Day 21 of the 21-Day Ab Challenge. Fire up 🔥 your abs with our final workout in the series.

Sorry, this workout is not osteoporosis-friendly.

Tools: BOSU or stability ball (optional)

2 x 50sec
Crunch (Alt: on floor)
Plank (Alt: on floor)
Oblique crossover (Alt: 1-side bicycle)
Oblique crossover (Alt: 1-side bicycle)
Double crunch (Alt: on floor)