Credit: Freepik

Credit: Freepik

Day 1-3: 20 seconds

Day 4: 30 seconds

Day 5: 40 seconds

Day 7-8: 45 seconds

Day 9-11: 60 seconds

Day 12: 90 seconds

Day 14-16: 90 seconds

Day 16-18: 150 seconds

Day 20-23: 150 seconds

Day 23-24: 180 seconds

Day 26-27: 240 seconds

Day 28: Until you fall down

For better challenge, you can verify the plank. Choose some of these exercises and include them in your challenge. But, if you prefer a classic plank, keep doing it without any addition! You'll get the result anyway!