A strong core is the foundation of proper movement patterns, injury prevention, and athletic prowess yet deciding which exercises to program for which client may pose a challenge. Per usual, I’m an advocate of using any training tools, programs, exercises, and modalities that are safe and motivate users to exercise. Spoiler alert: I won’t make an attempt to suggest that any type of core training is inherently better than the others. However, there are nuances when choosing planks or crunches that, once understood, can be leveraged (you’ll get that pun shortly) to provide even more successful workouts your clients.

The Core

Although professionals might disagree slightly on exactly which muscles should be defined as part of the “core”, the generally accepted definition consists of:

While the rectus abdominis is associated with flexion in the trunk, a crunch or sit up, the transverse abdominis is associated with bracing, or compression of, the spine, like in a plank or while trying to stand tall in mountain pose during yoga class. Our obliques help to rotate us, or laterally flex at the waist, like during bicycle crunches. And the multifidi and erectors help to extend the trunk or brace the spine.

As much as these muscle help us with movement, it might be even more important that they can prevent unwanted movement. Lower back injuries are the most common types of workplace injuries. Properly conditioning the core muscles can help to prevent instances of sciatica, slipped disks, and pulled muscles.


Planks, “hollow body”, and mountain pose all rely on the proper engagement of the transverse and rectus abdomini. Most thorough, safe, and exciting workout programs will feature planks in some variations. Unlike crunches, sit-ups, back extensions, or bicycle riders, planks require very little extension or flexion in the trunk. Planks, if practiced safely, are a great tool for developing better core strength in athletes, desk workers, laborers, and most of the general public.

When prescribing a plank there are a few things to remember:

  • Planking on the hands is great, but if clients feel too much work in their wrists, lowering on to the forearms will still challenge the core, and it may provide better stability for those who need it.
  • In the plank position the spine is essentially a “support beam”. When you are on your toes and arms, you have to really engage the transverse abs in order to brace the support beam. Lowering to the knees can shorten the “lever” that is providing stress to the spine, and give a much-needed modification to exercisers.
  • Elevated planks, mountain pose, or breathing exercises that stress posture can be great for clients who have suffered various injuries, and help build a great foundation for stability strength. Be sure to have your clients see a doctor and get cleared before any exercise are prescribed.


The most classic of classic exercises, the crunch. We have all likely used a number of versions of crunches; pause, pulse, full sit-up, oblique crunch, bicycles, v-ups, etc…

A strong core will not only provide safety and vigor, but it can allow us to be nimble, react quickly, and perform at our best. For the footballer to rocket across the field, from side to side, they not only need to have strong legs but a strong core. For a construction worker to load a pile of lumber on their shoulder they need to prevent compression on their spine but also curl their torso under the pile of 2 x 4s and extend the spine into a comfortable walking position. Bracing has its many values, but so does mobility.

When training the core through various planes of motion it is important to remember:

  • Safety first, make sure a client is cleared to perform all exercises, and set a foundation of stability first.
  • Lower back, neck, or hip discomfort may be contraindications for that client, take a step back and reassess.
  • Short time based sets, with rest, is a great way to start to develop your clients core stamina.
  • Generally, more challenging compound movements, or heavy weight training, should be done before the core is exhausted.

So…Planks or Crunches?

What you use in your clients’ program will always be subjective. Not just to the needs of your clients, but also in regard to the things that excite you as a trainer. You do this because it’s your passion after all. So be sure to incorporate into your workouts not only what is safe and effective, but what is enjoyable and engaging. And don’t forget, the world record for plank is currently 8 hours 8 minutes & 15 seconds..so start training!

Andrew Gavigan

Andrew Gavigan is a recognized speaker in the fitness industry, master trainer, Creator of the mostFit Core Hammer, and serves as Director of Education for Aktiv Solutions. He is a NASM and NFPT Certified Personal Trainer and Behavioral Change Specialist and has developed comprehensive fitness and exercise programs for health club & workplace wellness facilities. Andrew’s passion centers around user engagement and human behavior.