Aging and Bimanual Effects on Finger Center of Pressure during Precision Grip: Different Strategies for Spatial Stability.

The purpose of this study was to examine aging and bimanual effects on finger spatial stability during precision grip. Twenty-one older and 21 younger adults performed precision grip tasks consisting of a single task (grip and lift an object with the thumb and index finger) and a dual task (the grip-lifting task with one hand and a peg board task with the other hand). The center of pressure (COP) trajectory and the grip force were evaluated using a pressure sensor with a high spatial resolution. In the COP trajectory, the main effects of age for the thumb (F1,140 = 46.17, p < 0.01) and index finger (F1,140 = 22.14, p < 0.01) and task difficulty for the thumb (F1,140 = 6.47, p = 0.01) were significant based on ANCOVA. The COP trajectory was statistically decreased in the older adults. The COP trajectory was also decreased in the dual task, regardless of age. The results suggest the existence of a safety strategy to prioritize the spatial stability in the elderly group and in the dual task. This study provides new insights into the interpretation of the COP trajectory.

Effects of varying fixed lingual apex positions on tongue pressure during straw drinking.

We investigated the impact of tongue-thrusting on lingual pressure during fluid intake with a straw. In this study, 12 healthy young dentate individuals (two women and 10 men; 19-33 years) were instructed to drink 15 mL of water with a regular drinking straw at 37 °C, when indicated by the investigator. Participants drank after adjusting tongue position to one of the following patterns: (i) Holding the tip of the straw between the lips (Normal Position: NP), (ii) Sticking out the tongue to the vermilion zone of the lower lip and inserting the straw 1 cm past the front teeth (Tongue-thrusting Position: TP). Five recordings were conducted for each participant in a randomised order. To measure tongue pressure during swallowing, a specially designed 0.1-mm thick sensor sheet (Nitta, Osaka, Japan) with a tactile system for measurement of pressure distribution (I-SCAN; Nitta) was used. Duration, maximal magnitude and integrated value of tongue pressure were analysed based on the wave of tongue pressure recorded while water was swallowed. Magnitude, duration and integrated value of tongue pressure were significantly lower in TP than in NP at the median line (Ch1-3). Magnitude and integrated value of tongue pressure at the lateral part of the tongue (Ch5) were significantly lower in TP than in NP. When duration, maximal magnitude and integrated values were compared by channel, no significant differences were observed in NP, but a significant difference was found between Ch3 and the lateral areas Ch4/Ch 5 in TP. When the tongue was thrust forward, movement dynamics of the entire tongue changed and influenced contact between the tongue and palate during liquid intake with a straw. The impact was noticeably weaker on the median line than in lateral areas.