Training practices of Japanese elite team and combat sport athletes during the COVID-19 pandemic: an interview study with support staff

Background: The coronavirus disease 2019 (COVID-19) pandemic had a profound impact on the world of sports, particularly elite athletes. This study aimed to investigate how elite athletes adapted their training during the pandemic through semi-structured interviews with performance support staff from national (NT) and professional (PT) teams.

Methods: Thirteen Japanese support staff (NT = 9, PT = 4) provided insights into the challenges of maintaining training duration, intensity, and quality, as well as strategies adopted to navigate specific phases, including “during” and “after” the nationwide State of Emergency and “during” and “following” two-week quarantines, through semi-structured interviews.

Results: During the nationwide State of Emergency and subsequent quarantines, most NT and PT support staff reported that athletes had limited access to conventional training equipment and facilities, often relying on makeshift alternatives. When these options were insufficient, the support staff modified training content based on equipment availability. Moreover, many athletes voluntarily refrained from outdoor workouts to avoid negative public attention, despite no legal ban on outdoor training. Most NT and PT support staff relied on online platforms for group or personal sessions to help maintain fitness and motivation, although these methods were considered inadequate for achieving optimal outcomes. Upon returning from quarantine, support staff implemented phased return-to-play programs. For some athletes, the cancellation of competitions presented an opportunity to focus on thorough rehabilitation for chronic injuries. Furthermore, social isolation and uncertainty increased mental health concerns among athletes, emphasizing the need for greater psychological support. Elite athletes faced challenges, including limited indoor space, inadequate equipment, and lack of “domestic rivals” to optimize training performance.

Conclusion: Overall, the pandemic experience emphasized the importance of robust, adaptable athlete-support systems capable of modifying training under constrained conditions. These findings highlight the value of well-defined return-to-play approaches, better communication among support staff, and holistic support strategies (well-being, etc.) to enhance resilience during future disruptions.

1 Introduction

The coronavirus disease 2019 (COVID-19) pandemic had a profound impact on the world of sports. Global lockdowns and subsequent restrictions in the first half of 2020 severely disrupted athletic activities, leading to facility closures, travel limitations, and social distancing protocols among other measures. These restrictions varied based on governmental and local regulations. Athletes faced considerable challenges, including the cancellation or postponement of major sporting events, such as the Tokyo 2020 Summer Olympics and various national and international competitions.

In response to these disruptions, many athletes personalized their training at home to maintain or increase their fitness and performance (1). In a large global cohort, Washif et al. (2) reported substantial reductions in key training variables (e.g., frequency, duration, intensity, type) during lockdowns. Notably, elite athletes engaged in more intensive and high-volume daily training than lower-level athletes, and a higher proportion of them reported being able to maintain their training (3). They coped relatively better with the training restrictions due to the greater availability of training equipment and support staff (2, 4), although these resources were limited in scope (1). However, the cancellation of international competitions due to travel restrictions further reduced opportunities for athletes to practice and compete against their rivals. Unlike recreational or lower-level athletes, whose involvement in sports activities is related to leisure and non-career pursuits, elite athletes [i.e., national team (NT) and professional team (PT) athletes] train vigorously on a full-time basis as part of their career objectives, striving to earn a living and win major events such as the Olympic Games.

Elite athletes, who typically depend on support staff for their training (5), faced considerable challenges during the lockdowns (1), with only half continuing to receive guidance from coaching staff (2). Lockdown training often required modifications to comply with restrictive policies, such as home-based training, and further constrained by resource availability (e.g., using household items) (1). This lockdown-induced training adaptation yielded variable outcomes, including improvements in certain fitness parameters, possibly due to a shift in focus towards previously neglected physical components (1, 6). In Japan, the nationwide State of Emergency brought about various restrictions, similar to other countries. These restrictions were either voluntary (7) or legally mandated under the Infectious Diseases Control Law (8, 9) and the Quarantine Act for Overseas Entry (9) (summarized in Table 1). For high-performance sports, these circumstances are particularly significant: (a) Japan was the host of the Tokyo 2020 Olympics (held in 2021); (b) there was substantial preparation by Japanese athletes and support staff for the Olympics, and its prominent Professional leagues (i.e., baseball, soccer, and basketball). Japan's third-place in gold medals at the 2020 Olympics may reflect its success in navigating the pandemic challenges. Nevertheless, training adaptations and strategies of Japanese athletes and support staff under these circumstances during the COVID-19 pandemic are virtually unknown, and have not been emphasized in previous studies regarding different national contexts (11–14).

Table 1

Table 1. COVID-19 control measures and restrictions in Japan across different periods.

Previous studies have conducted questionnaire surveys of athletes at different competitive levels during the COVID-19 pandemic, revealing substantial limitations to continue with regular training (2, 13, 15). However, these questionnaire surveys for athletes did not detail the specific restrictions faced (e.g., noted above) and how the support staff planned and implemented training programs to help athletes navigate the restrictions. Most, if not all, previous studies have primarily focused on the overall pre- and post-lockdown effects (2, 13, 15, 16), without the nuanced impact of multiple, evolving restrictions. Thus, we conducted interviews with support staff to enable a deeper exploration of context-specific details, with nuanced information about strategies and adaptations used to support athletes in training during different restriction conditions. Therefore, this study aimed to explore the training restrictions and practices of elite Japanese athletes during the COVID-19 pandemic through semi-structured interviews with NT and PT support staff. We focused on the support staff involved in team sports and combat sports training because they require diverse physical demands and typically involve multiple individuals training together, and they faced particularly severe restrictions during the pandemic (3). The findings will enhance our understanding of training management during major disruptions, such as pandemics, geopolitical or religious restrictions, adverse weather and climatic conditions, or local government impositions, where athletes must adapt to limited resources, confined spaces, and the absence of traditional team and support environments (1).

