Injury and illness in short-course triathletes: A systematic review

Highlights

• •Overuse, lower limb injuries, mainly attributed to running, were the most frequently reported injuries.
• •Gastrointestinal and altered cardiac function (arrythmias and altered ventricular function) due to poor water quality and thermal strain were the most frequently reported illnesses.
• •Additional high-quality studies exploring health problems in short-course triathletes are required to improve injury and illness prevention strategies.

Abstract

Background

Determining the incidence and prevalence of injury and illness in short-course triathletes would improve understanding of their etiologies and therefore assist in the development and implementation of prevention strategies. This study synthesizes the existing evidence on the incidence and prevalence of injury and illness and summarizes reported injury or illness etiology and risk factors affecting short-course triathletes.

Methods

This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Studies reporting health problems (injury and illness) in triathletes (all sexes, ages, and experience levels) training and/or competing in short-course distances were included. Six electronic databases (Cochrane Central Register of Controlled Trials, MEDLINE, Embase, APA PsychINFO, Web of Science Core Collection, and SPORTDiscus) were searched. Risk of bias was independently assessed by 2 reviewers using the Newcastle–Ottawa Quality Assessment Scale. Two authors independently completed data extraction.

Results

The search yielded 7998 studies, with 42 studies eligible for inclusion. Twenty-three studies investigated injuries, 24 studies investigated illnesses, and 5 studies investigated both injuries and illnesses. The injury incidence rate ranged 15.7–24.3 per 1000 athlete exposures, and the illness incidence rate ranged 1.8–13.1 per 1000 athlete days. Injury and illness prevalence ranged between 2%–15% and 6%–84%, respectively. Most injuries reported occurred during running (45%–92%), and the most frequently reported illnesses affected the gastrointestinal (7%–70%), cardiovascular (14%–59%), and respiratory systems (5%–60%).

Conclusion

The most frequently reported health problems in short-course triathletes were: overuse and lower limb injuries associated with running; gastrointestinal illnesses and altered cardiac function, primarily attributable to environmental factors; and respiratory illness mostly caused by infection.

Graphical abstract

1. Introduction

Triathlon consists of 3 consecutive disciplines: swimming, cycling, and running, with races over a variety of distances. Elite triathletes typically specialize in either short-course or long-course racing.¹ Short-course races in triathlon include the standard distance (1.5-km swim, 40-km cycle, and 10-km run) and shorter sprint and super-sprint distances.² A typical elite short-course season consists of 8–18 races between March and September.³ Weekly training for elite short-course triathletes consists of 16 ± 4 sessions/week (mean ± SD) divided into the various disciplines (swimming = 6 ± 1, cycling = 4 ± 1, running = 5 ± 2, and strength = 1 ± 1 sessions).³ Training and competition strategies as well as physiological requirements for performance vary greatly between short and long-course triathlons (i.e., distances greater than the standard distance),^4,5 hence the importance of differentiating between the two when characterizing injury and illness in triathletes. The training requirements for triathlon can lead to adaptations and improvements in performance or to maladaptation and health problems,¹ which may directly or indirectly affect performance.^6,7 Further, understanding the main health problems affecting short-course triathletes and the pathways by which they occur would provide valuable insight about the factors leading to injury and illness, along with potential approaches to minimize risk and maximize performance.

The physiological and training demands of different triathlon races vary greatly.³ The majority of triathlon-related research undertaken to date fails to clearly define the athlete groups included, specifically regarding distance specialty and baseline demographic information (sex, age, and ability level).¹ Additional high-quality studies exploring health problems in short-course triathletes are required to improve current health prevention measures for high-risk subgroups within the sport.⁸ Despite existing literature on the physiological requirements of different triathlon race distances and how these affect performance,^4,5 the relationship between training demands and injury and illness incidence in short-course triathletes warrants further investigation.⁸

Existing injury and illness data specific to short-course triathlon is scarce, limiting the ability to profile the nature and incidence of health problems in this population.^9,10 Reliable epidemiological health data are critical to understanding the etiology of injury and illness in short-course triathletes and assist with the promotion of a multidisciplinary approach to improving health and performance outcomes.11, 12, 13 The Translating Research into Injury Prevention Practice (TRIPP) framework¹⁴ has evolved from a previous framework proposed by van Mechelen et al.,¹⁵ and is a well-recognized injury-prevention framework in the current sporting landscape. This framework outlines a staged progression for injury prevention approaches, designed to facilitate the development of sports injury prevention strategies in real-world contexts.¹⁴ This systematic review aims to evaluate the current literature on short-course triathlon injury and illness epidemiology by addressing Stages 1 and 2 of the TRIPP model to inform the development of effective preventative strategies to optimize athlete health and performance. Therefore, the research questions are: What is the incidence and/or prevalence of injury and illness within short-course triathletes; and what are the proposed etiological and environmental factors that contribute to injury or illness in short-course triathlete specialists?

2. Methods

2.1. Literature search

This systematic review was registered on the PROSPERO International prospective register for systematic reviews website (http://www.crd.york.ac.uk/PROSPERO) (registration number: CRD42018114627) and was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.¹⁶

A comprehensive, electronic search of the literature was conducted without date restrictions in Cochrane Central Register of Controlled Trials, MEDLINE, Embase, APA PsychINFO, Web of Science Core Collection, and SPORTDiscus on July 21, 2021 using a search strategy developed by 3 authors (SAG, PC, and MD). Various combinations of the following keywords were used in each database: “triathlete”, “injury”, “illness”, “psychological wellbeing”, and “epidemiology” to identify the appropriate population for the study and associated injuries or illnesses. Refer to Appendix 1 of online Supplementary materials for MEDLINE search strategy details. Search limitations included original research articles published in the English language in peer-reviewed journals, without restriction on publication year. All potential references were imported into Covidence systematic review software (Veritas Health Innovation, Melbourne, VIC, Australia) and duplicates were removed. Backward citation searching was undertaken by SAG and MLC, where the reference lists of the included studies as well as other review articles were screened to identify any additional studies for inclusion.

2.2. Selection criteria

Studies involving short-course triathletes (i.e., triathletes competing in standard or shorter distances) of all sexes and across age and sport-experience levels that reported health problems (defined as injury, illness, or psychological complaint) were included in this review. Participants were mapped, according to their sports level, to The Foundations, Talent, Elite, Mastery framework,¹⁷ which integrates phases of athlete development within active lifestyle, sport participation, and sport excellence pathways.

