PURPOSE:The best way to apply precooling for endurance exercise in the heat is still unclear. Therefore, we analyzed the effect of different preparation regimes on pacing during a 15-km cycling time trial in the heat.METHODS:Ten male subjects completed four 15-km time trials (30°C), preceded by different preparation regimes: 10 min cycling (WARM-UP), 30 min scalp cooling of which 10 min cycling (SC+WARM-UP), ice slurry ingestion (ICE), and ice slurry ingestion + 30 min scalp cooling (SC+ICE).RESULTS:No differences were observed in finish time and mean power output, although power output was lower for WARM-UP than for SC+ICE during km 13-14 (17±16 and 19±14 W, respectively) and for ICE during km 13 (16±16 W). Rectal temperature at the start of the time trial was lower for both ICE (~36.7°C) than both WARM-UP (~37.1°C) conditions and remained lower during the first part of the trial. Skin temperature and thermal sensation were lower at the start for SC+ICE.CONCLUSIONS:The preparation regime providing the lowest body heat content and sensation of coolness at the start (SC+ICE) was most beneficial for pacing during the latter stages of the time trial, although overall performance did not differ

Daanen, H.A.M.

de Haan, A.

de Koning, J.J.

Levels, K.

Teunissen, L.P.J.

van Os, B.

English

PURPOSE: The best way to apply precooling for endurance exercise in the heat is still unclear. Therefore, we analyzed the effect of different preparation regimes on pacing during a 15-km cycling time trial in the heat. METHODS: Ten male subjects completed four 15-km time trials (30°C), preceded by different preparation regimes: 10 min cycling (WARM-UP), 30 min scalp cooling of which 10 min cycling (SC+WARM-UP), ice slurry ingestion (ICE), and ice slurry ingestion + 30 min scalp cooling (SC+ICE). RESULTS: No differences were observed in finish time and mean power output, although power output was lower for WARM-UP than for SC+ICE during km 13-14 (17±16 and 19±14 W, respectively) and for ICE during km 13 (16±16 W). Rectal temperature at the start of the time trial was lower for both ICE (~36.7°C) than both WARM-UP (~37.1°C) conditions and remained lower during the first part of the trial. Skin temperature and thermal sensation were lower at the start for SC+ICE. CONCLUSIONS: The preparation regime providing the lowest body heat content and sensation of coolness at the start (SC+ICE) was most beneficial for pacing during the latter stages of the time trial, although overall performance did not differ

NARCIS 

Effect of warm-up and precooling on pacing during a 15-km cycling time trial in the heat

