Effects of 4-Week Inspiratory Muscle Training on Sport Performance in College 800-Meter Track Runners

ackground and objectives:Respiratory muscle fatigue is one of the important factors limiting sports performance due to the metabore ex. This re ex will cause a decrease in blood ow to the extremities and accelerate exercising limb fatigue. Previous studies found that inspiratory muscle training (IMT) can effectively enhance the respiratory muscle endurance and reduce fatigue during long-duration exercise or aerobic exercise, thereby enhancing athletic performance. However, the mechanism between inspiratory muscle strength, change of limb blood ow and sports performance still requires investigation, especially in short-duration exercise, anaerobic or both aerobic and anaerobic exercise. The purpose of this study was to investigate the effects of 4-week

effectively enhance the respiratory muscle endurance and reduce fatigue during long-duration exercise or aerobic exercise, thereby enhancing athletic performance. However, the mechanism between inspiratory muscle strength, change of limb blood ow and sports performance still requires investigation, especially in short-duration exercise, anaerobic or both aerobic and anaerobic exercise. The purpose of this study was to investigate the effects of 4-week inspiratory muscle training on respiratory muscle strength, limb blood ow change rate and sports performance in recreational 800-m college runners.Materials and Methods:Twenty healthy 800-m college runners randomized into the IMT group (11 subjects) and control group (9 subjects). IMT consisted of 30 inspiratory efforts twice daily, 5 days a week, with intensity at 50%, 60%, 70% and 80% of maximum inspiratory pressure (MIP) for 4 weeks, while a control group kept 50% of MIP for 4 weeks. An 800-m trial test, limb blood ow change rate by using Impedance Plethysmography, and MIP were as the outcome measured variables and be evaluated. All measured variables were assessed before and after 4-week IMT training. Two-way ANOVA was conducted for statistical analysis.Results:The results showed signi cantly interaction between groups and pre-posttest. IMT group signi cantly decreased limb blood ow change rate from 19.91 11.65% to 9.63 7.62% after received the IMT training program (p< 0.05). The MIP signi cantly improved from 112.95 27.13 cmH 2O to 131.09 28.20 cm H 2O in IMT group, and the 800-m trial test also shorted the running time from 162.97 24.96 s to 156.75 20.73 s. But the control group no signi cantly changed in MIP and 800-m trial test.Conclusions:Our results indicated that the 4-week IMT training (twice a day, 5 days a week) signi cantly improves participants' inspiratory muscle strength, 800-m running performance and decreases the limb blood ow change rate. Keywords:respiratory muscle capability; athletic performance; muscle fatigue 1. Introduction Jogging has become one of the popular activities and aerobic exercise in the worldwide recently. As an aerobic-based exercise, cardiopulmonary endurance and respiratory muscle Medicina2021,57, 72.

limb blood ow change rate. Keywords:respiratory muscle capability; athletic performance; muscle fatigue 1. Introduction Jogging has become one of the popular activities and aerobic exercise in the worldwide recently. As an aerobic-based exercise, cardiopulmonary endurance and respiratory muscle Medicina2021,57, 72.

Medicina2021,57, 72 2 of 8 strength are fundamentally required and should develop to enhance cardiorespiratory health. The diaphragm, one of the respiratory muscles, is essential to and functions as the skeletal muscles for respiratory movement [1,2]. While individuals engage in high-intensity exercise or experience a period of effort, the fatigue of respiratory muscles will re exly increase sympathetic vasoconstrictor activity and vasoconstriction of the vasculature of the exercising limb, as a result, blood ow cannot reach the muscles of the limbs [3–6]. Therefore, insuf cient blood ow in limbs decreases the oxygen exchange rate and increases the feelings of soreness and discomfort, thereby affecting their sports performance. According previous studies, during constant-load exercise, the work of respiratory muscle was reduced about 60% by proportional assisting ventilation, and end-exercise quadriceps fatigue decreased by 25–30% compared with the control group [7]. Furthermore, during constant-load leg cycling (adding supplemental O2 to the inspired air), when exercise-induced arterial desaturation was prevented, it was found that quadriceps fatigue was nearly 50% less compared with the control group [8]. Thus, training for the respiratory muscles may extend the period of fatigue, thereby improving sports performance, balance of arterial blood, gas and acid–base [9]. From the athletic perspective, previous studies have indicated that inspiratory muscle training (IMT) signi cantly reduces fatigue and improves athletic performance. Johnson and colleagues [10] used the threshold IMT (PowerBreathe ®® ) (POWERbreathe Interna- tional Ltd., England, UK) intervention for 6 weeks on cyclists. Their results indicated that after six weeks of training, the endurance the continuous power output increased and cycling performance improved. The same results were found in Romer and colleagues' work [11]. In this study, sixteen trained cyclists were randomly assigned into IMT group and sham IMP group and received 6-week IMT training. The pulmonary function and 20 and 40 km time-trial performance were measured. The result improved the 20 and 40 km time-trial performance and pulmonary function. Kilding et al. also investigated the IMT effect on 16 competitive club-level swimmers. Their results also are similar those previous studies. Their results indicated that decreased the timing in the 100 m

