Pre-swing deficits in forward propulsion, swing initiation and power generation by individual muscles during hemiparetic walking

Abstract

Clinical studies of hemiparetic walking have shown pre-swing abnormalities in the paretic leg suggesting that paretic muscle contributions to important biomechanical walking subtasks are different than those of non-disabled individuals. Three-dimensional forward dynamics simulations of two representative hemiparetic subjects with different levels of walking function classified by self-selected walking speed (i.e., limited community=0.4-0.8 m/s and community walkers = or > 0.8m/s) and a speed-matched control were generated to quantify individual muscle contributions to forward propulsion, swing initiation and power generation during the pre-swing phase (i.e., double support phase proceeding toe-off). Simulation analyses identified decreased paretic soleus and gastrocnemius contributions to forward propulsion and power generation as the primary impairment in the limited community walker compared to the control subject. The non-paretic leg did not compensate for decreased forward propulsion by paretic muscles during pre-swing in the limited community walker. Paretic muscles had the net effect to absorb energy from the paretic leg during pre-swing in the community walker suggesting that deficits in swing initiation are a primary impairment. Specifically, the paretic gastrocnemius and hip flexors (i.e., iliacus, psoas and sartorius) contributed less to swing initiation and the paretic soleus and gluteus medius absorbed more power from the paretic leg in the community walker compared to the control subject. Rehabilitation strategies aimed at diminishing these deficits have much potential to improve walking function in these hemiparetic subjects and those with similar deficits.

2010 Elsevier Ltd. All rights reserved.

Figures

Fig. 1

Experimental data of the gait cycle with minimum difference in joint angles and ground reaction forces (GRFs) compared to the subject’s average for the limited community walker at self-selected speed (with ± 1 standard deviation (S.D.) of the 30 s walking trial) and the control walking at 0.6 m/s. Data are normalized to the paretic (ipsilateral) gait cycle. Joint angle subtitles correspond to positive directions. Positive pelvic obliquity, rotation and tilt correspond to positive rotations about the X, Y and Z pelvis segment axes, respectively (see bottom right).

Fig. 2

Experimental data of the gait cycle with minimum difference in joint angles and ground reaction forces (GRFs) compared to the subject’s average for the community walker at self-selected speed (with ± 1 standard deviation (S.D.) of the 30 s walking trial) and the control walking at 1.0 m/s. Data are normalized to the paretic (ipsilateral) gait cycle. Joint angle subtitles correspond to positive directions. Positive pelvic obliquity, rotation and tilt correspond to positive rotations about the X, Y and Z pelvis segment axes, respectively (see bottom right).

Fig. 3

Primary muscle contributors to forward propulsion (i.e., average horizontal pelvis acceleration) and the total average pelvis acceleration and deceleration (Total) and net by all paretic (ipsilateral for control) and non-paretic (contralateral for control) muscles during pre-swing. (A) For the limited community walker, forward propulsion provided by paretic and non-paretic muscles were decreased and increased, respectively, compared to the speed-matched control. (B) Forward propulsion provided by paretic muscles (i.e., SOL and GMED) was increased in the community walker relative to the speed-matched control.

Fig. 4

Primary muscle contributors to average swing initiation during pre-swing by paretic (ipsilateral for control) and non-paretic (contralateral for control) leg muscles. (A) For the limited community walker, swing initiation by paretic muscles was similar to the ipsilateral control leg, but paretic muscles absorbed less power compared to the control. (B) For the community walker, swing initiation by the paretic GAS, IL and SAR was decreased and paretic AM was increased compared to the control. Paretic muscles absorbed much more power from the paretic leg compared to the ipsilateral control leg.

Fig. 5

Average power generated by paretic (ipsilateral for control) and non-paretic (contralateral for control) leg muscles during pre-swing. (A) Paretic muscles generated less power in the limited community walker relative to the speed-matched control as paretic GAS generated much less power. (B) The community walker generated and absorbed much power with the paretic and non-paretic leg muscles, although power generated by the paretic SOL and GAS was decreased relative to the control.