Background: Older adults use different ankle muscle activation patterns during difficult static balance conditions. It has been suggested that this is related to a decline in proprioception with age, resulting in reduced postural balance. However, the association between proprioception and ankle muscle activity during quiet standing has not been directly assessed.
Objects: This study aimed to investigate the effects of age and sensory condition on ankle muscle activity and the association between ankle proprioception and ankle muscle activity. Methods: We recruited 10 young women and 9 older women. Ankle proprioception was evaluated using joint position sense (JPS) and force sense (FS) divided by dorsiflexion and plantarflexion. The electromyographic activity of the tibialis anterior (TA) and gastrocnemius (GCM) muscles was collected during quiet standing.
Results: Older women activated GCM muscle more than young during quiet standing and when performing difficult tasks. Older women had more errors in JPS dorsiflexion and FS plantarflexion than did young. The GCM muscle activity is related to JPS dorsiflexion and FS plantarflexion.
Conclusion: Lower proprioception of the GCM with age leads to increased muscle activity, resulting in reduced postural balance. There was no difference in TA proprioception or muscle activity among older women with frequent physical activity.

INTRODUCTION
MATERIALS AND METHODS
    1. Participants
    2. Procedure
    3. Statistical Analysis
RESULTS
    1. Ankle Muscle Activities
    2. Age Differences in Ankle Proprioception
    3. Association Between Proprioception and AnkleMuscle Activities
DISCUSSION
CONCLUSIONS
FUNDING
ACKNOWLEDGEMENTS
CONFLICTS OF INTEREST
AUTHOR CONTRIBUTIONS
ORCID
REFERENCES

• Seo-hyun Kim(Department of Physical Therapy, The Graduate School, Yonsei University)
• Chung-hwi Yi(Department of Physical Therapy, College of Software and Digital Healthcare Convergence, Yonsei University, Wonju, Korea) Corresponding Author
• Gyu-hyun Han(Department of Physical Therapy, The Graduate School, Yonsei University)
• Su-bin Kim(Department of Physical Therapy, The Graduate School, Yonsei University)