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Effect of cold water immersion on repeated 1-km cycling performance in the heat
Available online at www.sciencedirect.com
Journal of Science and Medicine in Sport 13 (2010) 112–116
Original paper
Effect of cold water immersion on repeated 1-km cycling performance in the heat Jeremiah J. Peiffer a,∗ , Chris R. Abbiss b , Greig Watson b , Kazunori Nosaka b , Paul B. Laursen b a
Centre of Excellence for Alzheimer’s Disease Research and Care, School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Australia b School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Australia Received 20 May 2008; received in revised form 8 August 2008; accepted 13 August 2008
Abstract This study examined the effect of a short cold water immersion (CWI) intervention on rectal and muscle temperature, isokinetic strength and 1-km cycling time trial performance in the heat. Ten male cyclists performed a 1-km time trial at 35.0 ± 0.3 ◦ C and 40.0 ± 3.0% relative humidity, followed by 20 min recovery sitting in either cold water (14 ◦ C) for 5 min or in 35 ◦ C air (control); a second 1-km time trial immediately followed. Peak and mean cycling power output were recorded for both time trials. Rectal and muscle temperature, and maximal isokinetic concentric torque of the knee extensors were measured before and immediately after the first and second time trials. Rectal temperature was not different between cold water immersion and control conditions at any time points. After the second time trial, however, muscle temperature was significantly lower (−1.3 ± 0.7 ◦ C) in cold water immersion compared with the control trial. While peak and mean power decreased from the first to second time trial in both conditions (−86 ± 54 W and −24 ± 16 W, respectively), maximal isokinetic concentric torque was similar between conditions at all time points. The 5 min cold water immersion intervention lowered muscle temperature but did not affect isokinetic strength or 1-km cycling performance. © 2008 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved. Keywords: Recovery; Neuromuscular; Intervals; Environment
1. Introduction To maintain performance over multiple exercise sessions, various recovery strategies have been used.1–3 The recovery benefits of a cold water immersion (CWI) intervention have been examined in both sprint and endurance exercise and have produced conflicting results. For example, after 90 min of submaximal running in the heat, CWI in 12 ◦ C for 15 min significantly improved 2 mile running time trial (TT) performance compared with a control condition.4 Conversely, CWI can reduce sprint cycling performance. Two studies have observed that, compared with passive sitting at room temperature, CWI in 12–14 ◦ C for 15 min decreased peak and average power of sprints performed immediately after immersion.5,6 Nevertheless both studies were conducted ∗
Corresponding author. E-mail address: [email protected] (J.J. Peiffer).
at thermoneutral (<27 ◦ C) temperatures, and it is possible that the sprint response may be different in warmer ambient temperatures.7 The most likely cause of the reduction in cycle sprint power output following CWI is a decrease in the contractile speed of the cooled muscle during maximal contraction.8 Indeed, cold exposure can increase action potential propagation time in muscle,8,9 and decrease dynamic contractile force by 4–6% for each 1 ◦ C decrease in muscle temperature (Tmus ).9 Therefore, the CWI interventions used (12–14 ◦ C for 15 min) in the abovementioned sprint studies5,6 likely decreased subsequent cycling performance through the lowered Tmus .9 In addition, the recovery time available for some sport settings can be limited, decreasing the applicability of longer CWI recovery interventions. For these reasons, an investigation into the influence of a short duration (<15 min) CWI intervention on acute power production under high environmental temperatures is needed.
1440-2440/$ – see front matter © 2008 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jsams.2008.08.003
J.J. Peiffer et al. / Journal of Science and Medicine in Sport 13 (2010) 112–116
The purpose of the present study was to determine the effect of a 5 min CWI intervention on rectal temperature (Tre ), Tmus , maximal isokinetic force and 1-km cycling TT performance in the heat (35 ◦ C and 40% relative humidity). We hypothesised that the shorter CWI intervention would significantly lower Tmus compared with a control condition; however, the short exposure time to CWI would limit the deleterious cooling effect on isokinetic force and 1-km TT performance. The findings from this study could be used to improve understanding of the effect of cold exposure on acute power production in sport.