Studies conducted in non-triathlete populations or in triathletes training or competing for distances longer than short-course distances were excluded from this review, as were those that did not specify the triathlon distance. Studies were also excluded if there was no form of epidemiological data published, or if specific data were unable to be extracted from published articles, or if the outcome of an intervention, such as surgery or drug trial, was being investigated. Articles that were published in languages other than English, or in non-peer reviewed journals, or that were systematic or narrative reviews, opinion pieces, editorials, abstracts, conference proceedings, or non-scientific magazines were also excluded.

2.3. Study selection

Titles and abstracts of the articles from the initial search were independently screened for eligibility by 2 reviewers (SAG and MLC) using Covidence systematic review software (Veritas Health Innovation). Articles were screened according to the eligibility criteria and then placed into separate “yes”, “no”, and “maybe” folders. Two reviewers (SAG and MLC) compared “yes” folders for agreement with attempts to resolve any discrepancies. All articles in the “maybe” folder, or where consensus was not reached, were assessed by a third reviewer (PC), who resolved all remaining discrepancies. The full texts were obtained for all articles in the “yes” folder at the conclusion of the screening process. Full-text eligibility of published studies was independently examined for final inclusion by 2 reviewers (SAG and MLC) according to the eligibility criteria. Where insufficient data were reported to answer the research question, the reviewers contacted the author group to seek clarification or request access to the raw data to allow for secondary calculations to be undertaken. If there was no response in the 2 weeks following this e-mail, a second correspondence was sent to seek clarification, and if no response was received after a further 4 weeks, the articles were excluded due to an inability to confirm the triathlon distance or specific triathlon data. A third author (PC) was consulted in the event of a disagreement between authors for consensus. All studies were able to be classified using the track and field consensus statement, which defined a recordable health-related incident as “any physical or psychological complaint or manifestation experienced by an athlete, irrespective of the need for medical attention or time loss from athletics activities”.¹⁸

2.4. Data extraction

Data extraction was independently completed by 2 of the authors (SAG and MLC) using a structured form that included extraction of the following: study design, surveillance period, participants characteristics (sex, age, race distances, experience level—mapped to The Foundations, Talent, Elite, Mastery framework classification,¹⁷ which is a tool designed to assist sporting stakeholders in reviewing, planning and supporting athlete pathways). Injury and illness definitions were mapped to the Injury Definitions Concept Framework classifications, which considers the clinical examination, sports performance, and athlete self-perception.¹⁹ Injury characteristics (number, type, location, nature, and mechanism), illness characteristics (number, illness symptoms, and affected system), and summary measures of injury and illness (prevalence, incidence) were extracted if reported. A third author (PC) independently verified the extracted data. The authors of 17 studies^9,10,20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 clarified questions regarding raw data.

2.5. Strength of evidence

The “Oxford Centre of Evidence-based Medicine—Levels of Evidence” was used to determine the hierarchical level of evidence of the articles according to the type of research question and study design adopted by the full-text studies included in this review. The highest level of evidence (Level 1) referred to “systematic reviews”, and the lowest level of evidence (Level 4) referred to “case-series and case reports”.³⁵

2.6. Risk of bias

Risk of bias was assessed using the Newcastle–Ottawa Quality Assessment Scale created for assessment of non-randomized studies, including case-controls and cohort studies.³⁶ The Newcastle–Ottawa Quality Assessment Scale allows question customization to reflect the review questions of interest.³⁷ A tailored version of the Newcastle–Ottawa Quality Assessment Scale, based on Toohey et al.,³⁸ was created in a checklist format for specific injury and illness research (Appendix 2 of online Supplementary materials). Cohort and case-control studies were assessed in accordance with their study design in 3 categories: selection of participant groups, comparability of different participant groups, and outcome/exposure result. Assessed studies could score a maximum score of 4, 2, and 3 for these respective categories. Each category was considered independently and not combined, as recommended by the PRISMA guidelines. Two authors (SAG and PC) independently completed risk-of-bias assessments for all included studies. For any discrepancies not resolved through discussion, a third independent assessor (MD) was consulted to reach consensus. Case studies were not assessed using a risk of bias tool, as these tools are designed to assess intervention-based studies, and in this review case studies only included reporting on the occurrence of specific health problems and not interventions.

3. Results

3.1. Search results

The electronic search of the relevant databases yielded 7998 potentially relevant articles that were imported into the Covidence online platform (Veritas Health Innovation). After removing 3840 duplicates and excluding another 4017 articles following the independent screening of titles and abstracts by 2 reviewers (SAG and MLC), 143 articles remained to be assessed in full text. One article was identified through the backward citation search after cross-referencing the reference lists of the included articles and another through author correspondence. The most common reasons for exclusion were not specifying the race distance (short-course or long-course) or including athletes competing in both short- and long-course races, where the epidemiologic data could not be separated. This resulted in 42 articles (26 cohort studies (Level 3), 1 case-control, and 15 case report studies (Level 4)) that were deemed eligible and included in this review; a total of 9824 short-course triathletes were observed by the included studies (Fig. 1).

Fig. 1.

Preferred Reporting Items for Systematic Review and Meta-Analyses flow chart.

3.2. Characteristics of included studies

Twenty-six of the 42 (62%) included studies were of a cohort design,^{9,10,21,23,26,28,29,31,}39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56 1 study was a case-control design,⁵⁷ and 15 (36%) were case reports.^{20,22,24,25,27,30,}32, 33, 34^,58, 59, 60, 61, 62, 63 Over a third (n = 15; 36%) of the included studies were published in 2017 or later. Twenty-three of the included studies (55%) investigated injury,^9,10,21, 22, 23^,25, 26, 27, 28^{,34,39,41,43,45,46,51,53,55,56,59,60,62,63} 24 (57%) investigated illnesses,^{9,10,20,24,25,}29, 30, 31, 32, 33^,40,42,44, 45, 46, 47, 48, 49, 50^{,52,54,57,58,61} including 5 (12%) that investigated both injuries and illnesses.^{9,10,25,45,46} Twenty (48%) studies investigated male and female triathletes;^{10,21,26,28,29,31,}39, 40, 41, 42, 43, 44^,47,49,50,52, 53, 54, 55^,57 however, the number of male triathletes included in each cohort was substantially higher than the number of females. Two studies consisted of a para-triathlete cohort,^31,44 with equal numbers of males and females. Eight (19%)^22,27,30,32, 33, 34^,59,63 and 7 (17%)^24,25,56,58,60, 61, 62 of the included studies reported injury and illness outcomes exclusively in male or female triathletes, respectively.

3.3. Risk of bias and strength of evidence

Risk of bias and hierarchical level of evidence are summarized in Table 1 and Table 2.

Table 1.

Risk of bias scores for the cohort studies and 1 case-control study using the Newcastle–Ottawa Scale (NOS) and Oxford Centre for Evidence Based Medicine (OCEBM) levels of evidence.

