Effect Of Personalized Water Immersion To Promote Recovery And Energy Metabolism After High-intensity Aerobic Intermittent Training In College Players Under High-Temperature Environment

Background:Football is one of the sports that are susceptible to high-temperature environments,Therefore,it is particularly important to use scientific methods to ensure the effectiveness of athletes’recovery after training and competition in high-temperature environments.Cold water immersion（CWI）is one of the most commonly used recovery methods for football players after training and competition.Some studies have confirmed the beneficial effects of CWI on the athlete’s ability to regain movement.However,the same CWI has also been shown to have no effect,or even a detrimental effect,on athletes’post-exercise recovery outcomes.To address this issue,we introduced a personalized CWI（CCWI）protocol designed based on a well-validated chronophysiological model,and although initial validation of the protocol has been conducted,whether single,as well as continuous CCWI,can positively affect specific environments,specific populations,and after the use of specific exercise protocols has not been well investigated.In addition,studies have reported that the effects of different relative Humidity（RH）conditions in high-temperature environments on human physiology and re-exercise capacity are different,and which high-temperature environment has the greatest effect on the physiological response and subsequent exercise performance of football players after completing a specific training regimen is one of the important questions that need to be urgently investigated.In addition,it has been demonstrated in animal studies that acute CWI reduces energy metabolism and that regular CWI causes changes in mitochondrial synthesis factors associated with energy metabolism.Therefore,this study investigates the effects of CCWI as a means of recovery and the physiological responses and subsequent exercise performance of college football players after completing high-intensity aerobic intervals training（HIAIT）in a high-temperature environment to investigate the effects of single and continuous CCWI in high-temperature different humidity environments on the physiological responses,subsequent athletic ability and changes in the energy metabolism of college football players after HIAIT training.Objective:Three experiments were conducted in this study:[Experiment 1]To investigate the physiological indices and subsequent athletic ability of college football players after HIAIT exercise in high temperature（35°C）and different humidity（20%RH,40%RH,80%RH）environments.[Experiment 2]To investigate the effects of CCWI after HIAIT in high-temperature environments on college football players’physiological indices,subsequent athletic ability,and potential changes in energy metabolism.[Experiment 3]To investigate the effects of continuous CCWI after HIAIT in a high-temperature environment on physiological indices,subsequent athletic ability,and potential changes in energy metabolism in college football players.Finally,based on the data related to the above three experiments,we conducted[Experiment 4]:A decision model based on neural network regression analysis of the application protocol for CWI.Methods:A randomized controlled,crossover experimental design was used in this study.[Experiment 1]Twelve college football players volunteered in this study and completed HIAIT in four different environmental conditions:（1）25℃/20%RH（control group）;（2）35℃/20%RH（H20 group）;（3）35℃/40%RH（H40 group）;（4）35℃/80%RH（H80 group）.[Experiment 2]Twelve college football players chose to take part in the study,and after completing HIAIT in 35°C/40%RH environmental conditions,then recovered using three different therapies:passive recovery（C）,General cold water immersion（GCWI）,CCWI.[Experiment 3]Twelve college football players were selected for this study.These subjects performed 3 consecutive HIAIT,each one day between trials,according to a randomly generated sequence underwent recovery after each trial using the appropriate recovery means:C,GCWI,CCWI,and after completing the above recovery means,the scheduled other recovery means were performed at two-week intervals.Physiological indexes were recorded continuously throughout the exercise,such as the heart rate（HR）,mean arterial pressure（MAP）,lactate,core temperature（T_C）and skin temperature（TS）,thermal sensation（TS）,and rating of perceived exertion（RPE）.The heart rate variability（HRV）,squat jump height（SJH）,cycling time to exhaustion（TTE）,and sweat rate（SR）were monitored pre-exercise and post-exercise.Furthermore,urine was collected 50 minutes after exercise in Experiments 2 and 3.[Experiment 4]The 120 data collected from the 3 experiments above,selected from directly measured physiological and biochemical data,were used to find the relationship between environment,whether or not CWI was used,exercise test time（biorhythm data）,age,height,post-exercise weight,adiposity,heart rate,MAP,blood lactate,T_C,Ts,TS,RPE,SR,HF,RMSSD,and TTE using back propagation（BP,Back Propagation）neural network.Results:[Experiment 1]Within-group comparisons revealed that after exercise,the HR,lactate,MAP,T_C,T_s,TS,and RPE in the 4 groups showed a trend of rapid increase,then decreased gradually.Comparison between groups revealed after exercise,there was no significant difference in HR,MAP,T_C,or RPE between the 4 groups at the same time point（P>0.05）,in addition to this,when compared to C group,the lactate,T_s,TS in other 3 groups significant differences were observed at the corresponding time points（P<0.05）.The HF,LF,RMSSD,and SDNN level in the 4 groups before exercise was not significantly different（P>0.05）.The HF,and RMSSD in the H40 and H80 groups were significantly decreased（P<0.05）and other HRV indicators were no significant difference after exercise（P>0.05）.In sports performance measurement,the SJH and TTE were significantly decreased,but there was no significant difference in the 4 groups（P>0.05）.The SR was no significant difference in the4 groups after exercise（P>0.05）.