There are a few different reasons for that shaky feeling you may get during class or towards the end of a hard series. Trembling sensations while you’re in class is not something to worry about! If it persists consistently after you’re out of class, it’s worth consulting with your doctor.
Fatigue is often the cause of muscle shakes during exercise. To understand this, we need to
think about what happens inside the body, and the muscle when we exercise.
Muscles contract for us to be able to move, this begins with our nervous system sending
chemical messengers to the muscle which tells the muscle fibers (cells) to contract. When this happens, all of those muscle fibers in the muscle, or group of muscles don’t all contract at exactly the same time – some will work while the others rest and then alternate. The longer you are holding a position or repeating a movement, the more fatigued the muscle fibers become and the less efficient those muscle contractions are. These alternating resting and working periods of the muscle fibers can become a bit more haphazard and the result… shakes!
As with other forms of fatigue, the more you do the movement and the stronger the muscles and movement pattern, the longer it takes to fatigue – the less likely you’ll get the shakes! Just as the muscles get stronger, the nervous system, the chemical messengers and the muscle fibers get more efficient at this process (becoming more coordinated) and reducing your shakes!
If you think about this increase in efficiency, it also makes sense that with new exercises or patterns that you’ve never done before you may also get the shakes! While your body is learning how to coordinate this movement and send all those signals at the right times it can result in a similar shake to fatigue. With practice, your body will learn how to send those signals, and do the action at the right place, at the right time.
Lastly, dehydration can also affect muscle efficiency and exercise performance. Dehydration slows blood flow and your blood transports key nutrients and electrolytes which the body needs to exercise. While muscles aren’t receiving adequate blood flow (or nutrients) they are unable to work as efficiently; again resulting in the shakes. So don’t forget to hydrate!