Do Long-Haul Travel and Jet Lag Affect Athletes’ Physiological, Humoral and Performance Outcomes? A Systematic Narrative Review

TL;DR

This review explores how long-haul travel and jet lag impact athletes' health and performance, and suggests strategies to reduce these effects.

Contribution

The study systematically reviews the physiological and performance effects of long-haul travel on athletes and differentiates travel fatigue from jet lag.

Findings

Long-haul travel disrupts sleep, hormonal balance, and physical performance in athletes.

Eastward travel causes stronger circadian disruption and affects aerobic capacity and coordination more than westward travel.

Mitigation strategies like melatonin, caffeine, and light exposure can help reduce travel-related impairments.

Abstract

Background: Long-haul travel and jet lag can disrupt athletes’ circadian, physiological, and performance systems, potentially impairing competition outcomes. This review aimed to study the effects of long-haul travel on athletes’ health and performance, differentiate travel fatigue from jet lag, and review mitigation strategies. Methods: A systematic narrative review was conducted following PRISMA 2020 guidelines. PubMed, Scopus, and Web of Science were searched for studies on jet lag, travel fatigue, and long-haul travel in athletes. Eligibility included studies reporting physiological, hemodynamic, or performance outcomes in athletes of any level and sex. Data were extracted on travel characteristics, interventions, physiological and performance markers, and risk of bias. Results: Overall, 284 records were identified, with 89 studies included. Travel directions were equally distributed between eastward and westward journeys, crossing 1–12 time zones. Interventions to mitigate travel effects were reported in 17 studies, primarily melatonin, caffeine, and light exposure. Common physiological changes included sleep disturbances (n = 36), body temperature alterations (n = 18), blood pressure changes, hormonal shifts (n = 9), heart rate variability (n = 4), and immune alterations (n = 4). Travel effects comprised fatigue (n = 25), sleep changes (n = 21), decreased physical performance (n = 18), mood changes (n = 15), and cognitive impairments (n = 9). Physical performance outcomes included anaerobic power (n = 18), strength (n = 14), velocity (n = 12), aerobic capacity (n = 10), coordination (n = 8), and reaction time (n = 7). Risk of bias was low in 49%, moderate in 17%, and high in 34% of studies. Conclusions: Long-haul travel negatively affects multiple physiological and performance domains in athletes, including sleep, hormonal balance, autonomic function, and physical performance. The magnitude of these effects seems to be influenced by travel direction, number of time zones crossed, and individual susceptibility. Eastward travel is generally associated with stronger circadian disruption and impaired aerobic capacity, coordination, and technical performance, whereas westward travel often induces greater fatigue and adversely affects team-sport outcomes. Monitoring key markers such as heart rate variability, sleep, and cortisol, combined with personalized strategies including circadian management, sleep hygiene, nutrition, recovery interventions, and training load adjustments, is essential to mitigate travel-related impairments and optimize performance.

Figures

Full text

1. Introduction

The modern athlete, whether elite or recreational, spends a substantial portion of the competitive season traveling for training and competition [1]. This is a direct consequence of the increasingly globalized nature of sport and may involve long-haul intercontinental flights or, more commonly, frequent short-distance travel. Such travel exposes athletes to two related but distinct challenges: travel fatigue and jet lag [2]. These conditions share several symptoms and, due to limited awareness, athletes often incorrectly attribute all travel-related effects exclusively to jet lag [3,4,5]. Although these conditions share several symptoms and are often conflated in practice, they represent different phenomena. However, travel fatigue and jet lag are distinct phenomena that may co-occur when traveling eastward or westward [6]. Travel fatigue is a condition arising from the inherent stressors of the journey itself, such as airport procedures, travel logistics, sleep loss, dehydration, and cramped seating, and can occur regardless of the distance or number of time zones crossed. Jet lag, however, results from a misalignment between the body’s internal clock and the destination’s local time and typically occurs only when crossing 3 or more time zones [6].

Regardless of flight direction or duration, any form of travel can induce fatigue [7,8,9]. These symptoms may occur acutely after a single journey or develop chronically as a cumulative consequence of repeated travel throughout a competitive season [6]. Travel fatigue can occur independently of the number of time zones crossed and results from the inherent stressors associated with travel itself. It often begins prior to departure due to factors such as prolonged airport procedures, flight delays, and pre-competition anxiety. During the flight, contributing factors include cramped seating position, reduced physical activity, mild hypoxia, and dehydration caused by low cabin humidity. Upon arrival, additional stressors such as unfamiliar environments and cultural differences may further exacerbate travel fatigue symptoms [4].

