In recent years, there has been an increase in the number of applications of CW-fNIRS technology in areas related to mobility, accessibility, and integrability. These include activities such as cycling, dancing, or fitness. Use of fNIRS in training on cognitive function is finding its unique application in studying human cognition in motion.
Harold et al. 2018  ‘s review aimed to summarize the current methodological knowledge on using fNIRS in studies of hemodynamic responses during cognitive testing in two exercise-related categories. The first involved studies in which measurements were made before and after exercise. In the second category, the studies were cross-sectional, taking into account the participants’ fitness levels.
Among the 7184 publications collected, the researchers identified that 35 met the review’s criteria. The classification was based on information about the first author, year of publication, population characteristics including age, gender, health status, level of cardiorespiratory fitness, exercise characteristics (e.g., intensity, duration, type of exercise), cognitive tests (e.g., cognitive domain studied, administration after exercise cessation), and the fNIRS processing details.
Applications of CW-fNIRS in sports studies
This review allows general conclusions about how fNIRS data can be acquired, applied, and processed. In addition, it introduces methodological recommendations for future research using the effects of physical activity on cognitive performance and cortical hemodynamics.
We also found two quotes in the text that is close to our hearts because of the philosophy behind creating the Photon Cap ecosystem.
“fNIRS eminently suitable for application in special cohorts such as children or neurological patients. (p. 4)”
Comment: Our Photon Cap Baby solution is dedicated to studies of the youngest participants. Thanks to the specially designed soft optodes, the child is guaranteed comfort and peace of mind, and the textile caps can fit even the smallest head because of their multidimensionality.
”In the majority of the reviewed studies cortical hemodynamics were assessed during cognitive tests targeting executive functions. Thereby, in fifteen studies, a Stroop test, in one study a flanker test, a Go/No-Go test, and in another one, a random number generation test were used. In two studies, a modified Sternberg task , or in one study, a spatial working memory task, were applied to assess the cortical hemodynamic responses during a short-term working memory task. (p. 5)”
Comment: Cognitive experiments with CW-fNIRS registration require efficient data transmission and signal quality control. These needs are addressed by the Cortivision ecosystem, which supports the LSL protocol, which is the primary method of synchronization with other platforms such as PsychoPy, Eprime, and others. The LSL project page shows many devices using this standard.
To provide a broader overview of the applicability of CW-fNIRS technology in sports training-related research, we will present some studies that show the best use of the functionalities mentioned above.
In a study by Byun et al. 2014 , the effect of an acute session of mild exercise on executive function was examined. Along with an attempt to identify the neural basis of actions housed in brain activity. Near-infrared spectroscopy measured three regions-of-interest: dorsolateral prefrontal cortex (DLPFC), ventrolateral prefrontal cortex (VLPFC), and frontal pursuit area (FPA). Twenty-five young people (12 women and 13 men) participated in the study. The procedure consisted of three steps.
First, maximal oxygen uptake (VO2 peak) was measured to determine the appropriate individual intensity for the subject to perform the mild exercise. This was defined as 30% of a subject’s VO2 peak, based on a physical intensity classification. Next, physiological signals not originating from cortical areas were measured for each subject to eliminate them as signal contamination. The next part separated two control and exercise sessions, with counterbalanced measurements on different days.
Before each session, participants filled out a psychological mood scale. All subjects participated in two experimental conditions, a control and an exercise condition. In the exercise condition, subjects performed the color-word matching Stroop task (CWST) before and 5 minutes after 10 minutes of exercise on a bicycle ergometer with an individual load. In the control condition, the subjects also performed the CWST, but instead of exercise, they rested.
Changes in the prefrontal area were monitored using fNIRS during CWST in both sessions. The results showed that after the intensive session of mild exercise there was an improvement. Especially in Stroop test scores, which showed a positive relationship with increased arousal. Moreover, cortical activations in this test were also induced in areas such as, left dorsolateral prefrontal cortex (l-DLPFC) and FPA. These activations were then found to be significantly associated with improved cognitive performance and increased arousal.
Another study by Chen et al. 2017  compares the effects of a Baduanjin mind-body (BMB) intervention and a conventional relaxation training program in enhancing executive function. It similarly aimed to learn more about the neural basis of the actions underlying the effects of the BMB intervention. Forty-two college students were randomly assigned to the Baduanjin intervention study group or the relaxation training control group. This training lasted eight weeks (90 min/day, five days a week).
Each person received an abbreviated profile of mood states to assess mood and a flanker task to assess executive function before and after training. The hemodynamic response was measured during the flanker task. The results showed that after training with BMB exercises, subjects showed a significant reduction in depressive mood compared to pre-intervention results.
A similar reduction was not observed in the control group. In addition, an increase in oxygenated hemoglobin in the left prefrontal cortex during the test (incongruent) was observed only after the BMB intervention. The study shows that Baduanjin is an effective and easy-to-perform exercise that improves executive function and perhaps promotes brain self-regulation in healthy and young individuals.
We believe that this review will provide a better understanding of the application of tools such as fNIRS within the framework of the effects of physical activity on cognitive performance.
 Herold, F., Wiegel, P., Scholkmann, F., & Müller, N. G. (2018b). Applications of Functional Near-Infrared Spectroscopy (fNIRS) Neuroimaging in Exercise–Cognition Science: A Systematic, Methodology-Focused Review. Journal of Clinical Medicine, 7(12), 466., p. 5-9, https://doi.org/10.3390/jcm7120466
 Byun, K., Hyodo, K., Suwabe, K., Ochi, G., Sakairi, Y., Kato, M., Dan, I., & Soya, H. (2014). Positive effect of acute mild exercise on executive function via arousal-related prefrontal activations: An fNIRS study. NeuroImage, 98, 336–345. https://doi.org/10.1016/j.neuroimage.2014.04.067
 Chen, T., Yue, G. H., Tian, Y., & Jiang, C. (2017). Baduanjin Mind-Body Intervention Improves the Executive Control Function. Frontiers in Psychology, 7. https://doi.org/10.3389/fpsyg.2016.02015