2 Methods

2.1 Participants

Thirteen Japanese support staff (12 men and 1 woman; age: 47 ± 8 years) who were either working for NT (n = 9) or PT (n = 4) participated in this study. PT support staff belonged to one of three team sports: baseball (Nippon Professional Baseball League; NPB League), soccer [Japan Professional Football League; J.League (first division)], and basketball [Japan Professional Basketball League; B.League (first division)] (Table 2). To prevent the potential identification of NT staff interviewees, each sport was classified into a category as in Washif et al. (3) (Table 2). Participants provided written informed consent to participate in the study, which was conducted in accordance with the Declaration of Helsinki and was approved by the Japan Institute of Sports Sciences Ethics Committee (No. 2021-056).

Table 2

Table 2. Response and position summary of national team (NT) and professional team (PT) support staff (interviewees).

2.2 Procedures

Interviews were conducted either in person or via online meeting platforms between January and April 2022. The duration of each interview was approximately 47 ± 8 min. The session began with a quantitative question, where interviewees were asked to evaluate or report their training duration, intensity, and quality during the nationwide State of Emergency, using their regular training benchmarks set at (equivalent to) 100% as reference. This assessment was applied to the following specific training categories: cardiorespiratory, strength and power, speed and agility, mobility, and sports-specific skills. Following the quantitative evaluation, the interviews transitioned to semi-structured inquiries based on pre-defined core themes/questions, allowing for open-ended responses. NT support staff responsible for individual athletes, rather than the entire team, were asked to reflect only the circumstances of those individuals.

The research team formulated these core questions with the following focuses:

1. Challenges encountered in maintaining training duration, intensity, and quality, and the strategies adopted to navigate those challenges during specific times such as “during the nationwide State of Emergency”, “after the nationwide State of Emergency”, “during the two-week quarantine”, “following the two-week quarantine”, and “throughout the COVID-19 pandemic period”.

2. Insights into changes in athletes' physical fitness following “the nationwide State of Emergency” and “two-week quarantine”. This encompassed the duration required for athletes to return to their baseline fitness and the incidence of injuries, along with their potential causes.

Finally, we asked a broad question to the support staff: “Reflecting on the COVID-19 pandemic, please freely share the tangible outcomes, challenges that became evident, and any recommendations or insights for the future”.

The interviewees' responses included not only their own actions but also observation of their athletes and actions taken by other team staff. In addition to the core question items, we addressed topics brought up by the interviewees, provided they were aligned with the research objectives. The interview was concluded when all the pre-prepared core question items were covered and the interviewee's narrative concluded smoothly. All interviews were recorded with interviewees' agreement. Verbatim transcripts were then generated and converted into text. Subsequently, a qualitative content analysis was conducted, following the methods of Elo and Kyngas (17). The transcripts were carefully read, and descriptions were extracted and coded based on their semantic content. Subcategories and categories were derived by comparing similarities and differences while raising the level of abstraction. Subsequently, these categories were integrated and themed. The analysis was conducted collaboratively by multiple researchers, including an experienced researcher of content analysis. Regular discussions (i.e., category generation) were held to ensure reliability and validity. In addition, the authors were involved in the entire analytical process, and discussions persisted until a consensus on the interpretation of the data was reached.

2.3 Data collection and analysis

Although a total of 13 support staff were interviewed, four participants did not provide responses for all periods or questions owing to variations in their roles and timelines. Specifically, one NT support staff member (from a combat sport) had not started working with the team during the nationwide State of Emergency and, therefore, could not comment on that period. Additionally, two NT and one PT support staff were not involved in team management or activities; thus, they did not participate in the quantitative survey, but contributed to the semi-structured interviews.

The semi-structured interviews were not standardized across all participants because the questions asked depended on each staff member's role and experience. Consequently, the frequency of responses was not quantified. Instead, we highlighted the key insights that emerged from the interviews, irrespective of whether they were mentioned by multiple or single participants. This approach ensures that unique and potentially important strategies or challenges were fully documented. From the 241 extracted descriptions, only the primary categories and their key representative examples (195 descriptions) are included in the main table, while the remaining descriptions (46 descriptions) are summarized in the Supplemental Materials (Supplementary Tables S1–S6).

For the quantitative part of the interview, interviewees provided specific numbers regarding the training duration, intensity, and quality during the State of Emergency. However, some of the answers provided had a range (e.g., 5%–10%). Given that some responses were presented as ranges, we opted to categorize them at 25% intervals to facilitate the analysis.

Regarding two-week quarantine periods, we classified them into four scenarios: (1) quarantine due to being infected with COVID-19; (2) quarantine due to close contact and other factors; (3) group isolation (including “Athlete Track”), a special measure for the Tokyo 2020 Olympics and Paralympics approved by the Japanese government, allowing athletes entering Japan to be exempt from the standard 14-day self-isolation required for international arrivals from qualifying competitions and pre-camp events (10); and (4) quarantine from international competitions. Athletes who tested positive were isolated according to government guidelines.

3 Results

One notable impact of the nationwide State of Emergency on training was the limitation in sports-specific skill training for athletes (Table 3). All five NT support staff reported that the duration, intensity, and quality of sports-specific training decreased to below 50% of the normal levels. Among the four PT, one reported maintaining over 75% of their usual sport-specific training in terms of duration, intensity, and quality, while others did not manage to maintain it to the same extent. In contrast, cardiorespiratory and mobility training durations remained close or exceeded the normal levels in most NT and PT, with similar intensity and quality. For strength and power training, six teams (3 NT and 3 PT) achieved over 50% of their usual duration, but only four maintained over 50% of the typical intensity and quality. For speed and agility training, only three (1 NT and 2 PT) support staff secured over 50% of the usual duration and intensity.

Table 3

Table 3. Training duration, intensity, and quality during the State of Emergency.