In contrast, jet lag results specifically from a circadian misalignment between the body’s internal clock and the local time at the destination. Jet lag shares symptoms with travel fatigue; however, these are often more severe and longer lasting [6,10,11]. Both travel direction and duration have direct implications for symptom manifestation, but jet lag typically occurs when journeys involve crossing 3 or more time zones [6]. Depending on the timing of training or competition, this circadian disruption can directly impair athletic performance [6]. Both physical and cognitive performance may be adversely affected by jet lag, leading to symptoms such as insomnia and/or excessive daytime sleepiness, fatigue, reduced muscular strength and psychomotor coordination, impaired cognition and memory, anxiety, depression, and somatic complaints including constipation and loss of appetite [12]. These manifestations occur because the body continues to function according to the circadian rhythm of the departure time zone [13]. Despite frequent references to performance impairment, there remains a gap in the literature regarding which specific domains are most affected. Figure 1 summarizes the practical stressors and manifestations of travel fatigue and jet lag described in the current literature.

Westward travel lengthens the day, resulting in a delay of the biological clock, whereas eastward travel shortens the day, leading to an advance of the biological clock [14]. Consequently, the time required to resynchronize the internal circadian rhythm with the local time varies according to the direction of travel. Westward travel generally requires approximately 0.5 days of adjustment per hour of time difference, eastward travel typically requires about 1.5 days per hour of difference [11,12,14]. It is also important to note that eastward travel tends to produce more pronounced jet lag symptoms, as the human circadian system is naturally better adapted to extending the day than shortening it [14,15].

Circadian rhythms, from the Latin circa dies (about a day), govern the daily rhythm of human physiology and performance [15,16]. Most physiological functions exhibit circadian rhythmicity, characterized by 24 h oscillations with maximum (acrophase) and minimum (nadir) values occurring at specific times of day [8,15]. Circadian rhythms are expressed as oscillations in physiological systems, including body temperature, heart rate, and hormonal levels such as cortisol. These parameters respond to both internal (e.g., neurotransmitters or metabolic substrates) and external (e.g., environmental factors, drugs, food) stimuli [8,15,17]. In humans, the primary synchronizer of circadian rhythms is the light–dark cycle [4,8,15,18].

The circadian rhythm is regulated by the suprachiasmatic nucleus (SCN), located in the hypothalamus, which is considered the master biological clock. The SCN regulates, among other functions, the production of melatonin by the pineal gland and interacts with neurotransmitters such as serotonin, which indirectly participates in sleep regulation and serves as a precursor to melatonin. Through these mechanisms, the body transitions from daytime alertness to nighttime drowsiness [4]. The SCN sends signals to different regions of the hypothalamus, influencing processes such as thermoregulation, hormone secretion, feeding and sleeping, thereby highlighting its central role in coordinating the organism’s physiological functions [8].

External timing cues, known as zeitgebers (German for “time-givers”), synchronize the body’s internal clock network with the external environment. In humans, light is the most potent zeitgeber. The SCN receives photic input from the retina and uses it to reset subordinate clocks throughout the brain and peripheral tissues through direct neural projections, humoral signaling, or by regulating behavioral rhythms such as the sleep–wake and feeding–fasting cycles [19]. Restricting food intake to the normal rest phase (nighttime in humans, daytime in nocturnal rodents) can uncouple peripheral clocks from the SCN pacemaker, with glucocorticoids playing a key role. This internal desynchronization is characteristic of shift work and may contribute to an increased risk of obesity, type 2 diabetes, cardiovascular disease, and mood disorders [19]. In fact, cellular clocks assist to regulate blood pressure, heart rate, and endothelial function [19]. When these clocks are disrupted, the risk of conditions such as heart disease, heart failure, myocardial infarction, and arrhythmias increases.

Humans exhibit interindividual differences in the timing of behavioral patterns, including social activities, daytime routines, and sleep patterns [20]. These differences are commonly described along a chronotype continuum, ranging from morning types to evening types, with intermediate types occupying the midpoint [20]. Morning types display phase-advanced tendencies, showing a preference for early awakening and morning activity, and often experience difficulty remaining awake beyond their habitual bedtime [20]. In contrast, evening types are phase-delayed, preferring later bedtimes and experiencing difficulty waking early [20]. In the general adult population (ages 19–31), chronotype distribution indicates that most individuals are intermediate types (70%), with smaller proportions classified as morning (14%) or evening types (16%) [21]. In elite sports, athletes’ sleep–wake patterns are strongly influenced by training and competition schedules [22]. It is important to underline that the knowledge produced for the benefit of those who often operate at the extreme boundaries of human capacity, such as elite athletes, could be applied to improve the quality of life of the general population. Indeed, there are various examples of this transfer from elite sport to general population. Optimal training adaptation and performance are thought to depend on the alignment between an athlete’s chronotype and their training schedule [23]. Accordingly, athletes engaged in predominantly morning-based sports tend to be morning types, whereas those participating in evening-based sports tend to be evening types [20] (Figure 2).