Haan, A. de

Koning, J.J. de

Os, B. van

DSpace at VU

307
www.IJSPP-Journal.com
ORIGINAL INVESTIGATION
International Journal of Sports Physiology and Performance, 2013, 8, 307-311 
© 2013 Human Kinetics, Inc.
The authors are with the MOVE Research Inst Amsterdam, VU 
University Amsterdam, Amsterdam, The Netherlands. Levels, 
Teunissen, and Daanen are also with TNO, Behavioral and 
Societal Sciences, Soesterberg, The Netherlands. de Haan is also 
with the Inst for Biomedical Research into Human Movement 
and Health, Manchester Metropolitan University. de Koning is 
also with the University of Wisconsin-La Crosse.
Effect of Warm-Up and Precooling on Pacing  
During a 15-km Cycling Time Trial in the Heat
Koen Levels, Lennart P.J. Teunissen, Arnold de Haan, Jos J. de Koning,  
Bernadet van Os, and Hein A.M. Daanen
Purpose: The best way to apply precooling for endurance exercise in the heat is still unclear. The authors 
analyzed the effect of different preparation regimens on pacing during a 15-km cycling time trial in the heat. 
Methods: Ten male subjects completed four 15-km time trials (30°C), preceded by different preparation 
regimes: 10 min cycling (WARM-UP), 30 min scalp cooling of which 10 min was cycling (SC+WARM-UP), 
ice-slurry ingestion (ICE), and ice slurry ingestion + 30 min scalp cooling (SC+ICE). Results: No differences 
were observed in finish time and mean power output, although power output was lower for WARM-UP than 
for SC+ICE during km 13–14 (17 ± 16 and 19 ± 14 W, respectively) and for ICE during km 13 (16 ± 16 W). 
Rectal temperature at the start of the time trial was lower for both ICE conditions (~36.7°C) than both WARM-
UP conditions (~37.1°C) and remained lower during the first part of the trial. Skin temperature and thermal 
sensation were lower at the start for SC+ICE. Conclusions: The preparation regimen providing the lowest 
body-heat content and sensation of coolness at the start (SC+ICE) was most beneficial for pacing during the 
latter stages of the time trial, although overall performance did not differ.
Keywords: thermoregulation, power output, ice slurry, scalp cooling
Athletes generally perform active warm-up to pre-
pare for an upcoming event. This is proposed to induce 
beneficial physiological responses.1–4 However, warm-up 
also elevates the core temperature, causing fatigue and 
reduced endurance performance in the heat.5–7 Precool-
ing may attenuate this detrimental effect by increasing 
the heat-storage capacity of the body and is therefore 
suggested to be a more beneficial preparation regimen 
than warming up.6
Ice-slurry ingestion appears to be an effective and 
practical method to precool the body core.8–10 The lower 
core temperature resulting from ice-slurry ingestion may 
prevent or delay the reduction in central neural drive that 
leads to performance decrements in the heat.11
Next to cooling the core, cooling the skin could also 
affect performance.8,12 Recently, a new convective cooling 
method for reducing chemotherapy-induced hair loss has 
become available, using glycol-perfused caps to cool the 
skin of the scalp. Possible mechanisms include a positive 
effect on the perception of coolness, motivation to continue 
exercise, and reduction of cardiovascular and thermoregu-
latory demands. The scalp may be a suitable cooling area, 
as it is easily accessible13 and close to the thermosensitive 
region of the face. In addition, possible brain cooling may 
help maintain the central neural drive during exercise in the 
heat.14 Both the sensation of coolness and possible brain 
cooling might translate into an improvement in self-paced 
exercise performance mediated by the rating of perceived 
exertion (RPE), even when core temperatures are well 
below critical values associated with fatigue.15
Although both warm-up and precooling have proved 
to be beneficial for endurance-exercise performance, 
it remains unclear which preparation regimen should 
be preferred for relatively short self-paced endurance 
exercise in the heat. Furthermore, the additive effect of 
scalp cooling when the core is cooled or heated remains 
unclear. Therefore, the main goal of this study was to 
investigate the effect of different preparation regimens 
