What Dose Does It?
When it comes to the dose-response relationship in therapy after SCI, we’re still learning.
When we pick up a bottle of aspirin and read the label for information about how many tablets to take, the label clearly indicates that we should take one to two tablets. That is a fairly specific dose recommendation, isn’t it?
Years ago, during the time when during the time when it was thought that everyone should take low-dose aspirin to prevent stroke, I heard a lecture by a leading cardiologist. He said the best dose of low-dose aspirin was much like the number of eyes a person should have,“One is not enough, and three is too many.” After I stopped laughing from the images that came to my mind, I remember being amazed by the preciseness of this recommendation about dosage. How did they know that? As it turns out, many millions of dollars are spent each year determining the best dose of medicine for the average consumer.
Questions of dosage are crucial to most areas of medicine and health. For example, the American College of Sports Medicine/American Heart Association’s joint guidelines for physical activity make very specific recommendations about exercise for adults between the ages of 18 and 65 (Haskell et al. 2007). They recommend moderately intense cardio activities 30 minutes per day, five days per week or vigorously intense cardio 20 minutes per day three days per week, plus eight to 10 strength-training exercises with at least one set (eight to 12 repetitions) of each exercise two days per week. These recommendations provide us with excellent guidelines for cardiovascular health, an area that is of such great importance to our lives. Unfortunately, these guidelines are among very few that are available and specific enough to help with planning health-promoting activity.
A recent systematic review, a large analysis of many published research articles, asked the question, “What is the best approach to improving function after spinal cord injury?”
The results of this review concluded that the most effective approaches to improve function after spinal cord injury are not the exciting, high-tech cellular transplants or pioneering drug treatments that get such great coverage in the news media. In fact, the most effective approaches were those that included rehabilitation (Gomes-Osman et al. 2016). Despite the fact that, as the systematic review shows, rehabilitation is the best medicine we have for improving function after spinal cord injury (and likely other health conditions that affect movement,) the challenge is that we know surprisingly little about the best dose of rehabilitation for each individual.
In part, the difficulty in identifying the best dose of rehabilitation treatments is because dose is typically measured in terms of hours in therapy, rather than by the number of repetitions of the skill that is being developed. In animal studies of skill, the animals perform hundreds, even thousands of repetitions of a task before meaningful changes in skill are observed. In contrast, according to one rehabilitation study, the average number of steps taken during walking training in outpatient rehabilitation is 292 steps per training session (Lang et al. 2007). This number of steps is about one-tenth the number of steps per day taken by community-dwelling individuals with chronic stroke (Michael et al. 2005).
The Shepherd Step program was developed for that very reason – to meet the need for an intensive walking program for people with spinal cord injury who have some movement and for whom functional ambulation is a realistic goal. Because Shepherd Step is so focused on walking, it gives clients a more realistic amount of therapy that mimics the number of steps they would take if they were out in their community.
We all know the saying that practice makes perfect. Understanding the dose of rehabilitation that is needed to improve movement is an important research question in itself – and one that we are addressing in some of our research. Assuming that some movement is possible, there is good evidence to show that the nervous system is plastic and amenable to training, as well as evidence that movement can be improved if there is adequate opportunity for practice.
On the other hand, it is also important not to overdose on rehabilitation. When all is said and done, having a well-rounded life that includes many different types of activities and opportunities for social participation is the real key to happy and healthy life.
EDELLE FIELD-FOTE, PT, Ph.D., is the director of spinal cord injury research at Shepherd Center. She joined the staff in May 2014 after serving for 20 years as the director of the Neuromotor Rehabilitation Research Laboratory at the Miami Project to Cure Paralysis. Her research focuses on restoring motor function after spinal cord injury by making use of spinal pathways not damaged by injury.
Shepherd Center, located in Atlanta, Georgia, is a private, not-for-profit hospital specializing in medical treatment, research and rehabilitation for people with spinal cord injury, brain injury, multiple sclerosis, spine and chronic pain, and other neuromuscular conditions. Founded in 1975, Shepherd Center is ranked by U.S. News & World Report among the top 10 rehabilitation hospitals in the nation. In its more than four decades, Shepherd Center has grown from a six-bed rehabilitation unit to a world-renowned, 152-bed hospital that treats more than 935 inpatients, 541 day program patients and more than 7,300 outpatients each year.