Thus, the primary aims of this systematic narrative review were: (i) to explore the importance of circadian rhythms for athletes’ health and performance, (ii) to distinguish between the terms jet lag and travel fatigue, (iii) to examine how athletes and teams prepare for long-haul travel before competitive events, (iv) to identify the markers used to assess athletes’ readiness, and (v) to investigate whether long-haul travel induces physiological, hemodynamic, or performance-related changes.

2. Materials and Methods

2.1. Eligibility

While adhering to the rigorous search standards of a traditional systematic review, we adopted a “systematic narrative review” design, which differs from a traditional systematic review by substituting statistical quantification with a narrative synthesis to effectively integrate data from diverse methodologies. The elements of this systematic narrative review methodology that were applied and those which were not are reported at the International Prospective Register of Systematic Reviews (PROSPERO; registration number: CRD42025630974). This systematic narrative review was conducted and reported in accordance with the PRISMA 2020 (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines (https://www.prisma-statement.org/ accessed on 3 December 2024) [24] (see the PRISMA 2020 checklist as Supplementary File S1). Three databases were assessed for the research: PubMed, Scopus and Web of Science (search dates: until January 2025). The search string and Boolean operators used were: ((“jet lag”) OR (“travel fatigue”) OR (“long travel”) OR (“transmeridian travel”) AND (“performance”) AND (“athletes”). Participants, interventions, comparators, outcomes, and study design (PICOS) were defined as follows:

• Participants—Athletes of all levels, ages, and both sexes (male and female);
• Interventions—Jet lag and long-haul travel. Long-haul travel refers to journeys that typically exceed 4000 km and often involve crossing multiple time zones or continental boundaries. While long-haul travel offers significant economic and cultural benefits, it may also pose specific challenges, including health and performance-related impacts;
• Comparators—Athletes who are frequently exposed to long-haul travel for training and/or competition;
• Outcomes—The primary outcomes in this review include humoral alterations, gastrointestinal disturbances, circadian rhythm disruptions, psychophysiological responses, hemodynamic changes, and variations in blood biomarkers. Additionally, secondary outcomes encompass physical fitness and performance-related indicators such as cardiorespiratory fitness, body composition, bone health, and various measures of muscular strength (isometric, dynamic, explosive, and reactive), as well as flexibility, agility and speed;
• Study Design—The review did not impose restrictions on study design, and all types of studies were deemed eligible for inclusion.

To ensure methodological rigor, the following systematic elements were implemented: prior protocol registration in PROSPERO, adherence to PRISMA 2020 reporting guidelines, and predefined eligibility criteria based on the PICOS framework. The process included a comprehensive multi-database search, dual independent screening and selection, structured data extraction using a predefined template, and independent risk of bias assessment using the JBI Critical Appraisal Tools.

2.2. Study Selection

After defining the Boolean operators and keywords for the literature search (Table 1), all retrieved references were imported into an EndNote 21 database (version 21.5); https://endnote.com, London, UK. Automatic duplicate removal tool was performed, followed by manual verification to identify and remove any remaining duplicates. Subsequently, two authors independently screened the titles and abstracts to determine eligibility for full-text review or exclusion. Disagreements between the two reviewers were resolved by consultation with a third author, who made the final decision. Full-text articles selected for inclusion were then read in detail, and a third stage of selection was applied: studies whose topic was not related to the aim of the review were excluded at this stage. The full-text assessment was performed independently by the same two reviewers using predefined eligibility criteria, with disagreements resolved through consultation with a third reviewer following the same procedure.

2.3. Data Extraction

From the eligible studies that were included in this review, data that was extracted from the studies were: publication details (first author, study tittle, year of publication), study design, participants (sex, sample size, competitive level), travel details (direction, number of time zones crossed), supplementation (exogenous strategies to mitigate travel effects), main results and conclusions.

2.4. Risk of Bias Assessment

The methodological quality of the included studies was assessed independently by two reviewers using the appropriate Joanna Briggs Institute (JBI) Critical Appraisal Tools, according to the specific study design. Each criterion within the tool was rated as “yes,” “no,” “unclear,” or “not applicable.” The results of the risk of bias assessment were used to inform the interpretation of findings but did not serve as exclusion criteria for studies. The following thresholds were established: low risk of bias (“yes” scores ≥ 70%), moderate (50 ≤ “yes” scores < 70%), and high (“yes” scores < 50%). Specifically, the JBI Critical Appraisal Checklists for Case Series, Case Reports, Quasi-Experimental Studies, Systematic Reviews, Cohort Studies, Randomized Controlled Trials, Qualitative Research, Expert Opinion, and Analytical Cross-Sectional Studies were applied according to the specific design of each included study.

3. Results

Overall, a total of 284 records were identified using the search strategy as described above. Of the 100 studies retained for full-text screening, 11 did not meet inclusion criteria and were removed. 89 studies were therefore deemed eligible for inclusion in the review (Figure 3). Table 2 shows the 89 studies included in the review.