2. Methods Ten male cyclists (age: 29 ± 6 years; stature: ˙ 2 max: 56.5 ± 5.0 ml 181.7 ± 4.0 cm; mass: 79.3 ± 6.3 kg; VO kg−1 min−1 ) were recruited to participate in this study. All subjects had been training for at least 1 year and at the time of the study, had a weekly training volume that was greater than 200 km week−1 . At the time of the study, 8 of the 10 subjects were racing primarily in Australian road cycling events at the grade A/B level. Subjects were provided with the procedures and risks associated with participation in the study and gave their written informed consent prior to participation. Subjects were required to complete three testing sessions at similar times of the day, separated by 7.0 ± 1.0 days. Subjects were asked to maintain a similar diet and refrain from intense physical activity in the 24 h period before each testing session. The study was approved by the University’s Human Research Ethics Committee. During initial testing, subjects completed a maximal graded exercise test on a Velotron cycle ergometer (Racermate, Seattle, USA) starting at resistance of 70 W and increasing by 35 W min−1 until volitional fatigue. During the subsequent trials, subjects were required to complete two, 1km TTs on a Velotron cycle ergometer in an environmental chamber maintained at 35.0 ± 0.3 ◦ C and 40.0 ± 3.0% relative humidity. For each TT, subjects sprinted from a standing start using a fixed resistance (gear ratio of 53 × 14). The gear ratio selected for this study was the largest ratio, determine from pilot research, which would allow a rapid increase in cadence during the first 10 s of the TT and did not limit maximal power production. Subjects were asked to finish each TT in the shortest time possible by sprinting as fast as possible from the start. Prior to the trial, subjects were familiarised with the 1-km TT protocol. The TTs were completed without a preceding warm-up. During the subjects’ initial TT, the total time spent in the standing or seated position was recorded and subjects were instructed to follow a similar procedure during subsequent TTs. During the TT, peak power (W), average power (W) and completion time (s) were recorded. Following completion of the first TT, subjects were given 20 min of passive recovery, during which they were randomly assigned to either 5 min of CWI in 14 ◦ C or a control condition, in which the subject sat in the environmental chamber. The 20-
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min recovery interval was selected, as this recovery duration is similar to that used in previous CWI sprint studies.5,6 Cold water immersion occurred from 7.5 to 12.5 min of the 20min recovery period. The timing of the CWI allowed for completion of the isokinetic testing, and for subjects to prepare for the CWI and subsequent TT. Before and after the CWI, subjects sat passively in the environmental chamber (35 ◦ C and 40% relative humidity). Within 2 min following the recovery period, subjects completed a second TT. Rectal temperature, Tmus and isokinetic muscle function were measured before and immediately after the first and second TT. During the 5 min CWI, subjects were submerged in an inflatable water bath in the seated position to the mid-sternal level, wearing only their cycling shorts. Water temperature was maintained at a constant 14 ◦ C by a specially designed water refrigeration unit (iCool Portacovery, Queensland, Australia). The water temperature selected for this study (14 ◦ C) was chosen as it appears as the most commonly used water temperature in previous CWI studies,4,5,10 has been shown to be effective at lowering body temperature4,10 and is tolerable to most subjects. Rectal temperature was measured using a disposable rectal thermometer (Monatherm Thermistor, 400 Series; Mallinckrodt Medical, St. Louis, MO, USA) inserted ∼12 cm past the anal sphincter. Rectal temperature measurements were recorded via a data-logger (Grant Instruments, Shepreth Cambridgeshire, UK) at a sampling rate of 1 Hz. For simplicity and statistical analysis, Tre data are presented as an average of a 60 s sample measured before and immediately after the first and second TT and at 4-min intervals during the 20-min recovery session. Left quadriceps Tmus was measured with the use of a needle thermistor probe (model N451; Nikkiso-YSI Ltd., Tokyo Japan) inserted at a 45◦ angle into the belly of the rectus femoris to a depth of 30 mm. The insertion site was standardised at a distance 2/3 the length of the femur, inferior to the superior iliac spine. The thermometer remained inserted until a stable recording was observed (∼10 s) at which time a single value was recorded. All Tmus measurements were conducted on the left leg in order to eliminate any negative effects the procedure may have had on the muscle function testing (see below). Isokinetic concentric torque production was measured from the right knee extensors using a Biodex isokinetic dynometer (Isokinetics Inc. De Queen, AR, USA). During the measurement, subjects were seated with a trunk angle of 85◦ and were restrained from extraneous movement with nylon straps. Subjects completed three isokinetic concentric contractions of the knee extensors at a velocity of 240◦ s−1 throughout a 90◦ range of motion (0–90◦ ) with 30 s of rest between contractions. This movement velocity was selected as it represents the angular velocity of the knee joint consistent with cycling at a common cadence of 90 rev min−1 .11 Isokinetic torque was recorded at a frequency of 100 Hz, and the highest value recorded during the three contractions
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Fig. 1. Rectal (a) and muscle (b) temperature (◦ C), measured before (TT1pre ), and after the first 1-km time trial (TT1post ), before (TT2pre ), and after the second time trial (TT2post ) in the cold water immersion () and control () conditions. # Significant (p < 0.05) difference from baseline values. † Significant (p < 0.05) difference between conditions.