(involving warm-up, ice-slurry ingestion, and scalp cool-
ing) on pacing and performance during a 15-km cycling 
time trial (TT) in the heat.
Methods
Subjects
Ten healthy and physically active male recreational 
cyclists (age 24 ± 5 y, height 187 ± 7 cm, weight 77 ± 6 
kg) familiar with cycle-ergometer testing participated in 
this study. The study was approved by the ethics com-
mittee of TNO, The Netherlands.
308  Levels et al
Overview
Subjects visited the laboratory 5 times. On the first visit 
they were familiarized with the experimental setup and 
distance of the TT. The 4 following sessions involved 
the 15-km TT in the heat preceded by 1 of the different 
preparation regimens: active warm-up of 10 minutes of 
cycling (WARM-UP), scalp cooling + active warm-up 
of 10 minutes of cycling (SC+WARM-UP), ice-slurry 
ingestion (ICE), or scalp cooling + ice-slurry ingestion 
(SC+ICE).
Interventions
In the precooling trials (ICE and SC+ICE), a decrease in 
core temperature was created by ingesting 2 g/kg body 
mass (BM) ice slurry within 5 minutes. Syrup (containing 
~6 g carbohydrates) was added for flavor. This period was 
followed by 15 minutes of rest. In the prewarming trials 
(WARM-UP and SC+WARM-UP), the subjects cycled at 
a moderate power of 2 W/kg BM for 10 minutes. SC was 
accomplished by wearing a neoprene-covered silicone 
cooling cap (Paxman, Huddersfield, UK) connected to 
a cooling machine (Paxman cooler PScalpC-1, Paxman, 
Huddersfield, UK) for 30 minutes. Temperature of the 
coolant was–9°C to –10°C.
Protocol
Each session started in a 22°C climatic chamber (Weiss 
Enet, Tiel, The Netherlands) with 20-minute habituation, 
followed by baseline measurements and the intervention 
protocol. Subsequently, during a 5-minute break, sub-
jects were transferred to an adjacent 30°C, 50% relative 
humidity climatic chamber. This was followed by a short 
final preparation period of 3-minute cycling at 120 W. 
Hereafter, subjects performed the 15-km TT on a cycle 
ergometer (Lode, Groningen, The Netherlands). During 
the trial subjects were blind to performance measures 
but were informed of completed distance each kilometer. 
The 4 TTs were allocated in balanced order and at least 
3 days apart.
Measurements
During the TTs, power output (PO) was recorded every 
second. Rectal temperature (Tre) was measured every 
second using a rectal thermistor (Yellow Springs Instru-
ments 700 series, Yellow Springs, OH, USA) inserted 
10 cm beyond the anal sphincter. A weighted average of 
8 iButtons (DS1922L, Maxim Integrated Products Inc, 
Sunnyvale, CA, USA) resulted in 10-second values for 
mean skin temperature (Tsk), as described by ISO9886.16 
Heart rate was recorded at 5-second intervals (Polar 
Electro, Finland). For the TT, data were reduced to 1-km 
values.
Thermal sensation (TS) and thermal comfort (TC) 
were measured every 5 km on a 9-point and 5-point scale, 
respectively.17 RPE was measured every kilometer on a 
20-point scale.18
Statistics
Experimental condition was the independent variable, 
whereas PO, Tre, Tsk, heart rate, RPE, TS, and TC were 
the dependent variables. Significance of effects over time 
was determined using 2-way ANOVAs for repeated mea-
surements with Bonferroni correction (SPSS 17.0, SPSS 
Inc, Chicago, IL, USA). One-way ANOVAs were used 
to determine the significance of effects of the experi-
mental conditions at separate kilometers, as well as on 
finish times and average PO. Statistical significance 
was set at the 5% level. Values are reported as mean 
± SD.
Results
Effect of Preparation Regimens
In Figure 1, Tre and Tsk before and during the TT are 
shown. Before the start of the intervention, Tre and Tsk 
were similar. Ice-slurry ingestion resulted in a cooler core 
at the start of the TT than performing a warm-up (P < .05). 
There was a trend that Tre was more reduced in SC+ICE 
than in ICE (P = .06). At the start of the TT, both Tsk and 
TS were lower for SC+ICE than for the other conditions 
(P < .05). TC was similar.
Time-Trial Performance
In Figure 2a, the average PO per kilometer of the TT is 
shown. There was no overall effect between conditions on 
PO and finish time. However, during kilometers 13 and 
14, PO for SC+ICE (231 ± 23 and 239 ± 24 W, respec-
