Surface electromyography (sEMG) and biofeedback serve a large purpose when it comes to analyzing muscle activity and teaching proper exercise form. First, by using sEMG, rehab providers can understand the activity of specific muscle groups during different exercises.(1) This provides tremendous benefit when it comes to selecting the best exercise for a targeted muscle or injury. Second, biofeedback provides a way to ensure patients are activating those target muscles correctly through proper muscle activation. Even if an exercise targets a specific muscle, if it is not performed correctly, the benefit is lost. This is where the use of mTrigger biofeedback becomes essential.
A recent study, found here, reviewed the current literature on core muscle activation during different core exercises used across the spectrum of rehab and fitness, from a traditional crunch to stability ball exercises and squats.(1) Through the use of sEMG, rehab providers are able to appreciate how different exercises more strongly engage different muscles and from there discern what the “best” core exercise may be. 
The core is made up of several muscle groups coming together to form what is often referred to as an “anatomical box” or “canister”. This is formed by the rectus abdominis, external obliques, internal obliques, erector spinae, multifidus, and quadratus lumborum.(1) The diaphragm and pelvic floor create the top and bottom of the box/canister but were not analyzed in this study.(1)
Core exercises are used in the treatment of several different conditions. They can help decrease the risk of musculoskeletal disorders, hip imbalances, muscle atrophy, or postural deficiencies just to name a few.(1) Furthermore, the core is the only thing connecting the upper and lower extremities. It plays a huge role in the transmission of forces across the kinetic chain to the extremities.(1) Therefore, the use of core exercises are merited in rehabilitation and training programs across the continuum from injuries to sports performance.(1)
Breaking Down the Findings
Rectus Abdominus
For the rectus abdominis, the highest EMG was found when performing the following exercises: a sit up, v-sit, front plank, side plank, plank roll out, suspended front plank, back squat, and an unstable Bulgarian split squat.(1)
Knowing the highest EMG exercises for the rectus abdominis is only step one. Making sure the exercise is performed correctly is a bigger obstacle. This is where mTrigger biofeedback comes in. Using biofeedback during exercises helps patients to understand and achieve proper exercise form. In this v-sit exercise, mTrigger biofeedback on the rectus abdominis helps cue the patient on proper form.
Internal Obliques
The highest EMG for the internal obliques was observed during the following exercises: curl up, front plank, front plank on Swiss Ball with hip extension, stir-the-pot (similar to a palloff press), kettle bell swing, and a unilateral Bulgarian split squat.(1)
External Obliques
For the external obliques, the highest EMG activity was demonstrated during the following exercises: curl up, front plank, front plank on Swiss Ball with hip extension, stir-the-pot, Bulgarian split squat, standing unilateral dumbbell press.(1)
* This is an excellent reminder that even though a Bulgarian Split Squat is often used for quad strengthening, the core plays a very active and important role during the execution of this exercise.
Erector Spinae
EMG activity was highest for the erector spinae muscles during the following exercises: back extensions, suspended bridge, deadlift, hip-thrust, and back squat.(1)
Lumbar Multifidus
For the lumbar multifidus, EMG activity showed the highest activation level during these exercises: prone trunk extension, bridge, bird dog, front plank on Swiss ball with hip extension, bent over row, deadlift, and squat.(1)
Transverse Abdominis
Finally, the highest EMG activity of the transverse abdominis was found during these exercises: curl up and bird dogs.(1)
An added benefit of sEMG is the insight it provides into muscle activation during multi-joint movements. Previously, core muscles were often targeted with isolated exercises such as sit ups and curl ups. However, investigating the role of unstable surfaces and multi-joint movements on the core has shed light on the benefit of other exercises. In fact, of all the exercises tested, the highest activity of the rectus abdominis, external obliques, and erector spinae was found during free weight exercises such as squats, deadlifts, rows, and unilateral press.(1) This highlights the importance of using a variety of exercises to target and train the core.
Summary
sEMG along with biofeedback can provide immense benefit when trying to find the best exercise to target a specific muscle group. It also provide patients with a means to make sure they are performing the exercise correctly. Make sure you are using sEMG to get most out of your exercise programing, and mTrigger biofeedback to make sure your patients are getting the most out of every rep.
Biofeedback for the Pelvic Floor
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More on the Core
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References
1. Oliva-Lozano JM, Muyor JM. Core Muscle Activity during Physical Fitness Exercises: A Systematic Review. Int J Environ Res Public Health. 2020;17(12):1-42. doi:10.3390/IJERPH17124306
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