was used for analysis. Isokinetic testing was completed 3 min before and after each TT. Changes in Tre , Tmus , isokinetic strength and average power during the 1-km TTs were compared by a two-way analysis of variance (ANOVA), with repeated measures. Significant main effects and interactions were analysed with a Student’s t-test and Bonferroni corrected for multiple analyses. Statistical analyses were conducted using SPSS data analysis software (SPSS, USA, Version 15) with a significance level of 0.05. All data are presented as means ± standard deviations (S.D.). Fig. 2. Isokinetic concentric torque (N m) of the knee extensors before (TT1pre ) and after (TT1post ) the first 1-km time trial, and before (TT2pre ) and after (TT2post ) the second 1-km time trial for cold water immersion () and control conditions (). # Significantly (p < 0.05) different from baseline values.
3. Results Examination of the Tre data revealed a main effect for time (p < 0.001). Compared with baseline values (37.1 ± 0.2 ◦ C), Tre significantly increased immediately after the first TT (37.2 ± 0.2 ◦ C) and reached a peak difference of 0.3 ± 0.2 ◦ C
Fig. 3. Peak power (a), average power (b) and completion time (c) measured during the initial and subsequent 1-km time trials (TT1 and TT2 , respectively) in the cold water immersion () and control () conditions. # Significant (p < 0.05) difference between TT1 and TT2 .
J.J. Peiffer et al. / Journal of Science and Medicine in Sport 13 (2010) 112–116
before the start of the second TT; however, no interaction effect (p = 0.36) was observed between conditions (Fig. 1a). A significant interaction effect (p < 0.001) was evident for changes in Tmus between the CWI and control condition. Muscle temperature was significantly (p < 0.001) greater in the control condition (37.7 ± 0.3 ◦ C) compared with the CWI condition (36.4 ± 0.8 ◦ C), immediately after the second TT (Fig. 1b). Analysis of isokinetic torque data revealed a main effect for time (p = 0.01). The average isokinetic torque for both conditions was significantly lower than baseline values (119.8 ± 18.6 N m) immediately after the second TT (105.7 ± 23.8 N m), but no interaction effect was evident (p = 0.32; Fig. 2). Peak power output during the 1-km TTs also showed a main effect for time (p < 0.001). Compared with the initial 1-km TT (783 ± 77 W), peak power was less (p < 0.01) in the second TT (697 ± 69 W; Fig. 3a) in both conditions. However, no interaction was observed between conditions (p = 0.42). Average power also showed a main effect for time (p < 0.01), with a lower average power shown in the second compared with the first 1-km TT (481 ± 49 W vs. 505 ± 56 W; p < 0.01; Fig. 3b) for both conditions. Again, no interaction effect was observed between conditions (p = 0.48). Analysis of completion time revealed a main effect for time (p < 0.01) with a longer completion time observed in the second TT for both conditions (Fig. 3c). No interaction (p = 0.50) was observed between conditions for completion time.
4. Discussion Cold water immersion can rapidly reduce the Tre of individuals after exercise in the heat.4,12,13 Nevertheless, in our study, Tre was not significantly altered by CWI when compared with the control condition (Fig. 1). The similarities in Tre observed between trials in this study could be due to the relatively low pre-immersion Tre (37.2 ± 0.2 ◦ C). Although the protocol was conducted under high ambient temperatures (35.0 ± 0.3 ◦ C), the 1-km TT did not increase Tre to hyperthermic levels.14,15 High Tre (>39 ◦ C) facilitates the cooling effects of CWI by attenuating vasoconstriction during cold exposure and increasing blood contact time with the cooler periphery.16 In our study, vasoconstriction of peripheral blood vessels likely occurred during cold water exposure, redistributing blood flow away from the cooler periphery towards the core, thus attenuating a drop in Tre . This hypothesis is supported by the findings of Park et al.,17 who observed a significant increase in central blood volume in subjects with normal (37 ◦ C) Tre during immersion in 30 ◦ C water. It is not uncommon to observe a delay in core cooling after cold exposure.18 In the present study, however, this phenomenon was not observed (Fig. 1). Neither isokinetic torque nor Tmus were different between conditions before the second TT (Fig. 2). Conversely, Tmus was higher after the second TT in the control condition