tively) was significantly higher than for WARM-UP (214 
± 28, P = .01, and 219 ± 27 W, P = .02, respectively). In 
addition PO for ICE (230 ± 32 W) was higher than for 
WARM-UP during kilometer 13 (P = .03).
Physiological and Perceptual Responses
Differences in Tre and Tsk between the ice-slurry and 
warming-up conditions were observed during the first 
half of the trial (P < .05). Overall, Tsk was significantly 
lower for SC+ICE than for WARM-UP (P = .02). Heart 
rate for WARM-UP was higher than for SC+ICE and ICE 
during the initial stages of the trial, but no differences 
were found after 3 km.
No overall effect for RPE was observed, but at sepa-
rate kilometers in the final stages of the TT, some RPE 
scores deviated (Figure 2b). No effects for TS and TC 
were observed during the trial.
Discussion
This study showed that the lower the body temperature 
and sensation of coolness at the start of the TT, the more 
beneficial it was for the pacing profile at the final stages. 
This finding agrees with previous precooling experiments 
on longer cycling trials (40–90 min), showing physi-
Effect of Warm-Up and Precooling on Pacing  309
Figure 1 — (a) Rectal and (b) skin temperature preintervention (PI), at the start of the time trial (km 0) and averaged per kilome-
ter of the time trial. *Significant difference between scalp cooling (SC) + warm-up and SC + ice-slurry ingestion (ICE) (P < .05). 
#Significant difference between SC+WARM-UP and ICE (P < .05). For clarity of the figure, no error bars are displayed.
ological differences in the first part of the trial and pacing 
adjustments at the final stages.7,8 However, we did not 
find an overall effect on performance, which is in contrast 
to the referenced studies. Although direct comparison is 
difficult due to methodological differences, it appears 
that exercise duration is important for obtaining overall 
performance benefits from precooling. Nevertheless, a 
higher work rate near the finish as a result of precooling 
may still be beneficial during tactical races.
Precooling the core with ice-slurry ingestion appeared 
to be more effective in accomplishing pacing benefits than 
precooling the scalp. Scalp precooling led to a marginal 
decrease in thermal strain and a slightly cooler sensation 
at the start of the TT, but pacing and performance benefits 
310  Levels et al
Figure 2 — (a) Power output and (b) rating of perceived exertion during the time trial. *Significant difference between warm-up and 
scalp cooling (SC) + ice-slurry ingestion (ICE) (P < .05). #Significant difference between warm-up and ICE (P < .05). †Significant 
difference between warm-up and SC+ICE (P < .05). For clarity of the figure, no error bars are displayed.
during the trial were negligible. The limited physiologi-
cal effects of scalp cooling may be due to the insulative 
capacity of the skull19 and the small cooling area. The 
absence of a perceptual effect on performance confirms 
the results of Barwood et al,20 who found no effect of 
thermal perception on the anticipatory selection of PO.
RPE differed during the final stages of the TT. The 
higher RPE for WARM-UP was accompanied by a signifi-
cantly lower PO than with SC+ICE. This finding seems to 
disagree with the concept that athletes maintain a similar 
RPE template across conditions of similar duration and 
adjust their work rate accordingly.21
Carbohydrate ingestion via syrup might be consid-
ered a confounding factor. However, it is unlikely that the 
ingestion of only 6 g carbohydrates 20 minutes before 
medium-duration aerobic exercise (<45 min) improves 
Effect of Warm-Up and Precooling on Pacing  311
performance in the final stages by extending body glyco-
gen content22 or by nonmetabolic pathways.23
In conclusion, the preparation regimen providing 
the lowest body-heat content and sensation of coolness 
at the start of the TT (ICE+SCALP) appeared to be 
most beneficial for pacing in the latter stages. However, 
overall performance was not significantly improved after 
precooling, possibly because of the limited trial length.
Acknowledgments
Authors Levels and Teunissen contributed equally to this article.
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VU Research Portal