Study and OCEMB level of evidence	Selection (n = 4)	Comparability (n = 2)	Outcome (n = 3)
Level 3–Cohort studies
Aragon-Vargas et al. (2013)54	4	2	1
Bertola et al. (2014)39	2	1	1
Brockman et al. (2010)40	2	0	0
Chapman et al. (2010)41	2	2	2
Cipriani et al. (1998)21	1	1	0
Coates et al. (2017)42	4	2	2
Collins et al. (1989)43	2	2	1
Derman et al. (2018)44	4	0	1
Engebretsen et al. (2013)9	4	2	1
Fett et al. (2017)23	3	1	1
Gosling et al. (2008)66	1	0	1
Gosling et al. (2008)46	1	2	2
Medema et al. (1997)47	3	0	0
Migliorini (1991)26	1	1	0
Newsham-West et al. (2014)28	4	1	2
Pages et al. (2016)29	2	1	2
Parkkali et al. (2017)48	2	1	0
Reyes-Casas et al. (2020)55	4	1	1
Ruddick et al. (2019)56	3	2	2
Steffen et al. (2020)10	4	2	1
Stephenson et al. (2019)31	2	0	2
Sullivan (1987)49	2	0	0
Van Asperen et al. (1998)50	2	1	0
Vleck et al. (1998)53	0	2	1
Vleck et al. (2010)51	0	2	1
Worme et al. (1990)52	1	1	0
Level 4–Case-control study
Plews et al. (2012)57	2	0	2

Table 2.

Oxford Centre for Evidence Based Medicine (OCEBM) level of evidence for case report studies (Level 4).

Studies and OCEMB level of evidence
Brunelle et al. (2016)20
Casey et al. (2014)58
Collins & Gilden (2016)59
Cushman & Rho (2015)22
Francis et al. (2017)62
Gajda (2020)32
Harper et al. (2009)24
Jordan (2013)33
Martin (2017)25
Mollica (1998)27
Pietrzak (2013)60
Rodriguez (2021)63
Scott (2003)30
Shapiro et al. (2006)61
Shyu & Boudier-Revéret (2020)34

Twenty-six cohort studies and 1 case-control study were included in the risk of bias assessment. No cohort studies’ domains demonstrated a low risk of bias. The selection domain (average score 2.19/4; 55%) and the comparability domain (1.04/2; 52%) both had a moderate risk of bias, and the outcome domain had a high risk of bias (0.96/3; 32%). The single case-control study reported a moderate level of selection bias (2.00/4; 50%), a high level of comparability bias (0.00/2; 0%), and a moderate level of outcome bias (2.00/3; 67%). Only 11 studies^{9,10,23,26,28,31,42,}44, 45, 46^,54 reported on data collected by medical staff. Additionally, only 11 studies^{9,10,23,28,31,41,42,44,47,54,55} reported on the presence of the outcome of interest at the start of the study. Only 5 studies^{23,31,42,51,53} reported a follow-up period longer than 6 months, and most used a surveillance period that reflected competition periods (2–14 days), which may have led to an under-reporting bias due to the shorter surveillance periods⁶⁴ wherein conditions (e.g., overuse injuries or dormant illnesses) may not present immediately.⁶⁵

3.4. The incidence and prevalence of injury in short-course triathletes

Injury incidence rates were reported in only 1 study.⁴⁵ This study reported an average injury incidence of 20.1 injuries per 1000 h of competition over a surveillance period of 1 triathlon season, with data collected for athletes with varying levels of experience during 6 short-course triathlons. This study further reported injury incidence rates across 3 race distances from the events (Fun: 24.3 per 1000 h of competition; Sprint: 20.4 per 1000 h of competition; and Standard: 15.7 per 1000 h of competition).⁴⁵ Injury prevalence during competition phases (period prevalence) was reported in 17% of studies that reported on injuries^9,10,45,46 and ranged between 2% and 15% over time periods that varied from 2 months to 1 triathlon season (1 year).^9,10,45,46 Knee and lower limb injuries were the most frequently reported,^{21,26,28,39,43,45,51,53,59} followed closely by ankle/foot (Table 3).^{21,26,39,43,53} Over half of the included injury studies (n = 13; 57%) reported injuries that occurred while training,^{21,22,25,26,39,43,51,53,55,59,60,62,63} 39% during competition,^{26,39,45,46,51,53} and in 26% it was unspecified (Table 3).^23,27,28,41 The 2 studies that reported both training and competition injury prevalence indicated that a higher proportion of athletes were injured during training (79%–83%) than during competition.^21,39

Table 3.

Injuries and etiology in short-course triathletes.

