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  • Title: Modulation of the Hoffmann reflex in soleus and medial gastrocnemius during stair ascent and descent in young and older adults.
    Author: Johannsson J, Duchateau J, Baudry S.
    Journal: Gait Posture; 2019 Feb; 68():115-121. PubMed ID: 30472523.
    Abstract:
    BACKGROUND: The Hoffmann (H) reflex can provide relevant information on spinal control of leg muscles during locomotor tasks in young and older adults. RESEARCH QUESTION: Is the H reflex in the leg muscles differently modulated during stair gait in young and older adults? METHOD: The H reflex in soleus (SOL) and medial gastrocnemius (MG) (normalized to the maximal M-wave amplitude obtained during upright standing; Mmax) was recorded in 19 young and 18 older adults during upright standing, and stair ascent and descent of a 3-step staircase. RESULTS: H-reflex amplitude during upright standing was greater in young than older adults for SOL (48% vs. 26% Mmax; p = 0.001) and MG (23% vs. 14% Mmax; p = 0.02). When data were averaged across groups during stair ascent, H-reflex amplitude in SOL increased from 15% Mmax at the beginning of the stance phase to 29% Mmax at mid-stance, then decreased to be 4% Mmax in the swing phase. During stair descent, H-reflex amplitude was maximal (20% Mmax) at the beginning of the stance phase, decreased to 5% Mmax at the end of stance, and increased to 11% Mmax in the swing phase. Similar adjustments were observed for the H reflex in MG for both ascent and descent. H-reflex modulation during gait cycle (relative to upright standing) is less pronounced in older adults (p < 0.05). However, no difference was observed between subgroups of young and older adults matched for H-reflex amplitude in upright standing. In both groups, H-reflex modulation was not associated with changes in background electromyographic activity. SIGNIFICANCE: This study indicates that the H reflex is modulated within the stair gait cycle during ascent and descent. Although its magnitude was slightly reduced, the overall modulation of the H reflex is not affected in healthy older adults.
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