VU Research PortalEffect of warm-up and precooling on pacing during a 15-km cycling time trial in theheatLevels, K.; Teunissen, L.P.J.; de Haan, A.; de Koning, J.J.; van Os, B.; Daanen, H.A.M.published inInternational Journal of Sports Physiology and Performance2013DOI (link to publisher)10.1123/ijspp.8.3.307document versionPublisher's PDF, also known as Version of recordLink to publication in VU Research Portalcitation for published version (APA)Levels, K., Teunissen, L. P. J., de Haan, A., de Koning, J. J., van Os, B., & Daanen, H. A. M. (2013). Effect ofwarm-up and precooling on pacing during a 15-km cycling time trial in the heat. International Journal of SportsPhysiology and Performance, 8, 307-311. https://doi.org/10.1123/ijspp.8.3.307General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            • Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            • You may not further distribute the material or use it for any profit-making activity or commercial gain            • You may freely distribute the URL identifying the publication in the public portal ?Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.E-mail address:vuresearchportal.ub@vu.nlDownload date: 26. May. 2021307www.IJSPP-Journal.comORIGINAL INVESTIGATIONInternational Journal of Sports Physiology and Performance, 2013, 8, 307-311 © 2013 Human Kinetics, Inc.The authors are with the MOVE Research Inst Amsterdam, VU University Amsterdam, Amsterdam, The Netherlands. Levels, Teunissen, and Daanen are also with TNO, Behavioral and Societal Sciences, Soesterberg, The Netherlands. de Haan is also with the Inst for Biomedical Research into Human Movement and Health, Manchester Metropolitan University. de Koning is also with the University of Wisconsin-La Crosse.Effect of Warm-Up and Precooling on Pacing  During a 15-km Cycling Time Trial in the HeatKoen Levels, Lennart P.J. Teunissen, Arnold de Haan, Jos J. de Koning,  Bernadet van Os, and Hein A.M. DaanenPurpose: The best way to apply precooling for endurance exercise in the heat is still unclear. The authors analyzed the effect of different preparation regimens on pacing during a 15-km cycling time trial in the heat. Methods: Ten male subjects completed four 15-km time trials (30°C), preceded by different preparation regimes: 10 min cycling (WARM-UP), 30 min scalp cooling of which 10 min was cycling (SC+WARM-UP), ice-slurry ingestion (ICE), and ice slurry ingestion + 30 min scalp cooling (SC+ICE). Results: No differences were observed in finish time and mean power output, although power output was lower for WARM-UP than for SC+ICE during km 13–14 (17 ± 16 and 19 ± 14 W, respectively) and for ICE during km 13 (16 ± 16 W). Rectal temperature at the start of the time trial was lower for both ICE conditions (~36.7°C) than both WARM-UP conditions (~37.1°C) and remained lower during the first part of the trial. Skin temperature and thermal sensation were lower at the start for SC+ICE. Conclusions: The preparation regimen providing the lowest body-heat content and sensation of coolness at the start (SC+ICE) was most beneficial for pacing during the latter stages of the time trial, although overall performance did not differ.Keywords: thermoregulation, power output, ice slurry, scalp coolingAthletes generally perform active warm-up to pre-pare for an upcoming event. This is proposed to induce beneficial physiological responses.1–4 However, warm-up also elevates the core temperature, causing fatigue and reduced endurance performance in the heat.5–7 Precool-ing may attenuate this detrimental effect by increasing the heat-storage capacity of the body and is therefore suggested to be a more beneficial preparation regimen than warming up.6Ice-slurry ingestion appears to be an effective and practical method to precool the body core.8–10 The lower core temperature resulting from ice-slurry ingestion may prevent or delay the reduction in central neural drive that leads to performance decrements in the heat.11Next to cooling the core, cooling the skin could also affect performance.8,12 Recently, a new convective cooling method for reducing chemotherapy-induced hair loss has become available, using glycol-perfused caps to cool the skin of the scalp. Possible mechanisms include a positive effect on the perception of coolness, motivation to continue exercise, and reduction of cardiovascular and thermoregu-latory demands. The scalp may be a suitable cooling area, as it is easily accessible13 and close to the thermosensitive region of the face. In addition, possible brain cooling may help maintain the central neural drive during exercise in the heat.14 Both the sensation of coolness and possible brain cooling might translate into an improvement in self-paced exercise performance mediated by the rating of perceived exertion (RPE), even when core temperatures are well below critical values associated with fatigue.15Although both warm-up and precooling have proved to be beneficial for endurance-exercise performance, it remains unclear which preparation regimen should be preferred for relatively short self-paced endurance exercise in the heat. Furthermore, the additive effect of scalp cooling when the core is cooled or heated remains unclear. Therefore, the main goal of this study was to investigate the effect of different preparation regimens (involving warm-up, ice-slurry ingestion, and scalp cool-ing) on pacing and performance during a 15-km cycling time trial (TT) in the heat.MethodsSubjectsTen healthy and physically active male recreational cyclists (age 24 ± 5 y, height 187 ± 7 cm, weight 77 ± 6 kg) familiar with cycle-ergometer testing participated in this