Study	Number of participants (N), gender (M/F), age (year), experience, number of injuries (n)	Injury site (%)	Injury mechanism (%)	Triathlon discipline (%)	IDCF19
Bertola et al. (2014)39	N = 190 (152/38); age: M, 36 ± 9; F, 33 ± 9; sprint FTEM: F3 (117/28); standard; FTEM: E1/E2 (35/10); n = 145	M Training: Calf (39); ankle/foot (18); knee (18); M Competition: Calf (46); thigh (15); knee (11); ankle/foot (11) F Training: Ankle (35); calf (23); knee (18); F Competition: Thoracic spine (50); thigh (50)	Self-reported mechanisms: Excessive physical effort (70); pedestrianism (15); falls (10); collision with other athlete (4); bike position (1); cold days (68); warm days (32)	Running (79 M/92 F); cycling (16 M/8 F); swimming (5 M/0 F)	ASR
Chapman et al. (2010)41	N = 34 (21/13); age = 29.0 ± 3.6; standard; FTEM: T2–E1; n = 10 (5/5)	Leg	–	Running	CE/SP
Cipriani et al. (1998)21	N = 52 (44/8); age: M, 44 ± 13; F, 44 ± 13; sprint/standard; FTEM: F1–T4; n = 97	Knee (25); lower leg (12); ankle (9); hamstring (9); LB (8); foot (8); shoulder (7); AT (6); hip (6); groin (5); thigh (3)	Overtraining	Running	ASR/CE/SP
Collins et al. (1989)43	N = 257 (197/60); age: N = 199 ≤ 40, N = 58 > 40; FTEM: F1 100; F3–T2 127; T3-E1 30; n = 167	Overuse injuries Knee (25); shoulder (14); lower leg/calf (12) AT (10); ankle (7); LB (4); hip (4); knee (lateral) (3); groin (2); thigh (3); other (5)	Overuse injury (50)	Running (62); cycling (12); swimming (11); running + other (8); other (7)	ASR/CE/SP
Collins & Gliden (2016)59	N = 1; M; age = 34; standard; FTEM: F3; n = 2	Lower leg	Gradual, non-contact	Running	CE/SP
Cushman & Rho (2015)22	N = 1; M; age = 34; FTEM: T4; n = 1	Hamstring	Gradual onset	Running and cycling	CE/SP
Engebretsen et al. (2013)9a	N = 110; standard; FTEM: E1–E2; n = 16	Foot/toe (25); hip (12); elbow (12); lower leg (6); knee (6); at (6); thigh (6); shoulder/clavicle (6); finger (6); cervical spine (6); other (6)	Contact (stagnant object) (44) non-contact trauma (31); overuse (sudden onset) (12); contact (another athlete) (6); other (6)	–	ASR/CE
Fett et al. (2017)23	N = 1114 (N = 16 triathletes); age = 17; FTEM: T3–E2	LB	–	–	ASR
Francis et al. (2017)62	N = 1; F; age = 27; sprint/standard; FTEM: F2–F3; n = 1	Plantar fascia	–	Running program (30 min/week)	ASR/CE
Gosling et al. (2008)66a	N = 1884 (E1); n = 2000 (E2); FTEM: F3–E2 E1: n = 61; E2: n = 45	–	–	–	CE/SP
Gosling et al. (2010)45a	N = 5124; age = 30 ± 10; sprint/standard: 33 ± 10; FTEM: F3–E2; n = 322	Foot/toes (22); knee (14); lower leg (11); ankle (7); elbow (6); hand/fingers (5); upper leg (5); glute (4); other (18)	–	Swimming (12); cycling (18); running (54); mount/dismount (5); walking (3); other (5)	CE/SP
Martin (2017)25	N = 1; F; age = 30; sprint; FTEM: F3; n = 1	Hamstring	–	Running and cycling	CE
Migliorini (1991)26a	N = 22 (19/3); age = 26 ± 5; FTEM: T4–E1; n = 29	ITBFS (22); knee (33); tibia (15); calf (7); AT (7); foot (7); adductor (4); shoulder (4)	–	Running (67); cycling (19); swimming (3); cycling and running (11); 81 from T2, 19 from T1	CE
Mollica (1998)27	N = 1; M; age = 19; sprint; FTEM: F3; n = 2	Foot (50); tibia (50)	Gradual onset	Running	CE
Newsham-West et al. (2014)28a	N = 15 (8/7); age: 17–23 (21); standard; FTEM: T2; n = 10	Lower leg	Gradual onset, overuse	–	CE/SP
Pietrzak (2013)60	N = 1; F; age = 16; FTEM: T2; n = 1	Knee	Gradual onset	Running	CE/SP
Reyes-Casas et al. (2020)55	N = 84 (M = 76; F = 8) Pre-race: N = 44 (M = 89%; F = 11%) age = 25 ± 11 Post-race: N = 40 (M = 92%; F = 8%) age: 26 ± 10 Standard, sprint, super sprint FTEM: F2–F3 Injuries: Pre-race: 61%; post-race: 65%	Pre-race injuries: Foot (16); leg (7); knee (9); thigh (2); hip (0); arm (2) Post-race injuries: Foot (65); leg (15); knee (5); thigh (2.5); hip (0); arm (8)	Overuse	–	ASR/CE
Rodriguez (2021)63	N = 1; M; standard; FTEM: E1; n = 5	Thigh, knee, shoulder, hand	Traumatic	–	CE/SP
Ruddick et al. (2019)56	N = 5; standard; FTEM: T3–E1; n = 6	Foot (16); ankle (33); lower leg (16); thigh (16)	–	–	CE
Shyu & Boudier-Revéret (2020)34	N = 1; M; age = 45, standard; FTEM: F2–F3; n = 1	Knee	Insidious	–	CE
Steffen et al. (2020)10a	N = 64 (32/32); age: 16–17; Standard; FTEM: E1–E2; n = 9	Knee (33); foot/toe (22); thigh (11); neck (11); elbow (11); forearm (11)	Contact (stagnant object) (33); other (22); Contact (with another athlete) (11); non-contact trauma (11); overuse (gradual onset) (11); field of play conditions (11)	–	CE
Vleck et al. (1998)53	N = 12 elite (age = 27 ± 55), n = 22 development (age = 27 ± 5), 160 club (age = 35 ± 10)	Traumatic and overuse (M) Elite: LB (18); AT (14); knee (14) Development: Knee (18); AT (18); shoulder (14); Club: Knee (22); LB (16); AT (10) Sub-elite and elite overuse only (M/F)b AT (31/25; ankle (14/6); anterior thigh (17/19); hamstring (17/6); knee (45/31); LB (35/13); neck (7/0); other (14/25); shoulder (17/13); UB (0/6)	Overuse: Elite (75); development (75); club (56) Traumatic: Elite (41); development (38); club (56)	Elite: Running (62); cycling (35); Development: running (64); cycling (25); club: running (59); cycling (16)	ASR/CE/SP
Vleck et al. (2010)51	N = 12; M; age = 27 ± 5; standard; FTEM: E1–E2	Overuse only: LB (42); shoulder (8); knee (42); hamstring (25); calf (25); neck (17); anterior thigh (9); AT (50); ankle (17); other (17)	–	Running (62); cycling (35); swimming (15)	ASR/CE/SP

Note: – means missing data.

^aProspective studies.

^bTaken from direct correspondence with the author.⁹⁴

Abbreviations: ASR = athlete self-report; AT = Achilles tendon; CE = clinical examination; E1 = event 1; E2 = event 2; F = female; FTEM = Foundation, Talent, Elite, Mastery; IDCF = Injury Definitions Concept Framework; ITBFS = iliotibial band friction syndrome; LB = lower back; LCL = lateral collateral ligament; M = male; SP = sports performance; UB = upper back.

3.5. Etiological factors contributing to injury in short-course triathletes

Most of the reported injuries occurred during running (45%–92%), cycling (8%–34%), and swimming (3%–15%) (Table 3).^{26,39,43,45,51,53} Swimming had the lowest number of injuries of all 3 disciplines, but contributed to the highest percentage of upper limb injuries, specifically shoulder injuries, compared to running and cycling.^21,26,43 Acute injuries were reported in only 22% of the studies (n = 5),^{9,10,39,53,63} Over half of the included injury studies (n = 13; 57%) reported overuse injuries,^{9,10,21,22,27,28,34,43,51,53,55,59,60} and 4 reported the proportion of overuse injuries,^9,10,43,53 accounting for 11%–75% of all injuries investigated (Table 3). Two studies investigated overuse injuries specifically, reporting the knee to be the most frequently injured site (25%), followed by the shoulder (14%),⁴³ and lower leg/calf (12%).⁵¹ The most common types of injured structures were muscle, tendon, and joint.^26,39,43,53