6-week IMT training. The pulmonary function and 20 and 40 km time-trial performance were measured. The result improved the 20 and 40 km time-trial performance and pulmonary function. Kilding et al. also investigated the IMT effect on 16 competitive club-level swimmers. Their results also are similar those previous studies. Their results indicated that decreased the timing in the 100 m swim by 1.7% and in 200 m swim by 1.5% [12]. In addition, Volianitis and colleagues [13] conducted an 11-week of threshold IMT (PowerBreathe ®® ) on elite female rowers. Their results of the maximum inspiratory pressure in the IMT group were signi cantly higher than in the control group. It can be seen that IMT can improve respiratory muscle strength and sports performance. In past studies, the exercises for respiratory muscle training included running, swim- ming, and cycling [14–16]. Most of them focused on long-distance and aerobic exercise. However, there were fewer studies on respiratory muscle training for middle-distance and short-distance sports. Middle-distance running events include 800 m and 1500 m. The 800-m and 1500 m distance are the sport that includes both aerobic and anaerobic exercise event. A study for 1500 m runners has proved that respiratory muscle training can increase respiratory muscle strength and improve athletic performance [15]. However, the distance of 800 m is shorter than the distance of 1500 m. In terms of exercise physiology, it tends to more anaerobic exercise [1,2,14]. It is doubtful whether the effect of respiratory muscle training is as same as 1500 m distance. However, previous studies related IMT effect have focus on long-duration exercise. Few studies investigate the effect of IMT on shorter distance sports, like 800-m distance run. Brown and Kilding found that the occurrence of inspiratory muscle fatigue after a short-duration front crawl swim exercise [14]. Ohya et al. also reported that shorter- duration running exercise would induce inspiratory muscle fatigue [17]. Therefore, there is a need to better understand whether respiratory muscle training is helpful for middle distance events, like 800-m distance run. Further investigation is still needed to stablish the possible mechanism. Hence, the purpose

fatigue after a short-duration front crawl swim exercise [14]. Ohya et al. also reported that shorter- duration running exercise would induce inspiratory muscle fatigue [17]. Therefore, there is a need to better understand whether respiratory muscle training is helpful for middle distance events, like 800-m distance run. Further investigation is still needed to stablish the possible mechanism. Hence, the purpose of the study was to investigate the effects of 4-week inspiratory muscle training on respiratory muscle strength, limb blood ow change rate and sports performance in recreational college 800-m track runners. The research hypothesis was 4-week inspiratory muscle training increased respiratory muscle strength, decreased the limb blood ow change rate and improve 800-m sport performance.

Medicina2021,57, 72 3 of 8 2. Materials and Methods 2.1. Study Design and Participants This study was conducted with a two group compared, pre and post- test design. Ac- cording to the basic statistical power requirement from a previous study [18], the minimum number of subjects in each group should be at least 8. Finally, twenty-two recreational 800-m college runners from the track and eld Team of the university were recruited. After randomization of the IMT group and control group, two participants dropped out of the control group. Participants were recruited by nding athletes who had trained at least three times per week for a minimum of 60 min and were able to nish the full experi- ment. Moreover, three exclusive criteria were applied: (1) present or past cardiovascular, pulmonary and neurological disease; (2) smoker; (3) allergies to electro-conductive pads. All participants were informed of the study procedure and signed the informed consent form before the experiment. The present study was also approved by the Institutional Review Board of China Medical University Hospital in Taiwan (CRREC-102-027, 17 June, 2014). Table difference was found between the IMT group and the control group. Table 1.The detailed information of the participants (N= 20). Anthropological Information IMT Group (N= 11) Mean SD Control Group (N= 9) Mean SD p-Value Gender (M:F) 8:3 6:3 0.10 Age, years 21.64 2.06 20.78 1.48 0.31 Height, cm 170.59 6.7 172.33 9.94 0.64 Weight, kg 61.46 6.92 63.39 14.33 0.69 Abbreviations: SD, standard deviation. 2.2. Procedure Baseline data of the inspiratory muscle training (MIP) test, blood ow test and 800 m time-trial test were collected from all participants before inspiratory muscle training in- tervention. After Baseline data collection, all participants take a day's rest, the training group started a 4-week inspiratory muscle training and the control group started placebo training. Both groups did the same skill training and weight training for 4 weeks. All participants repeated data collection from MIP test, blood ow test, and 800 m time-trial test immediately after 4-week IMT. The procedure ow list in Figure.Medicina 2021, 57, x FOR PEER REVIEW 4 of 9 Figure