During the nationwide State of Emergency, limitations on facility access greatly impacted training routines for both indoor and outdoor sports (Table 4). Nonetheless, support staff and athletes implemented various strategies to address these challenges. Due to information uncertainty and public sentiment, four teams (2 NT and 2 PT) voluntarily refrained from outdoor training. Support staff often provided guidance on recommended training (4 NT and 2 PT) and/or facilitated online training sessions (3 NT and 3 PT). The majority of support staff mentioned that athletes prepared small training equipment (e.g., dumbbells, training tubes) for their workouts (4 NT, 4 PT), and fewer support staff (2 NT, 2 PT) reported that their athletes had access to larger equipment (e.g., power racks, cycle ergometers). Additionally, training programs and their management were often independently determined by the athletes or by non-NT/PT support staff, such as personal support staff from their home teams (5 NT and 2 PT). Due to their body size and dynamic, powerful movements, athletes faced limitations in training spaces (1 PT) and found commercial equipment inadequate for their training needs (1 PT). Mental health challenges emerged among athletes, partly due to the inability to train as usual (2 NT and 1 PT).

Table 4

Table 4. Support staff [8 national team (NT) and 4 professional team (PT)] response in interviews regarding the situation of athletes and support staff during the nationwide State of Emergency (39 descriptions).

Even after the end of the nationwide State of Emergency, training restrictions persisted (Table 5). The support staff divided the athletes into small groups for training sessions (3 NT and 1 PT) and provided information about retraining (2 NT). The majority of support staff (4 NT and 3 PT) reported a gradual increase in training load. Regarding athletes' physical fitness, only one PT support staff reported no change, while all other support staff reported some form of detraining (Table 6). The majority of support staff observed a decline in strength and power, indicating that approximately two months were required to return to pre-pandemic levels (2 NT and 2 PT). Regarding endurance, two to four months were necessary for athletes to regain their normal levels (5 NT and 3 PT). None of the support staff reported a need for more than two months to recover body composition. Remarkably, four support staff (3 NT, 1 PT) reported that more than six months were required for athletes to recover their sports skills or performance. Regarding unusual injuries or disorders, five support staff (4 NT and 1 PT) reported none, but there were reports of muscle cramps (1 NT and 1 PT) and joint pain (2 NT and 1 PT).

Table 5

Table 5. Support staff responses [9 national team (NT) and 4 professional team (PT)] in interviews regarding the situation of athletes and support staff after the nationwide State of Emergency (11 descriptions).

Table 6

Table 6. Support staff responses [9 national team (NT) and 4 professional team (PT)] regarding changes in performance elements and time taken to return to baseline after the nationwide State of Emergency (31 descriptions).

For quarantine due to close contact and other factors, many support staff communicated with athletes online, provided training program information (2 NT and 1 PT), and conducted online training sessions (1 NT and 4 PT) (Table 7). Athletes trained using large equipment or small equipment, as primarily reported by PT support staff. In cases of quarantine following international competitions, only NT encountered this scenario. Five support staff reported that, since there was usually an off period after international competitions, athletes initially prioritized rest, as was typical during the pre-pandemic period. When group isolation was possible, such as with the “Athlete Track”, staff members accompanied the teams and conducted training sessions.

Table 7

Table 7. Support staff responses [9 national team (NT) and 4 professional team (PT)] in interviews regarding the situation of athletes and support staff during a two-week quarantine (32 descriptions).

After two weeks of isolation, the majority of support staff (5 NT and 3 PT) reported a gradual increase in training load (Table 8). Among them, four (2 NT and 2 PT) support staff adopted strategies to partially modify training content while rejoining other athletes. In fact, few support staff reported maintaining fitness levels during the two-week isolation, with most suggesting a recovery period of 1–4 weeks (Table 9). For athletes who tested positive, the common recovery time reported was 2–4 weeks. While specific injuries upon resuming training were not commonly prevalent, there were some reports of lower limb muscle pain.

Table 8

Table 8. Support staff responses [9 national team (NT) and 4 professional team (PT)] in interviews regarding the situation of athletes and support staff after a two-week quarantine (5 descriptions).

Table 9

Table 9. Support staff responses [9 national team (NT) and 4 professional team (PT)] in interviews regarding changes in performance elements and time taken to return to baseline after a two-week quarantine (25 descriptions).

Finally, Table 10 provides a summary of overall responses, while Table 11 outlines achievements and challenges specific to the nationwide State of Emergency. Many support staff struggled to balance in-person training with the COVID-19 infection risks, prompting the use of online tools. Also, mental support needs increased as issues such as “loss of value” in their sports activities and connection with others became prevalent. Regular physical check-ups during and after the pandemic, proved to be valuable and emphasized the importance of planning for post-COVID retraining. Some issues were unique to NT; for example, six NT support staff reported difficulties in enhancing performance domestically due to a lack of competitive rivals, and three of them noted that training camps abroad were organized to avoid domestic quarantine and improve technical skills through competition with foreign athletes. Additionally, three staff emphasized the need for inter-organizational collaboration to secure large equipment. Another three staff organized the athletes' training in public park spaces and used playground equipment.

Table 10

Table 10. Support staff responses [9 national team (NT) and 4 professional team (PT)] in interviews regarding the situation of athletes and support staff during the COVID-19 pandemic in general (including periods that cannot be specifically determined) (18 descriptions).

Table 11

Table 11. Support staff responses [9 national team (NT) and 4 professional team (PT)] in interviews regarding achievements and challenges observed during the COVID-19 pandemic (34 descriptions).

4 Discussion

This study explored the training practices of elite team and combat sport athletes during the COVID-19 pandemic, as reported by Japanese NT and PT support staff through semi-structured interviews. During the nationwide State of Emergency, most elite Japanese athletes received online training and training information from their team's support staff, which was deemed insufficient to achieve the desired training outcomes. After the nationwide State of Emergency, restrictions on training facility use remained in many areas in Japan, allowing only small-group training, and support staff were sometimes restricted from attending training sessions. Asymptomatic close-contact (non-infected) athletes were quarantined for two weeks, whereby they had access to large training equipment at their quarantine locations; however, some athletes experienced declines in physical fitness after this period. These findings suggest a degree of adaptability among elite athletes and support staff in managing training-related challenges during the early COVID-19 pandemic.

