17th Annual ECSS-Congress, Bruges 2012

Abstract details

Abstract-ID: 991
Session: [MO-PM18] Ageing: Balance and stability
Lecture room: /West
Date & time: 07.07.2017 / -
Title of the paper: POSTURAL STRATEGY ADOPTED DURING PROLONGED UPRIGHT STANDING DIFFERS BETWEEN YOUNG AND OLDER ADULTS
Authors: Booghs, C., Duchateau, J., Baudry, S.
Institution: Université Libre de Bruxelles
Department: Laboratory of Applied Biology
Country: Belgium
Abstract text Introduction: Upright standing requires the activation of the plantar flexor muscles to avoid forward falling (Loram et al. 2004). The extent of muscle activity needed to keep upright standing, that can increase with prolonged standing (Kuorinka et al. 1978) and ageing (Benguya et al. 2004), influences upright standing steadiness (Billot et al. 2010). Up to now, however, no study has compared the postural strategy used by young and older adults during prolonged unperturbed upright standing. Methods: Eighteen young (22.6 ± 2 yr, 8 women) and twenty older adults (68.3 ± 4 yr, 11 women) maintained an upright standing position on a foam mat positioned over a force platform during 30 min. Subjects were instructed to keep their feet in the same position and to avoid any intentional movement during this period. The mean position (CoPmean) and the path length (CoPpath) of the centre of pressure were computed for 1-min epoch during the first, 10th, 20th and last minute of the 30-min period. The surface electromyogram (EMG) of soleus and tibialis anterior was recorded for the same epochs, and normalized to the EMG measured during a maximal voluntary contraction (MVC). The changes in CoP and EMG parameters during the 30-min period were analysed within each age group. Results: During the 30-min period, young adults exhibited a progressive backward shift of the CoPmean that was significant at the 20th (0.6 ± 0.9 cm, p = 0.022) and 30th min (0.9 ± 1.1 cm, p<0.001), whereas no change (p>0.05) was observed in older adults. The CoPpath increased progressively and similarly during the 30-min period in young (+401.9 cm) and older (+255 cm) adults to reach statistical threshold in the 30th min (p<0.001). The soleus EMG did not change across time for young adults (p<0.05) whereas it increased at the 20th (+4.0 ± 4.6% MVC, p = 0.035) and 30th min (+5.3 ± 6.3% MVC, p=0.002) in older adults. For both groups, no change was observed for the tibialis anterior EMG (p>0.05). Discussion: The results indicate that young adults use of backward shift of the CoP position that likely minimizes the activity of the main anti-gravitational leg muscle (soleus). In contrast, older adults adopt a more secure position relative to the backward balance boundaries even though this strategy induces a progressive increase in soleus activity. Regardless of the strategy adopted, however, balance steadiness decreased progressively over time. Overall, this study suggests different postural strategies in young and older adults during prolonged upright standing. 1. Loram et al. (2004) J Physiol, 556.3,683-89 2. Kuorinka et al. (1978) Biomechanics, VI-B, 207-211 3. Benguya et al. (2004) J Gerontol, 59, 166-71 4. Billot et al. (2010) Eur J Appl Physiol, 109, 669-80
Topic: Motor Learning and Motor control
Keyword I: Ageing
Keyword II: balance
Keyword III: EMG