Do you know that our muscle tissue is not made exclusively of muscle cells, but different kinds of cells? These cells communicate with each other by sending chemical signals. This communication is important for normal muscle movement and post-workout recovery. But, until now, no one really understood what the chemical signals that allowed the cells to communicate were.

In an article published in the journal Cell, scientists investigated the signals that kick start muscle changes after exercise in humans and mice. 

They found that succinate, a metabolite released by the muscle cells' mitochondria, triggers the communication network. During exercise, a mildly acidic environment is temporarily generated in the muscle cells. This acidic environment activates succinate, which is then transported out of the muscle cells as a messenger. 

Then scientists found that another protein (known as MCT1) acts as a portal in the muscle cell wall to channel succinate out of the muscle cells. But this protein portal is selective, and only allows activated succinate to pass through. 

In the same way that an antenna receives a signal only when tuned to a particular frequency, cells also need the right receiving proteins (called receptors) to catch the signals. The receptor for succinate, researchers discovered, is not produced by the muscle cells, but by the neighboring cells that support muscle growth and adaptation. Once succinate attaches to the receptor, the signal is complete, which further orchestrates action by many other genes and proteins to support muscle growth and adaptation after exercise.