4.1 Training practices during the nationwide State of Emergency

In addition to previously discussed factors such as facility closures and travel restrictions (2, 4), the internal dynamics and organizational structure within teams were identified as additional factors negatively impacting training practices. Many Japanese NT athletes predominantly train with their respective affiliated teams, including university, company-sponsored, or club teams, and only assemble as a NT for training camps or international competitions. In these circumstances, support staff were often unable to provide guidance outside of these specific events (i.e., training camps or international competitions), resulting in many athletes largely managing their own training or relying on coaching from their affiliated teams. The environment surrounding NT athletes is therefore multi-layered, involving support staff from the national team, affiliated clubs, and personal coaching entities (18). Silva et al. (18) emphasized that effective communication among national, club, and personal staff is essential for enhancing players' performance and health, noting that responsibilities vary according to the specific period. Many NT support staff reported having no direct responsibilities for overseeing athletes' training, resulting in greater reliance on the support staff of their affiliated teams. These findings highlight the need for improved coordination and communication among all members of the athletes’ support network.

Many NT and PT support staff provided online training and training information, similar to other cases (3, 15, 16). They encouraged athletes to utilize the available training equipment to enhance training intensity. When existing equipment was deemed insufficient to achieve the desired training effects, they prescribed training programs tailored to the athletes' available resources, including equipment and environment. However, if the desired outcomes could not be achieved, they altered the training objectives and prescribed alternative exercises, such as increasing the number or speed of repetitions with lighter loads or incorporating bodyweight-based exercises. Nonetheless, commercially available small equipment often proved inadequate to provide the required training intensity for elite athletes, particularly for strength development or muscle hypertrophy. Additionally, training locations such as homes or hotels often lacked sufficient space, limiting dynamic training and extensive movements required by these athletes. Access to large equipment was available only to athletes from a limited number of NT and PT. Although outdoor training was permitted during the pandemic in Japan, elite athletes faced specific challenges, particularly voluntary restrictions imposed by the so-called “virus vigilantes”. Given the constraints, support staff had to design training plans that emphasized creativity and exercise variety. For instance, low-load training was adapted by adjusting the exercise volume, time under muscle tension, and training frequency to achieve hypertrophic outcomes comparable to traditional high-load training (19, 20). These approaches highlight the necessity of tailoring programs to the specific environment, ensuring that athletes can continue to make progress despite prevailing limitations.

Only two of the nine NT and PT support staff members reported that, due to having access to particular facilities, they were able to maintain sports-specific training intensity above 25% of pre-pandemic levels. This observation is considerably lower than the level reported in a previous study, where one-third of elite athletes were able to maintain their pre-lockdown training intensity (3). This discrepancy is likely attributed to the severe restrictions imposed on training during the pandemic, especially among team sports and combat sports, which require diverse physical demands and typically involve multiple participants training together in close proximity or through actual physical contact (3). Additionally, since the survey was conducted with NT and PT support staff, it is possible that the athletes' training prescribed by other support staff or self-managed by the athletes was not fully reflected or captured. In any case, the closure of dedicated training facilities for NT and PT had a pronounced impact on the ability of elite-level athletes in these sports. On the other hand, many NT and PT support staff reported that athletes were able to allocate more time than usual to cardiorespiratory and mobility exercises.

Conversely, there were positive aspects of the pandemic. Some athletes used this period to address long-standing injuries, undergoing surgical procedures and intensive rehabilitation that would have been challenging to accommodate during regular competitive seasons. Research has shown that a substantial proportion of elite athletes —up to 36%— experience chronic conditions that persistently affect their performance (21). Furthermore, by pausing intense training and competition, athletes were able to concentrate on treatments aimed at resolving these issues (22), potentially enhancing their overall physical health and longevity in sports. For some athletes, the lockdown proved to be a “blessing in disguise”, providing an “opportunity” to enhance some aspects of training and recovery that had previously been neglected (1).

Some support staff reported varying successes in maintaining athletes' motivation through online training. While some found virtual sessions effective, others encountered difficulties to keep athletes engaged over a prolonged period. This observation was particularly true for team and combat sports athletes accustomed to group training dynamics, as the absence of training partners was a critical factor contributing to decreased motivation (3). Consistent with previous studies, issues related to mental health and motivation were prevalent during the pandemic (23), highlighting the need for better access to mental health professionals or counselors (24). Reduced social interaction and collaborative training during the global pandemic also led to a deterioration in mental well-being among athletes (25, 26). While online meetings and training helped to some extent (e.g., motivation), athletes generally expressed a preference for training in environments with real partners. A supportive network of coaching staff, teammates, friends, and family (team environment) plays a vital role in maintaining emotional well-being and motivation (27). A study on Canadian national team athletes revealed that the pandemic caused significant disruptions in athletes' mental health, leading to low mood, anxiety, and stress, but also offered a rare opportunity for rest and recovery, as athletes with stronger mental performance skills coped better with challenges (24). These findings underline the need for integrated training programs that prioritize both physical and mental well-being, as well as recovery from chronic injuries, especially during prolonged isolation.

