Effect Of Endurance Training With Different Intensities On The Autonomic Nervous System And Its Significance In Preventing Acute Mountain Sickness

Objective This study examined the effect of endurance training with different intensities on the autonomic nervous system(ANS) and its significance in preventing acute mountain sickness(AMS) so as to provide the troops who will be on a military mission at high altitude with a good fitness training project based on scientific theory.Methodsâ… .Field research of acute ascent to Tibet high altitude from plain.99 healthy male recruits were transported by airplane from Shuangliu,Sichuan(560m in altitude) to Lhasa,Tibet(3675 m in altitude).In plain and on day 4 in Tibet,subjects were tested in their grip strength,4×10 meter shuttle run and step test index.Besides their plasma lactic acid was measured after the step test.In plain and on day 2-4 in Tibet,their ANS was examined by means of 5min heart rate variability(HRV) and cold pressor test (CPT).On day 1-5 in Tibet,symptoms of the subjects were scored in accordance with principles of diagnosis and treatment of benign form of acute mountain sickness (GJB1098-91).According to their AMS symptomatic scores on day 1 in Tibet,subjects were divided into four groups:moderate to severe AMS,mild AMS,nearly non-AMS group and non-AMS group.â…¡.Study on the effect of endurance training with different intensities in plain on ANS.72 healthy male recruits were randomly divided into current military drill group(n= 24),aerobic endurance group(n=24) and anaerobic endurance group(n=24).They were trained according to different exercise programs for 8 weeks.Before the training,at the end of week 4 and at the end of week 8,subjects were tested in step test index,VO2max, PWC₁₅₀,3000m and 50m running.HRV,CPT and head-up tilt test(HUTT) were also measured to examine their ANS function.Before and after the training plasma concentration of Epinephrine(EPI),Norepinephrine(NE),renin activity(PRA) and neuropeptide Y(NPY) were analyzed.â…¢.Study on acute exposure to a simulated altitude of 4500m after endurance training with different intensities.In the 5^th to 8^th day after training,43 trained recruits were exposed to a simulated altitude of 4500m in a hypobaric chamber for 24 hours(h) by 3 terms.HRV,rest HR and BP were measured 2h,10h and 20h after the beginning of exposure and CPT was performed 4h after the beginning of exposure.Plasma concentration of EPI,NE,NPY and PRA were analyzed at the end of the exposure.Their symptoms were scored according to principles of diagnosis and treatment of benign form of acute mountain sickness(GJB1098-91).In addition,their psychological scores were evaluated.Resultsâ… .Field research of acute ascent to Tibet high altitude from plain.1.Physical ability and the incidence of AMSâ‘ Compared with those in plain,their shuttle running speed and blood lactic acid were significantly decreased on day 4 in Tibet(both P＜0.01).â‘¡AMS occurred mainly on day 1 in Tibet,Of the 99 subjects,9 made up the moderate to severe AMS group;33 made up the mild AMS group;50 made up the nearly non-AMS group;and 7 made up the non-AMS group.2.The function of ANSâ‘ Compared to those of plain,SDNN,RMSSD,PNN₅₀,HF,HFn decreased and LFn,LF/HF,HR increased significantly(all P＜0.01) after acute exposure to high altitude,TP decreased significantly(P＜0.05),too.At high altitude,the increase of BP,HR during CPT were decreased significantly(P＜0.01).â‘¡In the for different groups,AMS scores from high to low accompanied the trend of LF/HF,LFn decreasing and HFn increasing both in plain and at high altitude.Subjects in the three AMS groups have markedly higher SBP in plain(P＜0.05) and higher HR at high altitude than non-AMS.In plain,the more HR increased during CPT,the lower AMS scores were,and the increase in HR of the moderate to severe groups was significantly lower than that of nearly non-AMS group(P＜0.05).At high altitude the increase in the SBP and HR of the three AMS groups was significantly lower than that of the non-AMS group(all P＜0.05); the increase in DBP was lower than that of non-AMS group,too;the difference between the mild AMS group and non-AMS group was of statistical significance(P＜0.05).3.Correlation analysis In plain,AMS scores were negatively correlated with the concentration of plasma lactic acid after the step test(r= 0.469,P= 0.001) and the increase in HR during CPT(r=-0.35,P=0.01),but positively correlated with LF/HF(r=O.437,P= 0.00);the concentration of plasma lactic acid after the step test was weakly correlated with the increase in HR during CPT(r=0.31,P=0.51).