Asymmetry exists in about 70% of the population in a civilized society. There is a longer functioning limb that becomes dominant and is largely responsible for unilateral symptoms & complaints.

Although the goal of care should not be symmetry, it should be treated if there is a positive TIP Sign:

Article The Inclined Posture (TIP): A New Clinical Entity

Dennis Shavelson

Thank you,

However I'm asking specifically about asymmetry in EMG measures, regardless of injuries.

Dear Uri,

I think the following manuscript is helpful.

https://www.sciencedirect.com/science/article/abs/pii/S1360859217303200

Thank you AmirAli Jafarnezhadgero

Your welcome. Also, the following link could be helpful:

https://www.sciencedirect.com/science/article/abs/pii/S1360859217300943

Uri Gottlieb

As I do not work much with EMG's, possibly I can be of assistance as I can apply my experience with lower extremity kinetics, kinematics and kinesiology to offer that the most important muscle engines to monitor are posterior tibial and peroneus longus for your study. These are the primary balance and stabilizing muscle engines of the feet.

Too often, Gastrocs, Anterior tibial and Soleus are monitored. Unfortunately, these muscle engines are compensatory and would be late to tell tales and be a good location for treatment and monitoring.

This may be relevant to some people who were interested in this question.

Surprisingly test-retest reliability of EMG signals are not well studied. Also interesting is that the researchers report EMG signals higher than 100%MVIC (especially for larger muscles) - what makes me question if this is the appropriate method to normalize EMG data.

Conference Paper BETWEEN-DAY REPEATABILITY OF LOWER LIMB MUSCLES DURING RUNNING