Simplistically, a “plank” can be defined as follows:
“An isometric exercise for the core. It is performed by lying flat on the ground and bringing yourself up on your toes and forearms. The objective of this exercise is to hold the position without movement for as long as possible.”
In this author’s opinion, a broader and more useful definition of a plank exercise might be:
“An exercise where the torso is horizontally aligned (prone, supine, or sideways), and held rigid above the ground with the spine in its neutral curves with two to four support points that typically involve at least one arm and one leg.”
Plank exercises have gained recognition as an effective way to stabilize the core through sustained isometric holds (McGill, 2009). Prone planks have been shown to activate superficial abdominal musculature such as the rectus abdominis as well as the internal and external obliques (Schoffstall, Titcomb & Kilbourne, 2010). As a result, the plank is one way to increase strength or hypertrophy of the superficial abdominal muscles in the clients or athletes you train. Studies indicate that endurance in standard plank exercises – performed with the client resting on the forearms and feet – may not directly transfer to movement performance like jumping, running and throwing (Shinkle, Nesser, Demchak & McMannus, 2012). Nevertheless, an extended plank – performed with the client resting on hands and feet, hands placed on the ground with the shoulder joint near full flexion – may develop the ability of the abdominal musculature to stabilize the spine against the extension torques created from the pull of the latissimus dorsi and psoas during, for example, a volleyball jump or spike (Chek, n.d.). Further, hypertrophy of the rectus abdominis and internal and external obliques as a result of performing plank exercises, may – together with optimal bracing – help protect the internal organs of an athlete participating in combat sports that involves strikes to the abdominal region.
Significant transfer from plank exercises to activities of daily living like lifting should not be expected. Planks require the abdominal muscles to work in an “anti-extension” role. During everyday lifting the opposite function – anti-flexion – is required. Strength gained in extended plank exercise, however, may be helpful in tasks such as placing or removing bins or other items from high places.
Hypertrophy Parameters for Isometric Training
While all levels of clients may perform plank exercise sets up to several minutes in duration, the advanced client may use plank exercises in combination with other abdominal exercises in an attempt to induce hypertrophy in the superficial abdominal musculature i.e., the rectus abdominis.
It is not uncommon for an intermediate client to be able to hold a standard plank for two to three minutes, which is equivalent to 20-40% MVC (AAstrand & Rodahl, 1986). Maximal voluntary contraction (MVC) is the force produced during a maximal isometric contraction. Thus, it could be said that the MVC is an isometric 1RM (1 repetition maximum). This may be too low an intensity, however, to stimulate hypertrophy. Scientific investigation points to contractions of 6-30 seconds in duration as an effective duration to induce hypertrophy with isometric training; Twelve 6-second isometric muscle actions at 100% MVC result in significantly greater hypertrophy than four 30-second muscle actions at 60% MVC. However, four 30-second isometric muscle actions can also result in hypertrophy (Fleck & Kraemer, 2004).
Based on the above, to expect a hypertrophy response of the abdominal musculature from plank exercises, the selected exercise variation should result in significant to complete fatigue within 6 to 30 seconds.
Four Ways to Increase the Intensity of Planks
So, how do you increase the intensity of your client's planks to maximize results and reach isometric fatigue within 6 to 30 seconds?
The four techniques described below are reserved for the client with a pain-free back, who has extensive experience with unloaded, basic plank exercises and can maintain a neutral spine at all times.
These techniques are highly challenging and require complete control of the core. Introduce these techniques conservatively by using a little lower intensity than you think the client can handle, then gradually increase the training intensity based on the client's progress.
1. Use external load.
Have the client wear a weighted vest or place weight plates on the client’s back. The client may initially use a load that allows him or her to hold the plank position for 10 to 15 seconds, with the ultimate goal of holding the position for up to 30 seconds. When the client can hold the position for 30 seconds, the load is increased by 5 to 10 pounds. When first attempting to hold a plank with external load added, a client may be able to handle only 20 to 40 pounds. The highly advanced client, however, may be able to work up to 150 to 200 pounds with months and even years of dedicated training.
2. Lift one arm and/or one leg off the floor.
Single-leg abdominal bridge exercises produce greater muscle activation than the general abdominal bridge exercise (Oliver, Stone & Plummer, 2010). This strategy includes more dynamic plank variations, where the support points are alternated throughout the set. For example, changing support points between the hands and the forearms means that the arms are moving, but the abdominal muscles are still contracting isometrically.
3. Increase the distance between the arms and the feet.
To increase the distance between the arms and the feet, the client can rest on the elbows, which are placed slightly in front of the shoulder joint to form a “scope” with the hands – the so-called Sniper Plank. There are many intermediate variations of this strategy; placing the hands as an extension of the body – 1 or 2 inches short of full elbow extension – is the most challenging progression.
