Effects Of Respiratory Muscle Training On Athletes’ Respiratory Muscle Function And Sports Performance:a Systematic Review And Meta-analysis

Objective:To systematically appraise the impact of respiratory muscle training(RMT)on the respiratory muscle function,pulmonary ventilation function,and sports performance of athletes by using the Meta analysis method to further grasp the mechanism of RMT’s impact on sports performance.Through the statistical analysis of the existing evidences,the most suitable program for respiratory muscle training is summarized,which provides strong evidence support for the practical application of RMT in athletes.Methods:Applying the inclusion and exclusion criteria of this study were performed with the PICOS principle of Cochrane systematic review.Searches in four databases(PubMed,Web of Science,EBSCO,CNKI,Wanfang databases),and collected randomized controlled trials(RCTs)on the impact of RMT on athletes’respiratory muscle function,lung ventilation function,and performance up to June 2020 were completed.Two review authors independently selected the literature and extracted the data and assessed the risk of bias and methodological quality for all included trails using the RCT bias risk assessment tool.The meta-analysis was carried out using the Stata version 16.0 and RevMan version5.4 software which including heterogeneity,data merging,subgroup analysis,sensitivity analysis and Meta regression analysis.The funnel chart was drawn,Egger and Begg test was used to quantify publication bias.Power analyses for the test of null hypothesis in this research were performed using the G*Power3.1 softwareResults:Thirty one trails involving 610 average and high-level athletes in various events revealed significance different among groups in favour of the intervention group(RMT)on maximum inspiratory pressure(MIP)[MD=27.93,95%CI[21.12,34.75],P<0.01],forced vital capacity(FVC)[MD=0.13,95%CI[0.03,0.23],P<0.05]maximum voluntary ventilation(MVV)[MD=7.65,95%CI[1.86,13.44],P<0.05],time trail(TT)[d=-0.53,95%CI[-0.77,-0.29],P<0.01].The difference of expiratory volume in one second(FEV1.0)[MD=0.11,95%CI[-0.01,0.22],P>0.05]was not statistically significant.Meta regression analysis found that training duration was the main cause of the heterogeneity between studies.The specific performance is that the influence of inspiratory pressure threshold load training on MIP reaches a very significant level(P<0.01),the training effect of 8-12 weeks is better than that of 4-6 weeks,and the training frequency of 5-7 days/week is better 2-4 days/week.In terms of pulmonary ventilation,in favour of intervention of the voluntary isocapnic hyperpnea training on FEV1.0 and MVV(P<0.05),and the influence of inspiratory muscle pressure threshold load training on FVC reached a very significant level(P<0.01).In view of sports performance,no significant difference were observed when compared of general and high-level athletes in TT.A subgroup analysis of sports events found that RMT only improved the TT of swimming athletes with small effects(d=0.34),while athletes of other events reached medium effects size.The main outcomes,MIP and TT,have test powers of 100%and 99%,respectively,while the test powers of FVC,FEV1.0,and MVV are all lower than 80%.Conclusion:RMT can improve the MIP of athletes at diverse levels.IPTL training with the duration of 8-12 weeks and a training frequency of 5-7 days/week is more likely to achieve ideal training effects.Voluntary isocapnic hyperpnea training requires athletes to maintain a high level of ventilation for a long time,therefore,the stimulation of lung ventilation function is more profound.RMT can improve the performance of athletes in different sports,its main influence mechanism on exercise performance is:by promoting the growth of MIP,it can then increase the exercise economy of the respiratory muscles and the metaboreflex threshold,and reduce the demand of VO2 and blood of respiratory muscles during high-intensity race,which lead to improve the blood flow and oxygenation capacity of the limb locomotor muscle.In addition,the decrease of RPE level during exercise and the regulation of cytokine release by RMT can also explain the improvement of exercise performance to a certain extent.