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(1.3 ± 0.7 ◦ C; Fig. 1). Despite the lower Tmus with CWI, we found a similar reduction in isokinetic torque for both conditions. Our findings contradict previous studies9,19 that observed decreases in isokinetic force (4–6% ◦ C−1 ) following CWI. In contrast to previous studies9,18 ; however, we measured isokinetic torque following a bout of high-intensity exercise. Thus, the effect of lowered Tmus on isokinetic function could not be determined in this study due to similar levels of fatigue observed between conditions after the second 1-km TT. In the present study, peak and average power output during the 1-km TTs were not significantly influenced by the CWI intervention (Fig. 3). In contrast, previous studies examining sprint cycling have shown a decrease in peak and average power output during the second of two cycle sprints performed in <27 ◦ C after 15 min of CWI.5,6 Differences in Tmus between studies are the most likely explanation for the disparate findings. Indeed, reductions in Tmus are not as severe following short (5 min) compared with longer (10 and 20 min) bouts of CWI (J. Peiffer, unpublished observations). Thus, it is likely that the longer CWI duration (15 min) used with previous sprint research resulted in a greater decrease in Tmus compared to the present study (5 min). However, it is not possible to confirm these presumed differences, as Tmus was not measured in these studies.5,6 The fact that a warm-up was not performed before the 1-km TTs of the present study may limit the applicability of our findings in the applied sport setting. Nevertheless, Bishop and Maxwell20 recently showed the detrimental effects of warm-up on intermittent sprint cycling performance in hot conditions. Moreover, previous studies examining the effects of longer (15 min) CWI durations on sprint cycling performance did not apply a warm-up5,6 ; this methodology isolated the influence of their CWI interventions on muscular function. As a result, we did not apply a warm-up. In contrast to longer (15 min) CWI durations, our results indicate that a 5 min CWI does not negatively affect cycling sprint performance. Future studies are needed to understand the interplay between warm-up and CWI in order to optimise their application in a sport setting. Practical implications • Rectal temperature was not affected by 5 min of CWI following short high-intensity cycling in the heat. • A short (5 min) CWI intervention did not influence muscle function in the heat. • A 5 min CWI intervention did not influence repeated sprint performance in the heat. References 1. Toubekis AG, Douda HT, Tokmakidis SP. Influence of different rest intervals during active or passive recovery on repeated sprint swimming performance. Eur J Appl Physiol 2005;93(5–6):694–700.
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2. Vaile J, Halson S, Gill N, Dawson B. Effect of hydrotherapy on recovery from fatigue. Int J Sports Med 2008;29(7):539–44. 3. Robertson A, Watt JM, Galloway SD. Effects of leg massage on recovery from high intensity cycling exercise. Br J Sports Med 2004;38(2):173–6. 4. Yeargin SW, Casa DJ, McClung JM, Knight JC, Healey JC, Goss PJ, et al. Body cooling between two bouts of exercise in the heat enhances subsequent performance. J Strength Cond Res 2006;20(2):383–9. 5. Schniepp J, Campbell TS, Powell KL, Pincivero DM. The effects of cold-water immersion on power output and heart rate in elite cyclists. J Strength Cond Res 2002;16(4):561–6. 6. Crowe MJ, O’Connor D, Rudd D. Cold water recovery reduces anaerobic performance. Int J Sports Med 2007;28(12):994–8. 7. Tucker R, Marle T, Lambert EV, Noakes TD. The rate of heat storage mediates an anticipatory reduction in exercise intensity during cycling at a fixed rating of perceived exertion. J Physiol 2006;574(Pt 3):905–15. 8. Bigland-Ritchie B, Thomas CK, Rice CL, Howarth JV, Woods JJ. Muscle temperature, contractile speed, and motoneuron firing rates during human voluntary contractions. J Appl Physiol 1992;73(6):2457–61. 9. Bergh U, Ekblom B. Influence of muscle temperature on maximal muscle strength and power output in human skeletal muscles. Acta Physiol Scand 1979;107(1):33–7. 10. Clements JM, Casa DJ, Knight J, McClung JM, Blake AS, Meenen PM, et al. Ice-water immersion and cold-water immersion provide similar cooling rates in runners with exercise-Induced hyperthermia. J Athl Train 2002;37(2):146–50. 11. Sanderson DJ, Martin PE, Honeyman G, Keefer J. Gastrocnemius and soleus muscle length, velocity, and EMG responses to
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17. 18. 19.