Age and sex seem to influence injury occurrence in triathletes. Two studies characterized injury prevalence according to participant age.⁴³,⁴⁵ One study found that young triathletes (12–19 years) had an injury prevalence almost two-fold greater than triathletes aged 30–39 years (relative risk = 1.89, 95% confidence interval (95%CI): 1.32–2.72).⁴⁵ In contrast, another study found no significant difference in injury incidence rates in triathletes over 40 years of age compared to those younger than 40.⁴³ Differences in injury site between males and females were reported in 2 studies.^39,53 The Achilles tendon, knee, and lumbar spine were the most commonly injured body sites in male triathletes, compared to anterior thigh and knee in female triathletes.⁵³ Another study found that males sustained more calf injuries and females sustained more ankle and foot injuries.³⁹ This study also reported differences in injury nature between males and females, with muscle (54%) being the most prevalent tissue type injured in male triathletes, followed by tendon (19%), ligament (17%), and bone (9%).³⁹ In female triathletes, muscle, bone, and tendon (32% each) were equally the most frequent tissue types injured.³⁹ While bone injuries were found to be as common as muscle and tendon injuries in the female population in this study,³⁹ these results should be interpreted with caution as only 25% of the population were female (n = 38), and they may have been overestimated. Therefore, the proposed etiological factors contributing to injury in short-course triathletes are running volume, age, and sex. The majority of injuries are reported as overuse injuries and are mainly attributed to running. Triathletes in the 12–19 year age-group reported more injuries than older triathletes, and the injury profiles were different between sexes, with a greater number of bone-related injuries reported in females (32%) compared to males (9%).³⁹

3.6. Incidence and prevalence of illness in short-course triathletes

One study with a surveillance period of 2 weeks reported illness incidence rates ranging between 1.8 and 13.1 illnesses/1000 athlete days.⁴⁴ Illness prevalence was reported by 5 studies, ranging between 6% and 84%,^{9,10,29,44,54} with time periods varying from 1 race (point prevalence)^40,54 to 1 month.²⁹ The most common illnesses reported were gastrointestinal issues,^25,29,40,47, 48, 49, 50^,52,54,61 followed by altered cardiac function (arrhythmias),^{20,24,30,33,45,46,54,58} and respiratory illnesses (Table 4).^{9,10,29,31,33,47,49,50,54} Two studies evaluated illness in elite para-triathletes,^31,44 with 1 specifically investigating respiratory infections in this population.³¹

Table 4.

Illness and etiology in short-course triathletes.

Study	Number of participants (N), (M/F), age (year), experience, illnesses (n)	Most common illness symptoms (%)	Cause of illness (%)	Triathlon discipline (%)	IDCF
Aragón-Vargas et al. (2013)54	N = 92 (54/38) Junior M: 11 ± 2; F: 11 ± 2 Senior M: 16 ± 1; F: 15 ± 1 Sprint distance Juniors: swim 500 m, bike 15 km, run 3.5 km; Seniors: swim 800 m, bike 30 km, run 8 km FTEM: F3–T3 n = 109 illness symptoms	Fatigue (43); side stitch (36); dehydration (35); dizziness (23); nausea (14); stomach ache (8); cramping (5); leg pain (4); vomiting (3); difficulty breathing (3); bloating (1); chest pain (1)	Environmental (heat), exercise induced	–	ASR
Brockman et al. (2010)40	N = 142 (116/26); age = 35 ± 8 for case patients; 37 ± 8 for health patients Standard distance; FTEM: F3; n = 5	Fever (100); headache (80); muscle pain (80); diarrhea (20); renal impairment (20)	Bacterial infection: wounds	Swimming	ASR/CE/SP
Brunelle et al. (2016)20	N = 1; M; age = 25; standard distance; FTEM: E1; n = 1	Abdominal cramps, muscle pain, limb weakness	Gradual onset, exercise related, artery stenosis	–	CE
Casey et al. (2014)58	N = 1; F; age = 55; standard distance; FTEM: E1; n = 1	Shortness of breath, coughing up pink frothy sputum	Sudden onset, environmental (cold water immersion)	Swimming	CE
Coates et al. (2017)42	N = 13 (8/5) age: (22 ± 3/23 ± 11) Sprint and standard; FTEM: E1/2 (4/4) FTEM: T3/4 (4/1); n = 15	–	Gradual onset, exercise related, metabolic disturbance	–	CE
Derman et al. (2018)44a	N = 58 (29/29) Para-triathletes Age: 10 × 12–25, 20 × 26–34, 28 × 35–75; sprint; FTEM: E1; n = 4	–	–	–	CE
Engebretsen et al. (2013)9a	N = 110; standard; FTEM: E1–E2; n = 7	Pain (43); syncope/collapse (14); other (28)	Infection (57); environmental (14); exercise induced (14)	–	CE
Gajda (2020)32	N = 1; M; age = 47; standard; FTEM: F3; n = 1	Effort provoked AVNRT	Exercise related	–	CE/SP
Gosling et al. (2008)46a	N = 1884 (E1), n = 2000 (E2); FTEM: F3–E2 E1: n = 15; E2: n = 12	–	Environmental (heat), exhaustion/hypotension (59); environmental (jelly fish) (41)	–	CE/SP
Gosling et al. (2010)45a	N = 5124; Fun distance age = 30 ±10; Sprint/standard age = 33 ± 10; FTEM: F3–E2; n = 29	Pain (n = 13; 45) Collapse (n = 16; 55)	Environmental (heat), exhaustion/ hypotension (55); environmental (jelly fish) (45)	–	CE/SP
Harper et al. (2009)24	N = 1; F; age: 32; standard; FTEM: E2; n = 1	Dizziness, palpitations	Gradual onset, exercise related	–	CE
Jordan (2013)33	N = 1; M; age = 34; sprint; FTEM: F3; n = 1	Hyperthermia: (pale, profusely diaphoretic, tachycardic, tachypneic, altered mental status—confusion, agitation, and obtundation, low BP)	Environmental (heat), gradual onset, exercise related	–	CE/SP
Martin (2017)25	N = 1; F; age = 30; sprint; FTEM: F3; n = 1	Sweating, sleep disturbance, anxious, constipation	Idiopathic	–	CE
Medema et al. (1997)47a	N = 314 (273/41); age: 25–29; standard; FTEM: F3–E1; competition: n = 126; following week: n = 4	Pain, vomiting, nausea, belching	Ingested water (75); symptomatic (20)	Swimming	ASR/SP
Pages et al. (2016)29	N = 76 (55/21); age: adolescent: 12, adult: 38; adult relay: 31; standard; FTEM: F3; n = 13	Fever (70); joint pain (Arthralgia) (70); chills (6); fatigue (61); vomiting (30); diarrhea (8); neurological signs (15); rash (8); pulmonary signs (15); ENT symptoms (15)	Ingested water; wounds	Swimming (70)	CE/SP
Parkkali et al. (2017)48	N = 215; (age range: 15–67); sprint/standard; FTEM: F3; n = 72	Stomach pain (71); nausea (77); diarrhea (59); vomiting (38); fever (23)	Environmental: viral infection; swallowing >3 mouthfuls of water (RR = 2); swam in the event (RR = 8)	Swimming	ASR/CE
Plews et al. (2012)57a	N = 2; age: M: 22; F: 20; standard; FTEM: E1; n = 1	Fatigue, pain	Gradual onset, exercise related, metabolic disturbance (immuno-suppression)	–	CE/SP
Scott (2003)30	N = 1; age: 37:M; standard; FTEM: F3; n = 1	Collapse	Sudden onset; exercise related	–	CE
Shapiro et al. (2006)61	N = 1; F; age = 19; sprint; FTEM: F3; n = 1	Headache, nausea, emesis (vomiting), malaise (general discomfort)	Gradual onset, nutritional, exercise related; environment (heat)	–	CE
Steffen et al. (2020)10a	N = 64; (32/32); age = 16–17; standard; FTEM: E1–E2; n = 10	Pain (40); fever (20); dyspnea/cough (10); diarrhea/vomiting (10); other (20)	Infection (50); environmental (10); exercise induced (10); other (30)	–	CE
Stephenson et al. (2019)31a	N = 7 (6/1) para-triathletes; age = 30 ± 10; sprint FTEM: E1; n = 22	–	Exercise related, gradual onset	–	ASR/SP
Sullivan (1987)49	N = 110 (72/38); age: M: 37; F: 38; FTEM: F3; n = 958 symptoms	Abdominal stitches (10); bowel dysfunction (7); muscle cramps (14); flatulence (8); abdominal cramps (6); belching (8); wheeze/cough (6); skin problems (8); nausea/vomiting (5); gastroesophageal reflux (6); headache (6); urinary incontinence (3); hematuria (2); loss of vision (2); bloody bowel movements (1); interrupted exercise (8)	Exercise intensity (24.2); anxiety (8.5); time of day (7.8); recent meals (26.6); specific foods (14.3);	Running 588 symptoms, swimming 288 symptoms, cycling 204 symptoms	ASR/SP
Van Asperen et al. (1998)50a	N = 827 (757/70); age = 33; standard; FTEM: F3	GI symptoms (54); stomach ache, nausea/vomiting (26), diarrhea, side aches, gripes, flatulence, urge to discharge (25); skin complaints (5); respiratory complaints (12); eye complaints (4); ear complaints (2); headaches (2)	Swallowing water, environmental, infection	Swimming	ASR/CE/SP
Worme et al. (1990)52	N = 71 (50/21); age: M: 39 ± 1; F: 32 ± 2; standard; FTEM: F3	GI symptoms (50): upper GI: heartburn, bloating, vomiting, abdominal gas, loss of appetite; lower GI: diarrhea; hematemesis (<10)	Metabolic disturbances and nutritional factors	–	ASR

