Is the OP curious about what helps cycling or general injury prevention or physical appearance? We don't know.

I do full body workouts at the gym twice a week, stretch every morning, and ride my bike. I can plank 2 minutes no problem, but I never do them because why? What's actually going on when one planks? One is forming one's body into a beam. From our engineering education, we know that an evenly loaded beam experiences compression above the neutral axis, tension below the neutral axis, with the loads increasing from the neutral axis to the beam's upper and lower surfaces. In the case of the human body, the neutral axis will be somewhere in the middle of the body. Therefore the spine is in compression, the back muscles are relatively relaxed and the abdominal muscles are in tension, with those closest to the skin under the most tension.

All this won't help cycling at all, which doesn't require much ab muscle, but does require substantial strength and endurance in the back muscles. It does help the 6-pack a little, but not the deep abs which are actually more important for injury prevention and mobility. Gym equipment is designed to target many specific muscles and muscle groups and I get good results from using it.

Transverse abdominals are what you really want to work: https://www.livestrong.com/article/4...inis-workouts/
Note that these exercises are done with a straight back. Crunches should never be done. Other good back exercises are the superman and face-down snow angels.