4.2 Training practices after the nationwide State of Emergency

Even after the nationwide State of Emergency, restrictions on training facility access persisted in different parts of the country. To minimize contact risk, training was often conducted in small groups, with limited access to support staff. In alignment with the return-to-training guidelines (28, 29), most NT and PT support staff implemented a gradual training progression to safely resume training activities. It's important that some studies reported maintenance of body mass, skinfold thickness, jump height among professional soccer players following a supervised remote-based physical training (30, 31). Among elite Japanese fencers, no changes in body composition were observed in males, while female fencers experienced a temporary increase in fat mass that returned to baseline within four months (32). In terms of “recovery” duration, studies on elite badminton players and combat sport athletes have shown that jump height, lower body strength, and body composition returned to pre-pandemic levels within eight weeks of retraining (33, 34). In a similar context, eight support staff (5 NT and 3 PT) perceived that endurance took longer to recover, typically two to four months. This perception of a more prolonged recovery for endurance capacity aligns with findings from professional soccer (35), where teams in leagues with shorter interruptions (e.g., German Bundesliga: 9-week match interruption, 3 weeks of group training cessation) maintained physical match performance, whereas those with prolonged disruptions (e.g., Spain's La Liga: up to 15-week match interruption, 8 weeks of group training cessation) showed pronounced performance declines. Although detraining effects generally become apparent after four or more weeks of training cessation (36), the present findings suggest that the nature and extent of training practices (including the potential effect on training supervision) during the State of Emergency were crucial in modulating these effects.

Regarding sports-specific skills, while objective assessments were not conducted in this study, some staff (3 NT and 1 PT) believed that the recovery would take even longer (i.e., over six months) due to severe restrictions on sports-specific training and the implementation of gradual, low-risk retraining protocols. This subjective view is consistent with observed changes in match characteristics and skill decrements in professional sports post-pandemic. For instance, studies noted declines in tennis service performance (37) and tactical shifts in soccer, such as increased conservatism and reduced attacking depth (38). These observations imply challenges in restoring optimal sports performance, particularly because highly specialized sports skills often require specific environmental cues, interactions with opponents, or team dynamics, all of which were severely constrained during the State of Emergency. Regardless of above, implementation of “bubble camps”, where athletes, coaches and support staff isolate together from society to continue regular training with full facility access (sport-specific practice, conditioning, recovery, etc.), emerged as a practical solution during lockdown situations (2, 39).

Almost half of the NT staff (4 out of 9) reported no unusual injuries, likely due to reduced training and less pressure to return to competition. In contrast, only one fourth of the PT staff reported no unusual injuries. Since professional leagues resumed within the same year, PT athletes were required to return to competition sooner, which led to injuries from inadequate pre-season preparation. For instance, the J.League (soccer) resumed on July 4, 2020, and a notable increase in muscle injuries was observed shortly after the State of Emergency (40). According to the study, the incidence reached 4.8 injuries per 1,000 h of exposure in May 2020, compared to 1.0 in May 2019. Conversely, B.league (basketball) resumed three months later, on October 2, and attested no notable increase in injuries, according to the league's official report (41). Furthermore, restrictions on international travel led to fewer opportunities for NT to train with world-class opponents and reduced international matches and training camps. To address these limitations, some NT organized training camps abroad to avoid domestic quarantine measures. One NT support staff member, however, expressed satisfaction with their training environment, attributing it to the local presence of strong rivals in Japan. Overall, following the nationwide State of Emergency, while general fitness was perceived to be restored within two months, the prolonged recovery of sports-specific performance emphasizes the necessity of balancing low-injury risk training protocols with comprehensive return-to-play plans (including management of the infection risks).

4.3 Training practices during and after two weeks quarantine

During the pandemic, athletes infected with COVID-19 were isolated in accordance with government guidelines and could not continue their training. Infected athletes may experience declines in performance capacity regardless of symptom status, though those exhibiting persistent, performance-impairing symptoms (such as cough, tachycardia, and fatigue) experience reduced ventilatory parameters and lower peak oxygen consumption values compared to those who remain symptom-free (42, 43). On the other hand, athletes quarantined due to close contact or other factors—particularly those without symptoms—were able to continue training within their quarantine settings. Among PT, all support staff reported securing large training equipment for athletes at their quarantine locations. This effort was likely driven by the financial resources of professional sports and the urgent need to resume competition within league schedules. However, many support staff noted declines in physical fitness following a two-week quarantine, though some observed a return to baseline within two weeks. Previous research has shown that a two-week break during a typical off-season increased skinfold thickness but maintained or even improved other fitness indicators among Australian football players, potentially due to recovery (44). However, these findings may not directly apply to the context of quarantine. Similarly, a study on university sprinters showed reductions in knee eccentric strength and fast concentric strength over a two-week off-season, while slow concentric strength and body composition remained unaffected (45). Fitness changes after a two-week quarantine may vary depending on physical activity levels. During the nationwide State of Emergency in Japan, physical activity levels clearly declined (46). A systematic review on bed rest indicated that endurance, neural function, and muscle strength can decline within just five days (47), suggesting substantial declines in physical performance are plausible after a two-week quarantine.

4.4 Limitation

This study used semi-structured interviews with support staff working with elite athletes, which may have introduced a recall bias. Furthermore, as this study relied on interviews with NT and PT support staff, training prescribed by other staff (e.g., from the athletes' clubs) or performed independently by athletes may not have been fully captured. Additionally, the subjective nature of evaluating training approaches (including quality, intensity, creativity, and innovation) may have been influenced by individual interpretation, potentially compromising precision.

5 Conclusion

This study highlights the diverse training approaches employed during the COVID-19 pandemic, as well as challenges faced by Japanese elite team sport and combat sport athletes due to restricted access to conventional training facilities and equipment. Online group and/or personal training sessions were considered valuable for maintaining fitness and motivation, although they were deemed inadequate for achieving optimal performance outcomes. The importance of mental health became evident as reduced social interaction, the absence of training partners, and uncertainty called for better mental health support that prioritizes athletes' overall well-being. Despite these difficulties, the pandemic also presented opportunities for some athletes to address chronic injuries, engage in thorough rehabilitation, explore alternative training methods (e.g., low-load exercises), and implement periodized return-to-play planning to preserve or regain physical aspects. These adaptive approaches, driven by the many initiatives of the support staff, were highly beneficial for the athletes. These findings emphasize the need for robust and flexible athlete-support systems capable of managing sudden uncertain situations and converting them into opportunities. Such systems should focus on alternative training approaches, communication networks, and holistic prioritization of athlete physical and mental health, and well-being through strong interdisciplinary collaboration to enhance preparedness and resilience for future challenges in high-performance contexts.

