Planks are one of the most simplistic but yet effective exercises that people can perform to help strengthen their core. Planks have become more and more popular with trainers and physiotherapists prescribing them for clients or patients so that they can develop a strong core to help their performance, decrease their low back pain or to improve their core stability so that they are less susceptible to injuries. Gone are the days where situps were the only option for core strengthening exercises, where athletes or gym goers would rep out hundreds of twisting sit ups with their gym partner holding onto their feet. Yes twisting situps, enough to make your lumbar discs wince in pain. Today there are many options to strengthen your core and a plank is up there as one of the more effective, efficient and less prone to causing injuries exercises for your core. Done correctly then they can be hugely beneficial to strengthen your core/abdominals. Of course like any exercise there is a right way to perform it and a suboptimal way, ways to ensure you get stronger and ways which may in fact leave you injured.
At its simplest form a plank is to suspend your body on your toes and forearms and keep your pelvis from touching the floor. In doing this you will be trying to work your abdominals. A plank is an isometric exercise meaning the abdominals are working to hold you in one position without the muscles shortening or lengthening. The benefits of an isometric exercise is that you do not take the joints to the extremes of their movements where the joints are more at risk. Therefore isometric exercises are good beginner exercises, especially where you lack joint position awareness or are rehabilitating from an injury and don’t want to create any irritations or pains.
One point to note is that repeated studies have shown that strength changes or increases in neuromuscular function (brain telling the muscles to work) occur in the range that is being trained. This is less of a concern for your core than say your biceps, because when you are training your core you are training your body to be strong in it’s ideal posture, you are training a neutral pelvis and a properly alignment spine, something you will be trying to maintain when you are exercising, working or going about your daily activities. Compared to your bicep which needs to be strong through it’s full range otherwise it will become susceptible to injuries. Training your core at the extremes could theoretically have benefits in helping you return to your correct posture, neutral spine or because you are just doing a specific exercise or movement that requires your spine to bend in a particular way. However this is risky and often can lead to injuries, and where you aren’t even strong in a good posture, why risk the injury as the stress on your lumbar discs, joints, ligaments aren’t worth the potential gains.
A major benefit of planking over other traditional core exercises is that planking works your abdominals with low compressive forces on your lumbar vertebrae. Forces of 1600N to 1800N are placed on the lumbar spine during a plank (Freeman et al. 2006). This may seem a lot, however traditional bent knee situps, the seemingly go to exercise for core strengthening has been shown to impose compressive forces on the lumbar spine of 3300N (Axler & McGill 1997).
While we mostly think of the plank as a core stability exercise we shouldn’t forget that it also trains your scapular stabilisers, neck muscles as well as contributing to your general conditioning. Below is a list of the most common technique faults we see while observing someone planking.
Technique fault number 1 – Dropping your hips
This fault is by far the most common fault we see with people planking and it isn’t just beginners who get this wrong. It is the saging of the pelvis towards the ground during a plank. This may happen when people become worried about cheating by having their hips too high, or their abdominals are failing and they are trying desperately to keep planking in the belief the longer they plank the better it is. Which is incorrect, if you no longer feel your abdominals working then you are quite possibly transferring your body weight from your abdominals onto the zygapophyseal or facet joints in your lower back. These joints will in fact support you during the plank if you ask them to, however this will contribute to lower back pains, cause wear and tear of your lower back and your abdominals won’t even be working properly anyways. Leading to the question if all you are doing is causing yourself discomfort and a potential future of lower back degeneration would you be better off just stopping the exercise, rest and then try again later?
Technique fault number 2 – Anterior Pelvic Tilt
Not to be confused with technique fault 1 dropping your hips. An anterior pelvic tilt during a plank will also cause irritation of the facet joints in your lower back. This will occur with a similar mechanism to dropping your hips, however it will present more as your pelvis rotates forwards, your lower back arches and your bum goes up into the air. Many people do a plank to help them avoid this position, therefore if you fatigue and move into this position then again it makes sense to stop.
