Load rather than length sensitive feedback contributes to soleus muscle activity during human treadmill walking
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Load rather than length sensitive feedback contributes to soleus muscle activity during human treadmill walking. / af Klint, Richard; Mazzaro, Nazarena; Nielsen, Jens Bo; Sinkjaer, Thomas; Grey, Michael James.
In: Journal of Neurophysiology, Vol. 103, No. 5, 2010, p. 2747-2756.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Load rather than length sensitive feedback contributes to soleus muscle activity during human treadmill walking
AU - af Klint, Richard
AU - Mazzaro, Nazarena
AU - Nielsen, Jens Bo
AU - Sinkjaer, Thomas
AU - Grey, Michael James
N1 - CURIS 2010 5200 090
PY - 2010
Y1 - 2010
N2 - Walking requires a constant adaptation of locomotor output from sensory afferent feedback mechanisms to ensure efficient and stable gait. We investigated the nature of the sensory afferent feedback contribution to the soleus motoneuronal drive and to the corrective stretch reflex by manipulating body load and ankle joint angle. The volunteers walked on a treadmill ( approximately 3.6 km/h) connected to a body weight support (BWS) system. To manipulate the load sensitive afferents the level of BWS was switched between 5 and 30% of body weight. The effect of transient changes in BWS on the soleus stretch reflex was measured by presenting dorsiflexion perturbations ( approximately 5 degrees, 360-400 degrees/s) in mid and late stances. Short (SLRs) and medium latency reflexes (MLRs) were quantified in a 15 ms analysis window. The MLR decreased with decreased loading (P = 0.045), but no significant difference was observed for the SLR (P = 0.13). Similarly, the effect of the BWS was measured on the unload response, i.e., the depression in soleus activity following a plantar-flexion perturbation ( approximately 5.6 degrees, 203-247 degrees/s), quantified over a 50 ms analysis window. The unload response decreased with decreased load (P > 0.001), but was not significantly affected (P = 0.45) by tizanidine induced depression of the MLR (P = 0.039, n = 6). Since tizanidine is believed to depress the group II afferent pathway, these results are consistent with the idea that force-related afferent feedback contributes both to the background locomotor activity and to the medium latency stretch reflex. In contrast, length-related afferent feedback may contribute to only the medium latency stretch reflex.
AB - Walking requires a constant adaptation of locomotor output from sensory afferent feedback mechanisms to ensure efficient and stable gait. We investigated the nature of the sensory afferent feedback contribution to the soleus motoneuronal drive and to the corrective stretch reflex by manipulating body load and ankle joint angle. The volunteers walked on a treadmill ( approximately 3.6 km/h) connected to a body weight support (BWS) system. To manipulate the load sensitive afferents the level of BWS was switched between 5 and 30% of body weight. The effect of transient changes in BWS on the soleus stretch reflex was measured by presenting dorsiflexion perturbations ( approximately 5 degrees, 360-400 degrees/s) in mid and late stances. Short (SLRs) and medium latency reflexes (MLRs) were quantified in a 15 ms analysis window. The MLR decreased with decreased loading (P = 0.045), but no significant difference was observed for the SLR (P = 0.13). Similarly, the effect of the BWS was measured on the unload response, i.e., the depression in soleus activity following a plantar-flexion perturbation ( approximately 5.6 degrees, 203-247 degrees/s), quantified over a 50 ms analysis window. The unload response decreased with decreased load (P > 0.001), but was not significantly affected (P = 0.45) by tizanidine induced depression of the MLR (P = 0.039, n = 6). Since tizanidine is believed to depress the group II afferent pathway, these results are consistent with the idea that force-related afferent feedback contributes both to the background locomotor activity and to the medium latency stretch reflex. In contrast, length-related afferent feedback may contribute to only the medium latency stretch reflex.
U2 - 10.1152/jn.00547.2009
DO - 10.1152/jn.00547.2009
M3 - Journal article
C2 - 20237313
VL - 103
SP - 2747
EP - 2756
JO - Journal of Neurophysiology
JF - Journal of Neurophysiology
SN - 0022-3077
IS - 5
ER -
ID: 21014731