4-week inspiratory muscle training and the control group started placebo training. Both groups did the same skill training and weight training for 4 weeks. All participants repeated data collection from MIP test, blood ow test, and 800 m time-trial test immediately after 4-week IMT. The procedure ow list in Figure.Medicina 2021, 57, x FOR PEER REVIEW 4 of 9 Figure 1. Experimental Procedure. 2.3. Measurements 2.3.1. Maximal Inspiratory Pressure (MIP) Assessment The MIP assessment in the present study was measured by the MicroRPM (Micro Medical/CareFusion, Kent, United Kingdom) with inserted the PUMA PC Software (Mi- cro Medical, Kent, England) in the laptop. The PUMA PC software works with the Mi- croRPM Respiratory Pressure Meter to measure respiratory muscle strength and calcu- lated the MIP from the one-second average maximum pressure. During the test, the par- ticipants should be sitting, then the investigator explained the MicroRPM device usage procedure to the participants. When performed the MIP assessments, participants were asked to exhale slowly and completely first with sealed lips around the mouthpiece, and then inhale hard rapidly. The investigators record the data for the largest value which show on the MicroRPM and its software. Participants were allowed to rest between each trial for 1 min and were asked to repeat the protocol 5 times [19]. Accord to the previous study, the MicroRPM reliably measured MIP [20]. 2.3.2. Limb Blood Flow Assessment Impedance Plethysmography RheoScreen compact (Medis, Ilmenau, Germany) was used to evaluate limb blood flow. The device had been calibrated and guaranteed high quality of the recorded signal, as well as high reproducibility [21]. The test used measure- ment by a four-electrode technique. The two outer electrodes were used to apply the cur- rent, and the two inner electrodes were used for delineating the quadriceps under meas- urement (Figure 2). To clearly assess limb blood flow change rate among the participants, every single assessment was conducted 2 times and cooperated with the respiratory muscle fatigue induction. After the first blood flow assessment, the participants were asked to breathe in, maintaining 60% of inspiration pressure by the POWERbreathe respiratory training de- vice.

for delineating the quadriceps under meas- urement (Figure 2). To clearly assess limb blood flow change rate among the participants, every single assessment was conducted 2 times and cooperated with the respiratory muscle fatigue induction. After the first blood flow assessment, the participants were asked to breathe in, maintaining 60% of inspiration pressure by the POWERbreathe respiratory training de- vice. The intensity of the inspiration pressure was based on the MIP assessment, and the time ratio of inspiration and expiration was 1:2. Participants were encouraged to maintain their breath. Once the participant failed to maintain the inspiration pressure more than 2 times, the process was ended. Then, the lower limbs’ blood flow was immediately meas- ured. The limb blood flow change rate were calculated the value of the second test minus the value of the first test, then divided by the value of the first test, and multiplied by 100%. 22 subjects (pre-test) •MIP test •blood flow test •800-m time- trial test Randomlize to •IMT Training group (N=10) •Control group (N=10) •Two participated drop out by screening exclusive criteria 4 weeks IMT training intervention •IMT Training group (intensity: 50%-60%-70%- 80% of MIP) •Control group (intensity:50% of MIP) 20 subjects (post-test) •MIP test •blood flow test •800-m time- trial test Figure 1.Experimental Procedure. 2.3. Measurements 2.3.1. Maximal Inspiratory Pressure (MIP) Assessment The MIP assessment in the present study was measured by the MicroRPM (Micro Medical/CareFusion, Kent, United Kingdom) with inserted the PUMA PC Software (Micro Medical, Kent, England) in the laptop. The PUMA PC software works with the MicroRPM