[Experiment 2]Within-group comparisons revealed that after exercise,HR at 50 min,lactate at 40 min,and core temperature were still higher than the baseline in the C group（P<0.05）.MAP at 30 minutes,T_S at 30 minutes,and TS at 5 minutes were lower than the baseline,while lactate at 30 minutes,T_C at 10 minutes,and RPE at 15minutes after exercise were not significantly different from the baseline in the GCWI group（P>0.05）.MAP at 45 min,T_S at 50 min,and TS at 15 min were lower than the baseline in CCWI,while lactate at 40 minutes,T_C at 20 minutes,and RPE at 10 minutes were not significantly different from the baseline in the CCWI group（P>0.05）.HRV,SJH,and TTE decreased significantly after exercise in 3 groups（P>0.05）.Comparison between groups revealed after exercise,MAP was significantly lower in the CCWI group than in the control group at 10 and15 minutes（P<0.05）.T_C was significantly lower in the GCWI group at 10 minutes and in the CCWI group at 10 to 30 minutes than in the C group（P<0.05）.T_S temperature was significantly lower in the GCWI group at 20 to 30 minutes and in the CCWI group at 20 to 45 minutes than in the C group,in addition,T_S was significantly lower in the CCWI group at 20 to 50 minutes were significantly lower than that C group（P<0.05）.The TS in the CCWI group was significantly lower than that in the C and GCWI groups at 10 to 15 minutes（P<0.05）.The RPE in the GCWI group at 15 minutes and the CCWI group at 10 to 15 minutes were significantly lower than that in the C group（P<0.05）.A comparison of energy metabolism indicators showed that glycerol 3-phosphate was significantly smaller in the CCWI group than in the C group and that succinate was significantly smaller in the CCWI group than in the GCWI（P<0.05）.[Experiment 3]Within-group comparisons revealed that after exercise,HR and T_C in the C group were still higher than baseline at 50 minutes（P<0.05）.T_S in GCWI and CCWI groups were still lower than baseline at 30 minutes（P<0.05）.HF,RMSSD in the C group,and RMSSD in the GCWI group decreased significantly,however,there was no significant change in CCWI group before and after exercise（P>0.05）.TTE and SJH in all three groups decreased significantly post-exercise（P<0.05）.Comparison between groups revealed after exercise,no significant differences were found in HR,MAP,lactate,HRV,SR,SJH indices of 3 groups（P>0.05）.T_C was significantly lower in the GCWI and CCWI groups than in the control group at 10 to 50 minutes（P<0.05）.T_S was significantly lower in the GCWI group at 20 to 30 minutes and in the CCWI group at 20 to 35 minutes than in the C group（P<0.05）.TS was significantly lower in the GCWI group at 10 to 20 minutes and in the CCWI group at 10 to 15 minutes than in the C group（P<0.05）.The RPE in the GCWI group at 15 minutes and the CCWI group at 10minutes was significantly lower than that in the C group（P<0.05）.TTE was significantly longer in the GCWI and CCWI groups than in the control group（P<0.05）.Comparison of energy metabolism indicators showed that adenosine diphosphate was significantly greater in the CCWI group than in the C group,with no significant difference between the other two groups（P>0.05）.[Experiment 4]Two hidden layers and 38 nodes are used in this BP neural network.Each hidden layer contains 10 nodes.The other parameters of this network are 0.01 and 1000,which are the learning rate and number of iterations,respectively.Conclusion:[Experiment 1]In conclusion,heat and humidity environments elicited generally greater physiological effects compared with the normal environment but did not affect sports performance in college football players.[Experiment 2]After HIAIT,CWI significantly reduced MAP,Tc,Ts,TS,and RPE compared to passive recovery,in addition,CWI promoted autonomic and endurance performance in college football players.Compared with GCWI,CCWI was effective in reducing Ts,TS,and promoting endurance recovery.[Experiment 3]After HIAIT,CWI significantly reduced Tc,Ts,TS,RPE and TTE compared to passive recovery,in addition,CWI promoted autonomically and endurance performance.Compared with GCWI,CCWI was slightly effective in promoting autonomic and endurance recovery in college football players.[Experiment 4]The model constructed by the BP neural network derived from this study is accurate and can be used to predict the time of its exhaustive movement by bringing in the above 17 data to reverse the decision of which recovery method to choose,and this method is a decision model for the recovery program before personalized cold water immersion.However,we found that there is still a certain amount of error between the training and test sets,so the sample size should be expanded in subsequent studies to make the model prediction more accurate.