Charly Keytsman, PhD, on HIIT for Patients With MS

It is well-known that certain patients with multiple sclerosis (MS) can benefit from an exercise regimen. The type of exercise, however, has been debated over the years. A recent study1 investigated the long-term effects of adding periodized high-intensity interval training (HIIT) to an MS treatment regimen.

Lead author of the study, Charly Keytsman, PhD, who is Faculty of Rehabilitation Sciences at the REVAL Rehabilitation Research Center at the Biomedical Research Institute (BIOMED) at Hasselt University in Diepenbeek, Belgium, answered our questions relating to this study.

NEUROLOGY CONSULTANT: How did this research come about?

Charly Keytsman: My research mainly focusses on exercise therapy in the rehabilitation of MS patients. More specifically, I have focused on the optimization of high-intensity exercise therapy in this population.

HIIT is a type of exercise that has been used for several years in high-performance sports athletes. However, we know this type of training is also very useful and efficient in the rehabilitation of MS patients. However, HIIT is very demanding and intense, and warrants a high dose of perseverance and motivation to adhere to longer term, especially in MS patients.

Therefore, I have explored the use of strategies used in the high-performance sports community in order to optimize HIIT protocols for MS patients and to facilitate the integration of this type of exercise in the rehabilitation of these patients. By doing this, I believe that both adherence to longer term, as well as superior clinical outcomes, can be achieved in these patients.

NEURO CON: Previous studies of exercise therapy among patients with MS have shown positive outcomes. How does your research add to the literature?

CK: MS is a disease that causes a variety of symptoms, which can be divided into primary symptoms (such as visual/sensory loss) and secondary symptoms (such as reduced mobility, limb weakness). These secondary complications are often related to or caused by physical inactivity. Such inactivity causes secondary problems, which can be divided into functional (such as reduced exercise capacity, muscle strength, mobility, quality of life) and health-related impairments (such as development of cardiovascular diseases). Therefore, it is of high importance that we address these secondary functional- and health-related parameters.

As we have known for many years in other populations, exercise therapy is a very efficient strategy to improve such parameters. But if we look throughout the history of exercise therapy in MS, we see that about 2 decades ago, exercise was contraindicated in these patients. Fortunately, we have realized that activation of these patients did indeed induce beneficial effects on exercise capacity and muscle strength. Therefore, we have steadily started to increase the intensity of our exercise programs in these patients (from low to moderate) with a likewise increase in clinical outcomes.

Finally, we have reached the high-intensity exercise protocols. Again, here we see the likewise increase in functional outcomes, with improvements in exercise capacity (+22%), muscle strength (+40%), and even cognitive function (+8%) in 3 to 12 weeks of rehabilitation. As such, we now know that HIIT is a very efficient strategy to improve functional parameters such as exercise capacity and muscle strength in this population, and this induces improved mobility, reduced disability, and improved quality of life.

NEURO CON: How might your results change clinical practice or treatment course?

CK: So we now know that HIIT is a very useful type of exercise in the rehabilitation of our patients. However, HIIT is a very demanding and intense form of exercise. Therefore, I believe that we have to explore strategies to improve long-term therapy adherence of HIIT, as well as strategies to keep optimizing these exercise protocols, in order to achieve maximal clinical outcomes. I believe that one of these strategies may lie within the training principles of our rehabilitation programs.

We still tend to train our patients in a linear progressive manner, compared with the high-performance exercise community where training periodization principles are used to improve training adaptations, ensure maximal exercise performances throughout the (often long) season, and prevent overtraining injuries. I believe that (HIIT-oriented) periodized rehabilitation may improve long-term outcomes and therapy adherence in our patients.

By varying exercise duration (high-volume vs low-volume), intensity (moderate vs high intensity), and frequency (3 times per week vs recovery weeks), we may optimize the rehabilitation of MS patients. As such, I would like to be able to advise rehabilitation centers to integrate our exercise interventions (that we are currently investigating) in the daily rehabilitation of their MS patients.

NEURO CON: What knowledge gaps still exist when it comes to exercise therapy among patients with MS?

CK: I believe that we still often tend to “undertrain” our patients. HIIT does ask a lot of these patients, but by optimizing the HIIT protocols, I believe that patients can really benefit from this training. Very often, when I visit rehabilitation centers, I see MS patients sitting on stationary bicycles for hours during their weekly rehabilitation. Not only is this psychologically exhausting for these patients (training for hours and hours), but moreover the effects of this type of training is inferior to the results of HIIT.

Furthermore, from personal communication with my patients, I have learned that they actually enjoy HIIT, because they tend to create the feeling of, “Look what I still can achieve, despite my disease!” So I think that the knowledge gap lies in the fact that physiotherapists and rehabilitation specialists are still afraid to use HIIT, because they believe it will be too stressful for their patient.

NEURO CON: What key take-home message do you want to leave your peers with today?

CK: I actually only have one message to my peers, and that is: just do HIIT! Your patient will enjoy this type of exercise and he/she will benefit from the impact on functional- and health-related parameters. By integrating periodization principles, you can improve long-term adherence (and exercise enjoyment) in your patients.


  1. Keytsman C, Van noten P, Spaas J, Nieste I, Van Asch P, Eijnde BO. Periodized home-based training: A new strategy to improve high intensity exercise therapy adherence in mildly affected patients with multiple sclerosis. 2019;28:91-97. https://doi.org/10.1016/j.msard.2018.12.018.