Data availability statement

The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author.

Ethics statement

The studies involving humans were approved by Japan Institute of Sports Sciences. The studies were conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study.

Author contributions

DY: Conceptualization, Formal analysis, Funding acquisition, Investigation, Methodology, Writing – original draft, Writing – review & editing. KY: Conceptualization, Formal analysis, Investigation, Methodology, Writing – original draft, Writing – review & editing. TY: Formal analysis, Investigation, Methodology, Writing – original draft, Writing – review & editing. HT: Formal analysis, Investigation, Writing – original draft, Writing – review & editing. JW: Writing – original draft, Writing – review & editing. IM: Supervision, Writing – original draft, Writing – review & editing.

Funding

The author(s) declare that financial support was received for the research and/or publication of this article. This study was conducted as part of the “Functional Development Project for Resilient Athlete Support”, a project commissioned by the Japan Sports Agency.

Acknowledgments

The authors would like to express their deepest gratitude to Professor Norikazu Hirose from Waseda University for his invaluable advice.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

The handling editor CM declared a past collaboration with the author IM.

Generative AI statement

The author(s) declare that no Generative AI was used in the creation of this manuscript.

Any alternative text (alt text) provided alongside figures in this article has been generated by Frontiers with the support of artificial intelligence and reasonable efforts have been made to ensure accuracy, including review by the authors wherever possible. If you identify any issues, please contact us.

Publisher's note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fspor.2025.1557774/full#supplementary-material

References

1. Washif JA, Hettinga FJ, Ammar A, Van Rensburg DCJ, Materne O, Trabelsi K, et al. Supporting athletes during a challenging situation: recommendations from a global insight of COVID-19 home-based training experience. BMC Sports Sci Med Rehabil. (2024) 16:83. doi: 10.1186/s13102-024-00869-7

PubMed Abstract | Crossref Full Text | Google Scholar

2. Washif JA, Farooq A, Krug I, Pyne DB, Verhagen E, Taylor L, et al. Training during the COVID-19 lockdown: knowledge, beliefs, and practices of 12,526 athletes from 142 countries and six continents. Sports Med. (2022) 52:933–48. doi: 10.1007/s40279-021-01573-z

PubMed Abstract | Crossref Full Text | Google Scholar

3. Washif JA, Sandbakk Ø, Seiler S, Haugen T, Farooq A, Quarrie K, et al. COVID-19 lockdown: a global study investigating the effect of athletes’ sport classification and sex on training practices. Int J Sports Physiol Perform. (2022) 17:1242–56. doi: 10.1123/ijspp.2021-0543

PubMed Abstract | Crossref Full Text | Google Scholar

4. Zago M, Lovecchio N, Galli M. Players at home: physical activity and quality of life in 12–17 years-old football (soccer) players during the COVID-19 lockdown. Int J Sports Sci Coach. (2021) 17:626–36. doi: 10.1177/17479541211041703

Crossref Full Text | Google Scholar

5. Rynne SB, Mallett C, Tinning R. High performance sport coaching: institutes of sport as sites for learning. Int J Sports Sci Coach. (2006) 1:223–34. doi: 10.1260/174795406778604582

Crossref Full Text | Google Scholar

6. Paludo A, Karpinski K, Silva S, Kumstát M, Sajdlová Z, Milanovic Z. Effect of home training during the COVID-19 lockdown on physical performance and perceptual responses of team-sport athletes: a mini-review. Biol Sport. (2022) 39:1095–102. doi: 10.5114/biolsport.2022.117040

PubMed Abstract | Crossref Full Text | Google Scholar

7. Watanabe T, Yabu T. Japan’s voluntary lockdown. PLoS One. (2021) 16:e0252468. doi: 10.1371/journal.pone.0252468

PubMed Abstract | Crossref Full Text | Google Scholar

8. Kitahara K, Nishikawa Y, Yokoyama H, Kikuchi Y, Sakoi M. An overview of the reclassification of COVID-19 of the infectious diseases control law in Japan. Glob Health Med. (2023) 5:70–4. doi: 10.35772/ghm.2023.01023

PubMed Abstract | Crossref Full Text | Google Scholar

9. Ministry of Health, Labour and Welfare. Response to COVID-19 After Classification Change [Online]. (2023). Available online at: https://www.mhlw.go.jp/stf/covid-19/kenkou-iryousoudan_00006.html (Accessed December 24, 2024)

Google Scholar

10. International Olympic Committee. Fifth coordination meeting for COVID-19 countermeasures at the Olympic and Paralympic Games Tokyo 2020 [Online]. (2020). Available online at: https://olympics.com/en/news/fifth-coordination-meeting-for-covid-19-countermeasures-at-tokyo-2020 (Accessed December 24, 2024)

Google Scholar

11. Jagim AR, Luedke J, Fitzpatrick A, Winkelman G, Erickson JL, Askow AT, et al. The impact of COVID-19-related shutdown measures on the training habits and perceptions of athletes in the United States: a brief research report. Front Sports Act Living. (2020) 2:623068. doi: 10.3389/fspor.2020.623068

PubMed Abstract | Crossref Full Text | Google Scholar

12. Mon-López D, García-Aliaga A, Ginés Bartolomé A, Muriarte Solana D. How has COVID-19 modified training and mood in professional and non-professional football players? Physiol Behav. (2020) 227:113148. doi: 10.1016/j.physbeh.2020.113148

PubMed Abstract | Crossref Full Text | Google Scholar

13. Pillay L, Janse Van Rensburg DCC, Jansen Van Rensburg A, Ramagole DA, Holtzhausen L, Dijkstra HP, et al. Nowhere to hide: the significant impact of coronavirus disease 2019 (COVID-19) measures on elite and semi-elite South African athletes. J Sci Med Sport. (2020) 23:670–9. doi: 10.1016/j.jsams.2020.05.016

