Biomedical subjects

A R Den Otter

Publications and source records attributed to A R Den Otter.

3 recordsLinked to original sources

PubMed2006

Abnormalities in the temporal patterning of lower extremity muscle activity in hemiparetic gait.

Following hemiparetic stroke, the timing of lower extremity muscle activity during gait often undergoes radical changes. In the present study, we compared the duration of activity in Biceps femoris (BF), Rectus femoris (RF), Tibialis anterior (TA) and Gastrocnemius medialis (GM) for four subphases of the gait cycle: the first double support phase (DS1), the single support phase (SS), the second double support phase (DS2) and the swing phase (SW) and compared these between 24 hemiparetic stroke patients and 14 healthy controls. In the upper leg, durations of BF and RF activity during SS were significantly longer on the paretic side (70% for BF, and 78% for RF) as well as on the nonparetic side (71% for BF, and 81% for RF), when compared to controls (45% and 53% for BF and RF, respectively). As a result, the duration of BF-RF coactivity during SS was longer in both legs of patients with stroke (61% in the paretic and 62% in the nonparetic leg) relative to control values (25%). In addition, during DS1 of the paretic leg, the total amount of BF-RF coactivity was abnormally long (82% versus 57% in controls). In the lower leg, longer total durations of GM activity were found during DS1 on the paretic side in people with stroke (51%) than in controls (38%). In the paretic TA, longer durations of activity were observed during SW (73% versus 60% in controls), whereas smaller total durations of activity were found during SS (28% versus 48% in controls). No statistically significant differences were found between the paretic and nonparetic leg within patients, except for the mean total duration of TA activity during DS1 (50% and 69% for the paretic and nonparetic leg, respectively). Overall, these results suggest that, despite large interindividual differences, some common disturbances can be observed in the temporal layout of muscle activity and coactivity associated with hemiparetic gait. Although these disturbances are more pronounced in the paretic leg, muscle activation patterns of the nonparetic leg also display some clear abnormalities.

Adult↗

PubMed2005

Gait recovery is not associated with changes in the temporal patterning of muscle activity during treadmill walking in patients with post-stroke hemiparesis.

OBJECTIVE: To establish whether functional recovery of gait in patients with post-stroke hemiparesis coincides with changes in the temporal patterning of lower extremity muscle activity and coactivity during treadmill walking. METHODS: Electromyographic (EMG) data from both legs, maximum walking speed, the amount of swing phase asymmetry and clinical measures were obtained from a group of post-acute patients with hemiparesis, as early as possible after admission in a rehabilitation centre (mean time post-stroke 35 days) and 1, 3, 6, and 10 weeks later, while all patients participated in a regular rehabilitation program. EMG data from the first assessment were compared to those obtained from a group of healthy controls to identify abnormalities in the temporal patterning of muscle activity. Within subject comparisons of patient data were made over time to investigate whether functional gait recovery was accompanied by changes in the temporal patterns muscle (co-)activity. RESULTS: EMG patterns during the first assessment showed a number of abnormalities on the paretic side, namely abnormally long durations of activity in biceps femoris (BF) during the single support (SS) phase and in gastrocnemius medialis (GM) during the first double support phase (DS1). Furthermore, in both legs a prolongation of the activity was seen in the rectus femoris (RF) during the SS phase. In addition, the duration of BF-RF coactivation was longer on the paretic side than it was in controls. Over time, the level of ambulatory independence, body mobility, and maximum walking speed increased significantly, indicating that substantial improvements in gait ability occurred. Despite these improvements, durations of muscle (co-) activity and the level of swing phase asymmetry did not change during rehabilitation. More specifically, timing abnormalities in muscle (co-)activity that were found during the first assessment did not change significantly, indicating that these aberrations were not an impediment for functional gait improvements. CONCLUSIONS: Normalization of the temporal patterning of gait related muscle activity in the lower extremities is not a prerequisite for functional recovery of gait in patients with post-stroke hemiparesis. Apparently, physiological processes other than improved temporal muscular coordination must be important determinants of the restoration of ambulatory capacity after stroke. SIGNIFICANCE: Recovery of walking ability in post-stroke hemiparesis is not necessarily associated with, or dependent on, reorganization in the temporal control of gait related muscle activity. Normalization of the temporal coordination of muscle activity during gait may not be an important clinical goal during post-acute rehabilitation.

Adult↗

PubMed2004

Step characteristics during obstacle avoidance in hemiplegic stroke.

Whereas several animal studies have indicated the important role of the motor cortex in the control of voluntary gait modifications, little is known about the effects of cortical lesions on gait adaptability in humans. Obstacle avoidance tasks provide an adequate paradigm to study the adaptability of the stepping pattern under controlled, experimental conditions. In the present study, an exploratory assessment was made of the failure rate, the preferred stepping strategies (step lengthening vs step shortening), and the spatiotemporal stride characteristics (percentage increases in stride length, duration, and velocity of the crossing and postcrossing strides) during obstacle avoidance in 11 hemiplegic stroke patients and seven healthy controls. Patients were less successful in avoiding obstacles than controls (14% failure rate vs 0.5% in controls), independent of whether the affected or the unaffected leg led the obstacle avoidance. The number of failed trials increased systematically when the available response time became shorter. During successful trials, lengthening of the step was generally preferred over shortening. This bias towards step lengthening was more pronounced in stroke patients (step lengthening in 91% of the trials vs 75% in controls), irrespective of the side of obstacle presentation. For both groups, overall strategy preference did not adhere to a principle of minimal foot displacement, since step lengthening was used even if it would be more spatially efficient to shorten the step. No statistically significant group differences were found for the increases in length, duration, and velocity of the crossing and postcrossing strides. However, for a subgroup of more slowly walking patients, large percentage increases were found in crossing stride length, duration, and velocity. Similar results were obtained for the postcrossing stride, indicating that, for this subgroup of patients, restoration of the normal walking cadence was more difficult. Overall, no systematic differences were found between the affected and the unaffected leg in stroke patients with respect to failure rates, stepping strategies, or spatiotemporal measures of obstacle avoidance. The present findings suggest that the ability to adequately modify the stepping pattern in response to imposed spatiotemporal constraints is impaired in persons with stroke, especially when modifications have to be performed under time pressure. In addition, the stepping strategies employed by subjects with stroke are different from those found in controls, possibly to reduce the complexity of the avoidance maneuver and to enhance safety. Finally, unilateral cortical damage results in an impaired ability to avoid obstacles on both sides of the body, suggesting that the reduced ability of stroke patients to negotiate obstacles may be related to problems of a more general coordinative nature.

Adult↗