Note: – means missing data.

^aProspective studies.

Abbreviations: ASR = athlete self-report; AVNRT = atrioventricular nodal re-entrant tachycardia; BP = blood pressure; CE = clinical examination; E1 = event 1; E2 = event 2; ENT = ear, nose, and throat; F = female; FTEM = Foundation, Talent, Elite, Mastery; GI = gastrointestinal; IDCF= Injury Definitions Concept Framework; M = male; RR = relative risk; SP = sports performance.

3.7. Etiological factors contributing to illness in short-course triathletes

One study investigated illness symptoms for each discipline over 3 triathlon events.⁴⁹ Multiple physiological systems were reported to be affected by illness, mostly while running (with a total of 588 illness symptoms), followed by swimming (288 symptoms), and cycling (204 symptoms).⁴⁹ Half of the included illness studies (n = 12; 50%) reported on gastrointestinal illness symptoms in triathletes,^{9,20,25,29,40,}47, 48, 49, 50^,52,54,61 with a third (n = 8; 33%) reporting environmental factors as contributors to gastrointestinal symptoms (Table 4).^{9,29,40,47,48,50,54,61} Swimming in contaminated water was the most common cause of gastrointestinal symptoms.^{29,40,47,48,50} Four studies investigated heat-related cardiovascular symptoms,^33,45,46,54 and 1 study reported altered ventricular function in relation to cold water temperature while swimming in open water.⁵⁸ Four illness studies were case studies reporting cardiovascular symptoms in standard and shorter distance triathletes that were associated with abnormal ventricular function^24,30,32,58 and left ventricle hypertrophy.^30,58 Nine studies (38%) reported respiratory symptoms in triathletes,^{9,10,29,31,33,47,49,50,54} with infections being the main illness type (Table 4).^9,10,40,50 The proposed etiological factors contributing to illness in short-course triathletes are environmental factors, predominately related to water quality and heat stress.

4. Discussion

This systematic review characterizes the incidence, prevalence, and etiology of injury and illness in short-course triathletes and identifies the most critical injuries and illnesses that prevention strategies should prioritize. The most commonly occurring health problems in short-course triathletes were lower limb overuse injuries mainly attributable to running, gastrointestinal illnesses and cardiovascular symptoms primarily attributable to environmental factors (i.e., contaminated water and thermal stress), and respiratory illnesses, mostly caused by bacterial infection.

4.1. The incidence and prevalence of injuries in short-course triathletes

Injury prevalence research in short-course triathlon has focused on competition-related injuries, where between 2% and 15% of all competitors are reported as injured during competition.^9,10,45,46 The highest injury prevalence figures were from the 2012 London Olympic Games, where 15% of triathletes reported an injury.⁹ The wide range of athlete exposures reported⁴⁵ highlights the need for robust surveillance practices and a greater understanding of the incidence of injuries occurring during the extensive periods of triathlon training as compared to brief competition exposures. The injury incidence figures reported in this systematic review should be interpreted with a degree of caution due to inconsistencies with reporting and injury surveillance methods.⁶⁶

The majority of the current short-course triathlon literature focuses on reporting competition injuries; however, 79%–83% of injuries in short-course triathletes are reported to occur in the training environment.^21,39,66 The lack of training-related injuries in the published literature likely results in a substantial under-representation of total number of injuries sustained by triathletes. In addition, the potential for survival bias may influence competition data, with only healthy athletes being available for competition, which would substantially underestimate injury rates over an entire season. In contrast, epidemiological data focusing on long-course triathlon indicate injury incidence rates to be significantly less during training (0.7–5.4 per 1000 training hours) compared to competition, which could be due to lack of reporting and/or presentation for medical attention outside of competition.^67,68 Accurate quantification of training load exposure, and therefore injury incidence rates,⁶⁹ can be challenging, especially in the sport of triathlon, where training load monitoring requires different approaches across the disciplines. Injuries that occur within the training environment warrant further investigation to accurately analyze injury risk in training and competition across the entire season for short-course triathletes.

