What is the 300-Rep Leg Destroying Challenge ... felt like a test of mental grit. The standout challenge? Without question, the Cossack squats. Staying low while shifting side to side is ...

The fitness trainer and mum to 18-month-old daughter Winnie regularly shares snippets of her workouts online, but as she explains in a recent YouTube video, she swears by her 100-rep squat pyramid ...