We are going to delve into one of the characteristics that we study in our reports: shoelaces. To this day the origin of the shoelaces is not known with certainty. However, there are theories about how they are formed.
A few years ago it was believed that lactate crystallization was responsible for causing shoelaces. The lactate crystals would act like small needles that would prick the muscles causing that feeling of soreness.
But let's start at the beginning, what is lactate?
To understand the theory of lactate crystallization we have to know that metabolism can choose the aerobic or anaerobic route depending on whether or not the metabolism has oxygen.
In metabolism, a large number of chemical reactions take place in which some molecules are used to originate others. It is a really complex mechanism. Among all that complexity, we are only going to stay with the name of a molecule, the lactic acid. Lactic acid or lactate originates through the anaerobic route as a product of the breakdown of glycogen (energy stores).
And why do we only feel them when we do a lot of sport? This is where the oxygen arrangement comes into play. Lactic acid only occurs when oxygen is not available for metabolism, that is, when the supply of oxygen to the muscles decreases as a result of intense exercise.
Recently this theory has been discarded since there is an extremely rare disease, McArdle's disease, which is characterized by the inability to degrade glycogen (obtaining lactate from glycogen). People with this disease experience soreness in the same way that we do despite not being able to degrade glycogen.
The theory most supported by the scientific community defends that shoelaces could be caused by muscle pain and inflammation suffered as a result of small micro-tears of muscle fibers. In muscle cells we have a protein called creatine kinase that is released into the blood when muscle damage occurs. This new theory is supported by studies in which they associate high levels of creatine kinase in the blood with stiffness and muscle damage.