Page 165 - Functional impairment and cues for rehabilitation of head and neck cancer patients -

of the muscle mediated by osmosis increasing the amount of water molecules and therefore the T2-value (45). Since muscles activated with overload will strengthen, we may assume that exercises with the SEA results in strengthening of essential swallowing muscles (46).
Although increased T2-values can be interpreted as evidence for muscle activation, it is unknown what absolute increase in T2-value represents clinically meaningful muscle exertion expected to yield improvements in strength. Effects of the exercises on muscle strength should therefore further be objectified with other measuring instruments, such as the swallow muscle measuring system developed by Kraaijenga et al. (18). This instrument consists of a dynamometer mounted on the chin rest of an adapted ophthalmic examination frame enabling measurement of the effects of the CTAR+, and JOAR+ exercises. Additionally, the Iowa Oral Performance Instrument (IOPI) could be used to measure tongue strength, although intrinsic nor extrinsic tongue muscles seemed activated during exercises in this study (47).
Higher loading of individual muscles is more effective to quickly gain strength of those muscles, compared to lower loading. For patients with swallowing muscle strength below the minimum required strength to allow effective swallowing, this could translate into more effective rehabilitation on the level of muscle strength. It is, however, uncertain whether this will also lead to more effective swallowing rehabilitation in terms of clinical outcomes, as effective swallowing is not only dependent on the strength of individual muscles, but also, among other things, on intermuscular coordination. To demonstrate the added value of the SEA compared to conventional exercises, a randomized controlled trial is needed.
Limitations
Given the explorative nature of this study, the results presented have to be interpreted as inductive rather than conclusive. The T2-value is expected to increase substantially in activated muscles, and only a limited number of subjects was required for this study to indicate an effect with adequate precision. Nevertheless, the small sample size is still a limitation of this study as there is always a risk of atypical sampling. Also, again given this small sample size and the explorative nature of the study we refrained from correcting for multiple testing. However, our findings are largely consistent with expectations based on physiological understanding, which increases our confidence in the results. Still, we noted that in some muscles, the T2- value was lower after exercise, possibly due to variation between and within individuals or the measurements not being taken at the exact same position. Also, the used segmentation method included tissues other than muscle, such as blood vessels and fat. Therefore, concentration of non-muscular tissue might have influenced the susceptibility of T2-value increase after exercise. Another limitation is the supine position in which the exercises were performed in the scanner. Except for the Shaker, for which this is the prescribed position, the other exercises are supposed to be performed in upright position. The somewhat unnatural supine position may have caused the subjects to underperform, in which case effect sizes may have been underestimated.
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Muscle activation during swallowing exercises
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