The 89 studies were published between 1985 and 2024 and included the sports of soccer (n = 21); Rugby (n = 12); American Football (n = 8); Basketball (n = 8); Swimming (n = 7); Athletics (n = 7); Cycling (n = 6); Skeleton (n = 4); Super Rugby (n = 4); Tennis (n = 3); Track and field (n = 3); Rowing (n = 3); Triathlon (n = 3); Badminton (n = 2); Golf (n = 2); Ice Hockey (n = 2); Volleyball (n = 2); Gymnastics (n = 2); Boxing (n = 2); Sailing (n = 2); Cricket (n = 2); Hockey (n = 2); High Jump/Long Jump (n = 1); Baseball (n = 1); Wheelchair basketball (n = 1); Netball (n = 1); Speed skaters (n = 1); Biathlon (n = 1); Kite surfers (n = 1); Wrestling (n = 1); Clay target and shooting (n = 1); Diving (n = 1). Regarding study design, the included studies comprised narrative reviews (n = 21), critical reviews (n = 2), and systematic reviews (n = 2). Primary research designs included observational studies (n = 37) and cohort studies (n = 3). Experimental designs consisted of experimental studies (n = 3), quasi-experimental studies (n = 4), and randomized control trials (n = 2). Additional study types included case studies (n = 7), case reports (n = 1), qualitative studies (n = 2), commentaries (n = 3), a position statement (n = 1) and a cross-sectional survey (n = 1). It is noteworthy that although significant impairments are often emphasized, several included studies yielded non-significant findings or null effects across various performance parameters. Therefore, the evidence should be interpreted with caution, acknowledging that the absence of a statistically significant effect in certain cohorts is as informative as its presence (See Table 2).

3.1. Travel Details

Of the 89 studies included in this review, approximately 33 did not report any travel details (e.g., duration, direction, time zones crossed). 49 studies reported the direction of travel, with 23 studies for eastward and 23 studies for westward journeys, followed by northeast (2 studies). 1 study reported travels across all North America. Regarding time zones, 31 studies reported the number of time zones crossed. Overall, participants crossed between 1 and 12 time zones. The most frequently crossed time zones were: 8 time zones (n = 6), 5 time zones (n = 5), 7 time zones (n = 4), 12 time zones (n = 3), 9 time zones (n = 3), 4 time zones (n = 2), 10 time zones (n = 2), 1 time zone (n = 1), 2 time zones (n = 1), 3 time zones (n = 1), 6 time zones (n = 1) and 11 time zones (n = 1) (See Table 2).

3.2. Interventions to Mitigate Travel Effects

Of the 89 studies included in this review, 72 did not report any intervention to mitigate travel effects. Among those that did, melatonin was cited in 16 studies, caffeine in 6 studies and light exposure in 3 studies. Other reported interventions included physical exercise, probiotics and ramelteon being cited in 1 study (See Table 2).

3.3. Physiological and Hemodynamic Markers

In terms of physiological and hemodynamic changes, 36 studies cited sleep changes. Among these, 15 studies used objective measures (e.g., actigraphy, polysomnography), of which 10 also included subjective self-reports. Meanwhile, 24 studies relied on subjective measures (e.g., sleep diaries, questionnaires), with 10 of these also reporting objective sleep outcomes. Alongside sleep disturbances, other physiological markers were consistently reported. These included alterations in body temperature (n = 18), blood pressure, hormonal changes (n = 9), heart rate variability (n = 4), and immune system (n = 4). It should be noted, however, that HRV outcomes were reported in only 4 studies, underscoring the scarcity of evidence and necessitating a cautious interpretation of these results. (See Table 2).

Regarding immune and inflammatory outcomes, the findings demonstrate substantial heterogeneity rather than a consistent trend. While long-haul travel is associated with immune system disruption in some studies (n = 4), the specific markers and the direction of these changes vary significantly across the literature. This inconsistency suggests that immune responses may be more sensitive to individual variability, cabin environment, or the specific stressors of the travel itinerary rather than following a uniform temporal pattern of disruption.

Temporal analysis of these markers reveals that physiological disruption is immediate, with core body temperature rhythms markedly altered as early as Day 1 post-travel, regardless of flight direction. Regarding performance and psychophysical state, the most acute impact occurs between Days 1 and 2, a period characterized by peaks in fatigue, confusion, and reductions in anaerobic power. The recovery trajectory is variable and depends on the stabilization of the sleep–wake cycle. While improvements in mood and strength may occur within a few days, the full normalization of hemodynamic variables and core temperature is slower, typically extending for about 1 week, although in individual cases, the recovery period may range from 3 to 11 days.

