51 3 Discussion The aim of this study was to determine the reliability of the MAT for patients with HNC and healthy controls. The results showed a good reliability in patients with HNC and a moderate reliability in healthy controls. In addition, healthy controls showed a higher SEM and SDC in comparison to patients with HNC, indicating a greater difference between test and retest. In patients with HNC, an ICC of 0.886 was found, indicating a good reliability. In comparison, previous research tested the reproducibility in children with cerebral palsy and healthy children,15 in which a moderate ICC of 0.69 was found. The higher ICC in patients with HNC in comparison to children indicates that this MAT is more suitable to use in (older) patients with HNC. In comparison, a moderate correlation between test and retest was found for healthy controls (ICC=0.525), indicating that this MAT is less suitable for healthy subjects. Healthy controls displayed a better retest result in comparison to the test result, indicating a learning effect (Table 2). This effect was not visible in patients with HNC. In previous research, no learning effect or apparent optimization of jaw muscle activity was induced by a 1-hour training task.28 Therefore it is unlikely that the second MAT shows a better result caused by a learning effect in masticatory performance after just 20 chewing strokes and with at least half an hour time difference. The variability between test and retest can be influenced by natural individual variability, unfamiliarity with the wax tablet, or adjustment to the taste and structure.4,15 In addition, healthy controls have no problems regarding masticatory performance and oral functioning. They need less monitoring and regulating of their movements in comparison to patients, because their movements occur implicitly,29 which may lead to more variation in chewing outcome. Patients are more aware of their chewing ability, due to for example pain or reduced oral sensibility, and therefore perform their movements more consciously (explicitly).30 Healthy controls can show more variation in their chewing pattern, whereas patients already reached a ceiling effect. Significant differences were found between patients with HNC and healthy controls for age and sex; significantly more people were male in the patient group, with a higher age in comparison to the healthy control group. Age had a significant effect on MAT outcome. Previous research showed that age has a negative influence on mastication, because total body muscle mass and muscle mechanical performance decrease, indicating that elderly persons need more time and more chewing strokes before food can be safely swallowed.31 In addition, younger people may automatically chew food without additional effort for monitoring or regulating their movement.29 Older people have a more distinct experience in chewing, where they monitor their oral status continually. This can also be caused by