POWER Training Rapidly Improves Muscle Power Following Stroke in Veterans

Associations between change (Δ) in SSWS (self-selected walking speed) and muscle power generation on nonparetic (a) and paretic (b) sides. Closed circles (solid line) are young subjects; open circles (dotted line) are older subjects.

By Annette M. Boyle

CHARLESTON, SC—Each year about 15,000 veterans suffer a stroke. For many stroke survivors, regaining walking ability and, ultimately, walking speed is a primary goal of rehabilitation. Recent research might offer a more-effective way to boost muscle power and, consequently, walking speed than traditional strength training.

Poststroke Optimization of Walking using Explosive Resistance (POWER) training can help some patients quickly increase the muscle strength and power in their legs and improve their walking speed, according to researchers at the Ralph H. Johnson VAMC and the Medical University of South Carolina in Charleston. The therapy appears particularly effective in younger patients, though it seems to benefit everyone.

POWER training aims to improve poststroke muscular and locomotor function using standard exercises such as leg presses, calf raises and jump training performed as quickly as possible. In a pair of studies, patients participated in 24 training sessions over an eight-week period with the number of sets, number of repetitions and resistance increasing as tolerated. Patients also performed fast walking training at each session.1,2

The training differs from traditional strength training by addressing the disproportionate loss of power relative to strength experienced by stroke patients. “Muscle strength measures how much you can lift at one time, like lifting up a big barbell. Power has one other component: how quickly you can generate force or velocity. Jumping, for instance, is a powerful movement. If you generate it slowly, you wouldn’t leave the ground,” explained Christopher Gregory, PhD, PT, research health scientist at the Ralph H. Johnson VAMC and associate professor at the Medical University of South Carolina.

Previous studies in older patients who have not had strokes indicate that focusing on fast rather than controlled movement increased mobility, ability to stand, walk, do laundry, carry in groceries, move about the home and overall independence, Gregory told U.S. Medicine. The researchers hypothesized that improving power might have an even larger impact on those who have had strokes.

Nearly 3 out of 4 stroke patients experience hemiparesis or some degree of muscular weakness or partial paralysis on one side of the body. That weakness usually manifests in an inability to walk or slowed walking speeds, which could be related to insufficient leg power to propel the patient forward.

Because walking speed is associated with greater independence and better health status, it is an important measure quality of life and a frequent focus of rehabilitation.

The first study enrolled 12 participants ages 19-70 who had had a stroke six months to five years earlier. All could walk at least 10 meters without support but did so at lower than normal self-selected speed. Following just two months of training, all patients achieved clinically meaningful increases in walking speed comparable that gained through longer task-specific therapies.

In the second study, the researchers compared the gains achieved through POWER therapy in six stroke patients under age 40 to that achieved by 10 patients over age 60. All patients could walk 10 meters without assistance. The two groups had no notable differences in walking speed, muscle power generation or clinical status at baseline. Both age groups attained significant increases in knee extensor muscle power generation on the affected and unaffected sides and improvements in self-selected walking speeds, though the increase was only significant in the younger age group.

Aside from the improvements seen in walking speed from the POWER program, Gregory noted that the VA research had provided a number of insights and practical changes that could be applied in rehabilitation work with stroke patients elsewhere.

“In general, we don’t push patients hard enough in rehab,” he said. “The common ingredient for those who respond is the intensity of the exercise. We have to push them with exercises that are intense enough. We shouldn’t be OK with being just good enough. We need to personalize care and keep it intense enough so that patients see the maximum benefit from the therapies that we provide.”

Some clinicians might hold back because of traditional worries that high-exertion activities such as muscle strengthening could worsen spasticity following stroke, but Gregory and his colleagues note that contemporary studies have found no exacerbation of spasticity with high-exertion exercises and, to the contrary, have recognized that those are crucial to rehabilitation.

The exercises and improvement in muscle power can benefit even patients who cannot walk following a stroke, Gregory said. “Traditional therapy has people practice walking a lot,” he explained. That can be done on a treadmill, but for more–severely-affected patients, it requires fairly complex apparatus, including ceiling supports and body weight support.

In contrast, the Charleston VAMC uses a “sled that folks lie down on to do exercises that can be titrated to provide the foundation for walking. Patients can safely transfer to it from a wheelchair. We can set the resistance low enough that more-seriously-impaired patients can do the exercises and gain both strength and power,” Gregory said. As patients improve, the therapists add resistance. The sled has the advantage of also enabling the patients and therapist to work each side separately to maximize the increase in muscle strength and power.

Gregory said he looks forward to continuing research with the POWER program, both to identify what exercises and frequency works best for stroke patients of different ages and to find ways to help patients continue to improve over time.

“There’s a period of natural recovery following any injury, then everyone plateaus,” he said. “Can we get them better after that plateau? Can we speed up the initial recovery? That’s what we need to figure out.”

  1. Morgan P, Embry A, Perry L, Holthaus K, Gregory CM. Feasibility of lower-limb muscle power training to enhance locomotor function poststroke. J Rehabil Res Dev. 2015;52(1):77-84. doi: 10.1682/JRRD.2014.04.0109.
  2. Hunnicutt JL, Aaron SE, Embry AE, Cence B, Morgan P, Bowden MG, Gregory CM. The effects of POWER training in young and older adults after stroke. Stroke Research and Treatment. 2016; article ID 7316250. doi: 10.1155/2016/7316250

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