3.4. Travel Effects

Regarding the effects imposed by travel, fatigue was cited in 25 studies, sleep changes (e.g., insomnia, bad sleep quality) in 21 studies, decreased physical performance (e.g., strength, power, coordination, velocity) in 18 studies, mood changes (e.g., irritability, confusion, demotivation) in 15 studies, cognitive problems (e.g., attention, reaction time, concentration) in 9 studies (See Table 2).

3.5. Physical Performance Markers

In the 89 studies included, 69 reported physical performance outcomes. Anaerobic power (e.g., sprints, jumps) was cited in 18 studies. Strength (e.g., grip, isometric) was reported in 14 studies. Velocity was cited in 12 studies. Aerobic power and capacity were cited in 10 studies. Coordination was cited in 8 studies. Reaction time was reported in 7 studies.

3.6. Risk of Bias

Of all studies included in this systematic narrative review, 49% of studies showed low risk of bias, 17% of studies showed moderate risk of bias, and 34% of studies showed high risk of bias. The average score of all studies was 61%, which indicates an overall rating of moderate risk of bias (Table 3).

4. Discussion

Long-haul travel disrupts multiple physiological and performance systems in athletes. It is important to distinguish between the acute effects of travel fatigue (driven by non-circadian stressors such as sleep deprivation, dehydration, and logistical constraints) and the persistent physiological shifts caused by circadian misalignment (jet lag). While travel fatigue typically resolves with rest and hydration, the effects of circadian misalignment are influenced by travel direction, the number of time zones crossed, and individual variability. Despite their distinct etiologies, these stressors often coexist in elite athletic travel. As illustrated in the conceptual framework of Figure 2, these factors trigger a cascade of physiological disruptions. Consequently, their cumulative impact impairs aerobic and anaerobic performance, strength, velocity, coordination, and sport-specific skills, although some outcomes differ across studies. However, it is essential to acknowledge that associations, for example, between travel direction and match outcomes in team sports, may be influenced by several confounding factors, such as team quality, scheduling, tactics, and opponent level. Therefore, while a potential causal link is suggested, these findings should be interpreted with caution, as they may not solely reflect the direct physiological effects of jet lag. Targeted recovery, differentiating between acute fatigue management and circadian resynchronization, is essential to preserve performance. While some physiological disruptions are well-documented, other mechanistic explanations, such as specific hormonal imbalances, require further empirical validation in the context of elite athletic travel. Similarly, supplementation was not the focus of most studies, but repeated mentions of caffeine suggest potential benefits, though evidence remains inconclusive. Jet lag may be less pronounced when travel coincides with major competitions or meaningful events [98]. These changes may contribute to cardiovascular rhythm disturbances during and after long-haul travel.

4.1. Physiological and Hemodynamic Markers

Circadian rhythms that persist under constant conditions originate within the body, indicating an endogenous component [15]. Environmental and behavioral factors such as sleep, activity, and light exposure modulate these rhythms, representing the exogenous component [8]. During the day, body temperature is elevated due to the combined effect of the internal clock and alerting influences of environmental factors and activity. At night, the internal clock, environmental cues, and reduced activity all contribute to lower body temperature. This interaction illustrates the multifactorial regulation of physiological variables under travel conditions.

4.1.1. Body Temperature

Irrespective of flight direction, core body temperature rhythms were markedly disrupted on day 1. Eastward travel produced a phase advance, whereas westward travel induced a phase delay [29]. Core body temperature was strongly coupled to the sleep–wake cycle, and temperature regulation appeared to recover only after this cycle stabilized [30,31]. Recovery from disruption ranged from 3 to 11 days, although some individuals recovered by day 3 [35,77]. This suggests a potential causal link, although the underlying biological drivers remain to be fully elucidated. Restricted or fragmented sleep further impairs temperature regulation [4]. Transmeridian travel disrupts core temperature rhythms independent of direction, with recovery generally occurring within 1 week [29].

4.1.2. Blood Pressure

In German Olympic gymnasts, westward travel increased peak systolic and diastolic values, whereas eastward travel decreased them [29]. These direction-dependent effects are influenced by altitude, cabin pressure, vibration, and fatigue [8]. Westward flights tend to raise blood pressure, whereas eastward flights tend to lower it. These changes may contribute to cardiovascular rhythm disturbances during and after long-haul travel.

4.1.3. Sleep

Sleep is consistently disrupted after transmeridian travel. In professional soccer players, total sleep duration remained largely unchanged, but awakenings increased on days 1 and 3, and sleep latency decreased on days 2, 6, and 8 after westward travel [28]. Timed exercise, bright light exposure, and melatonin accelerate circadian re-synchronization [28,37,64,99]. Eastward travel delayed bedtime and wake times, increasing total sleep duration, whereas westward travel often reduced sleep quality [9,99]. Interventions such as timed exercise, light exposure, and melatonin mitigate these disturbances.

