could be a sign that your body that needs something e.g. food, more hydration or rest. If you can identify the trigger, then Dr Jackson-Spence says returning to exercise is OK, as long as you build it back up slowly.

However, if fainting episodes are happening more frequently it's important to consult your GP, before you continue with your exercise routine. Here are 5 common reasons you might faint after exercise:

Overexertion

Sometimes it’s good to stretch our capabilities, strive for a new PB on a 5K or lift heavier, but it has to be done carefully. "When we exercise we have to increase cardiac output - the amount of blood our heart pumps round the body each second to provide our working muscles with glucose and oxygen," Dr Jackson-Spence says. If you push beyond your physical capabilities you can overexert yourself and faint, so it's important to monitor your vital signs such as heart rate and breathing when you're pushing yourself further in a workout.

Dehydration

Drinking enough fluid is as important as monitoring your food intake when it comes to up keeping a regular exercise routine. A very common reason that people faint after exercise is dehydration as they haven't drunk enough fluids before, during or after a workout. Dr Jackson-Spence explains: "During exercise, water and electrolytes are lost through the skin via sweating and these need to be replaced to maintain blood pressure." This is why athletes who run marathons or do triathlons take fluids with them during their workout to stay hydrated throughout the endurance activity.

Low blood glucose

Even non-diabetics can experience low blood pressure especially during exercise, as Dr Jackson-Spence explains "exercise uses up a lot of glucose in our blood, and therefore sometimes blood sugar can drop if not eaten before a workout, or adequately fuelled up the day before." It's important to make sure you've had a substantial meal before or after rigorous exercise to keep your body working efficiently.

Warm environment

Sometimes fainting might be as a result of your environment, as your body overheats in warm weather or in a humid atmosphere. "Dehydration plays a part, but also in the heat, our blood vessels vasodilate and this can impact blood flow around the body and to the brain," Dr Jackson-Spence adds. Try to avoid working out in the hottest period of the day, even using a fan to cool down the area or take breaks if you feel yourself becoming too hot.

Not breathing properly

Breathing well is important during exercise to keep your heart beat steady with enough blood reaching your heart. If you aren't taking deep breaths during exercise then it can also cause you to faint. Dr Jackson-Spence calls this "vasovagal stimulation" which is where you aren't breathing properly when exerting yourself (such as lifting heavy weights or doing an intense dance routine) and this "can reduce blood return to the heart" and result in a faint.

Read more about Amy Dowden's health:

• What we know about Amy Dowden's health scare as Strictly replacement confirmed (Yahoo Entertainment, 4-min read)

• Is Amy Dowden returning to Strictly Come Dancing this week? (Cosmopolitan, 3-min read)

• Strictly's Amy Dowden "feeling much better" after post-show hospital trip (Digital Spy, 2-min read)