With interest we read the article by Kirmaci et al. about the muscle architecture, assessed by measuring the pennation angle, muscle fiber length, and muscle thickness, and lower limb muscle force in patients with multiple sclerosis (n=23) of whom 13 had relapsing remitting MS (RRMS), five primary progressive MS (PPMS) and 15 secondary progressive MS (SPMS) [1]. It was concluded that muscle architecture is affected in MS and that it may determine functional rehabilitation programs of these patients [1]. The study is appealing but raises concerns which require discussion.

The main limitations of the study are that spasticity and daily living and other physical activities were not included in the evaluation. Spasticity may strongly contribute to deterioration of muscle architecture and may reduce muscle performance, why it is crucial to include spasticity in the evaluation. Spasticity has been shown to reduce the locomotor performance in MS patients [2]. Additionally, physical activity may strongly determine muscle architecture, why it is essential to include it in the evaluation as well. Missing is the inclusion of fatigue and pain in the evaluation. Fatigue and pain are prominent features of MS and are highly prevalent even at mild disability levels [3]. Missing is the current medication of the 33 MS patients. Knowing the drug treatment is crucial as sedating or myotoxic drugs may reduce not only motivation but also may reduce muscle strength. 

According to table 4 there was absence of a correlation between muscle architecture and muscle force. Reduced muscle force should be correlated at least with muscle thickness. Even in muscles with reduced muscle force and impaired muscle architecture force and architecture parameters did not correlate. This surprising finding requires an explanation.

Missing are the correlation between EDSS and muscle architecture parameters respectively muscle force. Since muscle weakness correlates with the EDSS, we should know if the correlation between muscle strength and EDDS was positive and significant.

The number of patients with SPMS provided in the abstract is wrong [1]. It should be 15 instead of 5. 

Overall, the study has several limitations which challenge the results and their interpretation. Spasticity, pain, fatigue, physical activity, EDSS, and current medication should be included in the evaluation.