4.1.4. Cortisol

Cortisol is a key stress hormone and a central marker of the hypothalamic–pituitary–adrenal (HPA) axis [100]. However, the literature is inconsistent regarding the effects of travel on cortisol secretion. After eastward travel, cortisol levels increased [35,61], whereas Bullock et al. reported a decrease [33]. In contrast, Stevens et al. found no change in cortisol levels after travel [54]. When disruptions occurred, 7 to 11 days were required for cortisol levels to return to baseline in both eastward and westward directions [29,33,77]. Such changes can impair physiological processes related to performance, recovery, and immune function. The endocrine response is variable, emphasizing the need for personalized strategies to mitigate travel-related effects on cortisol and the endocrine system [34]. Therefore, monitoring athletes’ cortisol after transmeridian travel is essential, as disruptions can affect performance, recovery, and immunity. Interventions may include timed sleep and light exposure, scheduled exercise, appropriate nutrition and hydration (including easily digestible foods), stress-management techniques, and, where appropriate, supervised melatonin to support endocrine recovery.

4.1.5. Heart Rate Variability (HRV)

Heart rate variability (HRV) is a robust indicator of autonomic function and the balance between sympathetic and parasympathetic activity [101]. Its sensitivity to physiological changes makes HRV a relevant marker for the effects of long-haul travel [36]. The literature is inconsistent regarding HRV responses. HRV declined after transmeridian travel crossing more than 3 time zones [27,36,78], but values typically returned to baseline at a rate of 1 day per time zone crossed [36]. After crossing 5 time zones, HRV remained impaired on days 4 and 5, with progressive recovery until day 13, suggesting that the autonomic system requires several days to reestablish stability following circadian disruption [36]. HRV is also influenced by prior-day training loads, indicating an interaction between environmental factors (e.g., temperature, humidity) and training-related physiological stress. More recently, a temporary decrease in LnRMSSD (natural logarithm of the root mean square of successive R-R interval differences) was observed, more pronounced in non-starters, suggesting that exposure to competition and game load modulates autonomic responses to jet lag [78]. Therefore, HRV is a sensitive, non-invasive marker of autonomic disruption after long-haul travel, with recovery timelines proportional to the number of time zones crossed. Monitoring HRV can guide individualized training-load adjustments and recovery strategies, optimizing cardiovascular adaptations, mitigating the physiological impact of jet lag, and supporting athletes’ performance and readiness.

4.2. Physical Performance Markers

Physical performance outcomes are heterogeneous. The higher the performance level, the smaller the differences between athletes and the narrower the gap between winners and losers. In elite competitions, success often hinges on minute details. As professional athletes constantly seek a competitive edge, manipulating circadian rhythms may confer an advantage [17]. Most performance-related parameters (grip strength, anaerobic and aerobic power, hormonal secretion, and self-selected work rate) are closely linked to the body temperature rhythm, which peaks in the late afternoon (around 18:00) [8,17]. Notably, a disproportionate number of world records have been set during this period [17,18].

4.2.1. Anaerobic Power

Effects of long-haul travel on anaerobic power are inconsistent across studies. In athletes and healthy, physically trained individuals, long travel can reduce muscle performance, vertical jump height, and maximal acyclic power, regardless of travel direction, while simpler tasks typically recover more quickly [4,25,38,50,77]. Maximal and intermittent sprint performance may be impaired for up to 9 h post-travel [50]. In male professional soccer players, high-intensity actions, such as sprint distance and high-intensity running during games, were negatively affected after travel [68]. However, in skeleton athletes after eastward travel crossing 4 time zones, no differences were observed in post-travel 30 m sprint time [33]. Conversely, in highly trained rowers traveling westward across 9 time zones, the propulsive phase and eccentric velocity during loaded countermovement jumps (LCMJ) improved, resulting in higher mean power [76]. Similarly, speed skaters exhibited increased jump height after eastward travel across 10 time zones [94]. Overall, the effects of long-haul travel on anaerobic power are inconsistent, depending on sport modality, travel direction, and individual characteristics. Temporary impairments, particularly in high-intensity efforts after eastward travel, are common, though some athletes may experience enhanced outputs in specific power tasks. Therefore, strength and conditioning coaches, exercise physiologists, and medical staff should monitor athletes’ anaerobic performance after travel and implement individualized recovery, training, and adaptation strategies to optimize post-travel performance.

4.2.2. Strength

Strength responses vary by travel direction, sport modality, and circadian timing of assessments. Press–pull strength, at both slow and fast velocities, decreased after westward travel [25]. In elite athletes from multiple sports (e.g., track and field, swimming, cycling) traveling eastward, muscle strength declined for several days, exhibiting a circadian rhythm with the lowest values in the morning and peak strength in the early evening [35]. Among second-division American college basketball players, knee flexion strength decreased over a season of travel, accompanied by a reduction in vertical jump height [61]. In contrast, rugby players showed no change in muscle strength or range of motion after westward travel [46]. Conversely, in highly trained male rowers, eccentric velocity and jump height improved after westward travel [76], and speed skaters jumped higher after eastward travel across 10 time zones [94]. Therefore, sport scientists should monitor athletes’ muscle strength post-travel and implement individualized recovery and training strategies to optimize performance.