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changes in pedalling cadence. J Electromyogr Kinesiol 2006;16(6): 642–9. Peiffer JJ, Abbiss CR, Peake J, Nosaka K, Laursen PB. Effect of cold water immersion after exercise in the heat on muscle function, body temperatures, and vessel diameter. J Sci Med Sport 2009;12:91–6. Peiffer JJ, Abbiss CR, Wall BA, Watson G, Nosaka K, Laursen PB. Effect of a 5 min cold water immersion recovery on exercise performance in the heat. Br J Sports Med 2008 [Epub June 6, 2008] doi:10.1136/bjsm.2008.048173. 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(3):1032–9. Nybo L, Nielsen B. Hyperthermia and central fatigue during prolonged exercise in humans. J Appl Physiol 2001;91(3):1055–60. Casa DJ, McDermott BP, Lee EC, Yeargin SW, Armstrong LE, Maresh CM. Cold water immersion: the gold standard for exertional heatstroke treatment. Exerc Sport Sci Rev 2007;35(3):141–9. Park KS, Choi JK, Park YS. Cardiovascular regulation during water immersion. Appl Human Sci 1999;18(6):233–41. Harman KR, Herndon TM. Cold-water immersion in a 22-year-old service member. Mil Med 2006;171(5):459–62. Howard RL, Kraemer WJ, Stanley DC, Armstrong LE, Maresh CM. The effects of cold immersion on muscle strength. J Strength Cond Res 1994;8(3):129–33. Bishop D, Maxwell NS. Effects of active warm up on thermoregulation and intermittent-sprint performance in hot conditions. J Sci Med Sport 2009;12:196–204.
Journal of Science and Medicine in Sport 13 (2010) 112–116
Original paper
Effect of cold water immersion on repeated 1-km cycling performance in the heat Jeremiah J. Peiffer a,∗ , Chris R. Abbiss b , Greig Watson b , Kazunori Nosaka b , Paul B. Laursen b a
Centre of Excellence for Alzheimer’s Disease Research and Care, School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Australia b School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Australia Received 20 May 2008; received in revised form 8 August 2008; accepted 13 August 2008
Abstract This study examined the effect of a short cold water immersion (CWI) intervention on rectal and muscle temperature, isokinetic strength and 1-km cycling time trial performance in the heat. Ten male cyclists performed a 1-km time trial at 35.0 ± 0.3 ◦ C and 40.0 ± 3.0% relative humidity, followed by 20 min recovery sitting in either cold water (14 ◦ C) for 5 min or in 35 ◦ C air (control); a second 1-km time trial immediately followed. Peak and mean cycling power output were recorded for both time trials. Rectal and muscle temperature, and maximal isokinetic concentric torque of the knee extensors were measured before and immediately after the first and second time trials. Rectal temperature was not different between cold water immersion and control conditions at any time points. After the second time trial, however, muscle temperature was significantly lower (−1.3 ± 0.7 ◦ C) in cold water immersion compared with the control trial. While peak and mean power decreased from the first to second time trial in both conditions (−86 ± 54 W and −24 ± 16 W, respectively), maximal isokinetic concentric torque was similar between conditions at all time points. The 5 min cold water immersion intervention lowered muscle temperature but did not affect isokinetic strength or 1-km cycling performance. © 2008 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved. Keywords: Recovery; Neuromuscular; Intervals; Environment
1. Introduction To maintain performance over multiple exercise sessions, various recovery strategies have been used.1–3 The recovery benefits of a cold water immersion (CWI) intervention have been examined in both sprint and endurance exercise and have produced conflicting results. For example, after 90 min of submaximal running in the heat, CWI in 12 ◦ C for 15 min significantly improved 2 mile running time trial (TT) performance compared with a control condition.4 Conversely, CWI can reduce sprint cycling performance. Two studies have observed that, compared with passive sitting at room temperature, CWI in 12–14 ◦ C for 15 min decreased peak and average power of sprints performed immediately after immersion.5,6 Nevertheless both studies were conducted ∗
Corresponding author. E-mail address: [email protected] (J.J. Peiffer).
at thermoneutral (<27 ◦ C) temperatures, and it is possible that the sprint response may be different in warmer ambient temperatures.7 The most likely cause of the reduction in cycle sprint power output following CWI is a decrease in the contractile speed of the cooled muscle during maximal contraction.8 Indeed, cold exposure can increase action potential propagation time in muscle,8,9 and decrease dynamic contractile force by 4–6% for each 1 ◦ C decrease in muscle temperature (Tmus ).9 Therefore, the CWI interventions used (12–14 ◦ C for 15 min) in the abovementioned sprint studies5,6 likely decreased subsequent cycling performance through the lowered Tmus .9 In addition, the recovery time available for some sport settings can be limited, decreasing the applicability of longer CWI recovery interventions. For these reasons, an investigation into the influence of a short duration (<15 min) CWI intervention on acute power production under high environmental temperatures is needed.
1440-2440/$ – see front matter © 2008 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jsams.2008.08.003
J.J. Peiffer et al. / Journal of Science and Medicine in Sport 13 (2010) 112–116
The purpose of the present study was to determine the effect of a 5 min CWI intervention on rectal temperature (Tre ), Tmus , maximal isokinetic force and 1-km cycling TT performance in the heat (35 ◦ C and 40% relative humidity). We hypothesised that the shorter CWI intervention would significantly lower Tmus compared with a control condition; however, the short exposure time to CWI would limit the deleterious cooling effect on isokinetic force and 1-km TT performance. The findings from this study could be used to improve understanding of the effect of cold exposure on acute power production in sport.