study. The study was approved by the ethics com-mittee of TNO, The Netherlands.308  Levels et alOverviewSubjects visited the laboratory 5 times. On the first visit they were familiarized with the experimental setup and distance of the TT. The 4 following sessions involved the 15-km TT in the heat preceded by 1 of the different preparation regimens: active warm-up of 10 minutes of cycling (WARM-UP), scalp cooling + active warm-up of 10 minutes of cycling (SC+WARM-UP), ice-slurry ingestion (ICE), or scalp cooling + ice-slurry ingestion (SC+ICE).InterventionsIn the precooling trials (ICE and SC+ICE), a decrease in core temperature was created by ingesting 2 g/kg body mass (BM) ice slurry within 5 minutes. Syrup (containing ~6 g carbohydrates) was added for flavor. This period was followed by 15 minutes of rest. In the prewarming trials (WARM-UP and SC+WARM-UP), the subjects cycled at a moderate power of 2 W/kg BM for 10 minutes. SC was accomplished by wearing a neoprene-covered silicone cooling cap (Paxman, Huddersfield, UK) connected to a cooling machine (Paxman cooler PScalpC-1, Paxman, Huddersfield, UK) for 30 minutes. Temperature of the coolant was–9°C to –10°C.ProtocolEach session started in a 22°C climatic chamber (Weiss Enet, Tiel, The Netherlands) with 20-minute habituation, followed by baseline measurements and the intervention protocol. Subsequently, during a 5-minute break, sub-jects were transferred to an adjacent 30°C, 50% relative humidity climatic chamber. This was followed by a short final preparation period of 3-minute cycling at 120 W. Hereafter, subjects performed the 15-km TT on a cycle ergometer (Lode, Groningen, The Netherlands). During the trial subjects were blind to performance measures but were informed of completed distance each kilometer. The 4 TTs were allocated in balanced order and at least 3 days apart.MeasurementsDuring the TTs, power output (PO) was recorded every second. Rectal temperature (Tre) was measured every second using a rectal thermistor (Yellow Springs Instru-ments 700 series, Yellow Springs, OH, USA) inserted 10 cm beyond the anal sphincter. A weighted average of 8 iButtons (DS1922L, Maxim Integrated Products Inc, Sunnyvale, CA, USA) resulted in 10-second values for mean skin temperature (Tsk), as described by ISO9886.16 Heart rate was recorded at 5-second intervals (Polar Electro, Finland). For the TT, data were reduced to 1-km values.Thermal sensation (TS) and thermal comfort (TC) were measured every 5 km on a 9-point and 5-point scale, respectively.17 RPE was measured every kilometer on a 20-point scale.18StatisticsExperimental condition was the independent variable, whereas PO, Tre, Tsk, heart rate, RPE, TS, and TC were the dependent variables. Significance of effects over time was determined using 2-way ANOVAs for repeated mea-surements with Bonferroni correction (SPSS 17.0, SPSS Inc, Chicago, IL, USA). One-way ANOVAs were used to determine the significance of effects of the experi-mental conditions at separate kilometers, as well as on finish times and average PO. Statistical significance was set at the 5% level. Values are reported as mean ± SD.ResultsEffect of Preparation RegimensIn Figure 1, Tre and Tsk before and during the TT are shown. Before the start of the intervention, Tre and Tsk were similar. Ice-slurry ingestion resulted in a cooler core at the start of the TT than performing a warm-up (P < .05). There was a trend that Tre was more reduced in SC+ICE than in ICE (P = .06). At the start of the TT, both Tsk and TS were lower for SC+ICE than for the other conditions (P < .05). TC was similar.Time-Trial PerformanceIn Figure 2a, the average PO per kilometer of the TT is shown. There was no overall effect between conditions on PO and finish time. However, during kilometers 13 and 14, PO for SC+ICE (231 ± 23 and 239 ± 24 W, respec-tively) was significantly higher than for WARM-UP (214 ± 28, P = .01, and 219 ± 27 W, P = .02, respectively). In addition PO for ICE (230 ± 32 W) was higher than for WARM-UP during kilometer 13 (P = .03).Physiological and Perceptual ResponsesDifferences in Tre and Tsk between the ice-slurry and warming-up conditions were observed during the first half of the trial (P < .05). Overall, Tsk was significantly lower for SC+ICE than for WARM-UP (P = .02). Heart rate for WARM-UP was higher than for SC+ICE and ICE during the initial stages of the trial, but no differences were found after 3 km.No overall effect for RPE was observed, but at sepa-rate kilometers in the final stages of the TT, some RPE scores deviated (Figure 2b). No effects for TS and TC were observed during the trial.DiscussionThis study showed that the lower the body temperature and sensation of coolness at the start of the TT, the more beneficial it was for the pacing profile at the final stages. This finding agrees with previous precooling experiments on longer cycling trials (40–90 min), showing physi-Effect of Warm-Up and Precooling on Pacing  309Figure 1 — (a) Rectal and (b) skin temperature preintervention (PI), at the start of the time trial (km 0) and averaged per kilome-ter of the time trial. *Significant difference between scalp cooling (SC) + warm-up and SC + ice-slurry ingestion (ICE) (P < .05). #Significant difference between SC+WARM-UP and ICE (P < .05). For clarity of the figure, no error bars are displayed.ological differences in the first part of the trial and pacing adjustments at the final stages.7,8 However, we did not find an overall effect on performance, which is in contrast to the referenced studies. Although direct comparison is difficult due to methodological differences, it appears that exercise