Medicina2021,57, 72 4 of 8 Respiratory Pressure Meter to measure respiratory muscle strength and calculated the MIP from the one-second average maximum pressure. During the test, the participants should be sitting, then the investigator explained the MicroRPM device usage procedure to the participants. When performed the MIP assessments, participants were asked to exhale slowly and completely rst with sealed lips around the mouthpiece, and then inhale hard rapidly. The investigators record the data for the largest value which show on the MicroRPM and its software. Participants were allowed to rest between each trial for 1 min and were asked to repeat the protocol 5 times [19]. Accord to the previous study, the MicroRPM reliably measured MIP [20]. 2.3.2. Limb Blood Flow Assessment Impedance Plethysmography RheoScreen compact (Medis, Ilmenau, Germany) was used to evaluate limb blood ow. The device had been calibrated and guaranteed high qual- ity of the recorded signal, as well as high reproducibility [21]. The test used measurement by a four-electrode technique. The two outer electrodes were used to apply the current, and the two inner electrodes were used for delineating the quadriceps under measurement (Figure).Medicina 2021, 57, x FOR PEER REVIEW 5 of 9 Figure 2. The location of electrodes (a) and equipment (b) during the limb blood flow measure- ment. 2.3.3. Athletic Performance Assessment An 800-m time trial test was used as the athletic performance assessment and was carried out before and after four-week respiratory muscle training. According to studies from Hanon et al. and Ohya et al., the 800-m track running created a state of imbalance within the body, a decline in blood pH and the excessive functioning of certain compart- ments, which leads the body to exhaustion and respiratory muscle fatigue [17,22]. There- fore, this athletic performance test can be used as an outcome measured variable of the effectiveness of respiratory muscle training. Before the 800-m time trial test, the partici- pates warmed up for 5 min and then performed the test on the athletic track on campus. During the test, they ran 800 m on the track and recorded the time with a

this athletic performance test can be used as an outcome measured variable of the effectiveness of respiratory muscle training. Before the 800-m time trial test, the partici- pates warmed up for 5 min and then performed the test on the athletic track on campus. During the test, they ran 800 m on the track and recorded the time with a timer. 2.4. Interventions of Respiratory Muscle Training This study adopted a resistance-adjustable electronic respiratory training device called POWERbreathe K2 (POWERbreathe International Ltd., England, UK) for the train- ing intervention. Initially, the participants were asked to hold the disposable air nozzle with their mouth and applied a nose clip to prevent ventilation through the nasal passage. When the primary setting was done, the participants were allowed to start breathing fol- lowing the signals from the device and the investigators. The device provided resistance during inhalation while recording inspirational pressure. Participants were allowed to discontinue instantly once they felt any discomfort. This intervention was completed twice a day, 5 days a week for the IMT group. The training intensity was progressively set at 50%, 60%, 70% and 80% of MIP for weeks 1, 2, 3 and 4, respectively. Further, the control group was required to keep at the level of 50% MIP for 4 weeks. 2.5. Statistical Analyses The Statistical Package for Social Sciences (SPSS 20, SPSS Inc., Chicago, IL, USA) soft- ware was used for the statistical analysis. The participants’ anthropological information was first described, with the independent sample t-test and chi-square test in order to compare the group differences. The normality of variables was evaluated with the Shapiro–Wilk test. Subsequently, two-way ANOVA was conducted for the pre- and post- test results and group comparison. Data are presented as mean and standard deviation for continuous variables and as ratios for nominal variables. A significance level of α = 0.05 was adopted Figure 2. The location of electrodes (a) and equipment (b) during the limb blood ow measurement. To clearly assess limb blood ow change rate among the participants, every single assessment was conducted 2 times and cooperated with the respiratory muscle

standard deviation for continuous variables and as ratios for nominal variables. A significance level of α = 0.05 was adopted Figure 2. The location of electrodes (a) and equipment (b) during the limb blood ow measurement. To clearly assess limb blood ow change rate among the participants, every single assessment was conducted 2 times and cooperated with the respiratory muscle fatigue induction. After the rst blood ow assessment, the participants were asked to breathe in, maintaining 60% of inspiration pressure by the POWERbreathe respiratory training device. The intensity of the inspiration pressure was based on the MIP assessment, and the time ratio of inspiration and expiration was 1:2. Participants were encouraged to maintain their breath. Once the participant failed to maintain the inspiration pressure more than 2 times, the process was ended. Then, the lower limbs' blood ow was immediately measured. The limb blood ow change rate were calculated the value of the second test minus the value of the rst test, then divided by the value of the rst test, and multiplied by 100%. 2.3.3. Athletic Performance Assessment An 800-m time trial test was used as the athletic performance assessment and was car- ried out before and after four-week respiratory muscle training. According to studies from Hanon et al. and Ohya et al., the 800-m track running created a state of imbalance within the body, a decline in blood pH and the excessive functioning of certain compartments, which leads the body to exhaustion and respiratory muscle fatigue [17,22]. Therefore, this athletic performance test can be used as an outcome measured variable of the effectiveness of respiratory muscle training. Before the 800-m time trial test, the participates warmed

4-week inspiratory muscle training improves respiratory muscle strength and 800-m running performance.