2. Methods Ten male cyclists (age: 29 ± 6 years; stature: ˙ 2 max: 56.5 ± 5.0 ml 181.7 ± 4.0 cm; mass: 79.3 ± 6.3 kg; VO kg−1 min−1 ) were recruited to participate in this study. All subjects had been training for at least 1 year and at the time of the study, had a weekly training volume that was greater than 200 km week−1 . At the time of the study, 8 of the 10 subjects were racing primarily in Australian road cycling events at the grade A/B level. Subjects were provided with the procedures and risks associated with participation in the study and gave their written informed consent prior to participation. Subjects were required to complete three testing sessions at similar times of the day, separated by 7.0 ± 1.0 days. Subjects were asked to maintain a similar diet and refrain from intense physical activity in the 24 h period before each testing session. The study was approved by the University’s Human Research Ethics Committee. During initial testing, subjects completed a maximal graded exercise test on a Velotron cycle ergometer (Racermate, Seattle, USA) starting at resistance of 70 W and increasing by 35 W min−1 until volitional fatigue. During the subsequent trials, subjects were required to complete two, 1km TTs on a Velotron cycle ergometer in an environmental chamber maintained at 35.0 ± 0.3 ◦ C and 40.0 ± 3.0% relative humidity. For each TT, subjects sprinted from a standing start using a fixed resistance (gear ratio of 53 × 14). The gear ratio selected for this study was the largest ratio, determine from pilot research, which would allow a rapid increase in cadence during the first 10 s of the TT and did not limit maximal power production. Subjects were asked to finish each TT in the shortest time possible by sprinting as fast as possible from the start. Prior to the trial, subjects were familiarised with the 1-km TT protocol. The TTs were completed without a preceding warm-up. During the subjects’ initial TT, the total time spent in the standing or seated position was recorded and subjects were instructed to follow a similar procedure during subsequent TTs. During the TT, peak power (W), average power (W) and completion time (s) were recorded. Following completion of the first TT, subjects were given 20 min of passive recovery, during which they were randomly assigned to either 5 min of CWI in 14 ◦ C or a control condition, in which the subject sat in the environmental chamber. The 20-
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min recovery interval was selected, as this recovery duration is similar to that used in previous CWI sprint studies.5,6 Cold water immersion occurred from 7.5 to 12.5 min of the 20min recovery period. The timing of the CWI allowed for completion of the isokinetic testing, and for subjects to prepare for the CWI and subsequent TT. Before and after the CWI, subjects sat passively in the environmental chamber (35 ◦ C and 40% relative humidity). Within 2 min following the recovery period, subjects completed a second TT. Rectal temperature, Tmus and isokinetic muscle function were measured before and immediately after the first and second TT. During the 5 min CWI, subjects were submerged in an inflatable water bath in the seated position to the mid-sternal level, wearing only their cycling shorts. Water temperature was maintained at a constant 14 ◦ C by a specially designed water refrigeration unit (iCool Portacovery, Queensland, Australia). The water temperature selected for this study (14 ◦ C) was chosen as it appears as the most commonly used water temperature in previous CWI studies,4,5,10 has been shown to be effective at lowering body temperature4,10 and is tolerable to most subjects. Rectal temperature was measured using a disposable rectal thermometer (Monatherm Thermistor, 400 Series; Mallinckrodt Medical, St. Louis, MO, USA) inserted ∼12 cm past the anal sphincter. Rectal temperature measurements were recorded via a data-logger (Grant Instruments, Shepreth Cambridgeshire, UK) at a sampling rate of 1 Hz. For simplicity and statistical analysis, Tre data are presented as an average of a 60 s sample measured before and immediately after the first and second TT and at 4-min intervals during the 20-min recovery session. Left quadriceps Tmus was measured with the use of a needle thermistor probe (model N451; Nikkiso-YSI Ltd., Tokyo Japan) inserted at a 45◦ angle into the belly of the rectus femoris to a depth of 30 mm. The insertion site was standardised at a distance 2/3 the length of the femur, inferior to the superior iliac spine. The thermometer remained inserted until a stable recording was observed (∼10 s) at which time a single value was recorded. All Tmus measurements were conducted on the left leg in order to eliminate any negative effects the procedure may have had on the muscle function testing (see below). Isokinetic concentric torque production was measured from the right knee extensors using a Biodex isokinetic dynometer (Isokinetics Inc. De Queen, AR, USA). During the measurement, subjects were seated with a trunk angle of 85◦ and were restrained from extraneous movement with nylon straps. Subjects completed three isokinetic concentric contractions of the knee extensors at a velocity of 240◦ s−1 throughout a 90◦ range of motion (0–90◦ ) with 30 s of rest between contractions. This movement velocity was selected as it represents the angular velocity of the knee joint consistent with cycling at a common cadence of 90 rev min−1 .11 Isokinetic torque was recorded at a frequency of 100 Hz, and the highest value recorded during the three contractions
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Fig. 1. Rectal (a) and muscle (b) temperature (◦ C), measured before (TT1pre ), and after the first 1-km time trial (TT1post ), before (TT2pre ), and after the second time trial (TT2post ) in the cold water immersion () and control () conditions. # Significant (p < 0.05) difference from baseline values. † Significant (p < 0.05) difference between conditions.
