I used Alexa to time my wall sits for two weeks, and my core strength skyrocketed

One of the best exercises you can do for your legs and core is absolutely free, requires no equipment, and can be done while watching TV at home. What’s more, there’s no movement involved, you're not adding any extra weight, and there's no impact on your joints. This makes it perfect for beginner exercisers, seniors, and those with joint problems preventing them from doing other forms of exercise.

The wall sit is a great exercise, and very underrated in my book. People often use it in the lead-up to a skiing holiday, as it prepares your legs and glutes to adopt that crouching posture.  I made great use of it during COVID, when all the gyms were closed and I was getting bored repping out bodyweight squats, so I started doing a daily wall-sit challenge: four sets of one-minute holds every day for two weeks.