OBJECTIVE: To explore the relationship between physiological parameters changes and severe heatstroke induced by 5-km armed cross-country training. METHODS: A total of 521 male officers and soldiers from a special team who participated in the summer training of 5-km armed cross-country training from year 2016 to 2017 were enrolled. All trainees participated in 5-km armed cross-country training in high temperature and humidity environment of ambient temperature > 32 centigradeand (or) relative humidity > 65%. The trainees were divided into two groups according to the incidence of severe heatstroke in the course of training. The age, enlistment time, constitution score, body mass index (BMI), external environment (ambient temperature, relative humidity, wind speed, heat index) of trainees of the two groups, and the change rates of arterial blood oxygen saturation (SaO₂), body temperature, pulse and blood pressure within 5 minutes after the 5-km armed cross-country training were compared between the two groups. The risk factors of severe heatstroke were screened by two classified Logistic regression analysis, and the predictive value of various risk factors of severe heatstroke was analyzed by the receiver operator characteristic curve (ROC). RESULTS: In 521 trainees of 5-km armed cross-country training, 29 trainees suffered from severe heatstroke accounting for 5.57%. There was no significant difference in the age, enlistment time, constitution score, BMI, or external environment during 5-km armed cross-country training between severe heatstroke group and non-severe heatstroke group. Compared with those without severe heatstroke, the descending rates of body temperature, pulse, blood pressure and SaO₂ increased rate within 5 minutes after 5-km armed cross-country training of severe heatstroke trainees were significantly decreased [temperature descending rate: (0.67±0.30)% vs. (1.43±1.28)%, pulse descending rate: (7.53±5.21)% vs. (13.48±8.07)%, blood pressure descending rate: (9.28±6.84)% vs. (19.42±7.73)%, SaO₂ increased rate: (0.51±0.39)% vs. (1.50±1.43)%, all P < 0.01]. Two classification Logistic regression analysis showed that the temperature descending rate [odds ratio (OR) = 0.485, 95% confidence interval (95%CI) = 0.289-0.817], pulse descending rate (OR = 0.903, 95%CI = 0.845-0.965), blood pressure descending rate (OR = 0.841, 95%CI = 0.790-0.896), and SaO2 increased rate (OR = 0.421, 95%CI = 0.250-0.711) were the risk factors for severe heatstroke during 5-km armed cross-country training (all P < 0.01). ROC curve analysis showed that temperature descending rate [area under ROC curve (AUC) = 0.659, 95%CI = 0.604-0.714], pulse descending rate (AUC = 0.730, 95%CI = 0.762-0.900), blood pressure descending rate (AUC = 0.831, 95%CI = 0.659-0.801), SaO₂ increased rate (AUC = 0.711, 95%CI = 0.655-0.767) could be used for the incidence of severe heatstroke prediction during 5-km armed cross-country training (all P < 0.01), and the predicted value was the same. CONCLUSIONS Under the same conditions, the severe heatstroke during 5-km cross-country training is closely related to the descending rates of body temperature, pulse, and blood pressure as well as SaO₂ increased rate within 5 minutes after the training, whose predictive values for severe heatstroke were the same.
Blood Pressure ; Heart Rate ; Heat Stroke ; Hot Temperature ; Humans ; Male ; Risk Factors

Objective: To explore the relationship between physiological parameters changes and severe heatstroke induced by 5-km armed cross-country training. Methods: A total of 521 male officers and soldiers from a special team who participated in the summer training of 5-km armed cross-country training from year 2016 to 2017 were enrolled. All trainees participated in 5-km armed cross-country training in high temperature and humidity environment of ambient temperature > 32 ℃and (or) relative humidity > 65%. The trainees were divided into two groups according to the incidence of severe heatstroke in the course of training. The age, enlistment time, constitution score, body mass index (BMI), external environment (ambient temperature, relative humidity, wind speed, heat index) of trainees of the two groups, and the change rates of arterial blood oxygen saturation (SaO₂), body temperature, pulse and blood pressure within 5 minutes after the 5-km armed cross-country training were compared between the two groups. The risk factors of severe heatstroke were screened by two classified Logistic regression analysis, and the predictive value of various risk factors of severe heatstroke was analyzed by the receiver operator characteristic curve (ROC). Results: In 521 trainees of 5-km armed cross-country training, 29 trainees suffered from severe heatstroke accounting for 5.57%. There was no significant difference in the age, enlistment time, constitution score, BMI, or external environment during 5-km armed cross-country training between severe heatstroke group and non-severe heatstroke group. Compared with those without severe heatstroke, the descending rates of body temperature, pulse, blood pressure and SaO₂ increased rate within 5 minutes after 5-km armed cross-country training of severe heatstroke trainees were significantly decreased [temperature descending rate: (0.67±0.30)% vs. (1.43±1.28)%, pulse descending rate: (7.53±5.21)% vs. (13.48±8.07)%, blood pressure descending rate: (9.28±6.84)% vs. (19.42±7.73)%, SaO₂ increased rate: (0.51±0.39)% vs. (1.50±1.43)%, all P < 0.01]. Two classification Logistic regression analysis showed that the temperature descending rate [odds ratio (OR) = 0.485, 95% confidence interval (95%CI) = 0.289-0.817], pulse descending rate (OR = 0.903, 95%CI = 0.845-0.965), blood pressure descending rate (OR = 0.841, 95%CI = 0.790-0.896), and SaO₂ increased rate (OR = 0.421, 95%CI = 0.250-0.711) were the risk factors for severe heatstroke during 5-km armed cross-country training (all P < 0.01). ROC curve analysis showed that temperature descending rate [area under ROC curve (AUC) = 0.659, 95%CI = 0.604-0.714], pulse descending rate (AUC = 0.730, 95%CI = 0.762-0.900), blood pressure descending rate (AUC = 0.831, 95%CI = 0.659-0.801), SaO₂ increased rate (AUC = 0.711, 95%CI = 0.655-0.767) could be used for the incidence of severe heatstroke prediction during 5-km armed cross-country training (all P < 0.01), and the predicted value was the same. Conclusions Under the same conditions, the severe heatstroke during 5-km cross-country training is closely related to the descending rates of body temperature, pulse, and blood pressure as well as SaO₂ increased rate within 5 minutes after the training, whose predictive values for severe heatstroke were the same.