Whether you've tried a class and never gone back, or it's part of your cross-training routine, you're likely to be well-versed in the rising popularity of spinning.
For the uninitiated, however, spinning is a high-intensity form of stationary cycling, usually partnered with dumbbell routines and done near pitch-dark.
There's no denying it can be an effective workout when done safely and correctly, promising a high calorie-burn and a one-two punch to belly fat.
But, according to new research, you could be increasing your risk of kidney damage when you step on the bike and start sweating.
New medical reports from the American Journal of Medicine have found that these high-intensity spin classes may lead to bouts of rhabdomyolysis — a syndrome caused by muscle injury from trauma and lack of oxygen.
Rhabdomyolysis, simply put, is the breakdown of damaged skeletal muscle, releasing myoglobin into the bloodstream which can lead to kidney damage.
Not pretty, you'll agree. Interestingly, rhabdomyolysis is usually found in victims of car crashes or 'crush injuries' such as collapsed buildings or bad falls.
The symptoms are varied. For half of those with Rhabdomyolysis, there are no symptoms. It's not ideal for the less fortunate half — dark urine, muscle aches, nausea and weakness are all notable symptoms.
Our advice? Start with a lower-intensity class before you start grinding your way to the top of your next spinning class. Trust us, your kidneys will thank you.
A version of this article appeared on menshealth.co.uk