| Objective: Cold Water Immersion;CWI is a recovery technique that immerses the whole body or part of the body in cold water and is widely used by athletes.For team events,previous studies have shown that a short interval of whole-body CWI(2.5-5min)during the intermission can effectively inhibit the reduction of repetitive sprint ability in the second half,but the effect of this program on the performance in the second half under high temperature is unknown.In addition,CWIL can also improve thermoregulation and reduce the burden on the cardiovascular system,thus improving subsequent exercise ability.However,the effect of CWIL and whether it can be compared with WBCWI are still unknown.In view of this,this paper,based on the sports mode of football,focused on cold water immersion in different parts of the body,and compared the influence of WBCWI and CWIL on the subsequent sports ability and body temperature in high temperature environment during halftime.Methods: A randomized crossover design was used to recruit 11 healthy,non-thermally adapted male college students with exercise habits.Each subject completed 1 pre-experiment and 3 formal experiments.Three formal experiments were carried out in outdoor high temperature environment,and the ambient temperature was measured by dry bulb black bulb thermometer(Wet-bulb-globe temperature;WBGT).The sports program simulates the way of team competition,which is divided into upper and lower halves.There is a 15-minute interval between the first half and the second half.I will be intermittent with T-Test,20 m sprints,and YO-YO Intermittent Endurance Test Level-1,intermittent with a 5-minute break in between.Passive rest(3 min,CON),whole-body CWI(3 min,15℃,WBCWI)or CWIL(3 min,15℃,CWIL)were randomly administered at 8-10 min of intermission.During the whole experiment,t-test completion time,20 M completion time,moving distance of Yo-Yo IE 1,core temperature,skin temperature of upper arm,chest and thigh,and heart rate were collected respectively.The measures included t-test time,20-meter sprint time,Yo-Yo IE 1 distance traveled,upper arm skin temperature,chest skin temperature,thigh skin temperature,average skin temperature,core temperature,average body temperature,heat reserve,and physiological stress index(PSI).The data were statistically analyzed by SPSS 23.00 software.Univariate ANOVA was used to analyze the environmental temperature under different experimental conditions,and the variance of multiple repeated measurements(method × time)was used to analyze the changes of t-test time,20-meter sprint time,Yo-Yo IE 1 moving distance,skin temperature(upper arm,chest,thigh,average),thermal reserve,core temperature,average body temperature,and PSI.Bonferroni correction was used for post-mortem analysis.All measurements were presented as mean ± standard deviation.The statistical difference level was defined as P < 0.05.Results:(1)WBGT indexOne-way ANOVA showed that there was no significant difference in WBGT index among the three groups(F(2)= 0.059,Pη2= 0.003,P > 0.05).CON= 39.78 ±1.02℃,WBCWI = 39.72 ± 0.93℃,CWIL = 39.58 ± 1.15℃.(2)Athletic abilityFor t-test time,there was a significant interaction between intervention method and time(F(2,20)= 8.468,P < 0.05,Pη2= 0.459).Compared with the first half,the t-test time of CON group was significantly longer in the second half.WBCWI group was significantly shortened.There was no significant difference in CWIL group.Compared with CON group,the t-test time of WBCWI group was significantly shorter in the second half.CON and CWIL,WBCWI and CWIL have no significant differences.For 20 M,there was a significant interaction between intervention method and time(F(2,20)= 13.595,P = 0.000,Pη2 = 0.576).Compared with the first half,the time of 20 M in CON group was significantly prolonged in the second half.WBCWI group and CWIL group had no significant difference.Compared with the CON group,the time of 20 M in the WBCWI group in the second half was significantly shorter.For Yo-Yo IE 1,there was a significant interaction between intervention method and time(F(2,20)= 4.126,P < 0.05,Pη2 = 0.292).Compared with the first half,the distance of Yo-Yo IE 1 in CON group and CWIL group was significantly shortened in the second half.In the second half,Yo-Yo IE 1 movement distance was significantly longer in the WBCWI group than in the CON group.(3)Thermoregulation:For core temperature,there was no significant interaction between intervention method and time(F(46,460)= 0.714,P > 0.05,Pη2 = 0.067),however,there was a significant time main effect(F(23)= 70.810,P = 0.000,Pη2= 0.876).During exercise,there was no significant difference between CON group,WBCWI group and CWIL group.For upper arm skin temperature,there was a significant interaction between intervention method and time(F(46,460)= 12.605,P = 0.000,Pη2 = 0.558).The upper arm temperature of WBCWI group was significantly lower than that of CON group from the beginning of intervention to the end of YO-YO IE1.The upper arm temperature in the WBCWI group was significantly lower than that in the CWIL group from the beginning of intervention to the middle of YO-YO IE1.For chest skin temperature,there was a significant interaction between intervention method and time(F(46,460)= 6.448,P = 0.000,Pη2 = 0.392).The chest temperature in the WBCWI group was significantly lower than that in the CON and CWIL groups from the beginning of intervention to the middle of YO-YO IE 1.For thigh skin temperature,there was a significant interaction between intervention method and time(F(46,460)= 11.961,P= 0.000,Pη2 = 0.545).After the intervention,the average skin temperature of the WBCWI and CWIL groups was significantly lower than that of the CON group before the end of the intervention.For mean skin temperature,there was a significant interaction between intervention method and time(F(46,460)= 17.184,P = 0.000,Pη2 = 0.632).The mean skin temperature in the WBCWI and CWIL groups was significantly lower than that in the CON group from the beginning of intervention to the end of Yo-Yo IE 1.In addition,the mean skin temperature in the WBCWI group was significantly lower from the beginning of intervention to the middle of Yo-Yo IE 1 exercise than in the CWIL group.For mean body temperature,there was a significant interaction between intervention method and time(F(46,460)=4.799,P = 0.003,Pη2 =0.323).Mean body temperature in the WBCWI group was significantly lower from the beginning of intervention to the beginning of the second half of Yo-Yo IE 1 compared to the CON group.(4)Heat storage capacityFor heat storage capacity,there was a significant interaction between intervention method and time(F(2,20)= 14.196,P = 0.000,Pη2 = 0.587).In the second half,the thermal reserve level of WBCWI group was significantly better than CON group and CWIL group.(5)PSIFor PSI,there was no significant interaction between intervention method and time(F(2,20)= 0.569,P > 0.05,Pη2 = 0.054).There was no significant difference in PSI of CON group,WBCWI group and CWIL group during the whole exercise.Conclusion: The results show that WBCWI can significantly reduce skin temperature,average body temperature,improve thermal reserve,and effectively improve body agility,sprint ability and intermittent endurance ability in the second half.CWIL significantly reduced thigh skin temperature and effectively inhibited the decrease of agility and sprint ability in the second half of the body.In addition,the effect of WBCWI on mean skin temperature and heat reserve was due to CWIL.These results suggest that compared with CWIL,WBCWI has a better effect on improving subsequent exercise ability and body temperature regulation under high temperature environment,and the effect of WBCWI on improving exercise ability may be related to further reducing skin temperature and improving heat reserve.For team sports,we recommend a short Whole-body cold water immersion during the intermission to improve performance in the second half under high temperature conditions. |
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