Monotonous, long-lasting and low-intensity muscle contractions are considered a relevant physical risk factor for work-related muscle pain. There is some evidence that parafunction (bruxism) whilst awake is characterized by low-intensity and long-lasting muscle activity and that the masticatory muscles behave like the trapezius muscle during this type of contractions. Therefore, parafunction whilst awake has the potential but is not a sufficient cause to elicit masticatory muscle pain. This review briefly describes why parafunction whilst awake cannot cause by itself masticatory muscle pain by explaining analogies with work-related muscle pain, a condition that has been studied in great detail. Palabras clave: masticatory muscle pain, muscle pain, myofascial pain, bruxismus whilst awake, wake-time bruxism, bruxism