Discussion

The present study examined the acute effects of two 4v4 SSG formats on neurochemical, cognitive, and technical responses in young male soccer players. Overall, the findings were broadly consistent with our hypotheses. Compared with SSGf, SSGt was associated with greater acute serum BDNF responses, greater perceived mental effort, and faster completion time in the incongruent color‐word interference condition of the Stroop test, whereas errors and corrections did not differ between formats. The two formats also produced different technical performance with SSGt increasing successful passes and shots and reducing unsuccessful passes and lost balls. Importantly, these differences occurred despite comparable internal‐load responses. The findings provide novel insight into the possible potential role of touch restriction as a task constraint for shaping cognitive, peripheral neurochemical, and technical‐action responses during soccer‐specific SSG.

Serum BDNF Levels

A growing body of evidence indicates that acute and chronic exercise is a well‐established stimulus for increasing circulating BDNF levels across a wide range of populations, including adolescents, young adults, and older individuals (Dinoff et al. 2017; Erickson et al. 2011; Szuhany et al. 2015). Nevertheless, despite the consistency of these findings in general populations, evidence remains limited in trained athletic populations, particularly in studies utilizing soccer‐specific SSG formats. Soccer is relevant in this context because it combines physical exertion with continuous cognitive demands, making it a potentially important model for studying exercise‐related neurocognitive responses.

Studies investigating exercise‐induced BDNF responses in soccer players remain limited and yield inconsistent findings. A systematic review by Gutiérrez ‐Vargas et al. (2021) concluded that current evidence is insufficient to draw definitive conclusions regarding soccer‐specific exercise effects on BDNF levels, largely due to heterogeneity in exercise protocols, sampling procedures, and participant characteristics. Among the limited available studies, Yang et al. (2012) reported a significant acute increase in BDNF following a 90‐min competitive match in adolescent males. However, full match play and SSG may differ in terms of physiological load, tactical complexity, and technical action profiles, which may lead to distinct neurobiological responses. Evidence specific to SSG is scarce and has predominantly shown no significant BDNF changes. For instance, Williams et al. (2020) reported no acute BDNF response following a soccer‐specific session incorporating technical drills and a 5‐a‐side SSG, potentially due to moderate exercise intensity (∼75% HRmax). Similarly, our previous work demonstrated that free‐play 4v4 SSG formats do not elicit significant BDNF increases (Birinciet al. 2025). In contrast, the introduction of an additional task constraint (i.e., limiting ball touches) in the same SSG format resulted in a significantly greater BDNF response. These findings suggest that exercise conditions combining physical demands with increased cognitive load may exert a synergistic effect on acute BDNF release. Notably, despite comparable internal load responses, only the cognitively constrained condition showed significant BDNF elevations, suggesting that task‐related contextual factors may contribute to acute BDNF responses beyond exercise intensity alone. Consequently, exercise‐induced changes in BDNF appear to be highly sensitive to contextual modulation. Variations in protocol design (intensity, duration, modality), participant characteristics (sex and training status), and sampling methodology collectively contribute to the divergent findings reported in the literature (Behrendt et al. 2021; Birinci et al. 2026; Dinoff et al. 2017).