â…¡.Study on the effect of endurance training with different intensities on ANS in plain.1.EnduranceWhen the subjects were exercising,the HRs of aerobic endurance group,anaerobic endurance group and the current military drill group were about 140～160bpm,170～180bpm and above 180bpm respectively.Compared with those before the training,their 50m and 3000m running achievement,VO₂max,step test index and PWC₁₅₀ were significantly increased as time went by.At the end of week 8 the step test index,VO₂max and 3000m running achievement of aerobic endurance group were significantly higher than those of current military drill group(P＜0.05 or 0.01);the step test index and 50m running achievement of the anaerobic endurance group were much higher than those of the current military drill group(P＜0.05);noticeable difference on PWC₁₅₀ was not found among the three groups.2.The function of ANSâ‘ HRV1) Compared with those before training,PNN₅₀ and LF increased significantly(P＜0.05) but HR deceased markedly only in aerobic endurance group at the end of week 4(P＜0.01). However,to the end of week 8,HR decreased noticeably in three groups(all P＜0.01); RMSSD,PNN₅₀,HF,SDNN and LF of aerobic endurance group increased significantly(all P＜0.01),and HFn tended to increase while LFn and LF/HF tended to decrease;HFn of the current military drill group decreased markedly while their LF,LFn and LF/HF increased significantly(all P＜0.05);the anaerobic endurance group didn't demonstrate marked change in the above-mentioned parameters.2) At the end of week 8,RMSSD,PNN₅₀,HF,LF and SDNN of the aerobic endurance group were significantly higher than those of the other two groups(P＜0.01 or 0.05);HFn of the current military drill group was much lower than that of the aerobic endurance group while their LFn and LF/HF were markedly higher than those of the latter group(P＜0.05);LF/HF of the anaerobic endurance group was much higher than that of the aerobic endurance group(P＜0.05).â‘¡CPT and HUTT1) Compared with the record before training,HR in three groups tended to decrease at the end of week 4 and 8 and obvious change of SBP was not found in them;DBP of the anaerobic endurance group tended to decrease while that of the aerobic endurance group decreased significantly(P＜0.01).Marked change was not found in the SBP and DBP of each group during CPT.HR displayed a significant increase in the current military drill group(P＜0.05),a slight increase in the aerobic endurance group and a marked decrease in the anaerobic endurance group(P＜0.05).At the end of week 8 the increase of HR in anaerobic endurance group during CPT was much lower than that of the current military drill group and aerobic endurance group(all P＜0.05).2) HUTT positive cases in the current military drill group increased at the end of week 8, which was not statistically significant.3.Biochemical indices in bloodCompared with those before training,at the end of week 8 plasma concentration of NE and NPY decreased significantly in all groups(P＜0.05 or 0.01).PRA displayed a tendency to increase in the current military drill group,a marked decrease in the aerobic endurance group(P＜0.05) and a tendency to decrease in the anaerobic endurance group.NE and PRA in aerobic and anaerobic endurance groups were significantly lower than those of the current military drill group(P＜0.01).â…¢.Study on simulated exposure to high altitude after endurance training different intensities.1.ANS functionâ‘ HRV In the 24h of acute exposure to a simulated of 4500m,RMSSD and PNN₅₀ displayed a marked decrease in the current military drill group and aerobic endurance group(P＜0.01 or 0.05) but a decrease and then an increase in the anaerobic endurance group. HFn and LFn in each group tended to decrease and then increase.The increase in HFn began 10h after exposure in anaerobic endurance group but 20h after exposure in the other two groups.LF/HF of aerobic endurance group tended to decrease and then increase,while that of the anaerobic endurance group and current military drill group tended to change in the opposite way;LF/HF in the anaerobic endurance group began to decrease 10h after exposure and almost recovered to the state before exposure at 20h when LF/HF in current military drill group was still increasing;SDNN and TP of current military drill group and aerobic endurance group decreased significantly(P＜0.05) or displayed a tendency to decrease,but marked change was not found in the anaerobic endurance group.