Thermal stress in open water swimming :Thermal stress in open water swimming :estabilishing competition parameters for athlete safety

Research Project IOC/FINA/ITU & Otago University (NZ)S. Migliorini, M. Mountjoy, D. Gerrard

Aquatic Enviroment Health Risks

• Flora & Fauna• Current & wavesCurrent & waves• Pollution : air & water

W li• Water quality• Wind and air temperaturep• Water temperature hyperthermia & 

hypothermiahypothermia

Rationale for ProjectRationale for Project

While we have a good understanding of the effect of cold‐water immersion, there is no research thatspecifically addresses the question of heat stress in open water swimming.

Other IFs such as IAAF have competition criteria andOther IFs such as IAAF have competition criteria andsafety guidelines for the prevention and the treatment of heatrelated disorders : IAAF recommended cancelling or reschedulingraces if WGBT is above 28°C.(Enviromental influencing human performance 

d l l)IAAF Medical Manual)

OlympicMovement Medical CodeOlympicMovement Medical CodeAccording to the Olympic Movement Medical Code the International Sports Federations are tasked to evaluatecompetition venues and climates in which their athletes trainand compete and subquently develop guidelines to safeguardand compete and subquently develop guidelines to safeguardathlete health by minimizing the risk arising from potentially

dangerous enviromental conditionsdangerous enviromental conditions.

The legal system requires IFs and race organizers to produce a safe event andto identify and disclose all the know risks to the athletes. 

Rationale for Research Project

1) To prevent the fatalities

2) To improve and armonize the IF rules) p

Rationale for Project 

h f lTo prevent the fatalities.

S dd d h i h i li USA i FINA 10 k• Sudden death in marathon swim : elite USA swimmer FINA 10 km World Cup, UAE, 2010 (air T° 35C, water T° 29C).

• Sudden death in triathlon : most of them during the swim leg (30 out of 38 non traumatic athlete death between 2003 /2011 USAT fatality Incidents study).

• Data derived from FINA Medical Reports from the FINA Marathon and GP Circuits in open water swimming show that athletes haveand GP Circuits in open water swimming show that athletes haverequired treatment for exertional heat illness when competing in warm enviroments.

• Data derived from ITU  Medical Reports show that exertionalmuscle cramping, heat exhaustion and exertional heat illness are prevalent in many Triathlon eventsprevalent in many Triathlon events. 

Rationale for Project

T i d i h lTo improve and armonize the rules. 

• FINA. Water temperature at FINA sanctioned events rangefrom a minimum of 16°C up to 31°C. The use of wetsuit isforbiddenforbidden. 

• Notably, current FINA rules stipulate a minimum water temperature but the Federation is yet to establish a firmtemperature,  but the Federation is yet to establish a firmupper limit providing only a recommended limit of 31°C for FINA events. 

• ITU. Water temperature at ITU sanctioned events starts from a minimum of 13°C (1500m) or 14° (3000m‐4000m), but the Federation did not reccomend an upper temperature limit. Th t it i ll d f ll i th ITU lThe wetsuit use is allowed following the ITU rules. 

Open water swimming competitions

Whil th i li it f t t t f dWhile there is no upper limit for water temperatures enforcedby these organisations, it is not uncommon for events to be held in water temperatures of 30‐32° C in locations aroundpSouth‐East China, the Middle East and Central America. 

This can be accompanied by ambient temperatures of 35‐40° C and relative humidity of 50‐70%.

Research NeedsResearch Needs

• Determination of safe upper limit water temperature for training and competitions (core body temperature and performance 

capacity)capacity)

• Determining the influence of other enviromental factors (high‐low air temperature,humidity).p , y)

• Determining optimal strategies to better acclimatize athletes.

• Identify objective signs of developing exertional heat illness.de t y object e s g s o de e op g e e t o a eat ess

• Determining the validity of self‐perceived body temperature.

• Quantifying factors affecting athlete adaptation to and heatQuantifying factors affecting athlete adaptation to and heattolerance in water (inflammatory status)

• Study on thermal parameters with the use of a wetsuit in hot y pambient temperature. 