duration is important for obtaining overall performance benefits from precooling. Nevertheless, a higher work rate near the finish as a result of precooling may still be beneficial during tactical races.Precooling the core with ice-slurry ingestion appeared to be more effective in accomplishing pacing benefits than precooling the scalp. Scalp precooling led to a marginal decrease in thermal strain and a slightly cooler sensation at the start of the TT, but pacing and performance benefits 310  Levels et alFigure 2 — (a) Power output and (b) rating of perceived exertion during the time trial. *Significant difference between warm-up and scalp cooling (SC) + ice-slurry ingestion (ICE) (P < .05). #Significant difference between warm-up and ICE (P < .05). †Significant difference between warm-up and SC+ICE (P < .05). For clarity of the figure, no error bars are displayed.during the trial were negligible. The limited physiologi-cal effects of scalp cooling may be due to the insulative capacity of the skull19 and the small cooling area. The absence of a perceptual effect on performance confirms the results of Barwood et al,20 who found no effect of thermal perception on the anticipatory selection of PO.RPE differed during the final stages of the TT. The higher RPE for WARM-UP was accompanied by a signifi-cantly lower PO than with SC+ICE. This finding seems to disagree with the concept that athletes maintain a similar RPE template across conditions of similar duration and adjust their work rate accordingly.21Carbohydrate ingestion via syrup might be consid-ered a confounding factor. However, it is unlikely that the ingestion of only 6 g carbohydrates 20 minutes before medium-duration aerobic exercise (<45 min) improves Effect of Warm-Up and Precooling on Pacing  311performance in the final stages by extending body glyco-gen content22 or by nonmetabolic pathways.23In conclusion, the preparation regimen providing the lowest body-heat content and sensation of coolness at the start of the TT (ICE+SCALP) appeared to be most beneficial for pacing in the latter stages. However, overall performance was not significantly improved after precooling, possibly because of the limited trial length.AcknowledgmentsAuthors Levels and Teunissen contributed equally to this article.References 1. Gray S, Nimmo M. Effects of active, passive or no warm-up on metabolism and performance during high-intensity exercise. J Sports Sci. 2001;19:693–700. PubMed doi:10.1080/02640410152475829 2. Hajoglou A, Foster C, De Koning JJ, Lucia A, Kernozek TW, Porcari JP. Effect of warm-up on cycle time trial performance. Med Sci Sports Exerc. 2005;37:1608–1614. PubMed doi:10.1249/01.mss.0000177589.02381.0a 3. Proske U, Morgan DL, Gregory JE. Thixotropy in skeletal muscle and in muscle spindles: a review. Prog  Neurobio l .  1993;41 :705–721 .  PubMed doi:10.1016/0301-0082(93)90032-N 4. Ross A, Leveritt M, Riek S. Neural influences on sprint running: training adaptations and acute responses. Sports Med. 2001;31:409–425. PubMed doi:10.2165/00007256-200131060-00002 5. Gonzalez-Alonso J, Teller C, Andersen SL, Jensen FB, Hyldig T, Nielsen B. Influence of body temperature on the development of fatigue during prolonged exercise in the heat. J Appl Physiol. 1999;86:1032–1039. PubMed 6. Uckert S, Joch W. Effects of warm-up and pre-cooling on endurance performance in the heat. Br J Sports Med. 2007;41:380–384. PubMed doi:10.1136/bjsm.2006.032292 7. Duffield R, Green R, Castle P, Maxwell N. Precooling can prevent the reduction of self-paced exercise intensity in the heat. Med Sci Sports Exerc. 2010;42:577–584. PubMed 8. Ihsan M, Landers G, Brearley M, Peeling P. Beneficial effects of ice ingestion as a precooling strategy on 40-km cycling time-trial performance. Int J Sports Physiol Per-form. 2010;5:140–151. PubMed 9. Ross ML, Garvican LA, Jeacocke NA, et al. Novel pre-cooling strategy enhances time trial cycling in the heat. Med Sci Sports Exerc. 2011;43(1):123–133. PubMed doi:10.1249/MSS.0b013e3181e93210 10. Siegel R, Mate J, Brealey MB, Watson G, Nosaka K, Laursen PB. Ice slurry ingestion increases core tempera-ture capacity and running time in the heat. Med Sci Sports Exerc. 2010;42:717–725. PubMed 11. Nybo L, Nielsen B. Hyperthermia and central fatigue during prolonged exercise in humans. J Appl Physiol. 2001;91:1055–1060. PubMed 12. Schlader ZJ, Simmons SE, Stannard SR, Mundel T. The independent roles of temperature and thermal perception in the control of human thermoregulatory behavior. Physiol Behav. 2011;103:217–224. PubMed doi:10.1016/j.phys-beh.2011.02.002 13. Tikuisis P, Meunier P, Jubenville CE. Human body surface area: measurement and prediction using three dimen-sional body scans. Eur J Appl Physiol. 2001;85:264–271. PubMed doi:10.1007/s004210100484 14. Ansley L, Marvin G, Sharma A, Kendall MJ, Jones DA, Bridge MW. The effects of head cooling on endurance and neuroendocrine responses to exercise in warm conditions. Physiol Res. 2008;57:863–872. PubMed 15. Ely BR, Cheuvront SN, Kenefick RW, Sawka MN. Aerobic performance is degraded, despite modest hyperthermia, in hot environments. Med Sci Sports Exerc. 2010;42:135–141. PubMed 16. International Standardization Organization. Ergonomics—Evaluation of Thermal Strain by Physiological Measure-ments. Geneva. Switzerland: International Standardization Organization; 2004. 17. Gagge AP, Stolwijk JA, Hardy JD. 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PubMed doi:10.1080/02640414.2011.585473 23. Rollo I, Williams C. Effect of mouth-rinsing carbohy-drate solutions on endurance performance. Sports Med. 2011;41:449–461. PubMed doi:10.2165/11588730-000000000-00000

