Evan R. L. Baldwin

Ambulatory activity of stroke survivors: measurement options for dose, intensity, and variability of activity.

Background and Purpose— Walking activity is an important part of exercise prescription for stroke survivors. The purpose of this study was to: (1) compare ambulatory activity parameters in subacute stroke survivors over three time periods; and (2) discuss options for measurement of ambulatory activity data with respect to absolute activity, intensity of activity, and variability and pattern of activity. Methods— Ten subacute stroke survivors participated (mean±SD; age: 66±15 years; time from stroke to discharge: 75±31 days). Data collection was completed across three time periods, predischarge, 2 weeks postdischarge, and 6 weeks postdischarge. The Step Activity Monitor (Cyma Corporation) was used to measure daily activity parameters. Parameters representing dose, intensity, and variability/pattern of activity were determined using MatLab. Results— Minutes of activity and length of activity bouts significantly increased from predischarge to 6 weeks postdischarge (P=0.030). Conclusions— The measurement of a variety of ambulatory activity parameters may aid clinicians and stroke survivors to determine whether exercise recommendations are being met with daily activity.

Task dependent gain regulation of spinal circuits projecting to the human flexor carpi radialis

In humans, the flexor carpi radialis (FCR) and extensor carpi radialis (ECR) muscles act as antagonists during wrist flexion-extension and as functional synergists during radial deviation. In contrast to the situation in most antagonist muscle pairs, Renshaw cells innervated by the motor neurons of each muscle inhibit the motoneurons, but not Ia inhibitory interneurons, of the opposite motor pool. Here we compared gain regulation of spinal circuits projecting to FCR motoneurons during two tasks: flexion and radial deviation of the wrist. We also investigated the functional consequences of this organisation for maximal voluntary contractions (MVCs). Electromyographic (EMG) recordings were taken from FCR, ECR longus and ECR brevis using fine-wire electrodes and electrical stimulation was delivered to the median and radial nerves. Ten volunteers participated in three experiments.1.To study the regulation of the Renshaw cell-mediated, inhibitory pathway from ECR to FCR motoneurons, forty stimuli were delivered to the radial nerve at 50% of the maximal M-wave amplitude for ECR brevis. Stimuli were delivered during both isometric wrist flexions and radial deviation actions with an equivalent EMG amplitude in FCR (~5% wrist flexion MVC).2.To explore the homonymous Ia afferent pathway to FCR motoneurons, 50 stimuli were delivered to the median nerve at intensities ranging from below motor threshold to at least two times that which evoked a maximal M-wave during wrist flexion and radial deviation (matched FCR EMG at ~5% wrist flexion MVC).3.EMG amplitude was measured during MVCs in wrist flexion, extension and radial deviation.There was no significant difference in the inhibition of FCR EMG induced via ECR-coupled Renshaw cells between radial deviation and wrist flexion. However, the mean FCR H-reflex amplitude was significantly (P<0.05) greater during wrist flexion than radial deviation. Furthermore, EMG amplitude in FCR and ECR brevis was significantly (P<0.05) greater during MVCs in wrist flexion and extension (respectively) than radial deviation. ECR longus EMG was significantly greater during MVCs in radial deviation than extension. These results indicate that the gain of the Renshaw-mediated inhibitory pathway between ECR and FCR motoneurons is similar for weak flexion and radial deviation actions. However, the gain of the H-reflex pathway to FCR is greater during wrist flexion than radial deviation. Transmission through both of these pathways probably contributes to the inability of individuals to maximally activate FCR during radial deviation MVCs.

Neuromuscular electrical stimulation and exercise for reducing trapezius muscle dysfunction in survivors of head and neck cancer: a case-series report.

PURPOSE Damage to the spinal accessory nerve (SAN) can result in denervation of the trapezius muscle in patients undergoing surgery for head and neck cancer. Trapezius denervation leads to muscle weakness and dysfunction that, for some patients, persists despite the return of conduction along the SAN. This prospective case series describes an intervention involving a combination of a novel type of neuromuscular electrical stimulation (NMES) with bilateral exercise. METHODS Three survivors of head and neck cancer participated in the 6-week program. NMES was applied over the region of the SAN on the affected side while subjects performed bilateral voluntary scapular retraction and elevation exercises against resistance. The NMES was delivered using relatively wide pulse widths and high frequencies to enhance the electrically evoked sensory volley and was triggered by the onset of trapezius muscle activity on the non-affected side. Shoulder range of motion (ROM) assessments and patient-rated outcomes were administered at baseline and 6 weeks. RESULTS All patients showed improvements in shoulder flexion and abduction ROM and reported reductions in pain and disability. CONCLUSIONS This combination of NMES and bilateral exercise may prove to be an effective component of a comprehensive shoulder rehabilitation program for patients with persistent trapezius muscle dysfunction as a result of SAN damage.