C ll b i i iCollaboration LogisticsIdentification of the Project ConceptIdentification of the Project Concept.

Agreement of collaboration.

Determination of a timelineDetermination of a timeline.

Arrangement of financial logistics.

Agreement of pubblication andAgreement of pubblication and dissemination protocol.

THERMAL STRESS IN OPEN WATER SWIMMING

Establishing competition parameters f i i ffor competition safety

MethodologyMethodology• Range of distance (1.5 to10km) and water temperature  of 

most interest to FINA ITU and IOC in open water swimmingmost interest to FINA, ITU and IOC in open‐water swimming.

• Predetermined timed swims of 20, 60 and 120 min. with 3 water temperatures of 20° 27° and 32° C with warm andwater temperatures of 20 ,27 and 32 C, with warm and humid air (ambient temperature 30°C, 50‐70% relative humidity) and full radiant heat loading. 

• Radiant heat load needed to be incorporated with the heatstressful water temperatures, because of the additional heatload at low latitudes and the prone posture of swimming. 

• High calibre swimmers and triathletes have been recruitedf D di ’ li i d l d i h i lfrom Dunedin’s elite swim squad, supplemented with nationalopen water swimmers.

Flume in use

Swimmer’s stroke is recorded from four cameras (side, above, front , rear). Viewing panels in the side are used for filming and communication. 

Illustration of halogen heat lamps mountedIllustration of halogen heat lamps mounted

1.5 m above the swimmer to replicate radiant heatload. 

Field AnalysisFINA OWS Marathon Series 10 kmFINA OWS Marathon Series 10 km

Hong KongHong Kong

Shantou CHN

October 2012

Protocol and MeasurementsProtocol and Measurements

• 24 swimmers undertoook a total of 190 self paced• 24 swimmers undertoook a total of 190 self‐pacedperformance trial in water temperature of 20,27,32°C, with exposure durations (20‐120 min) corrisponding to distance of 1.5km to 10km races (air T° closely the respective water T°, relative humidity 50‐70%, radiant heat load).

• All trials are being ndertaken in the s imming fl me here• All trials are being undertaken in the swimming flume wherewater temperature can be controlled between 9° and 35°C. 

• Swimmers are instructed to swim as fast as possible becauseSwimmers are instructed to swim as fast as possible becausethis maximises validity by maximising rate of heat production.

• Swimming technique, stroke, velocity and distance are recordered continuosly.

• Swimmers are monitored for thermal, cardiovascular, psychophysical function throughout all swimspsychophysical function throughout all swims. 

Protocol and Measurements

• Core temperature : monitored and recorded continuoslyduring all swims using a flexible sterile and disposable rectalduring all swims using a flexible, sterile and disposable rectalthermistor.

• Heart rate : frequency of ventricular depolarization asdetected from R‐R intervals from a chest strap with transmitter.

• Blood measures : blood glucose lactate haematocrit• Blood measures : blood glucose, lactate, haematocrit, haemoglobin concentrations, are measured before and immediately upon each swim. Plasma concentrations of inflammatory cytokines and antiflammatory cytokines and other humoral factors . 

• Swimmer’s perception : thermal disconfort body• Swimmer s perception : thermal disconfort, body temperature, exertion, feeling state, are recorded usingvalidate scales.

• Swimming fitness and Anthropometry

Preliminary Results• In 190 swims trials (100 conducted in water temperatures of 

30°C or warmer) only 5% resulted in core (rectal) temperatureshi h h 39 0°C h hi h b i 39 55°Chigher than 39.0°C, the highest being 39.55°C.

• One female partecipant during the 2012 FINA OWS 10 km in Hong Kong hada high starting Tc peaked at 40°C (intestinal pill thermometry). Water 27.2°C,a high starting Tc peaked at 40 C (intestinal pill thermometry). Water 27.2 C, Ambient 27‐31°C, Humidity 73%

• No athletes were removed or voluntarily stopped due to discomfort, distress in the warm water swims.