The present findings should be interpreted within the broader distinction between open skill exercise (OSE) and closed‐skill exercise (CSE). OSE, characterized by externally paced, unpredictable environments requiring continuous perceptual monitoring and rapid decision‐making, has been proposed to elicit greater neurotrophic responses compared with CSE (Hung et al. 2018). This view is based on the premise that simultaneous physical and cognitive engagement may be associated with larger acute neurotrophic and better cognitive responses than physical exertion alone (Voelcker‐Rehage and Niemann 2013; Zhu et al. 2020). However, empirical evidence remains mixed (Birinci et al. 2024). For example, in a non‐soccer comparison of OSE and CSE with equivalent relative intensity, Behrendt et al. (2021) reported that both modalities acutely increased peripheral BDNF and related biomarkers, although longer‐term changes tended to favor OSE. Likewise, cross‐sectional data comparing athletes engaged in OSE versus CSE sports showed no significant difference in basal BDNF between groups (Gökçe et al. 2021), suggesting that the OSE advantage may not generalize across populations or study designs. Taken together, these findings indicate that categorizing exercise as OSE or CSE may be insufficient on its own; rather, the specific task properties embedded within an exercise (e.g., constraint‐induced spatiotemporal demands and executive‐control requirements) may determine the magnitude of neurotrophic responses. Although free‐play SSG are inherently OSE in nature, they may allow players to rely on habitual motor patterns and automatized decision‐making (Coutinho et al. 2022). By contrast, imposing a touch restriction may increase spatiotemporal pressure and require greater inhibitory control, anticipation, and rapid option selection. This manipulation likely increases cognitive engagement beyond that of unconstrained play, thereby creating a more cognitively demanding game‐based condition. This interpretation is also consistent with the broader concept of environmental enrichment, in which novelty and cognitive stimulation are considered relevant to cognitive outcomes and BDNF‐related responses (Sadegzadeh et al. 2020). The present findings suggest that, within soccer‐specific SSG, the task constraint itself may be an important factor in shaping acute BDNF responses. Manipulating SSG rules to increase cognitive load, such as touch restriction, may represent a practical strategy for coaches aiming to target not only physical and technical outcomes but also neurobiological processes related to cognitive function and brain plasticity.

Cognitive Responses

Beyond the neurochemical responses, the cognitively constrained SSG also resulted in greater improvements in executive performance, as reflected by faster Stroop completion time. The Stroop test primarily assesses inhibitory control and selective attention (Karakaş et al. 1999), which are relevant to game intelligence and adaptive behavior in soccer (Haugan et al. 2025). In this context, the touch‐restricted format may have increased executive demands by requiring players to process game information and select actions with fewer opportunities for additional ball manipulation and a greater need for early option selection during SSG.

To date, research examining the acute cognitive effects of soccer‐specific exercise remains limited. Evidence from SSG protocols suggests that exercise intensity and task characteristics may differentially influence executive outcomes. For instance, Lind et al. (2019) demonstrated that high‐intensity 3‐a‐side SSGs improved inhibitory control and attention‐related neurophysiological markers compared with moderate‐intensity formats in children. Longitudinal evidence also indicates that structured football programs incorporating SSG may enhance visual discrimination and selective attention (Alesi et al. 2015). Similarly, acute SSG formats have been shown to improve attentional performance in adolescents (Hammami et al. 2023) and visuomotor processing speed in young soccer players (Birinci et al. 2025). However, findings are not uniformly positive. Skala and Zemková (2023) reported faster reaction times but increased response errors following a 4‐a‐side SSG, suggesting that fatigue‐related factors may offset potential cognitive benefits. Collectively, these findings indicate that soccer‐specific cognitive responses may depend on exercise intensity, duration, and task structure, highlighting the importance of contextual variables in interpreting executive outcomes.

SSG inherently stimulate perceptual–cognitive processes due to their dynamic and interactive structure (Davids et al. 2013; Rodrigues et al. 2022). Limiting ball touches may increase attentional and action‐selection demands during SSG, which is consistent with previous evidence showing that touch restrictions modify technical behavior and decision‐making patterns (F. Clemente and Sarmento 2020; Coutinho et al. 2022). In the present study, the higher RSME scores observed in SSGt support the interpretation that the touch‐restricted format imposed greater cognitive load than free play. This interpretation is also supported by recent evidence showing that task constraints may partly dissociate cognitive demand from physical effort; for example, González‐Fernández et al. (2026) reported higher mental workload during smaller‐pitch SSG despite higher rating of perceived exertion in larger‐pitch formats. Although their manipulation involved pitch size rather than touch restriction, their findings suggest that the cognitive demands imposed by SSG constraints may not necessarily parallel internal load responses. Acute exercise has been associated with transient enhancements in executive functions, particularly inhibitory control (Piepmeier and Etnier 2015), and cognitively demanding or coordinatively complex activities may elicit more pronounced effects than repetitive closed‐skill tasks (Voelcker‐Rehage and Niemann 2013). Importantly, although internal load markers were comparable between conditions, only SSGt improved executive performance. This suggests that internal load alone, as reflected by heart rate and blood lactate responses, may not fully explain the observed Stroop improvement; rather, the combination of physical exertion and elevated cognitive demands may have provided a stronger stimulus for executive function performance.