High-quality injury surveillance data underpin Stage 1 of the TRIPP framework, and the majority of the current triathlon literature demonstrates significant limitations regarding quality surveillance practices.¹⁴ Injury definitions and length of surveillance periods varied considerably across different studies, from short periods during major competition to a triathlete's total participation history.70, 71, 72 Prospective studies are lacking in the current body of literature on short-course triathlon injury incidence rates, which is mostly limited to retrospective study designs, unvalidated recall timeframes, inconsistent injury and exposure definitions, and/or a failure to capture exposure data.⁶⁶ Only 6 studies utilized prospective study designs, where injury data were captured as injuries occurred, which minimizes the potential recall bias associated with retrospective self-report study designs.^{9,10,26,28,45,46} Establishing accurate injury profiles for triathlon from the current literature is challenging due to discrepancies with injury reporting, with some studies failing to discern between injury body site and injury tissue type.⁶⁶ While it is possible for athletes to sustain multiple injuries to different body sites during a single injury event, these injuries should be handled as separate injury episodes to allow for the recording of accurate injury sites and also duration.^73,74 Future prospective studies with robust methodology focusing on quality surveillance practices using standardized definitions will facilitate the capture of accurate exposure data for both training and competition to better characterize the most common and severe injuries in short-course triathletes.

Lower limb injuries, specifically at the knee, ankle, and foot are the most commonly reported injuries in short-course triathletes.^5,43,51,53 Most of these injuries are reported as overuse onset injuries (50%–75%)^43,53 associated with running (54%–92%) during training and competition,^{26,39,43,45,51,53} which is consistent with the evidence reported in runners, where 80% of running injuries are of an overuse onset and occur in the lower limb, predominately the knee, upper and lower leg, and foot.⁷⁵ Two 5-year retrospective studies on standard distance triathletes reported the knee to be the most frequently injured region in training and competition,^26,51 while another study stated contusions and abrasions/grazes were the most frequently reported injuries during a short-course triathlon competition.⁵¹ This outcome is consistent with the literature on road cyclists, where the most prevalent injuries are superficial skin injuries (e.g., abrasions, lacerations, and hematomas).⁷⁶ These findings support similar observations seen in other long-course triathlon reviews.^66,77, 78, 79 Despite inconsistencies with injury surveillance and methodology, lower limb injuries and abrasions/grazes occur frequently in long- and short-course triathletes.

It is critical to understand the impact of injuries in triathletes for prioritization of targeted prevention programs. Reporting injury incidence in isolation, without accurate exposure data, can provide an inaccurate and incomplete depiction of risk.⁸⁰ The International Olympic Committee consensus statement recommends that the recording and reporting of injury and illness data in sport should also include injury severity data, defined as “the number of days that have elapsed from the day after the onset of the incident to the day of full injury recovery”, be reported.⁷⁴ There are limited injury severity data available for short-course triathlon; however, in the available literature, injuries sustained during running are uniformly classified as the most severe with respect to time loss from training, followed by cycling injuries.⁵¹ For triathletes with injuries, modifications to training were reported to occur 17%–75% of the time across the 3 disciplines.⁸¹ Exclusively using time loss from sport to measure injury severity may considerably underestimate the true injury burden.⁸⁰ Evidence from other sports suggests that the risk of sustaining a more severe injury resulting in time loss in the 7 days following an initial non-time loss injury is 3–6 times greater post-injury, and that risk remains high for up to 12 weeks.82, 83, 84 Tertiary interventions designed to prevent further health complications and mitigate elevated risk should be prioritized for injured athletes. Establishing reliable time-loss data and developing a greater understanding of injury severity in short-course triathletes is required to inform injury prevention practices and optimize athlete health and performance according to the TRIPP framework.

Limited information regarding sex differences between injuries exists in short-course triathlon. One study reported injury nature and site differences between males and females,³⁹ and 1 study was able to differentiate injury sites according to sex.⁵³ From these 2 studies, the injury site was found to be similar between males and females;^39,53 however, the injury tissue type was different. Females had a larger proportion of bone, muscle, and tendon injuries compared to males, who predominately sustained muscle injuries.³⁹ These results need to be interpreted with caution as female athletes are under-represented in the literature. Studies focusing on long-course triathlete injuries have compared incidence rates between males and females and found no difference.¹ Constructing an accurate injury profile for male and female triathletes should therefore be a priority for future surveillance initiatives.

4.2. Etiological factors contributing to injury in short-course triathletes

To emphasize time loss from training and competition along with subsequent injury risk, it is critical to understand the underlying etiology of the most burdensome injuries in short-course triathletes. Stage 2 of the TRIPP framework highlights the importance of understanding why injuries occur in sport.¹⁴ Triathletes are prone to experiencing injuries, with 72% of a triathlete squad reporting an overuse injury, compared to 43% of the squad reporting traumatic injuries over a 5-year surveillance period.⁵¹ Identifying triathlon-specific injury mechanisms, activities, and risk factors is critical for efficient and effective implementation of targeted prevention strategies.

Most injuries reported by short-course triathletes are gradual onset overuse injuries.⁵¹ Overuse injuries are reported to occur 3 times more frequently than traumatic injuries in long-course triathletes, and 80% of all injuries sustained in runners are overuse, with the potential for this value to be higher given the inaccuracies associated with retrospective recall are more substantial for overuse injuries compared to traumatic injuries.^72,75,85, 86, 87 The absence of a consistent definition for overuse injuries in the literature makes comparing data problematic.^43,70,85,88 Three studies provided injury mechanism information for traumatic injuries.^9,10,39 Injuries resulting from contact with a stationary object were most frequently associated with traumatic injuries (33%–44%),^9,10 followed by non-contact trauma (11%–31%),^9,10 and trauma from contact with other athletes (4%–11%).^9,10,39 It is important to understand whether early intervention or training modifications can reduce the severity of overuse injuries and improve performance. Understanding the performance impact of injuries where triathletes are able to continue to train or modify training is required.

Overall, it is challenging to compare injury etiologies between studies due to a lack of consistent definitions for injury, triathlon experience, training, and competition exposure data, as well as a lack of validation of injury occurrence and self-reporting or data collection procedures.⁶⁶ This review has identified a high association of overuse injuries with running; however, the available literature lacks robust methodology and appropriate study designs to demonstrate adequate statistical power or sample sizes as Stage 2 of the TRIPP framework requires.^14,66 Therefore, future research should implement best practice surveillance methods to better inform targeted prevention strategies.