was used for analysis. Isokinetic testing was completed 3 min before and after each TT. Changes in Tre , Tmus , isokinetic strength and average power during the 1-km TTs were compared by a two-way analysis of variance (ANOVA), with repeated measures. Significant main effects and interactions were analysed with a Student’s t-test and Bonferroni corrected for multiple analyses. Statistical analyses were conducted using SPSS data analysis software (SPSS, USA, Version 15) with a significance level of 0.05. All data are presented as means ± standard deviations (S.D.). Fig. 2. Isokinetic concentric torque (N m) of the knee extensors before (TT1pre ) and after (TT1post ) the first 1-km time trial, and before (TT2pre ) and after (TT2post ) the second 1-km time trial for cold water immersion () and control conditions (). # Significantly (p < 0.05) different from baseline values.
3. Results Examination of the Tre data revealed a main effect for time (p < 0.001). Compared with baseline values (37.1 ± 0.2 ◦ C), Tre significantly increased immediately after the first TT (37.2 ± 0.2 ◦ C) and reached a peak difference of 0.3 ± 0.2 ◦ C
Fig. 3. Peak power (a), average power (b) and completion time (c) measured during the initial and subsequent 1-km time trials (TT1 and TT2 , respectively) in the cold water immersion () and control () conditions. # Significant (p < 0.05) difference between TT1 and TT2 .
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before the start of the second TT; however, no interaction effect (p = 0.36) was observed between conditions (Fig. 1a). A significant interaction effect (p < 0.001) was evident for changes in Tmus between the CWI and control condition. Muscle temperature was significantly (p < 0.001) greater in the control condition (37.7 ± 0.3 ◦ C) compared with the CWI condition (36.4 ± 0.8 ◦ C), immediately after the second TT (Fig. 1b). Analysis of isokinetic torque data revealed a main effect for time (p = 0.01). The average isokinetic torque for both conditions was significantly lower than baseline values (119.8 ± 18.6 N m) immediately after the second TT (105.7 ± 23.8 N m), but no interaction effect was evident (p = 0.32; Fig. 2). Peak power output during the 1-km TTs also showed a main effect for time (p < 0.001). Compared with the initial 1-km TT (783 ± 77 W), peak power was less (p < 0.01) in the second TT (697 ± 69 W; Fig. 3a) in both conditions. However, no interaction was observed between conditions (p = 0.42). Average power also showed a main effect for time (p < 0.01), with a lower average power shown in the second compared with the first 1-km TT (481 ± 49 W vs. 505 ± 56 W; p < 0.01; Fig. 3b) for both conditions. Again, no interaction effect was observed between conditions (p = 0.48). Analysis of completion time revealed a main effect for time (p < 0.01) with a longer completion time observed in the second TT for both conditions (Fig. 3c). No interaction (p = 0.50) was observed between conditions for completion time.
