Effects Of Two Different Cryotherapy Methods At Halftime On The Subsequent Exercise Performance As Well As Physiological And Perceptual Responses

Objective:Prolonged exercise in the heat can enhance a player’s core temperature(T_core)and skin temperature(T_skin),which results in a reduced performance.Therefore,for athletes competing in intermittent team sporting events,an optimal halftime（HT）countermeasure that addresses the effects of heat is critical to inhibit the impairment of performance during the second half in a high ambient temperature.As a type of cooling intervention,cold-water immersion（CWI）is an effective recovery intervention for various forms of exercise.Studies have investigated the effects of short period CWI carried out within a recovery interval such as HT（～15 min）on the subsequent exercise performance.To the best of our knowledge,no previous study has examined the effects of CWI during HT on a subsequent a battery of soccer-specific tests.Whole-body cryotherapy（WBC）involves short exposures to very cold air in a controlled room and is rising in popularity.Several studies have shown that WBC is beneficial for athletes competing in sports that are regularly characterized by one or more training sessions or even multiple competition times per day.No study has explored the effects of WBC during HT on subsequent exercise capacity and determined whether WBC provides any additional benefits beyond CWI.Therefore,the purpose of this study was to investigate effects of WBC and CWI during half time on outdoor subsequent exercise capacity,physiological and perceptual parameters in the heat.Methods:In a counter-balanced and cross-over design,twelve non-heat-acclimated healthy and active young males were performed the exercise that included a battery of soccer-specific tests.The exercise protocol consisted of two identical halves separated by a 15 min HT.The order of each half performed was the agility T test（T-test）,20m sprint（20M-ST）,and Yo-Yo intermittent endurance test level 1（Yo-Yo IE 1）,with 5min passive recovery separated each test.During HT,passive seated rest or WBC at-110℃or CWI at 15℃of the following 3 min recovery interventions were performed.Performance on T-test,20M-ST and Yo-Yo IE1,core temperature(T_core)and mean skin temperature(T_skin),heart rate（HR）,rating of perceived exertion（RPE）,thermal sensation（TS）were measured.All datas were analyzed by a two-factor（conditions×time）analysis of variance with repeated measures,post-hoc analyses were carried out with Bonferroni correction.All data were summarized as the mean±SD.p<0.05 was considered statistically significant.Results:1.Exercise capacityFor the duration of the T-test,there was a significant interaction（F（2,10）=6.247,P<0.05,Pη2=0.555）.With the CON intervention,the T-test duration was significantly longer during the second half than during the first half.In contrast,under the CWI and WBC conditions,there was no significant difference of the T-test duration between the first and second halves.During the second half,the T-test duration was shorter with the CWI intervention than with the CON intervention,but there was not a significant difference between the CON intervention and the WBC intervention.For the 20M-ST,there was a significant interaction（F（2,22）=13.087,P<0.05,Pη2=0.543）.For the CON intervention,the duration of the 20M-ST was significantly longer during the second half than during the first half.In contrast,the 20M-ST duration was significantly shorter during the second half with the CWI intervention compared with the first half.During the second half,the 20M-ST duration with the WBC or CWI intervention was significantly shorter than that with the CON intervention,but there was no significant difference between the WBC and CWI interventions.For the Yo-Yo IE 1,there was a significant interaction（F（2,22）=8.301,P<0.05,Pη2=0.430）.With the CON and WBC interventions,the completed Yo-Yo IE 1distance during the second half was significantly shorter compared with that of the first half.During the second half,the completed Yo-Yo IE 1 distances with the WBC and CWI interventions were significantly longer than that with the CON intervention,but the distance was similar between the WBC and CWI interventions.2.Physiological indexFor T_core,there was no significant interaction（F（46,506）=0.845,P=0.50,Pη2=0.071）,but there were significant main effects for the condition（F（2）=4.386,P<0.05,Pη2=0.285）and for the time（F（23）=54.391,P<0.001,Pη2=0.832）.In addition,there were significant differences of the T_coreafter the T-test and during the Yo-Yo IE 1 between the WBC and CON interventions.For T_skin,there was a significant interaction（F（46,506）=18.622,P<0.05,Pη2=0.629）.WBC resulted in a significantly lower mean T_skinthan the CON conditions from 9 min during HT to the start of the 20M-ST.Meanwhile,the T_skinwith CWI decreased significantly compared with that of the CON intervention from 9 min during HT to the end of the Yo-Yo IE 1.Moreover,the T_skinwith WBC was significantly lower than that with CWI at 9 min during HT,but it was significantly higher than that after CWI at the beginning of the Yo-Yo IE 1.For HR,there was no significant interaction（F（46,506）=1.212,P=0.302,Pη2=0.099）,but there were significant main effects for the time（F（23）=91.640,P=0.000,Pη2=0.893）.The HR was significantly lower with CWI compared with the WBC and CON interventions at 9 min during HT.3.Perceptual indexFor TS,there was significant interaction for TS（F（22,242）=21.429,P<0.001,Pη2=0.661）.The TS was significantly lower with the WBC intervention compared with the CON intervention from the start of the intervention to before the Yo-Yo IE 1.Similarly,the TS was significantly lower for the CWI intervention compared with the CON intervention from the beginning of the intervention to after the T-test.Moreover,at 1,2,and 3 min during the intervention,the TS was significantly lower for the WBC conditions compared with the CWI conditions.For RPE,there was no significant interaction of RPE（F（14,154）=2.035,P>0.05,Pη2=0.156）,but there were significant main effects for the time（F（7）=68.026,P=0.000,Pη2=0.990）.Conclusions:The findings of the present study indicate that WBC and CWI during HT both attenuate the reductions in the subsequent motor performance of athletes in the heat,with a decreased physiological and perceptual load,but CWI induces favorable ergogenic effects and decreases cardiovascular strain more than WBC.