The parallel increases in BDNF and Stroop performance observed in the SSGt may reflect converging responses to elevated cognitive engagement. BDNF has been implicated in synaptic plasticity and prefrontal‐dependent executive processes (Erickson et al. 2011), and acute exercise‐induced BDNF elevations have been proposed as a potential mechanism underlying transient improvements in cognitive performance (Dinoff et al. 2017; Szuhany et al. 2015). Although a direct causal pathway cannot be established, the present findings remain consistent with a possible link between acute neurochemical and executive‐performance responses. This pattern may provide a useful basis for further examining neurochemical and executive‐function responses to cognitively enriched soccer‐specific exercise.

Technical Actions

The touch‐limited SSG condition produced a distinct technical‐action profile compared with the free‐play format. Specifically, SSGt resulted in higher numbers of successful passes and successful shots, together with fewer unsuccessful passes and lost balls. Previous research has shown that limiting ball touches alters technical behavior by increasing passing involvement and reducing opportunities for prolonged ball possession as well as individual dribbling actions (F. Clemente and Sarmento 2020; Coutinho et al. 2022). In this context, the increase in successful passes and shots observed in the constrained condition may reflect a shift toward faster ball circulation and more direct attacking actions. Importantly, these technical changes occurred despite the higher perceived mental effort reported in SSGt, suggesting that the additional cognitive demands imposed by the touch restriction did not compromise technical effectiveness. These findings indicate that increasing cognitive demands within an ecologically valid game context does not necessarily compromise technical effectiveness when implemented through a soccer‐specific task constraint such as limiting ball touches.

In practical terms, the maximum two‐touch rule required players to perceive available passing or shooting options, regulate ball possession within the imposed rule, and execute technical actions with limited touches in the ongoing game context. These demands are consistent with executive processes such as inhibitory control, selective attention, and rapid response selection, which are relevant to game intelligence and adaptive behavior in soccer (Badin et al. 2016; Haugan et al. 2025). Accordingly, the higher perceived mental effort observed in SSGt supports the interpretation that the touch‐restricted format created a more cognitively demanding game‐based condition than free play. This may help explain why SSGt elicited more favorable executive function responses without compromising technical effectiveness.

The present study has limitations that should be acknowledged. BDNF concentrations were assessed at a single post exercise time point. Given that circulating BDNF levels are time‐sensitive and may peak approximately 15 min after exercise (Birinci et al. 2026), the selected sampling window may not have captured the maximal response across conditions, although an acute increase was still detectable following the touch‐restriction format. In addition, BDNF was measured only in serum, which may reflect platelet‐derived release and is affected by clotting‐related factors (Gejl et al. 2019), whereas plasma BDNF and platelet indices were not assessed. Plasma volume changes were also not estimated; therefore, potential hemoconcentration effects cannot be excluded. Regarding cognitive assessment, although the RSME provides ecologically valid insight into perceived cognitive load, subjective mental‐effort ratings do not directly quantify neural activation or cortical engagement (Otto et al. 2014). Furthermore, reliance on a single cognitive performance test (i.e., Stroop task), may have influenced the observed exercise related effects. The sample was also limited to young male soccer players; therefore, the findings may not generalize to other populations, including female players, youth athletes at different stages of neurodevelopment, or older adults. Future studies should incorporate a broader range of cognitive assessments, additional neurobiological markers, and multiple post exercise sampling time points to more comprehensively characterize the neurocognitive responses to game based training. Long term investigations examining repeated exposure to cognitively enriched SSG formats are warranted to determine whether the acute neurotrophic and executive benefits observed translate into sustained adaptations over time.