In the 2020 Organization for Economic Co-operation and Development (OECD) survey on depression prevalence among countries, South Korea recorded the highest rate of depression prevalence at 36.8%. That is, approximately 4 out of 10 individuals experience depression or feelings of sadness, highlighting the seriousness of the situation [1]. In fact, the number of patients diagnosed with depression in South Korea has reached nearly 1.02 million. Among them, the number of depression patients in their 20s was the highest, with 179,870 individuals (16.8%) [2]. Comparing the years 2013 and 2018, the increase in the diagnosis of depression among individuals in their 20s showed the highest growth rate among all age groups, at 93.2% [3]. Therefore, there is an urgent need to identify the potential remedies for depressive symptoms for young adults in South Korea.

Regular physical activity (PA) offers a diverse range of health benefits. Physical health improves cardiovascular endurance, lowers the likelihood of heart ailments, and aids in weight control by burning calories and regulating the metabolism. Moreover, it enhances muscle flexibility, hence aiding in the prevention of injuries and promoting improved bone density [4,5]. Furthermore, PA plays a crucial role in promoting mental health by reducing stress, increasing the release of endorphins to regulate mood, enhancing sleep quality, and supporting cognitive processes such as memory and focus. Indeed, PA has been found to mitigate mental disorders such as depression, stress, and anxiety [6–10]. In general, participating in regular physical activity not only increases lifespan and prevents chronic conditions, such as diabetes and some types of cancer, but also enhances immune system function, leading to a higher quality of life. Thus, the significance of incorporating and encouraging physical activity into daily routines is emphasized based on these comprehensive advantages [11].

Despite the benefits of engaging in PA, traditional in-person PA programs face limitations in terms of participation owing to the prevalent lack of time among individuals [12,13]. In fact, the structured nature of traditional programs, such as scheduled fitness classes or gymnasium sessions, often requires a significant time commitment, creating a barrier for those with busy schedules. Additionally, commuting to and from fitness centers or class locations, changing clothes, and taking showers add to the overall time investment, making it less feasible for individuals with tight schedules. The perception that engaging in such activities requires a substantial amount of time can be discouraging, leading many people to forego PA. Considering these challenges, it is essential to offer alternative options that are more adaptable.

One of the potential solutions may include utilizing technology for mobile-based PA programs [14]. In fact, there are numerous benefits to engaging in PA at home using mobile devices. First, mobile-based PA program provides flexible and convenient options and remove time limitations as it allows individuals to freely participate in PA according to their own availability and energy level compared to longer and continuous sessions [15,16]. Further, mobile-based PA improves the ease of access and convenience of PA at home, which promotes regularity and compliance with PA routines. This contributes to long-term health and overall wellbeing, as reported by Firth et al. [17]. Indeed, ample evidence has demonstrated that mobile-based PA programs have positive impacts on mental health issues such as depression, stress, anxiety, and quality of life among participants. For example, Kim et al. [14] found the significant effects of mobile phone-based PA programs on depression and perceived stress among adults. Furthermore, Vandelanotte et al. [18] investigated the effects of a three-month web-based intervention customized to individuals’ needs on various mental health outcomes, including depression, anxiety, stress, and quality of life. Among the 501 participants, the intervention group showed significant decreases in depression, anxiety, and stress at both three and nine months compared to their baseline levels. These results indicated that mobile-based PA program can promote positive outcomes in terms of reducing depression and perceived stress.

