Letter regarding the article entitled ‘assessment for cardiovascular fitness in patients with stroke: which cardiopulmonary exercise testing method is better?’

Letter to Editor, I read with great interest the article by Mustafa and Aytür in which they present the results of their study interrogating the appropriate cardiopulmonary exercise testing (CPET) to assess cardiovascular fitness. Cardiovascular disease is the leading prospective cause of death in people with chronic stroke and it is known that the risk factors for cardiovascular disease can be modified and the low cardiovascular fitness can be improved. Therefore, the study of Mustafa et al. focusing on the cardiovascular fitness of stroke patients and investigating the optimal method for assessment of cardiovascular fitness is strictly critical. However, I would like to make some comments for a better understanding of this report. First, the authors concluded that maximal oxygen consumption (VO2peak) after stroke can be used to determine cardiorespiratory fitness level, the risk of cardiovascular disease. However, the main objective of this study was to determine the most appropriate CPET and they based their results on a value of VO2peak which is shown to reflect the cardiorespiratory fitness and functional capacity in previous studies. Taken together, the study method does not allow to provide that conclusion, they rather formed their methodology based on that view. The authors hypothesized that CPET with treadmill would be more appropriate to determine cardiorespiratory fitness in patients with stroke since walking is more functional compared to cycling. The bicycle exercise recruits less body muscle mass and therefore, peak oxygen uptake has been generally found to be lower by about 10% than with treadmill. On the other hand, some researchers also did not find a significant difference between CPET with treadmill and bicycle ergometer. However, the general opinion is that treadmill exercise elicits circulatory reserve more than bicycle exercise, and these results derive from studies conducted in normal subjects or subjects with coronary artery disease. Taken together, the critical question is that may the preference of CPET in the determination of cardiovascular fitness differ in stroke patients and why? Remarkably, in the stoke group, Mustafa and Aytür found that VO2peak (gold standard value for determining cardiorespiratory fitness) measured CPET with treadmill was higher in comparison to the CPET with bicycle. Based on this result, they concluded that CPET with treadmill would be more suitable to determine cardiorespiratory fitness in the stroke population compared to CPET performed with bicycle. However, they also found that VO2peak values were higher at CPET with treadmill compared to that of CPET with bicycle in the healthy control group. Besides, the difference in the VO2peak values between the two tasks was higher in the healthy control group. The authors explain this with a view that the population is not accustomed to bike; and the healthy control group might have stopped CPET due to local muscle weakness. However, this cannot be a sensible explanation considering that the patient group also compromised from the same population and also, the possible additional lower limb muscle weakness (or spasticity) that might have developed due to stroke can constitute a limiting factor rather in the stroke group. On the other hand, they also discuss that the stroke population had a higher energy consumption during walking due to gait disorders, which resulted in a smaller difference in VO2peak between the two tests compared to the healthy group. I agree with this view; however, this may rather suggest that CPET with treadmill may not be an optimal method to evaluate cardiovascular fitness in stroke patients. Arrestingly, conflicting with TOPICS IN STROKE REHABILITATION 2022, VOL. 29, NO. 8, 616–617 https://doi.org/10.1080/10749357.2021. 1971478