â‘¡CPT Compared with those before exposure,resting HR in the three groups increased significantly 4h after exposure(P＜0.01) but marked change was not found in resting SBP;DBP of anaerobic endurance group increased significantly(P＜0.05) and that of current military drill group and aerobic endurance group displayed a tendency to increase; the increase in the SBP,DBP and HR of the current military drill group and aerobic endurance group during CPT tended to decrease,but that of the anaerobic endurance group was relatively stable or tended to increase.2.Biochemical indices in blood Compared with that before exposure,plasma NE concentration decreased significantly in the three groups 24h after acute exposure to a simulated altitude of 4500m(P＜0.01 or 0.05) and the decrease of plasma NE concentration of aerobic and anaerobic endurance groups was much less than that of the current military drill group(P＜0.05);compared with that before exposure,Plasma EPI concentration of the current military drill group and aerobic endurance group increased significantly but marked change was not found in the anaerobic endurance group(P＜0.01).PRA of the current military drill group and anaerobic endurance group decreased significantly(P＜0.01) and that of the aerobic endurance group tended to decrease;but the decrease in the current military drill group was larger than that in the other two groups(P＜0.01).NPY of the current military drill group and aerobic endurance group tended to decrease while that of the anaerobic endurance group tended to increase.3.AMS and psychological scores The incidence of AMS was 100%.AMS scores of current military drill group were higher than those of aerobic endurance group,which were in turn higher than those of anaerobic endurance group;furthermore AMS scores of current military drill group were much higher than those of anaerobic endurance group(P＜0.05). Marked difference on psychological marking was not found among the three groups,but AMS scores of current military drill group and aerobic endurance group were positively correlated with the psychological marking(r was 0.77 and 0.68,all P＜0.01).4.Correlation analysis Significant positive correlation was found between AMS scores and plasma concentration of NE,PRA and NPY before exposure to high altitude as well as the change of NE and PRA before and after exposure s(P＜0.05).1 Oh and 20h after acute exposure to simulated high altitude,AMS scores were strongly positively correlated with LF/ HF but strongly negatively correlated with SDNN,RMSSD,PNN₅₀ and HFn (P＜0.01 or 0.05).Conclusion1.ANS played an important role in AMS pathogenesis.Subjects with relatively enhanced sympathetic nervous activity(SNA) in plain were more predisposed to AMS; Subjects with severe symptoms were those whose SNA and parasympathetic nervous activity(PNA) were significantly suppressed and continuously predominant sympathetic nervous system.Thus measurement of ANS function in plain or after acute exposure to high altitude helped predict or diagnose AMS.2.Current military drill approximated the utmost of their physical ability,but it was less effective in improving their drill achievement and physical stamina when compared with scientific aerobic and anaerobic endurance training.Thus scientific and reasonable aerobic and anaerobic endurance training should be applied to the military drill.3.Current military drill and aerobic endurance training suppressed ANS regulation,for the former relatively enhanced SNA while the latter relatively enhanced PNA.They did not help for acclimatization for acute expoure to high altitude.However,anaerobic endurance training sustained the ANS' function stabilization and enhanced its regulating ability,which was conducive to improve their adaptability to acute exposure to high altitude.