Effect Of Single And Four Days Of Whole Body Cryotherapy On Fatigue Elimination In Shanghai Rugby Players

Objective:Current studies suggest that athletes elicit a range of physiological stress responses after high-intensity training and competition.If recovery between each competition and training is incomplete,resulting in cumulative fatigue,it is highly likely to produce excessive fatigue or even a decline in competitive ability and the occurrence of injury events.Therefore,an effective and simple and easy recovery method is particularly important for fatigue elimination in athletes.This paper aimed to investigate the effect of a single session of whole body cryotherapy on recovery after high-intensity sprint interval sports among rugby players;To investigate the effects of four days of continuous whole body cryotherapy on fatigue resolution after training in athletes,including effects on the inflammatory response,heart rate variability,lower limb bursting power,and sleep quality.Methods:In this study,16 Shanghai British 7-person rugby players were matched and randomized into 8 of each two groups of WBC and CON.After the athletes completed five sessions of high-intensity intermittent sprinting exercise（SIT）of climbing machine（30s duration,30s interval）at the maximum strength and speed before the single session of whole body cryotherapy,the WBC group immediately entered the whole body cryotherapy bin recovery（formal intervention 180s,the temperature is set to-120°C）and the control group recovered naturally.The changes of BLa,Sm O₂,HR and RPE before exercise,3^rd min,5^th min and 20^th min after exercise were recorded as well as the climbing height,Sm O₂,HR and RPE changes of each interval in sprint interval exercise.The program cycle of continuous WBC was 7 days,in which the cold treatment lasted for 4 days and was collected at the same time in the morning on days1,5（i.e.,the day after the end of continuous cold treatment）,and on day 7 for each index of the athlete,mainly including blood indicators,heart rate and heart rate variability,RPE,sleep quality questionnaires and squatting and reverse jumping.The hypothermia group received a therapeutic intervention of hypothermia once a day after the training was completed in the morning and afternoon,and the control group did not take the intervention measures.Results:（1）Before a single session of whole body cryotherapy,during SIT,the interaction effects between group and sprint number were not statistically significant for all indexes.The trend of height change covered by climbing was maintained in both groups,and the sprint number of athletes had a significant main effect on the related performance of climbing height.The separate effect of time was statistically significant for each indicator during the trial after SIT.At 3min,the difference of HR between athletes in CON and WBC group was statistically significant（P=0.027）.At 5 min,the difference in Sm O₂ between con and WBC group was 8（P=0.051）and that in RPE was statistically significant（P=0.031）.（2）The interaction effect between cold treatment and time on CK was significant during continuous hypothermia intervention,and the separate effect of group was significant on CK at day 2（F=6.545,P=0.043,η_p²=0.522）。The separate effect of time in the con group was significant for CK（F=9.360,P=0.005,η_p²=0.609）。The separate effect of time in WBC group was not significant for CK（P>0.05）.The interaction between cold therapy and time was significant for t in male athletes.（3）After four days of continuous intervention,testosterone and cortisol tended to be higher and lower,respectively,in athletes of both sexes in the WBC group.The time-domain indicators sndd（P=0.049）,sdsd（P=0.028）,and RMSSD（P=0.034）on the fifth day showed significant differences in group main effects.（4）Persisting for 4 days after WBC intervention,athletes’RPE values were significantly lower in the WBC group than in the con group（P=0.046）,but the effect was no longer maintained after cessation of the intervention.The quality of sleep in WBC group was significantly higher than that in con group after continuous intervention（P=0.045）.（5）Neither a single nor a four-day continuous WBC intervention had a significant effect on lower extremity burst force.Conclusions:（1）A single session of whole body cryotherapy can quickly and effectively reduce the physical stress response of the athlete’s body,thus accelerating the elimination of fatigue and bringing immediate recovery and positive psychological effects to the athlete.（2）An intervention of four days of whole body cryotherapy was beneficial in promoting recovery from muscle damage and strengthening of autonomic nervous system function after daily training in rugby players,accompanied by reduced subjective sensory fatigue and better sleep quality.