Abstract
Better mobility improves older adult health, independence, and quality of life. Unfortunately, walking performance declines with advanced age, as older adults expend 10-25% more metabolic energy during walking compared to young adults. This age-related increase in metabolic energy expenditure is partly because older adults characteristically produce less ankle mechanics during walking compared to young adults, in turn compensating with increased hip mechanics (distal-to-proximal redistribution). Such mechanical changes may be attenuated using functional electrical stimulation (FES) to enhance ankle extensors. Stimulating ankle extensors during walking likely increases joint output and underlying muscle metabolism, with concomitant reductions in hip mechanics. If so, the attenuated distal-to-proximal redistribution in leg joint mechanics may offset the metabolic increase of stimulated muscles. PURPOSE: The purpose of this study was to determine whether FES to bilateral soleus muscles during walking attenuates the age-related distal-to-proximal redistribution in joint mechanics without increasing metabolic rate. METHODS: Twenty adults participated (10 young: 21 ± 2 yrs; 10 older: 77 ± 5 yrs). Participants walked on the treadmill at 1.25 m/s for familiarization, baseline, and FES trials. Each trial lasted 5-min with a 5-min seated rest preceding each trial. FES was applied over the soleus when the respective leg’s propulsive ground reaction force was > 10% body weight. We recorded ground reaction forces, motion capture data, and metabolic power during walking. We conducted a two-way repeated measures ANOVA to test the effects of walking trial and age group on dependent variables. RESULTS: There was no interaction between walking trial and age group on any dependent variable (all ≥ 0.129). Peak ankle moments and mechanical power were both greater during walking with FES vs. Baseline (FES: 1.37 ± 0.23 Nm/kg, Baseline: 1.32 ± 0.23 Nm/kg, p=0.004; FES: 2.36 ± 0.45 W/kg, Baseline: 2.17 ± 0.47 W/kg, p=0.004). Peak hip moments and power did not differ between FES and Baseline (FES: 0.66 ± 0.44 Nm/kg, Baseline: 0.70 ± 0.44 Nm/kg, p=0.208; FES: 0.92 ± 0.21 W/kg, Baseline: 0.95 ± 0.23 W/kg, p=0.138). Due to the greater stimulated ankle mechanical output and minimal changes to hip mechanics, walking with FES required 3% more net metabolic power vs. Baseline (FES: 3.11 ± 0.54 W/kg, Baseline: 3.01 ± 0.58 W/kg, p=0.04). CONCLUSION: FES increases ankle mechanics and metabolic rate during walking in young and older adults. Our findings support the notion that older adults can physically walk with more youthful ankle mechanics, but aging neural strategies contribute to proximal redistribution in joint mechanics. Follow-up studies will evaluate the potential for FES to increase the corticospinal excitability of older adult leg muscles and to restore more youthful walking mechanics.
Recommended Citation
Zhao, Ningzhen; Griffin, Lisa; and Beck, Owen N.
(2025)
"Functional Electrical Stimulation of the Soleus Increases Ankle Mechanics with a Modest Increase in Metabolic Rate during Walking in Young and Older Adults,"
International Journal of Exercise Science: Conference Proceedings: Vol. 2:
Iss.
17, Article 45.
Available at:
https://digitalcommons.wku.edu/ijesab/vol2/iss17/45
