Walk the Plank, Matey.
Today I want to discuss a pretty common exercise: the plank. It’s a pretty fair assumption that the plank has become one of the most prevalent core exercises on the market. Folks like it because it’s fairly easy to modify (i.e. elevating your shoulders) and tracking your progress couldn’t be more simple (:30, :40, :50, etc.).
First of all, let’s preface that ‘the core’ is a lot more than just your abs. You have to think low back, abs, glutes, hip flexors and even into the mid back.
Men’s Fitness Magazine on the plank: “We don’t know too many people who get excited about doing planks. Generally, you stare down your timer as the minute (or more) runs down. And while we’re being candid, let’s just come out and say it: Planks destroy your abs. For a pretty basic isometric exercise, planks strengthen your entire body—they make your core pop, strengthen your lower back, and build your shoulders.”
So, Men’s Fitness isn’t wrong, but they’re not necessarily right either. A plank builds endurance and tone through most of the muscles they listed however raw strength is pretty difficult to develop. Why is that though?
The answer lies within surface electromyography. If you missed my glutes, golf and electricity article, I’ll explain EMG here for a second. Muscles have a certain maximal force they can produce and EMG measures their percent activation. So, for example, if muscle can produce 200 pounds of force and a certain movement pattern you’re performing exhibits an average of 150 pounds of force, you’re at 75% muscle activity or 75% mean EMG, to get science-y.
So, what’s the EMG activity for planks? How hard are we working the muscles? I looked at research from Snarr et al., Maeo et al. and some self investigation by a pretty well known exercise physiologist, Brett Cotnreras and averaged their numbers to get a somewhat ‘safe’ global number. The three muscle groups that were investigated were the rectus abdominus (responsible for ‘curling’ the trunk, as in sit-ups), external obliques (responsible for left to right leaning in the trunk) and erector spinae (responsible for extending your back, or leaning backwards).
The average activation during a normal plank in the rectus abdominus was 30%, eternal obliques at 30% and erector spinae at 6%. So if we’re talking about a low level activation in every muscle group, why is it so hard! Well probably the same reason it’s hard to hold a ten-pound weight out in front of you with one hand: it’s constant activation. Holding 30% effort for 30 seconds can be more difficult than 90% for one second (depending on your training status).
Therefore, when we look at the ability of a plank to develop true strength in the core, this might be a slight misnomer. Your muscles become more efficient, gain more tone and increase their endurance. However, a 60 second plank everyday wouldn’t really help a soccer player who wants to increase the strength of power of his abs in order to perform longer throw-ins.
Instead, that soccer player could perform 60 seconds of sit ups that require ~45% activation, experience a larger amount of stress to the system and better adaptations.
Ok, so maybe you’re bent on incorporating planks into your program. They are extremely effective for practicing abdominal bracing however the stress on the core during a heavy lift dwarfs the stress experienced during a plank. Alright, let’s cut to the chase and simplify all of this information.
Planks don’t build raw strength in the core as you would suspect however they are useful for improving the endurance of the system. Planks are hard because it’s a small amount of activation over a long period of time. True overload is introduced to the core when we lift heavy things (squat, deadlift, hip thrusts, etc).
Here’s a take home point: incorporating variations to the plank is the best way to increase the stress placed on the core. I’ve incorporated a video with different variations on the plank that will really blow up your core and provide you with more bang for your buck (i.e. dynamic movements for stability through movement).
I hope this ‘round-about’ blog helped you understand that the plank is a great starting point but progression has to be the goal in order to experience significant strength goals.
- Maeo S, Takahashi T, Takai Y, Kanehisa H. Trunk muscle activities during abdominal bracing: comparison among muscles and exercises. J Sports Sci Med. 2013;12(3):467-474.
- Snarr RL, Esco MR. Electromyographical comparison of plank variations performed with and without instability devices. J Strength Cond Res. 2014;28(11):3298-3305.