PubMed Abstract | Crossref Full Text | Google Scholar

14. Washif JA, Kok LY, James C, Beaven CM, Farooq A, Pyne DB, et al. Athlete level, sport-type, and gender influences on training, mental health, and sleep during the early COVID-19 lockdown in Malaysia. Front Physiol. (2023) 13:1093965. doi: 10.3389/fphys.2022.1093965

PubMed Abstract | Crossref Full Text | Google Scholar

15. Schneider F, Runer A, Burkert F, Aspang JSU, Reider S, Schneider H, et al. Digital workout versus team training: the impact of the COVID-19 pandemic on athletes. Sports Med Int Open. (2022) 6:E18–24. doi: 10.1055/a-1734-5457

PubMed Abstract | Crossref Full Text | Google Scholar

16. Taheri M, Irandoust K, Reynoso-Sánchez LF, Muñoz-Helú H, Cruz-Morales KN, Torres-Ramírez R, et al. Effects of home confinement on physical activity, nutrition, and sleep quality during the COVID-19 outbreak in amateur and elite athletes. Front Nutr. (2023) 10:1143340. doi: 10.3389/fnut.2023.1143340

PubMed Abstract | Crossref Full Text | Google Scholar

17. Elo S, Kyngäs H. The qualitative content analysis process. J Adv Nurs. (2008) 62:107–15. doi: 10.1111/j.1365-2648.2007.04569.x

PubMed Abstract | Crossref Full Text | Google Scholar

18. Silva JR, Buchheit M, Hader K, Sarmento H, Afonso J. Building bridges instead of putting up walls: connecting the “teams” to improve soccer players’ support. Sports Med. (2023) 53:2309–20. doi: 10.1007/s40279-023-01887-0

PubMed Abstract | Crossref Full Text | Google Scholar

19. Schoenfeld BJ, Grgic J, Ogborn D, Krieger JW. Strength and hypertrophy adaptations between low- vs. high-load resistance training: a systematic review and meta-analysis. J Strength Cond Res. (2017) 31:3508–23. doi: 10.1519/JSC.0000000000002200

PubMed Abstract | Crossref Full Text | Google Scholar

20. Fyfe JJ, Hamilton DL, Daly RM. Minimal-dose resistance training for improving muscle mass, strength, and function: a narrative review of current evidence and practical considerations. Sports Med. (2022) 52:463–79. doi: 10.1007/s40279-021-01605-8

PubMed Abstract | Crossref Full Text | Google Scholar

21. Clarsen B, Rønsen O, Myklebust G, Flørenes TW, Bahr R. The Oslo sports trauma research center questionnaire on health problems: a new approach to prospective monitoring of illness and injury in elite athletes. Br J Sports Med. (2014) 48:754–60. doi: 10.1136/bjsports-2012-092087

PubMed Abstract | Crossref Full Text | Google Scholar

22. Patatas JM, Winckler C. “We too will have to wait a year”: the impacts of COVID-19 and the postponement of the Tokyo 2020 paralympic games from Brazilian athletes and coaches’ perspectives. Sport Soc. (2022) 25:1252–72. doi: 10.1080/17430437.2021.1997987

Crossref Full Text | Google Scholar

23. Amos B, Tibbert SJ. Exploration of the COVID-19 mental health implications in elite disabled athletes. J Sports Sci. (2024) 42:918–29. doi: 10.1080/02640414.2024.2370151

Crossref Full Text | Google Scholar

24. Dithurbide L, Boudreault V, Durand-Bush N, Macleod L, Gauthier V. The impact of the COVID-19 pandemic on Canadian national team athletes’ mental performance and mental health: the perspectives of mental performance consultants and mental health practitioners. Front Psychol. (2022) 13:937962. doi: 10.3389/fpsyg.2022.937962

PubMed Abstract | Crossref Full Text | Google Scholar

25. Carnevale Pellino V, Lovecchio N, Puci MV, Marin L, Gatti A, Pirazzi A, et al. Effects of the lockdown period on the mental health of elite athletes during the COVID-19 pandemic: a narrative review. Sport Sci Health. (2022) 18:1187–99. doi: 10.1007/s11332-022-00964-7

PubMed Abstract | Crossref Full Text | Google Scholar

26. Andrew W, Kristin H, Kevin B, Allison S, Scott H, Claudia R, et al. Impact of COVID-19 on the physical activity, quality of life and mental health of adolescent athletes: a 2-year evaluation of over 17000 athletes. Br J Sports Med. (2023) 57:359. doi: 10.1136/bjsports-2022-105812

PubMed Abstract | Crossref Full Text | Google Scholar

27. Hussain T, Wang D, Li B. Psychological resilience in athletes during the COVID-19 pandemic: a qualitative insight. Acta Psychol. (2023) 240:104050. doi: 10.1016/j.actpsy.2023.104050

PubMed Abstract | Crossref Full Text | Google Scholar

28. Caterisano A, Decker D, Snyder B, Feigenbaum M, Glass R, House P, et al. CSCCa and NSCA joint consensus guidelines for transition periods: safe return to training following inactivity. Strength Cond J. (2019) 41:1–23. doi: 10.1519/SSC.0000000000000477

Crossref Full Text | Google Scholar

29. National Strength and Conditioning Association (NSCA) Covid-19 Return to Training Taskforce. COVID-19: NSCA Guidance on Safe Return to Training for Athletes. National Strength and Conditioning Association (NSCA). (2023). Available online at: https://www.nsca.com/contentassets/61c0fb0a476149848de009f1630fa457/nsca-covid-19-rtt.pdf (Accessed January 8, 2025)

Google Scholar

30. Cohen DD, Restrepo A, Richter C, Harry JR, Franchi MV, Restrepo C, et al. Detraining of specific neuromuscular qualities in elite footballers during COVID-19 quarantine. Sci Med Footb. (2021) 5:26–31. doi: 10.1080/24733938.2020.1834123

