Author(s): THEODOSIADOU, A., SAHINIS, C., PAPAVASILEIOU, A., FABRE, M., LAPOLE, T., PATIKAS, D.A., AMIRIDIS, I.G., BAUDRY, S., Institution: UNIVERSITÉ LIBRE DE BRUXELLES, Country: BELGIUM, Abstract-ID: 1599

INTRODUCTION:
Sense of position (SoP), one component of proprioception, is assessed with joint position reproduction (JPR) tests consisting of reproducing a reference joint position with the ipsilateral or contralateral limb. Previous research indicates divergent age effect on SoP, with studies revealing an inverted U-shaped curve in SoP acuity from childhood to senescence, and others reporting no age effect (1,2,3). These divergent results could partially reflect the variety of JPR protocols (ipsi vs. contralateral, amplitude, direction). This study investigated the effect of age on ankle SoP during ipsi (IPSI) and contralateral (CONTR) JPR tests with two amplitudes in dorsiflexion and one in plantarflexion direction.
METHODS:
One hundred sixty individuals (3-92 yr) were distributed into 6 groups: Before-Puberty (BP; 3–14 yr), After-Puberty (AP; 14–17 yr), both groups determined based on a maturity test, Young (Y; 20–39 yr), Middle-aged (M; 40–59 yr), Young-Old (YO; 60–75 yrs) and Old-Old (OO; >76 yr) adults. The IPSI test consisted of reproducing a predetermined target ankle position with the same limb, passively presented to the participant for a few seconds (passive-active modality). The CONTR test consisted of reproducing with one limb a target ankle position passively-hold by the contralateral limb (passive-active). Both IPSI and CONTR were performed blind-folded, to a constant dorsiflexion target position (5° dorsiflexion) from 5° (DF10) or 20° (DF25) plantarflexion position (dorsiflexion direction), and to a 10° plantarflexion target position from a 5° (PF15) dorsiflexion position (0°=90° ankle joint; plantarflexion direction). Error was measured as the absolute (absolute error, AE) and the relative (signed error, SE) showling the difference between the target position and the position reproduced by the participant.
RESULTS:
In IPSI, no significant difference was observed for AE (p>0.05) and SE (p>0.05) between groups, regardless of the direction and amplitude. In CONTR, similar results were obtained for AE (p>0.05) but SE showed that BP group underestimated the target position compared with Y, YO, OO, and YO and OO overestimated the target position compared with M group for DF25 (p<0.001) and DF10 (p<0.001). In contrast, PF15 did not revealed any age difference in SE.
CONCLUSION:
The lack of age difference in AE suggests that the overall SoP was not influenced by age. However, the differences in SE for dorsiflexion indicates opposite effects between childhood and advancing ages, with children under-estimating and older adults over-estimating the target position compared with young and middle-aged adults. This age effect only observed for CONTR suggests that online processing of proprioceptive inputs from the two limbs changes with age, which may rely on inter-hemispheric transmission of the proprioceptive signal.

References
1. Dunn et al. Am J Occup Ther 69, 1-9, 2015
2. Hu et al. Motor Control 27, 596–615, 2023
3. Yang et al. J Sport Health Sci 8, 548–554, 2019