The 25-year-old 'Bad Boys' singer endured a gruelling workout session on Wednesday (12 March), but the hard work and dedication didn't seem to faze her.
Posing in a purple crop top and black pants, Alex said: "Mug face ON!! Night workout DONE!! If you ain't having fun then what's the point !?"
Earlier this week (10 March), fitness fanatic Alex shared another selfie, in which she was working out on a cross trainer. Captioning the photo, she said: "No pain no gain."
Aside from keeping up with her fitness regime, former X Factor winner Alex is also training to be a life coach.
Speaking on ITV's Lorraine (28 January), Alex said: "I wanted some more balance in my life and it's definitely brought a different perspective.
"I'm really in a happy place, a very spiritual place, so I can't wait to get back on the road."
Earlier this year, Alex also flew out to the States to work on her third studio album, which she revealed has taken two years to record.
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Watch Alex's video for 'Bad Boys' below: