Physiologia

Background/Objectives: Executive function, which includes inhibitory control, working memory, and cognitive flexibility, tends to decline with aging. While traditional resistance training (TRT) has shown positive effects in mitigating these declines, limited evidence is available regarding flywheel resistance training (FRT). This study aimed to evaluate and compare the effects of TRT and FRT on executive function in older women. Methods: In this randomized controlled trial (clinicaltrials.gov NCT05910632), 29 older women were allocated into two groups: TRT (n = 15) and FRT (n = 14). The intervention lasted eight weeks with two weekly sessions conducted at the Federal University of Viçosa. The TRT group performed exercises using machines and free weights, while the FRT group used a multi-leg isoinertial device. Executive function was assessed using the Victoria Stroop Test (inhibitory control), Digit Span Test (working memory), and Trail Making Tests A and B (cognitive flexibility). Data were analyzed using a Multivariate Analysis of Covariance (p < 0.05). Results: No significant changes were observed in inhibitory control (p = 0.350). Working memory improved significantly within both groups in forward (p = 0.002) and backward (p = 0.002) span tasks. For cognitive flexibility, Trail Making Test A showed no significant changes (p > 0.05), but Test B showed significant within-group (p = 0.030) and between-group (p = 0.020) improvements. The B-A difference was also significant (p = 0.040). Conclusions: Both resistance training modalities enhanced working memory and cognitive flexibility. However, FRT produced greater improvements in cognitive flexibility, suggesting potential advantages in cognitive aging interventions. Full article

Objective: This study aimed to evaluate the effects of cold-water immersion (CWI) on post-training recovery in Kung Fu athletes. Methods: In a 3-week crossover design, 16 Kung Fu athletes (22.00 ± 5.95 years, 76.90 ± 9.74 kg) were divided into two conditions: CWI and passive recovery as a control (CON) measure. Through the study, muscle damage markers (creatine kinase [CK], lactate dehydrogenase [LDH], aspartate aminotransferase [AST] and alanine aminotransferase [ALT]), physical performance tests (upper limbs power, SJ and CMJ), skin temperature (from lower and upper limbs), and skin temperature asymmetries were measured. Results: CWI resulted in a higher reduction of CK concentration than CON 24 h after the intervention (−21.32%; p < 0.001). The SJ height 24 h after the intervention was higher in the CWI than in the CON (p < 0.001). Both CWI and CON resulted in skin temperature returning to baseline levels 24 h after intervention. Conclusions: CWI was effective in restoring muscle power, reducing muscle damage and reducing body temperature (BT) in Kung Fu athletes. Cold water recovery showed better muscle power and strength 24 and 48 h after training when compared to the passive method. CK and skin temperature were better 24 h after cold water recovery. Full article

Background/Objectives: Beetroot juice is a popular nutritional resource in sports due to its ergogenic effects, promoting vasodilation, hypotension, improved energy efficiency, and reduced oxygen cost. However, its role in modulating the autonomic nervous system during strength training remains understudied. This study assessed the effects of acute nitrate-rich beetroot juice supplementation on cardiovascular and hemodynamic responses to flywheel resistance exercise. Methods: Fifteen male participants (age 22 ± 3.64 years) from the Federal University of Viçosa completed a crossover, double-blind, placebo-controlled trial. Each participant consumed either 400 mg of standardized nitrate or a placebo before performing 4 sets of 8–12 repetitions at 100% of their maximum concentric strength using a leg extension exercise, with 90 s recovery intervals. Heart rate, blood pressure, oxygen saturation, and subjective perception of effort were measured after each set. Data were analyzed using SPSS 23, employing the Shapiro–Wilk normality test, t-test for related samples, and MANOVA with time and supplement factors. Results: NO₃⁻ supplementation led to a smaller increase in systolic blood pressure (SBP) during exercise compared to the placebo and reduced diastolic blood pressure (DBP) in the last set, reflecting decreased peripheral vascular resistance. However, no significant effects were observed for heart rate, rate–pressure product, oxygen saturation, time under tension, or subjective perception of effort. Conclusions: These findings suggest that NO₃⁻ supplementation can offer cardiovascular benefits by attenuating blood pressure increases during strength training, highlighting its potential as a low-risk ergogenic aid for healthy young men. Full article

Background/Objectives: The use of buoyant equipment in water fitness sessions appears to elicit a more intense physiological response in water exercises. However, it remains unknown whether the shape of the equipment influences these responses. The present study aimed to analyze and compare the physiological responses and perceived effort while older women using different buoyant dumbbells during horizontal adduction/abduction of the upper limbs (HA exercise). Methods: Ten older women (76.1 ± 5.3 years of age) attended two assessment sessions to perform HA exercise at a music cadence of 120 bpm with different buoyant dumbbells (one pair for each session): round hydro and hydro crystal. Mean heart rate (HR), systolic and diastolic blood pressures (SBP and DBP, respectively), double product (DPr), blood lactate concentration ([La⁻), and rate of perceived effort (RPE) were assessed according to pre-exercise (rest), warm-up and the HA exercise (five min effort). Results: The mean HR was also analyzed according to the percentage (%) of the predicted maximal theoretical HR (HRmax). Older women reached ~56 and 61% of HRmax using crystal and round dumbbells, respectively. Differences were found in mean HR, [La⁻], and RPE with the round dumbbell showing greater values than the crystal dumbbell. Although no differences were found in SBP and DBP, DPr was higher when women used the round dumbbells. Conclusions: The shape of buoyant dumbbells seems to define acute responses of older women as the round dumbbell promotes a more intense physiological response and perceived effort when compared to the crystal dumbbell. Full article

Objective: Protein supplements (PSs) are widely consumed by professional and non-professional athletes, yet research on non-athletic PS users’ perceptions, motivations, and health risk awareness is limited. This study aimed to investigate non-professional athletes’ PS patterns of use, motivations, and safety. Methods: A cross-sectional study was conducted using a constructed questionnaire reporting on PS usage trends, exercise habits, and demographic factors. Adult respondents were recruited from gyms, athletic organizations, amusement parks, and playing fields. Results: We received 1100 responses, and 327 were PS users. From the total of PS users, there was a prevalence of PS use in males [(203 (62%)]; adults in the age group of 25–34 [136 (42%)], p < 0.001; and participants with a normal BMI (189, 58%), p < 0.001. Following high-intensity fitness exercise sessions and engagement with more than two types of physical activity were associated with more than doubled odds of PS consumption (p < 0.001). The main reasons for PS intake were for muscle mass increase (35%) and recovery (18%), and protein powder was the most popular PS (279; 64%). The main channels of information for PS use were Web/social media (50, 40%) and coaches (54, 43.2%), while one out of two [35 (49%); p = 0.008] of those engaged in more than two types of physical exercise declared that PSs are good for health. Conclusion: The findings highlight demographic, behavioral, and informational factors shaping PS consumption in non-professional athletes. Despite the perceived benefits, reliance on non-expert sources and unregulated products raises concerns about consumer awareness and safety, while educational initiatives to promote evidence-based supplementation practices are deemed crucial. Full article

Background/Objectives: Creatine monohydrate (CRE) is a popular nutritional supplement that increases lean/muscle mass accretion. Although data regarding CRE and its effects on muscle protein synthesis are mixed, we hypothesized that CRE may potentiate/extend the anabolic response to essential amino acids given that CRE acts as a high-energy phosphate buffer to potentially amplify anabolic signaling. Therefore, we used an in vitro model to determine whether CRE synergistically enhances myotube protein synthesis and the anabolic signaling responses to EAA-rich whey protein (WP). Methods: C₂C₁₂ murine myotubes were treated with control media containing PBS (CTL), WP serum (5 mg/mL), CRE (10 mM), or WP + CRE. Myotubes were collected following 1, 4, and 24 h treatments (n = 6 replicates per treatment and time point) and assayed for relative creatine levels, myotube protein synthesis levels, and phosphorylation markers. Results: Cellular creatine levels were greater in CRE and WP + CRE versus CTL and WP at all treatment time points (p < 0.05). The protein synthesis levels with 4 hr treatments with WP and WP + CRE were greater compared to the CTL (p = 0.036 and p < 0.001, respectively), and 24 h levels were greater with WP versus other treatments (p < 0.05). p-p70S6K (Ser389) and p-rpS6 (Ser235/236) were greater with WP at 1 h compared to all other treatments (p < 0.05). No effects across time points were observed for p-mTOR (Ser2448), p-4E-BP1 (Thr37/46), or p-AMPKα (Thr172). Conclusions: WP increases protein synthesis and anabolic signaling with no additive effect from CRE. However, given that myotubes were not stressed nor stimulated to contract, such models are needed with the current treatment schematic to examine potential interactions. Full article

Introduction: Oral rehydration reduces thirst sensation (TS), which may negatively affect autonomic function, measured by heart-rate variability (HRV). However, it is unclear if this effect is independent of hydration changes. This study examines whether TS influences autonomic function between intravenous and oral rehydration. Methods: Twelve males (mean ± SD; age, 29 ± 12 years; 74.7 ± 7.9 kg; 179.4 ± 7.0 cm; VO2_max, 49.8± 6.6 mL·kg⁻¹·min⁻¹) cycled at 55% VO_2max for 90 min followed by a 12 km time trial. Two experimental conditions were performed in a counterbalanced, randomized order; (a) the high thirst (HT) group were infused 25 mL of isotonic saline every 5 min via an intravenous tube, and (b) the low thirst (LT) group ingested 25 mL of water every 5 min. TS and heart rate were collected every 5 min. HRV was assessed pre exercise, post steady-state exercise, and post time trial. HRV parameters included time domain, frequency domain, and non-linear measures analyzed by two-way repeated measures ANOVA. Results: There was a significant time x condition for the root mean square of successive RR interval differences (RMSSD_log), high-frequency (HF) power, and SD1 (p < 0.05). In LT, RMSSD_log decreased from Pre to Mid (3.71 ± 0.61 ms to 2.53 ± 1.15 ms, p < 0.01) and Pre to Post (2.18 ± 0.90 ms, p < 0.01) but stabilized from Mid to Post (p = 0.39). High-frequency (HF) power in HT was maintained from Pre (3.7 ± 0.6 nu) to Mid (3.4 ± 0.8 nu, p = 0.21) but decreased from Pre to Post (2.5 ± 0.7 nu, p < 0.01) and Mid to Post (p < 0.01). LT decreased in HF power from Pre (3.7 ± 0.5 nu) to Mid (3.0 ± 0.8 nu, p < 0.01) and Pre to Post (3.0 ± 0.7 nu, p < 0.01); Mid and Post was maintained (p = 0.99). SD1, decreased in HT (Pre: 3.4 ± 0.4 ms, Mid: 2.0 ± 1.1 ms, Post: 1.1 ± 0.5 ms; all comparisons p < 0.05). In LT, SD1 decreased from Pre (3.4 ± 0.6 ms) to Mid (2.18 ± 1.15 ms, p < 0.01) and Pre to Post (1.83 ± 0.90 ms, p < 0.01), but stabilized Mid to Post (p = 0.39). Conclusion: Satiating thirst through oral rehydration increases parasympathetic activity post exercise, reducing stress and increasing recovery between exercise bouts. These findings have implications for optimizing rehydration strategies in sports and occupational settings. Full article

Background/Objectives: Studies of the effects of anchor schemes (perceived intensity vs. relative intensity) on muscular performance have reported mixed findings. Therefore, the present study examined the effects of different anchor schemes on time-to-task failure (TTF), muscular performance, neuromuscular responses, and potentiated twitch torque (PTT). Methods: On separate days, 15 men (age = 21.5 ± 2.3 yrs) performed forearm flexion maximal voluntary isometric contractions (MVICs) before and after sustained tasks anchored to a rating of perceived exertion of 6 (RPEFT) and with the torque at RPE = 6 (TRQFT). Electromyographic amplitude (EMG AMP) and mean power frequency (EMG MPF) were recorded from the biceps brachii (BB). Supramaximal stimuli were delivered to the motor nerve of the BB following the MVICs to quantify the PTT. Repeated measures ANOVAs assessed the mean differences between anchor schemes for MVIC, neuromuscular, and PTT responses. Paired t-tests compared the magnitude of percent changes for the dependent variables. Results: The TTF for the RPEFT was longer (p < 0.001) than the TRQFT, but the MVIC decreased similarly (12.7 ± 9.5% vs. 20.3 ± 7.9%, p = 0.054). Electromyographic AMP did not change (p = 0.288), while EMG MPF decreased (15.7 ± 10.2%, p < 0.011) for the TRQFT only. Mean decreases in PTT were comparable for both tasks (p < 0.003), although the percent change was greater for the TRQFT (49.6 ± 16.1%, p < 0.001). Conclusions: The differences in TTF, but similar decreases in MVIC suggested that participants reached a sensory tolerance limit. Based on EMG MPF and PTT, the TRQFT caused greater peripheral perturbations to contractile function than the RPEFT. Full article

Background: Extensive data exists on external load during training and competition, but a significant gap remains in understanding internal physiological load, particularly in protocols conducted in ecological settings. Given the scarcity of studies on the on-field cardiorespiratory profiles of national-level athletes, especially in Argentine soccer, this study aimed to identify the on-field cardiorespiratory fitness profile of ten highly trained youth field soccer players (13.6 ± 1.3 years old) from both the first league of the Argentine Football Association and members of the national team in their age group category in the current year. Methods: Each athlete performed an on-field cardiorespiratory exercise test (20-m Shuttle Run Test, 20-m SRT) with the COSMED K5 wearable metabolic system (COSMED, Rome, Italy) in dynamic micro-mixing chamber mode. The 20-m Shuttle Run Test involves running back and forth between two lines set 20 m apart, following the pace set by an audio signal. The test starts at a running velocity of 8.5 km·h⁻¹ and increases by 0.5 km·h⁻¹ each min. Results: Mean velocity at maximal oxygen uptake (v$\dot{\mathrm{V}}$O_2max) was 12.3 ± 0.7 km·h⁻¹. The maximal oxygen uptake ($\dot{\mathrm{V}}$O_2max) on-field was 67.1 ± 5.3 mL·kg⁻¹·min⁻¹. The $\dot{\mathrm{V}}$O₂ at the first and second ventilatory thresholds (VT1 and VT2) were identified at 67.0 ± 3.0% $\dot{\mathrm{V}}$O_2max (44.9 ± 3.3 mL·kg⁻¹·min⁻¹) and 84.7 ± 3.7% $\dot{\mathrm{V}}$O_2max (56.8 ± 3.8 mL·kg⁻¹·min⁻¹), respectively. Conclusions: This is a scarce on-field gas exchange assessment, conducted in an ecological context using a portable analyzer with highly trained national-level youth soccer players from the Argentine youth national team, which underlines their cardiorespiratory fitness, showcases their high-performance potential, offers valuable insights into a selective group of players, and provides a reference for larger-scale research on elite youth soccer and the long-term development of aerobic power and capacity. Full article

Background/Objectives: Neurodegenerative diseases represent a growing global health challenge with limited therapeutic options. Physical exercise has emerged as a promising non-pharmacological intervention with potential neuroprotective effects. This narrative review examines the mechanisms through which exercise induces neuroplasticity and their implications for neurodegenerative disease prevention. Methods: We synthesized evidence from molecular, animal, and human studies on exercise-induced neuroplasticity and neurodegenerative disease prevention through a comprehensive literature review. Results: Exercise enhances neuroplasticity through multiple pathways: (1) neurotrophic signaling (BDNF, IGF-1, VEGF), (2) neuroendocrine regulation, (3) epigenetic modifications, and (4) metabolic pathway optimization. These molecular changes support structural adaptations including hippocampal neurogenesis, enhanced synaptic plasticity, improved cerebrovascular function, and optimized brain network connectivity. Exercise directly impacts pathological features of neurodegenerative diseases by reducing protein aggregation, attenuating excitotoxicity and oxidative stress, and enhancing mitochondrial function. Clinical evidence consistently demonstrates associations between physical activity and reduced neurodegenerative risk, with intervention studies supporting causal benefits on cognitive function and brain structure. Conclusions: Exercise represents a multi-target intervention addressing several pathological mechanisms simultaneously across various neurodegenerative conditions. Its accessibility, minimal side effects, and multiple health benefits position it as a promising preventive strategy. Future research should focus on understanding individual response variability, developing sensitive biomarkers, and creating personalized exercise prescriptions for optimal neuroprotection. Full article

Background: The aim of this systematic review was to collect, appraise, and synthesize the available information related to the cardiovascular and metabolic demands of commonly performed firefighting tasks while wearing personal protective equipment (PPE) inclusive of self-contained breathing apparatus (SCBA). Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, academic databases (PubMed, Embase, and SPORTDiscus databases) were searched for relevant records which were subjected to dedicated eligibility criteria with included articles quality appraised using the Critical Appraisal Skills Programme (CASP) checklist. Results: Of an initial 1463 identified records, 20 studies with a mean CASP of 8.26/11 informed the review. A myriad of varying field tests have been employed to determine physical preparedness and assess the metabolic demand of firefighting. Conclusions: The volume of evidence suggests that PPE and SCBA must be incorporated when assessing the demands of firefighting as they clearly increase the metabolic cost of combined simulated firefighting tasks. Although real-world scenarios are made up of a combination of individual firefighting tasks, there remains a clear need to determine the metabolic cost of isolated firefighting tasks such as forcible entry, hose drag, victim rescue, ladder raise, and stair climbing with and without PPE and SCBA. The quantification of the metabolic demand of these tasks may assist tactical trainers when designing simulated scenarios and training programs for firefighters. Full article

Background/Objectives The plants of the Lavandula genus are widely investigated because of their significance for pharmaceuticals and food. The composition of lavender essential oil is determined by genotype and can be induced by environmental, ontogenetic factors, and morphogenetic features. Linalool and linalyl acetate are the most abundant compounds, performing essential ecological functions and participating in lavender’s therapeutic properties. This review reports on the biosynthesis of lavender oil compounds and summarises the environmental, developmental, and molecular factors contributing to essential oil composition in lavender flowers. Results Floral developmental stage and ontogeny are fundamental for optimal harvest time. The harvesting period for high-quality lavender essential oil is affected by environmental and developmental factors that influence the gene expression of monoterpene biosynthesis. Conclusions These findings indicate the appropriate features for high-quality lavender essential oil and contribute to information that may allow for the manipulation of monoterpenes biosynthesis in lavender breeding efforts. Full article

Background: Building on our previous work, this study presents a cost-effective, non-invasive methodology for recording, identifying, and analyzing plant ultrasonic emissions in dynamic environments, both indoor and outdoor. While previous research has utilized contactless microphones to compare water-stressed and hydrated plants indoors, to the best of our knowledge, no similar studies have been conducted in outdoor conditions. The objective of this study is to address the need for scalable, accessible tools for monitoring plant stress in a variety of environmental settings. Methods: Pinto bean and tomato plants were exposed to water stress conditions and monitored in both indoor and outdoor environments, with plant acoustic emissions recorded using an ultrasonic microphone. Results: The proposed methodology successfully recognized plant ultrasonic emissions even in the presence of high levels of environmental noise typical of outdoor conditions (e.g., wind, rain, or insect chirping). Conclusions: We argue that this method, with its minimal equipment requirements, is a valuable addition to the range of tools available for Plant Acoustics research, offering the potential for non-invasive monitoring in a variety of different environments. Full article

Background/Objectives: Volleyball training camps are known to reduce salivary secretory immunoglobulin A (s-SIgA); however, when it begins to decrease is unclear. The validity of a simple device for quantifying s-SIgA is lacking; hence, this study aimed to observe detailed s-SIgA changes during a volleyball training camp after moving to a high altitude and to investigate the difference in s-SIgA response between the two quantification methods, namely, the enzyme-linked immunosorbent assay (ELISA) and lateral flow device (LFD). Methods: Twenty-four male university volleyball players participated in the observational study. Measurements were collected at three points of the training camp (days 1, 4, and 7). The s-SIgA was quantified using conventional ELISA and the new LFD method. Results: The s-SIgA concentrations quantified using the two methods decreased significantly by day 4 (p < 0.05) and continued to decrease until day 7 (p < 0.05). A significant positive correlation was found between the s-SIgA concentrations quantified using the LFD and ELISA (p < 0.05, r_s = 0.319). Conclusions: These results indicate that a high-altitude volleyball training camp may suppress oral immune function by day 4 and that the evaluation of s-SIgA concentration using the LFD method is beneficial. A faster and easier method for assessing s-SIgA could contribute to athletes’ condition management strategies. Full article

Background: Substance Use Disorders (SUDs) are chronic conditions characterized by high relapse rates and significant psychological, physical, and social complications. Despite the availability of traditional pharmacological and psychotherapeutic interventions, many individuals struggle to maintain abstinence. Recently, physical activity (PA) has emerged as a promising complementary intervention. This review aims to examine the existing evidence on the effects of PA in individuals with SUDs, with a particular focus on neurobiological mechanisms. Methods: A narrative review was conducted on 30 September 2024, searching relevant keywords on PubMed, Web of Science, Google Scholar, and Scopus. Randomized clinical trials, cohort studies, reviews, and meta-analyses published between 1988 and 2024 were considered. Results: Fifty studies were included. Key themes included the role of PA in inducing neuroadaptation in individuals with SUDs, which is crucial for relapse prevention and impulse control, and the effects of PA depending on the type of PA and the specific SUD. Neurobiological modifications related to PA are of particular interest in the search for potential biomarkers. Additionally, studies explored the effects of PA on cravings, mental health, and quality of life. The review overall discusses the psychological changes induced by PA during SUD rehabilitation, identifies barriers to participation in PA programs, and suggests clinical and organizational strategies to enhance adherence. Conclusions: Physical activity is a promising adjunctive therapy for the management of Substance Use Disorders. Long-time longitudinal studies and meta-analyses are needed to sustain scientific evidence of efficacy. The success of PA programs moreover depends on overcoming barriers to adherence, including physical, psychological, and logistical challenges. Full article

Background/Objectives: This study examines the utility of the 3-min all-out test (3MT) in determining exercise intensity domains through critical speed (CS), offering a practical alternative to traditional $V{O}_{2max}$-based methods. Methods: Eighteen trained runners completed both the 3MT and a graded treadmill test. CS, $V{O}_{2max}$, and $H{R}_{max}$ were measured and compared to markers such as ventilation threshold (VT), gas exchange threshold (GET), lactate threshold (LT), onset of blood lactate accumulation (OBLA), CS, and $V{O}_{2max}$, which are threshold markers for defining six exercise intensity domains. Results: Results demonstrate that CS reliably distinguishes among six exercise intensity domains with greater precision and less variability than heart rate (HR) or $V{O}_2$-derived metrics. Notably, HR was unable to differentiate between high-intensity domains, highlighting its limitations for performance prescription. Compared to $V{O}_{2max}$ testing, the 3MT offers a simpler, non-invasive, and time-efficient approach to identifying training zones and monitoring performance. CS effectively delineated moderate-to-heavy, heavy-to-severe, and severe-to-extreme intensity domains, with strong correlations to performance thresholds. The findings emphasize the accessibility and reliability of the 3MT, particularly in overcoming the logistical challenges of traditional testing methods. Conclusions: This research underscores the potential of the running 3MT as a valuable tool for individualized training prescription and performance monitoring in both research and applied sports contexts, paving the way for a broader adoption in athletic training methodologies. Full article

Background/Objectives: Plyometrics is a widely used method to enhance the physical performance of athletes. Studies have demonstrated that the effectiveness of plyometrics increases when combined with other training methods. This study aims to determine whether the direct combination of plyometric and sprint training improves linear sprint speed and change-of-direction speed in youth soccer players. Methods: Twenty-eight male youth soccer players were randomly assigned to an intervention group (INT, n = 14, 12.9 ± 0.4 years) and a control group (CON, n = 14, 12.9 ± 0.7 years). The INT group performed two sessions per week, each including nine drop jumps, followed by a hurdle jump and one sprint. The CON group only performed nine sprints without any jumps. Both groups continued their regular soccer training over the 20-week intervention period. Pre- and post-intervention tests included 5 m, 10 m, and 30 m linear sprints and a modified agility t-test for change-of-direction speed. Results: Largest improvements were observed in the INT group (5 m = 6.7%, 10 m = 4.8%, 30 m = 2.7%, change-of-direction speed = 3.6%, 3.1%). A significant difference between the groups was noted for the 10 m sprint distance (p = 0.02). Furthermore, moderate to large correlations between linear sprint speed and change-of-direction speed were found in both groups (r = 0.33–0.82). Conclusions: Results suggest that the direct combination of plyometric training and sprint training over a 20-week period can improve both linear sprint speed and change-of-direction speed in youth soccer players, thus enhancing physical performance. Full article

Background/Objectives: Functional near-infrared spectroscopy (fNIRS) may help quantify changes in brain haemodynamics during sport-related concussions (SRCs). This study compared post-match prefrontal cortex (PFC) brain haemodynamics measured by fNIRS during the King–-Devick test (K-DT) with players suspected of having sustained an SRC. It was hypothesized that changes in the K-DT would correspond with brain haemodynamic processes. Methods: Twenty-two male and female collegiate rugby players (six males and twenty-two females; age range: 18–22) completed a baseline K-DT+fNIRS assessment. Over the course of two to three matches, all participants were invited to complete at least one post-match K-DT+fNIRS assessment. If a player was suspected of having sustained an SRC, they were re-assessed with the K-DT+fNIRS. If a participant who was not suspected of having sustained an SRC performed worse on the K-DT post-match, they were included in the participant category of ‘concussion’ for the analysis. A repeated measures ANOVA was performed. Test–retest reliability was calculated using the intra-class correlation coefficient (ICC). A Pearson correlation coefficient (r) assessed the linear relationship between the changes in the K-DT and the measurements of the left and right PFC. Results: Differences were identified in the K-DT for the players with a suspected concussive injury post-match (χ2(1) =5.0; p = 0.0253; z = −2.0; p = 0.0431; d = 0.16). There were also significant differences between the baseline and post-match results for all concussed players in the right PFC (t(8) = 250; p = 0.0371; d = 0.92) and for the concussed females in the right PFC (t(6) = 2.78; p = 0.0319; d = 0.52). There were no correlations between the K-DT and PFC values in the suspected concussed group. Conclusions: The SRC group had decreased cognitive performance and a notable change in PFC activation, while the non-concussed group showed an increase in the activation in the PFC and no change in cognitive performance scores. This represents a possible acute adjustment in brain haemodynamics and provides insight into how SRCs can negatively impact cognitive performance. Full article