In addition to the mobile-based PA program, prioritizing shorter and more time-efficient PA routines may provide a feasible option for busy people. The rationale behind this is that it aligns with their busy schedules and minimizes barriers related to time constraints [19]. However, although ample evidence suggests that mobile-based PA has a positive impact on individual mental well-being, to the best of our knowledge, no study has integrated the principles of accumulated short bouts of PA into mobile device contexts, and it remains unclear whether such practices result in the same positive effects on mental health. In fact, the majority of research on the effects of accumulated short bouts of PA has typically focused on various physical health indicators of cardiovascular risks [20,21], weight and obesity indices [22]; and fitness indicators [23]. For example, Eguchi et al. [20] categorized participants into two physical activity groups: a long-bout group, which engaged in a single 30-min session per day for three days per week, and an accumulated short-bout group, which participated in three 10-min sessions per day for three days per week. The accumulated group experienced a substantial increase in VO₂max after 10 weeks. The implementation of physical activity programs resulted in a considerable decrease in oxidative stress, with no discernible distinction between the accumulated and continuous groups. In reference to psychological outcomes, previous literature on walking has demonstrated the mixed outcomes. Osei-Tutu et al. [24] found that engaging in accumulating 30-min of walking in three 10-min bouts was not sufficient to significantly reduce the feelings of tension and anxiety over eight weeks. On the other hand, Murphy et al. [25] found that engaging in three brief 10-min sessions of brisk walking was equally effective as a single continuous session of equal duration in reducing feelings of tension and anxiety.

The lack of studies on the effects of accumulated PA and the mixed results deserves attentions because it prevents a thorough understanding of the best methods for using mobile-based platforms to improve mental well-being. It is crucial to bridge this divide and create customized and efficient PA interventions that consider individuals’ limited time and personal preferences. We believe this endeavor will contribute to progress in both mobile-based physical activity programs and mental health promotion.

Taken together, this study aimed to investigate the effects of mobile-based PA programs delivered in the form of accumulated bouts on mental health indicators, including depression, perceived stress, and negative affectivity among healthy college students in South Korea. By identifying the significant implications associated with the adoption of accumulated bouts of PA programs, our objective was to offer alternative avenues, particularly for individuals with busy schedules and reservations about attending fitness gyms.

The primary objective of this study was to investigate the effects of accumulated short bouts of PA using mobile devices on mental health outcomes, specifically targeting depression, perceived stress, and negative affectivity among South Korean college students. This study included 44 healthy college students (23 in the accumulated group and 21 in the control group). The accumulated group showed significant decreases in depression and perceived stress, as demonstrated by paired-sample t-tests. The subsequent 2 × 2 RMANOVA confirmed these findings by showing a significant impact of time and interaction on depression. The following discussion synthesizes these findings to derive significant insights into the consequences of mental health interventions and effectiveness of mobile-based PA initiatives.

One of the main findings of this study was that there were statistically significant reductions in both depression and perceived stress in the accumulated group. This finding indicates that even short and frequent engagement in PA facilitated by mobile devices can offer tangible mental health benefits in terms of mitigating the symptoms of depression and perceived stress. Previous studies have reported that even brief periods of PA (10-min) have the potential to induce the secretion of endorphins and neurotransmitters that are positively correlated with the emotions of joy [36,37]. This neurochemical reaction has the potential to enhance mood and function as an inherent safeguard against symptoms associated with depression and stress [38,39]. This finding contributes to the existing body of knowledge supporting the effectiveness of mobile-based PA in promoting mental health. More importantly, this is the first study to identify the significant impact of accumulated PA interventions on depression and perceived stress within a mobile context. Previous studies have often focused on continuous PA interventions in the mobile context [15–18] or accumulated PA interventions in traditional in-person settings [20–23]. By integrating the two unique contexts of accumulated and mobile settings, the current study demonstrates the importance of short and frequent interventions, establishing mobile-based accumulated PA as a feasible approach to improve mental health.

Additionally, the findings from the 2 × 2 RMANOVA provided additional support for the significant efficacy of the accumulated PA program, revealing a significant interaction effect of group and time on depressive symptoms. The unique impact of the accumulated PA program on depression highlights its significant contribution to the improvement of mental health, thus adding to our understanding of the effects of diverse PA programs. This resonates with previous literature advocating diverse approaches to PA interventions for mental health, acknowledging the potential effectiveness of novel formats such as accumulated bouts within mobile settings. The theoretical implications of these findings extend to a broader framework of mental health intervention strategies. The distinctive impact of the accumulated PA program on depression, as evidenced by the interaction effects, challenges the traditional views of uniform mental health interventions. It suggests that tailoring interventions to include accumulated short bouts of physical activity can yield specific and favorable mental health outcomes. Integrating these findings into theoretical models of mental health interventions broadens our perspectives and encourages more context-specific approaches.