Practical experience makes it clear that planks with the hands extended in front of the body are more difficult than planks with the forearms placed more or less UNDER the body. From a biomechanical viewpoint, the increased intensity of the “extended” plank can be explained by the fact that gravity affects the body through the center of gravity. In a neutral position, the body’s center of gravity is at the S2-level (second sacral vertebra). With the arms placed in shoulder flexion, the center of gravity is moved slightly towards the head from its normal position the S2-level. Further, gravity tends to extend the spine and bring the body towards the floor with the feet and the hands as axis of rotation. The horizontal distance from the center of gravity to both the hands and the feet are greatly increased compared to the regular plank. Thus, gravity is creating a much greater torque that must be neutralized by the body’s muscles. Since the shoulder joint is strongly involved in the “extended” plank, neuronal energy may be dispersed between the shoulder and the core making the extended plank more difficult from the client’s perspective.
Of course, options 2 and 3 can also be combined to create a plank exercise for the highly advanced client.
4. Use static friction.
Static friction can be applied to any plank exercise by attempting to “pull the hands and feet towards each other.” If the contact points between feet and the floor create sufficient static friction, the movement is inhibited and a strong abdominal contraction is achieved.
Static Friction in Action
One example of how you can cue a client to apply static friction to a simple plank exercise called the Wide Horse Stance:
Place your hands and knees on the floor, with your knees as far apart as possible. The spine should maintain its natural curves (in other words, you’ll be in the neutral spine position). Grab the floor with your fingers and “screw your hands into the floor.” Make sure that you don’t sag. Instead, push your shoulders away from your ears.
The anterior oblique system connects one shoulder to the contralateral hip and includes the external obliques on one side and the internal obliques on the other side of the body (Chek, n.d.). To train the muscles of anterior oblique system (running from the right shoulder to the left hip, lift your LEFT hand and RIGHT knee 1 inch off the floor. Just by lifting your left hand and right knee off the floor, you will feel and significant contraction of your oblique abdominal muscles. Now the fun begins! “Curl the floor” by trying to move your RIGHT hand and LEFT knee toward each other with maximal effort. To achieve a good sense of curling the floor, the athlete/client must place most of the weight on the hand. The supporting elbow can be straight or bent slightly. When contact with the floor supplies sufficient friction, neither the hand nor the knee moves as the client tries to “curl the floor.” Instead, the result is a strong isometric contraction.
The technique of static friction can be applied to any plank exercise, but works best if the arms are placed under or only slightly in front of the body.
Adding Planks to Client Programs
Your personal training clients’ preferences, skills and fitness level will determine how you increase the intensity of plank exercises in their training programs. You could include as many as four planks in a fitness program, covering the sagittal plane (prone), the frontal plane, the transversal plane, and the sagittal plane (supine). Unless one very long set is used, planks will typically be done in multiple sets. For example, you could ask your clients to complete four sets of 30 seconds each.
Plank exercises are often placed towards the end of a program because they are less neurologically demanding than other exercises. At least one periodization method, however, sequences exercises by the priority principle and places planks first in the program in the early phases of the macro cycle in order to train these core exercises in the rested state, in a phase of the macro cycle where the development of stability and core strength has top priority (Jensen, 2010).
The plank has been a staple of fitness programming for a long time. Nevertheless, without an understanding of the hypertrophy parameters of isometric training, it can be difficult to effectively progress the movement to improve strength and function. Using any of the four specific strategies presented here, you can ramp up the intensity of your clients' planks to increase core stability and hypertrophy, while also adding new challenges to your training sessions.
- AAstrand, P.O., & Rodahl, K. (1986). Neuromuscular Function. Textbook of Work Physiology (3rd ed.). Columbus, OH: McGraw-Hill.
- Chek, P. (n.d.). The Outer Unit. Retrieved from http://www.coachr.org/outer.htm.
- Chek, P. (n.d). What is Functional Stability? Functional Stability Seminar. Seminar Manual. Retrieved from www.chekinstitute.com.
- Fleck, S., & Kraemer, W. (2004). Types of Strength Training. Designing Resistance Training Programs (3rd ed.). Champaign, IL: Human Kinetics.
- Jensen, K. (2010). In The Flexible Periodization Method the priority system of exercise supersedes that of decreasing neural demand. The Flexible Periodization Method. The Write Fit.
- McGill, S. (2009). Ultimate Back Fitness and Performance (4th ed.). Waterloo, ON: Wabuno Publishers.
- Oliver, G.D., Stone, A.J., & Plummer, H. (2010, Nov). Electromyographic examination of selected muscle activation during isometric core exercises. Clinical Journal of Sports Medicine, 20(6):452-7.
- Schoffstall, J.E., Titcomb, D.A., & Kilbourne, B.F. (2010, Dec). Electromyographic response of the abdominal musculature to varying abdominal exercises. Journal of Strength & Conditioning Research, 24(12):3422-6.
- Shinkle, J., Nesser, T.W., Demchak, T.J., & McMannus, D.M. (2012, Feb). Effect of core strength on the measure of power in the extremities. Journal of Strength and Conditioning Research, 26(2): 373–380.