Technique fault number 3 – The Harbour Bridge
Lifting your hips so high that you aren’t even working your core anyways. While this is less likely to lead to an injury, you are also doing less work. It’s a much easier position to maintain and while you will be doing some work, the work most likely won’t be done by your abdominals. So why do a core exercise that doesn’t work your core?
Technique fault number 4 – Not bracing through your shoulders
The plank will also work your shoulder stabilisers. These control the position of your scapula (shoulder blade) and your humeral head during movements. Having strong stabilisers goes a long way to maintaining the correct positioning of your shoulder blades and your humeral head (arm).
Technique fault number 5 – Pushing forwards with your arms and back with your toes.
By pushing out in opposite directions this means your core doesn’t have to work as hard to hold you off the ground. While this isn’t necessarily going to cause injury it does make the exercise easier and is often done by people trying to set new personal bests with their planking times.
Technique fault number 6 – Tucking your head under
This is most likely done to assist with a full-body crunch. This places a lot of strain on the neck, needless to say. While performing a plank, you don’t want to create a disc bulge in your neck.
Technique fault number 7 – Letting your neck go into hyperextension 
This just like letting your core sag will put strain on the facet joints in your neck. This additional pressure will be causing strain and excessive wear and tear.
Technique fault number 8 – Holding your breath 
Don’t hold your breath, use your core to brace not your diaphragm.
How should you plank?
When planking you should rest on your elbows and toes with your pelvis off the ground. You can even tuck your pelvis under a little to ensure you have good lower abdominal activation. The key is to hold this position until you feel your abdominals start to fail, once they fail and you start to sag then it’s time to stop, rest then reset and go again .
When should you stop a plank?
The number one reason you should stop your plank is when you feel pain. I’m not talking about your muscles feeling a little tired, feeling the burn as your abdominals cry out in pain, often this is more indicative of you loading your muscles correctly to enable strength changes to occur. I’m talking about a deep ache into your lower back, your neck or shoulders. An ache that often coincides with a change in your form. Maybe you go into anterior pelvic tilt, maybe your pelvis drops towards the floor or maybe your neck goes into hyperextension. It can be from any one of the above technique faults or many more that haven’t been included in this article. The thing to realise is why are you doing a plank in the first place? Are you doing planks to build up a strong core so that you have less lower back pain? If a plank is causing you more pain and aggravating your lower back then it’s time to rethink your plank and change your technique or difficulty of exercise that you have chosen.
Progressions of planks
While the majority of us think of a plank as someone on their toes and forearms it is important that we do a plank that is achievable for us and requires enough force to facilitate changes in your strength but also in a way that doesn’t cause injury. A safe way to think about this is if you cannot hold the plank for 20 seconds then you are quite possibly trying a variety that is too hard for you.
The simplest way to start planking is by doing a plank on your knees. This is a safe way to practice the correct technique. Often people will only require a few weeks of knee planks before their technique and strength improves enough to try a full plank, this time with a good technique. Once a full plank becomes too easy, an indication that you can progress to a harder exercise is that you can hold a plank with good form for over one minute. There is nothing wrong with holding your planks for two or more minutes, however if you wish you can now progress harder varieties. Examples of these would be planking with your arms on an unstable surface like an exercise ball, planking with your feet on an unstable surface like an exercise ball, planking while lifting one leg, planking during a dynamic movement. Remember when you are doing a pushup you are in fact doing a plank while you are doing the pushup. Therefore don’t let your good planking posture suffer in an effort to push out more pushups or your lower back may start paining again.
So in conclusion, a plank is a very effective exercise to perform and when done correctly there are many benefits to be had. However like all exercises there are it’s limitations, times when you will need to try a different exercise and times when you will need to rest.
References
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Freeman S, Karpowicz A, Gray J, McGill SM. 2006. Quantifying muscle patterns and spine load during various forms of the push-up. Medicine Science in Sports and Exercise. 38:570-77https://pubmed.ncbi.nlm.nih.gov/16540847/
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Axler C, McGill SM. 1997. Low back loads over a variety of abdominal exercises: searching for the safest abdominal challenge. Medicine Science Sports and Exercise. 29:804-11https://pubmed.ncbi.nlm.nih.gov/9219209/