4.2.3. Velocity

Maximal 30 m sprint and race times were unaffected in skeleton athletes and speed skaters after eastward travel [33,94]. Mean velocity during LCMJ increased after westward travel [76]. These findings align with a systematic review of elite athletes showing improved sprint performance after westward travel [77]. However, the same review reported negative effects on sprint performance in another group of athletes following westward travel [77]. Evidence on the effects of transmeridian travel on velocity is mixed: some studies report no change, while others show impairments or improvements, particularly after westward flights. These results suggest that jet lag effects on velocity depend on travel direction (typically worse after eastward travel) and sport type. Therefore, coaches and practitioners should closely monitor athletes’ speed-related performance after travel and apply individualized training and recovery strategies to maintain or optimize post-travel velocity.

4.2.4. Aerobic Power and Capacity

Aerobic power and capacity are compromised by long-haul travel, and its recovery depends on individual differences, travel direction, and timing of subsequent training or competition. College swimmers traveling westward experienced a measurable decline in endurance performance [18], and similar reductions were observed in male professional soccer players after eastward travel across 11 time zones [50]. Sleep disturbances and accumulated travel fatigue further compromise aerobic performance, reducing maximal oxygen consumption ( $[eqn]$ O_2max_). Aerobic power and capacity are particularly vulnerable to the combined stressors of time zone changes, sleep disruption, and travel-related fatigue. Therefore, exercise physiologists should monitor athletes individually and implement targeted interventions, including strategic training scheduling, sleep management, and recovery strategies, to minimize performance decrements in endurance sports.

4.2.5. Coordination and Reaction Time

Coordination is impaired by travel [12], generally more after westward travel [29]. German Olympic gymnasts showed declines in coordination after westward travel across 6 time zones, while eastward travel had less effect [29]. Similar patterns were observed in athletes from multiple sports [12]. In fact, coordination and reaction time are particularly sensitive to long-haul travel. These disturbances are likely driven by circadian misalignment and fatigue, which can compromise fine motor control and responsiveness, critical for technical performance in sports requiring precision and rapid decision-making. Coaches should assess technical and cognitive performance, and implement training recovery protocols, timing strategies, and fatigue mitigation techniques to preserve technical performance.

4.2.6. Sport Specific Tasks

Game performance in NBA, NFL, MLB, NHL, and rugby shows travel-related decrements. Westward travel often correlates with poorer performance, though eastward travel sometimes impairs outcomes. Most studies examining the effects of long-haul travel on physical performance used non-sport-specific tasks. However, several longitudinal studies in the USA and Australia assessed actual game performance and sport-specific statistics (e.g., free throws made, home runs, final match results). In the NBA, travel before a game negatively affected team performance, including win percentage, free throws, field goal percentage, and rebounds [13,53,69]. Travel direction was strongly correlated with performance, with westward travel linked to poorer outcomes [13,53,69], although some studies reported eastward travel associated with reduced performance [83,95]. In American football (NFL and NCAA), eastward travel impaired teams’ ability to win, while westward travel negatively affected overall performance [16,17,59]. One study found no effect of travel direction on match outcomes [53]. In the NHL, westward travel disadvantaged teams [53], but in general, travel negatively impacted overall performance regardless of direction [81]. In MLB, travel reduced team performance, with eastward travel having a greater negative effect than westward [52]. Outside North America, in rugby (NRL, Australia), travel adversely affected performance regardless of direction [84]. Overall, long-haul travel impairs sport-specific performance, with measurable effects on game statistics and team outcomes across professional leagues. Contrary to traditional assumptions that eastward travel produces more severe jet-lag symptoms, westward travel was frequently linked to poorer performance in game metrics. These decrements are likely driven by circadian disruption, fatigue, and travel-related stress, emphasizing the importance of strategic travel management in professional sports.

4.3. Integrated Pathways Linking Travel, Circadian Disruption, and Performance

Long-haul travel disrupts athlete performance through interacting, rather than isolated, mechanisms. Acute travel fatigue and jet lag often coexist and jointly disturb key physiological systems. These disturbances are closely linked to instability of the sleep–wake cycle and delayed recovery, which in turn constrain aerobic and anaerobic performance, strength, velocity, coordination, and sport-specific skills. At the same time, variability in performance outcomes across studies reflects differences in travel direction, number of time zones crossed, sport modality, and individual responses. Therefore, performance changes should be interpreted as the cumulative result of these interacting physiological disruptions rather than as isolated effects, reinforcing the need for targeted, individualized recovery and monitoring strategies after long-haul travel.