4. Discussion Cold water immersion can rapidly reduce the Tre of individuals after exercise in the heat.4,12,13 Nevertheless, in our study, Tre was not significantly altered by CWI when compared with the control condition (Fig. 1). The similarities in Tre observed between trials in this study could be due to the relatively low pre-immersion Tre (37.2 ± 0.2 ◦ C). Although the protocol was conducted under high ambient temperatures (35.0 ± 0.3 ◦ C), the 1-km TT did not increase Tre to hyperthermic levels.14,15 High Tre (>39 ◦ C) facilitates the cooling effects of CWI by attenuating vasoconstriction during cold exposure and increasing blood contact time with the cooler periphery.16 In our study, vasoconstriction of peripheral blood vessels likely occurred during cold water exposure, redistributing blood flow away from the cooler periphery towards the core, thus attenuating a drop in Tre . This hypothesis is supported by the findings of Park et al.,17 who observed a significant increase in central blood volume in subjects with normal (37 ◦ C) Tre during immersion in 30 ◦ C water. It is not uncommon to observe a delay in core cooling after cold exposure.18 In the present study, however, this phenomenon was not observed (Fig. 1). Neither isokinetic torque nor Tmus were different between conditions before the second TT (Fig. 2). Conversely, Tmus was higher after the second TT in the control condition
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(1.3 ± 0.7 ◦ C; Fig. 1). Despite the lower Tmus with CWI, we found a similar reduction in isokinetic torque for both conditions. Our findings contradict previous studies9,19 that observed decreases in isokinetic force (4–6% ◦ C−1 ) following CWI. In contrast to previous studies9,18 ; however, we measured isokinetic torque following a bout of high-intensity exercise. Thus, the effect of lowered Tmus on isokinetic function could not be determined in this study due to similar levels of fatigue observed between conditions after the second 1-km TT. In the present study, peak and average power output during the 1-km TTs were not significantly influenced by the CWI intervention (Fig. 3). In contrast, previous studies examining sprint cycling have shown a decrease in peak and average power output during the second of two cycle sprints performed in <27 ◦ C after 15 min of CWI.5,6 Differences in Tmus between studies are the most likely explanation for the disparate findings. Indeed, reductions in Tmus are not as severe following short (5 min) compared with longer (10 and 20 min) bouts of CWI (J. Peiffer, unpublished observations). Thus, it is likely that the longer CWI duration (15 min) used with previous sprint research resulted in a greater decrease in Tmus compared to the present study (5 min). However, it is not possible to confirm these presumed differences, as Tmus was not measured in these studies.5,6 The fact that a warm-up was not performed before the 1-km TTs of the present study may limit the applicability of our findings in the applied sport setting. Nevertheless, Bishop and Maxwell20 recently showed the detrimental effects of warm-up on intermittent sprint cycling performance in hot conditions. Moreover, previous studies examining the effects of longer (15 min) CWI durations on sprint cycling performance did not apply a warm-up5,6 ; this methodology isolated the influence of their CWI interventions on muscular function. As a result, we did not apply a warm-up. In contrast to longer (15 min) CWI durations, our results indicate that a 5 min CWI does not negatively affect cycling sprint performance. Future studies are needed to understand the interplay between warm-up and CWI in order to optimise their application in a sport setting. Practical implications • Rectal temperature was not affected by 5 min of CWI following short high-intensity cycling in the heat. • A short (5 min) CWI intervention did not influence muscle function in the heat. • A 5 min CWI intervention did not influence repeated sprint performance in the heat. References 1. Toubekis AG, Douda HT, Tokmakidis SP. Influence of different rest intervals during active or passive recovery on repeated sprint swimming performance. Eur J Appl Physiol 2005;93(5–6):694–700.
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2. Vaile J, Halson S, Gill N, Dawson B. Effect of hydrotherapy on recovery from fatigue. Int J Sports Med 2008;29(7):539–44. 3. Robertson A, Watt JM, Galloway SD. Effects of leg massage on recovery from high intensity cycling exercise. Br J Sports Med 2004;38(2):173–6. 4. Yeargin SW, Casa DJ, McClung JM, Knight JC, Healey JC, Goss PJ, et al. Body cooling between two bouts of exercise in the heat enhances subsequent performance. J Strength Cond Res 2006;20(2):383–9. 5. Schniepp J, Campbell TS, Powell KL, Pincivero DM. The effects of cold-water immersion on power output and heart rate in elite cyclists. J Strength Cond Res 2002;16(4):561–6. 6. Crowe MJ, O’Connor D, Rudd D. Cold water recovery reduces anaerobic performance. Int J Sports Med 2007;28(12):994–8. 7. Tucker R, Marle T, Lambert EV, Noakes TD. The rate of heat storage mediates an anticipatory reduction in exercise intensity during cycling at a fixed rating of perceived exertion. J Physiol 2006;574(Pt 3):905–15. 8. Bigland-Ritchie B, Thomas CK, Rice CL, Howarth JV, Woods JJ. Muscle temperature, contractile speed, and motoneuron firing rates during human voluntary contractions. J Appl Physiol 1992;73(6):2457–61. 9. Bergh U, Ekblom B. Influence of muscle temperature on maximal muscle strength and power output in human skeletal muscles. Acta Physiol Scand 1979;107(1):33–7. 10. Clements JM, Casa DJ, Knight J, McClung JM, Blake AS, Meenen PM, et al. Ice-water immersion and cold-water immersion provide similar cooling rates in runners with exercise-Induced hyperthermia. J Athl Train 2002;37(2):146–50. 11. Sanderson DJ, Martin PE, Honeyman G, Keefer J. Gastrocnemius and soleus muscle length, velocity, and EMG responses to
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