PubMed Abstract | Crossref Full Text | Google Scholar

31. Anderson L, Flannigan C, Polychronopoulos P, Mackenzie R, Drust B, Milsom J. Lessons from the COVID-19 pandemic: insights into effective training strategies for physical development in football. Int J Sports Sci Coach. (2023) 18:403–13. doi: 10.1177/17479541221081782

PubMed Abstract | Crossref Full Text | Google Scholar

32. Yasuda J, Kondo E, Takai E, Eda N, Azuma Y, Motonaga K, et al. The effects of the COVID-19 environments on changes in body composition in Japanese elite fencing athlete. Sports. (2021) 9:95. doi: 10.3390/sports9070095

PubMed Abstract | Crossref Full Text | Google Scholar

33. Valenzuela PL, Rivas F, Sánchez-Martínez G. Effects of COVID-19 lockdown and a subsequent retraining period on elite Athletes’ workload, performance, and autonomic responses: a case series. Int J Sports Physiol Perform. (2021) 16:1707–11. doi: 10.1123/ijspp.2020-0735

PubMed Abstract | Crossref Full Text | Google Scholar

34. Tan E, Montalvo S, Gonzalez MP, Dietze-Hermosa M, Min S, Dorgo S. Changes in vertical jump performance and body composition before and after COVID-19 lockdown. J Hum Sport Exer. (2023) 18:224–41. doi: 10.14198/jhse.2023.181.18

Crossref Full Text | Google Scholar

35. Thron M, Düking P, Härtel S, Woll A, Altmann S. Differences in physical match performance and injury occurrence before and after the COVID-19 break in professional European soccer leagues: a systematic review. Sports Med - Open. (2022) 8:121. doi: 10.1186/s40798-022-00505-z

PubMed Abstract | Crossref Full Text | Google Scholar

36. Mujika I, Padilla S. Detraining: loss of training-induced physiological and performance adaptations. Part II. Sports Med. (2000) 30:145–54. doi: 10.2165/00007256-200030030-00001

PubMed Abstract | Crossref Full Text | Google Scholar

37. Ishihara T, Robin N, Naito T, Murata M, Crespo M. Effects of the COVID-19 pandemic on professional tennis players’ match statistics: a large-scale population-based study. Scand J Med Sci Sports. (2022) 32:1516–8. doi: 10.1111/sms.14216

PubMed Abstract | Crossref Full Text | Google Scholar

38. Fernández-Cortés J, Gómez-Carmona CD, Mancha-Triguero D, García-Rubio J, Ibáñez SJ. Effect of COVID-19 on key performance indicators of Spanish professional soccer league. J Funct Morphol Kinesiol. (2024) 9:35. doi: 10.3390/jfmk9010035

Crossref Full Text | Google Scholar

39. Washif JA, Ammar A, Trabelsi K, Chamari K, Chong CSM, Mohd Kassim SFA, et al. Regression analysis of perceived stress among elite athletes from changes in diet, routine and well-being: effects of the COVID-19 lockdown and “bubble” training camps. Int J Environ Res Public Health. (2022) 19:402. doi: 10.3390/ijerph19010402

Crossref Full Text | Google Scholar

40. Matsunaga R, Nagao M, Akagi R, Fukai A, Sando T, Ikeda H, et al. Impact of the COVID-19 pandemic on injury incidence in Japanese male professional soccer players. Orthop J Sports Med. (2023) 11:23259671221149373. doi: 10.1177/23259671221149373

PubMed Abstract | Crossref Full Text | Google Scholar

41. Japan_Professional_Basketball_League. B.LEAGUE 2022-23 Season Injury Report (in Japanese) [Online]. (2023). Available online at: https://www.bleague.jp/files/user/Injury%20Report.pdf (Accessed January 8, 2025).

Google Scholar

42. Wilson MG, Hull JH, Rogers J, Pollock N, Dodd M, Haines J, et al. Cardiorespiratory considerations for return-to-play in elite athletes after COVID-19 infection: a practical guide for sport and exercise medicine physicians. Br J Sports Med. (2020) 54:1157–61. doi: 10.1136/bjsports-2020-102710

PubMed Abstract | Crossref Full Text | Google Scholar

43. Vollrath S, Bizjak DA, Zorn J, Matits L, Jerg A, Munk M, et al. Recovery of performance and persistent symptoms in athletes after COVID-19. PLoS One. (2022) 17:e0277984. doi: 10.1371/journal.pone.0277984

PubMed Abstract | Crossref Full Text | Google Scholar

44. Buchheit M, Morgan W, Wallace J, Bode M, Poulos N. Physiological, psychometric, and performance effects of the christmas break in Australian football. Int J Sports Physiol Perform. (2015) 10:120–3. doi: 10.1123/ijspp.2014-0082

PubMed Abstract | Crossref Full Text | Google Scholar

45. Yamashita D, Hirata K, Yamazaki K, Mujika I, Miyamoto N. Effect of two weeks of training cessation on concentric and eccentric knee muscle strength in highly trained sprinters. PLoS One. (2023) 18:e0288344. doi: 10.1371/journal.pone.0288344

PubMed Abstract | Crossref Full Text | Google Scholar

46. Yamada Y, Namba H, Date H, Kitayama S, Nakayama Y, Kimura M, et al. Regional difference in the impact of COVID-19 pandemic on domain-specific physical activity, sedentary behavior, sleeping time, and step count: web-based cross-sectional nationwide survey and accelerometer-based observational study. JMIR Public Health Surveill. (2023) 9:e39992. doi: 10.2196/39992

PubMed Abstract | Crossref Full Text | Google Scholar

47. Spiering BA, Weakley J, Mujika I. Effects of bed rest on physical performance in athletes: a systematic and narrative review. Sports Med. (2023) 53:2135–46. doi: 10.1007/s40279-023-01889-y

PubMed Abstract | Crossref Full Text | Google Scholar