4.4. Limitations

Heterogeneous populations, small sample sizes, observational designs, and uncontrolled contextual factors limit generalizability. Direct comparisons across studies are challenging due to variations in sport, competitive level, travel direction, number of time zones, and performance measures. Additionally, inter-individual variability (e.g., chronotype, sex, and training status) may influence individual responses to travel and circadian disruption, which complicates the interpretation of group-level findings. Future research should incorporate stratified analyses, larger and more diverse samples, and standardized assessments of individual characteristics to better account for these moderators and improve the applicability of findings.

Of the studies included, 49% were rated as low risk of bias, 17% as moderate, and 34% as high, resulting in an overall moderate methodological quality. The predominance of observational, narrative, and case-report designs, together with moderate-to-high risk of bias, may inflate, obscure, or contribute to inconsistencies in reported effects on physiological and performance outcomes. The limited number of intervention-based studies constrains causal inference, so findings should be interpreted as indicative rather than definitive. These methodological considerations highlight the importance of applying the findings cautiously, tailoring monitoring and intervention strategies to each athlete’s context, as discussed in the following practical recommendations.

4.5. Practical Applications

Long-haul travel and jet lag have multifactorial effects on physical performance, physiological markers, and athletes’ well-being. Coaches, medical staff, and sports managers should adopt preventive strategies and individualized monitoring to mitigate these effects. Trip planning should allow gradual adaptation to the new time zone. Physiological variables (e.g., HRV, cortisol, body temperature) should be monitored to evaluate recovery and readiness. Behavioral interventions, including sleep hygiene, strategic light exposure, proper nutrition, and hydration should be implemented, alongside education for athletes and technical staff to recognize early signs of travel fatigue and jet lag. Some physiological effects are well established, but other mechanisms, including hormonal imbalances, still need further confirmation in elite athletes. Likewise, although supplementation was not the experimental focus of most original articles analyzed, the recurring mention of caffeine in the included reviews underscores its potential relevance as a mitigation strategy; however, such interventions remain not fully conclusive. Figure 4 provides a schematic overview of the study’s main findings, illustrating the interactions between long-distance travel, jet lag, and the resulting physiological, humoral, and performance responses.

4.6. Future Research Directions

Despite the growing body of evidence on athletic travel, several gaps remain to be addressed to advance the field:

• Female athlete representation: There is an evident need for studies focusing on female athletes.
• Standardization of performance metrics: Standardized performance testing protocols are welcome;
• Mechanistic links: Future studies should move beyond descriptive observations to establish clearer mechanistic links between biological markers and sport-specific performance related outcomes;
• Diversified interventions: While light exposure and melatonin are well-studied, there is a need for randomized controlled trials (RCTs) exploring alternative interventions, such as nutritional ergonomics, blood flow restriction (BFR);
• Between-sport and within-sport comparisons: Comparative research is needed, for example, to determine if the social external timing cues (zeitgebers) and logistical demands of team sports result in different adaptation patterns compared to the highly individualized environments of individual sports.

5. Conclusions

Long-haul travel and jet lag appear to produce multidimensional effects on athletes by potentially perturbing circadian, autonomic, endocrine, and performance systems. The magnitude and trajectory of these disturbances are likely influenced by travel direction, number of time zones crossed, sleep disruption, prior training load, competitive context, and individual susceptibility. Although performance outcomes remain heterogeneous, evidence suggests that aerobic capacity, coordination, and technical execution may be particularly vulnerable, whereas anaerobic power and strength demonstrate variable responses, including temporary improvements in certain modalities and directions of travel. At the physiological level, disruptions in core body temperature, blood pressure, HRV, sleep architecture, and cortisol secretion often reflect misalignment between internal circadian rhythms and external environmental cues. These alterations may impair autonomic balance, recovery processes, and readiness to perform, potentially contributing to decrements in competition-specific performance and game statistics across multiple team sports, although null and mixed findings are also reported. HRV appears to be a sensitive non-invasive marker for tracking autonomic recovery, while endocrine responses, particularly cortisol, underscore the importance for individualized monitoring due to their variability. Overall, the available evidence suggests that travel-related performance changes are not solely determined by east–west directionality but likely reflect an interaction between circadian phase, competitive timing, home–away context, and logistical stress. Consequently, personalized management strategies, encompassing strategic scheduling, sleep and light manipulation, nutrition and hydration, training load adjustment, and athlete education, are likely beneficial to help mitigate the effects of jet lag, preserve performance, and optimize recovery. Future research should aim to refine mechanistic understanding, identify interindividual phenotypes of susceptibility, and develop evidence-based protocols tailored to sport modality, competitive calendar, and travel demands. However, given the heterogeneity in study designs, sports modalities, and athlete populations, these findings should be interpreted with caution, as they may not be directly generalizable to all sporting contexts.