• 4/8 swimmers (50%) did not complete the longer (1 or 2 h) swim in 20°C water. One athlete did not tolerate more than 20 min in 

20°C and three others were either stopped due to Tc dropping to 35°C or20 C and three others were either stopped due to Tc dropping to 35 C or voluntary stopped due to extreme disconfort.

• Potential safety problems in cool water due to autonomicy pnervous system conflict in open water swimming competition.

Preliminary ResultsPreliminary Results

• No swimmers became distressed or excessively hypherthermicin any of the warm water swims, making it difficult to determine predictive behaviours.

• Positive relationships were evident between the core t t d i d b d t t (th l titemperature and perceived body temperature (thermal sensation

and disconfort), which indicated that swimmers can accurately perceivechanges in body temperature while swimming in warm water, reducingexercise intensity to limit hyperthermia in racing.

S i ’ ti di t d t l• Swimmer’s perceptions, distance swum, and actual core temperature responses to swimming were unaffected by the imposition of a large increase in training load (5 days of heavilyimposition of a large increase in training load (5 days of heavily

increased training volume >50%)

38.6

38.8

38.2

38.4

38.6

re (°C)

37.8

38.0

an Core Tempe

ratu

32 deg 20 min

37 2

37.4

37.6Mea

32 deg 60 min

32 deg 120 min

37.2

0 10 20 30 40 50 60 70 80 90 100 110 120

Time (min)

Mean core temperature responses during 3 swim distances in 32°C water temperature with climatic heat stress.

Sweating rate and Sweating rate and dehydratationdehydratation in hot water in hot water 

Even in water, where the ability to evaporate is greatly Even in water, where the ability to evaporate is greatly reduced and the skin remain wetted our swimmers showedreduced and the skin remain wetted our swimmers showedreduced and the skin remain wetted, our  swimmers showed  reduced and the skin remain wetted, our  swimmers showed  sweat rates and dehydration not dissimilar to those  observed sweat rates and dehydration not dissimilar to those  observed in terrestrial athletes (in terrestrial athletes (i.e.marathoni.e.marathon runners).runners).(( ))

Normal sweating during swimming is encouraged by maintaining regular Normal sweating during swimming is encouraged by maintaining regular fluid loadingfluid loading

Swim 

d

% Net 

d

Fluid 

d

Gross Fluid 

( )

Rate of fluid 

l

fluid loading.fluid loading.

Condition Body Mass 

Loss

Consumed 

(L)

Loss (L) loss

(L.h‐1)

32°C, 20 min 0.91 ± 0.44 0.38 ± 0.20 0.80 ± 0.33 2.39 ± 0.91

32°C, 60 min 0.93 ± 0.79 0.54 ± 0.19 1.20 ± 0.60 1.20 ± 0.60

32°C, 120 min 1.84 ± 1.49 1.03 ± 0.53 2.35 ± 1.29 1.18 ± 0.64 

RecommendationsRecommendations

• Because no intollerance or unusually high exercising core• Because no intollerance or unusually high exercising core temperature were observed in maximal effort swims in 30‐32°C water T°such temperatures are to considered safe.p

• Potential variability in physiological responses to thermal stress exists between swimmers subjected to lab test versus the race enviroment.

• We recommended a more conservative limit, perhaps 31°C, because swimming in open‐water competition might produce hi h T h i d d i l b i lhigher Tc than is produced in lab trials.

• There is a potential safety problem with open‐water swimmingcompetitions in cool water especially relevant for lean swimmerscompetitions in cool water especially relevant for lean swimmers.

It will be never be possible to agree upon a finite water temperature  at wich the safety of every athetes can be guaranteed under every circumstance. 

No specific measure, scale or specifictemperature will be  a  surrogate for the combined vigilance of race officals, medical staff, coaches , athlete supportt ff d f t di l lstaff and of a correct medical plan.

May 2013 : Conclusion of the yResearch Project IOC/FINA/ITU