Finally, this study found that neither type of PA significantly reduces negative affectivity. This result is consistent with previous literature that has also found insignificant relationships between PA and negative affectivity [40,41]. The lack of impact may be attributed to the intensity and duration of the PA sessions. Research indicates that longer duration PA sessions, particularly those lasting 30-min or more, are often associated with greater improvements in mood. In this study, the participants engaged in PA for approximately 20-min, which may have been relatively short in duration, thereby potentially limiting its effectiveness in eliciting significant changes in negative affectivity.

This study has some limitations, and recommendations for future research are proposed. First, we encountered difficulties in randomizing the enrolled participants into intervention and control groups. Participants who demonstrated willingness to participate in PA and received approval from the researchers were enrolled in the treatment group. This self-selection process may have introduced bias, as individuals with specific characteristics or motivations may have been more inclined to participate in the study, potentially influencing the outcomes. Thus, caution should be exercised when interpreting the outcomes of the accumulated PA program in this study. Future studies should reassess the findings of this investigation using a randomized allocation study.

Moreover, the generalizability of this study is limited by its exclusive focus on healthy college students. Hence, these findings may not be broadly applicable to heterogeneous populations or varied mental healthcare environments. Future studies should explore a broader range of individuals to improve the generalizability of the results. For example, a follow-up study could include individuals diagnosed with depression to examine the impact of accumulated PA on depressive symptoms in the clinical environment. Further investigation should focus on the older adult population. In the similar vein, the relatively small sample size may restrict the generalizability of findings. As such, caution should be emphasized when applying the results to larger and more diverse populations. Future research efforts should aim to address this limitation by recruiting a larger and more heterogeneous sample to improve the external validity of the study findings. Additionally, expanding the sample size would enable researchers to explore potential subgroup differences and better understand the nuanced effects of the intervention across different demographic groups.

Furthermore, the study evaluated the participants’ results at two specific moments: the first assessment and the post-test. Nevertheless, a more extended period of observation would be beneficial in order to assess the long-term durability of the impacts of PA programs. Hence, it is recommended that future studies prolong the duration of follow-up in order to evaluate the enduring impact of PA interventions. This will allow for a better understanding of the sustainability of the reported results and the possibility of intervention benefits diminishing with time.

Finally, the nonsignificant results for negative affectivity should prompt a closer examination of the intervention components. Assessing whether the intervention addresses specific facets of negative affectivity could offer insights into potential areas for improvement or optimization. This in-depth examination sought to uncover the reasons for the lack of significant results in these areas. This provides an opportunity to pinpoint particular aspects of the intervention that may require refinement or optimization to enhance its efficacy in addressing negative affectivity. Essentially, it advocates a more nuanced evaluation of the intervention’s impact on specific outcomes, facilitating an informed and targeted approach to future interventions or adjustments to the existing program.

This study aimed to investigate the impact of mobile-based PA programs, conducted in short intervals, on mental health indicators with a specific focus on depression, perceived stress, and negative affectivity among college students in South Korea. The results indicated a significant decrease in depression and perceived stress in the experimental group, whereas the control group did not show any meaningful differences. The results of the 2 × 2 RMANOVA demonstrated a clear and significant relationship between time and depression scores. This finding highlights the potential influence of physical activity accumulated through mobile devices on mental health outcomes. These findings add to the increasing amount of research highlighting the positive effects of flexible and easily accessible PA programs on mental health. Furthermore, this provides a practical alternative for people with busy schedules who find it difficult to participate in longer, continuous physical activity sessions. These findings underscore the importance of integrating such interventions into public health policies aimed at promoting mental well-being among young adults. Furthermore, in the realm of mobile health application development, our study highlights the significance of incorporating features that support and encourage participation in mobile-based PA interventions tailored to the unique needs and preferences of college students.