Figure 9-5. The relationships between speed of walking during body weight-supported treadmill training and speed overground with assistive devices are shown for subjects who had a severe motor (A), sensorimotor (B), or sensorimotor with visual field (C) impairment. For subjects A and B, increasing treadmill speeds were associated with increasing speed of overground walking. Although overground walking speed did not increase with the increase in treadmill walking speed in subject C, the quality and safety of ambulation, by a kinematic assessment, did improve. Subject C, who had a right hemispheric infarction and visuoperceptual impairments, described a sense of fear about trying to walk faster overground.
ing of loading and unloading the stance leg. This finding is consistent with the load and hip extension studies described for spinal transected cats and patients with SCI (see Chapter 1). To test the effects of optimizing these kinematic and kinetic details of gait, we trained 24 patients with chronic hemiparetic stroke who walked slowly. The subjects were randomized to training at one of 3 treadmill speeds: slow (their overground walking speed), fast (approximately 2 mph) and varied (0.5-2 mph) speeds for 30-60 minutes per session as tolerated for 3 sessions of BWSTT weekly for 4 weeks. All improved their overground speed, but the patients assigned to fast treadmill training at 2 mph increased overground walking speed by 30%-50%.275 This approach also led to reorganization of activity in the supplementary motor cortex and primary sensorimotor cortex, as overground walking speed and se lective control of ankle dorsiflexion improved (see Color Fig. 3-8 in separate color insert).174,276 Another study supports the positive impact of training at faster treadmill speeds. Pohl and colleagues randomized 60 ambulatory patients who were a mean of 16 weeks postonset of stroke to conventional gait training, treadmill training with incremental increases in speed of 10% within sessions and rising to as much as the subject could manage, or to treadmill walking with a maximum 5% per week increase in speed.277 Subjects in the fast training group increased treadmill walking speeds by an average of 3.7 ± 1.9 times their initial speed. After 12 treatment sessions, this group achieved faster overground walking speeds (163 ± 80 cm/s) compared to the other 2 groups. The steady 5% increment group walked significantly faster (122 ± 74 cm/s) than the conventionally trained group (97 ± 64 cm/s). Stride length, cadence, and functional level for walking also significantly improved over conventional treatment. The maximum average belt speed for the last training session was 4.7 mph! Thus, training at walking speeds typical of at least the casual walking speed of healthy subjects, over 2 mph, may be essential, if faster overground walking is a goal of therapy.
Other treadmill studies of hemiparetic patients after stroke show that patients can safely exercise at a level of effort that provides a conditioning response266 and that the energy cost of walking may decrease by approximately 50% as walking speeds increase from 0.4 to 1.5 meters/second.278 This decline in energy cost especially holds for treadmill speeds >2 mph. As with any task-oriented approach, the intensity and specificity of practice drive functional gains for the practiced motor skill.279 Body weight-supported treadmill training is also being combined with functional neuromuscular stimulation with surface280 or implanted electrodes for patients with chronic stroke.281 The results to date show modest improvements in walking speed and kinematics within subjects, but the design of clinical trials with the combined approach seems premature, given that the optimal use of BWSTT has not yet been demonstrated.
Additional trials that compare BWSTT to conventional methods are needed before the approach can be generally recommended. Attention must be given to the use of continued weight support to allow training at higher treadmill speeds (progressing patients up to at least 2 mph) and to the details of how the therapists cue their patients. A study of patients entered within the typical time frame of 10-15 days poststroke, inclusion of subjects who cannot yet step, a combination of inpatient and outpatient training for 8-12 weeks, and an intention-to-treat analysis may produce more generalizable results.110
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