4.3. Incidence and prevalence of illness in short-course triathletes

Illness can significantly affect performance in triathletes. Illness prevalence for short-course triathletes ranged between 6% and 84%,^{9,10,29,44,54} and illness incidence rates ranged between 1.8 and 13.1 per 1000 athlete days.⁴⁴ While some studies have utilized prospective study designs, the majority were conducted over short surveillance periods during competition.^9,10,31,44, 45, 46, 47^,50,57 Methodologically robust studies reporting illness incidence rates in triathlon are scarce, with most studies being retrospective (and so subject to recall bias) and using inconsistent illness definitions. Preferably, illness rates are reported as illness incidence rates, which are calculated as the number of illnesses per 1000 h of exposure.⁸⁰ Combining severity of illnesses with illness incidence produces an illness burden metric.⁸⁰ Targeted prevention programs warrant further investigation in order to identify those illnesses that result in the greatest time loss, as opposed to those with the highest incidence.⁸⁹ Acquiring an understanding of the burden of illness in short-course triathletes throughout an entire season will allow targeted prevention programs to be implemented that will minimize the impact of illness on athlete health and performance.

The most frequently reported illnesses in short-course triathlon affect the gastrointestinal system (7%–70%),^9,29,47,50 followed by the cardiovascular (14%–59%),^9,45,46 and respiratory systems (5%–60%).^9,10,47,50 The majority of reported illnesses were reported to be caused by environmental factors^{9,10,33,45,46,48,50,54,58,61} and infections^{9,10,29,40,47,48,50} during competition. These findings are also commonly reported in long-course triathlon studies, with gastrointestinal illness reported to occur more frequently than injuries in some instances.^1,90 Five prospective studies reviewed herein reported surveillance periods from 1 week to 15 months;^{9,10,31,47,50} 2 studies encompassed major competitions and are thus limited by survival bias.^9,10 The quality of illness reporting is compromised by inconsistent illness definitions, inaccurate medical diagnoses, and a wide range of values; thus, it fails to demonstrate the true range of illnesses experienced by triathletes.^9,10 In addition, under-reporting of mild illnesses that do not result in time loss from training or competition can cause the true incidence rate to be underestimated. Acquiring a better understanding of illness severity in short-course triathlon is required to optimize prevention and progress along the TRIPP framework.

4.4. Etiological factors contributing to illness in short-course triathletes

The etiology of illness in short-course triathlon is multifactorial in most cases, with athletes reporting illness throughout the season experiencing hindered performance.^6,91 Thus, illness prevention strategies should focus on addressing the risk factors that may impact training and competition availability.⁹¹ Environmental factors are the main contributors to illness symptoms in short-course triathletes.^29,40,45, 46, 47, 48^,50,54,58,61 The main reported environmental factors leading to illnesses in short-course triathlon swimming were: water that was either contaminated^{29,40,47,48,50} or extremely cold⁵⁸ and environmental extremes, more specifically extreme heat.^45,46,54 Swimming is the discipline where illness symptoms are most frequently reported.^{29,40,47,48,50,58} Gastrointestinal illness and cardiovascular symptoms are the most common.^29,40,47, 48, 49, 50^,52,54,61

Extreme environmental temperatures are a risk factor contributing to the development of illness symptoms in short-course triathletes.^{45,46,54,58,61} Differences in intensity and duration of competition affect the thermal strain athletes experience;⁵⁴ however, the extent to which thermal strain affects short-course triathletes is relatively unknown.¹ The risk for hyperthermia and other heat-related illnesses in short-course triathlon may be related to environmental temperatures, humidity, solar load and air flow (wind speed), and previous heat acclimatization.⁴⁶ Future research should focus on investigating extreme environmental temperatures and the risk factors associated with illness in short-course triathletes with larger athlete numbers.

Illnesses caused by infections are commonly reported in short-course triathletes. Two prospective studies investigating illnesses at the 2012 London Olympic Games and the 2018 Youth Olympic Games reported that infections are responsible for 50%–57% of reported illnesses.^9,10 Evidence from other Olympic athletes suggests that close physical contact and shared living spaces during training camps and competitions increase the risk of infection transmission, with communal living associated with illness rates increasing 3-fold.⁹¹ Handwashing and hygiene behaviors can be effective in decreasing the incidence of viral respiratory tract infections and some gastrointestinal illnesses.⁹² A thorough understanding of the etiology of illnesses in short-course triathletes will enable the development of prevention programs to optimize health and performance in this population.

4.5. Limitations

The limitations of this systematic review mostly relate to the lack of robust study designs and surveillance practices presented in the existing literature. The search strategy was constrained to studies published only in the English language, and the database search was executed by one author. Twenty of the 26 cohort studies demonstrated a moderate risk of bias, and 4 demonstrated a high risk of bias. Eleven studies reported data that was collected and verified by medical staff; however, the remaining studies relied on participant recall (with recall periods ranging from 1 to 10 years) and unvalidated diagnostic information. Information regarding diagnosis and the nature of injury must be interpreted with caution due to potential reporting and recall bias as well as short data collection and follow-up periods, which may have affected the true incidence rate of health problems.⁶⁴ Although definitions for injury and illness are standardized in this review according to the Injury Definitions Concept Framework classification,¹⁹ there are some limitations regarding injury and illness definitions in included studies. Some studies report heat stress as an injury,^45,46 and as observed in another triathlon epidemiology review,¹ some authors chose to define illness as any health problem that was not related to the musculoskeletal system.⁹³

This systematic review highlights the knowledge gap surrounding injury and illness in short-course triathletes. Future research should focus on optimizing performance through targeted prevention practices addressing the etiology and risk factors associated with the highest burden health problems in short-course triathletes. Future studies should align with the latest consensus statements for injury and illness surveillance in sport and should include more female triathletes and Paralympic triathletes to ensure a more inclusive understanding of injury and illness. Prospective longitudinal studies over entire seasons would be beneficial for elucidating the scope of health problems experienced and for reducing their burden on short-course triathletes.

5. Conclusion

Lower limb overuse injuries that occur while running, gastrointestinal illnesses and altered cardiac function caused by environmental factors, and respiratory illnesses caused by infection are the most frequently reported health problems in short-course triathletes. This is despite the presence of inconsistent injury and illness definitions and the lack of high-quality prospective studies available. Implementation of best-practice surveillance methods inclusive of entire training periods, not just competitions, will provide a thorough understanding of the injury and illness profiles in short-course triathletes, enabling the development of prevention programs to optimize health and performance in this population.