Purpose:The best way to apply precooling for endurance exercise in the heat is still unclear. The authors analyzed the effect of different preparation regimens on pacing during a 15-km cycling time trial in the heat.Methods:Ten male subjects completed four 15-km time trials (30°C), preceded by different preparation regimes: 10 min cycling (WARM-UP), 30 min scalp cooling of which 10 min was cycling (SC+WARM-UP), ice-slurry ingestion (ICE), and ice slurry ingestion + 30 min scalp cooling (SC+ICE).Results:No differences were observed in finish time and mean power output, although power output was lower for WARM-UP than for SC+ICE during km 13–14 (17 ± 16 and 19 ± 14 W, respectively) and for ICE during km 13 (16 ± 16 W). Rectal temperature at the start of the time trial was lower for both ICE conditions (~36.7°C) than both WARMUP conditions (~37.1°C) and remained lower during the first part of the trial. Skin temperature and thermal sensation were lower at the start for SC+ICE.Conclusions:The preparation regimen providing the lowest body-heat content and sensation of coolness at the start (SC+ICE) was most beneficial for pacing during the latter stages of the time trial, although overall performance did not differ.</jats:sec

Koen Levels

Lennart P.J. Teunissen

Arnold de Haan

Jos J. de Koning

Bernadet van Os

Hein A.M. Daanen

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International Journal of Sports Physiology and Performance

Effect of Warm-Up and Precooling on Pacing During a 15-km Cycling Time Trial in the Heat

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Effect of warm-up and precooling on pacing during a 15-km cycling time trial in the heat

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