The medial and lateral gastrocnemius muscles are two key calf muscles that play an important role in walking, cycling, standing balance, and many other movement activities. They have historically been considered as two heads of the same muscle and as having the same functional role and behaviour.
In this perspective article, Francois Hug and Jeroen Aeles provide an overview of published evidence highlighting the difference between the two muscles from an anatomical, neural, biomechanical, and functional perspective.
In addition, they performed complimentary analyses on previously published data to quantify the impact of interchanging data between these muscles. This is commonly done for example when ultrasound images are collected on one of the two muscles and EMG signals are collected on the other muscles. They show this leads to large errors in muscle force estimations.
They propose that the biomechanics and wider scientific and clinical communities would benefit from considering these two muscles as two synergistic yet different muscles with different behaviours.
The article is freely available for 50 days at Journal of Biomechanics through the link below.
Synergistic yet different: Rethinking the gastrocnemii as two functionally distinct muscles.