Kessler scientists envision opportunities amid the challenges of rehabilitation research

Reliable and valid results can be achieved even in the absence of large sample sizes, according to rehabilitation researchers at Kessler Foundation

A team of scientists at Kessler Foundation have proposed solutions to the challenges of conducting rehabilitation research. Their article, “Considerations of power and sample size in rehabilitation research,” (doi: 10.1016/j.ijpsycho.2019.08.009 ) was e-published on October 23, 2019 by the International Journal of Psychophysiology. The authors are Olga Boukrina, PhD, research scientist in the Center for Stroke Rehabilitation Research, and N. Erkut Kucukboyaci, PhD, associate research scientist, and Ekaterina Dobryakova, PhD, research scientist, in the Center for Traumatic Brain Injury Research.

Link to abstract:
The challenges to conducting research in the field of medical rehabilitation are many. Inherent to the process of recruiting and conducting studies in people with disabilities are lower enrollment, higher costs, greater inter-individual variability, and lack of clarity regarding the application of standard measurement tools to these clinical populations.

According to the Kessler team, the challenges of rehabilitation research warrant a more nuanced approach to research design. The team acknowledges the impact that small sample size has on effect size, but suggests that this can be accommodated in rehabilitation research because benefits to small homogeneous groups of patients might outweigh statistical generalizability. They further propose that the reliability of results could be maximized even with small sample sizes by incorporating more trials per participant, conducting high-precision measurements, harnessing inter-individual variability, and validating statistical models within and across studies. Consideration of these design choices will be an essential step toward promoting transparency and encouraging the replication of findings with the potential to improve the lives of people with disabilities. Addressing the challenges of rehabilitation research requires creative thinking and innovative approaches to address the high variability. Meeting these challenges may fuel new advances in telemedicine, machine learning, and neuroimaging, with the potential to benefit all individuals.

Drs. Kucukboyaci and Dobryakova are former recipients of Switzer Research Fellowships awarded by the National Institute on Disability Independent Living and Rehabilitation Research.

About Kessler Foundation 
Kessler Foundation, a major nonprofit organization in the field of disability, is a global leader in rehabilitation research that seeks to improve cognition, mobility and long-term outcomes, including employment, for people with neurological disabilities caused by diseases and injuries of the brain and spinal cord. Kessler Foundation leads the nation in funding innovative programs that expand opportunities for employment for people with disabilities. For more information, visit

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Head shot of Dr. Olga Boukrina against a black background