The Effect of Trunk Muscle Exercise on Cardiopulmonary Resuscitation

Background: The purpose of this study is to nd how trunk muscles mainly used in cardio-pulmonary resuscitation, including pectoralis major, rectus abdominis, and erector spinae, inuence the result of 8-minute when the muscles have six-weeks plank exercise, and to analyze the duration time of exercise effect. Methods: Study subjects were 30 participants taking a relevant course for 24 months. After they had plank exercise for six weeks, they didn't have any exercises including plank exercise for six weeks. As such, the students participated in the 12-weeks program. For chest compression simulation, a practictical mannequin was used. Without any respiration, a single rescuer continued to perform only chest compression for 8 minutes. Results: Regarding their change in a muscle mass by plank exercise, there was a statistically signicant difference in the change from 4th to 8th week after the program (p<.01). The muscle activity change had a statistically signicant difference from 3rd to 10th week (p<.01). The chest compression depth had a statistically signicant difference from 4th to 8th week (p<.01). The chest compression rate didn't had a statistically signicant difference for 12 weeks. In addition, insucient chest relaxation height after compression had a statistically signicant difference from 4th to 10th week(p<.01). The chest compression maintenance time had a statistically signicant difference from 2nd to 12th week (p<.01). Conclusion: If the study subjects have three sets of plank exercise program for ve weeks, which consisted of one set of 10 times of 30-second motion and 20-second rest and does not have up to two weeks of detraining, the plank exercise is considered to be helpful for them in out of hospital cardiac arrest at the time when there is no use of mechanical chest compression device. If p value is less than 0.05, it is dened as statistically signicant.


Background
Currently in korea, two paramedics are in charge of assessment, rst aid and transportation of patients from the eld to the hospital [1]. Except for one ambulance driver, the number of rst aid personnel can be regarded as one paramedic. Therefore, in case of cardiac arrest, one paramedic should perform CPR and all necessary rst aid for an average time of 8 minutes [1]. However, in previous studies, the accuracy of chest compression decreased with increasing chest compression time [2], and it was appropriate to alternate the performers of chest compression two minutes after the onset of chest compression [3]. However, the current situation of the paramedics cannot apply these suggestions in practice. In general, chest compressions by only hands are reported to not provide enough blood ow as a life sustaining organ [4][5]. So an automated mechanical chest compression device is recommended [6][7][8], but it is not owned by 95% of 1,294 ambulances deployed in Korea [1]. In addition, due to personnel problems for the smooth use of mechanical chest compression devices, it is di cult to use in the eld. Therefore, current cardiopulmonary resuscitation for cardiac arrest patients occurring out-of-hospital is forced to use chest compressions by only hands without the help of mechanical compression. Based on the research that mainly uses erector spinae, pectoralis major, rectus abdominis during chest compressions [9], the researcher conducted a plank exercise to train trunk muscles anywhere, without any equipment. The purpose of this study is to investigate the training method and duration of training for more effective chest compression in out-of-hospital cardiac arrest without mechanical chest compression device.

Participants in the Research
The participants of this study were paramedic students who have been in the same curriculum for 24 months. Based on the research by previous [10], G * power 3.0 was used to calculate the effect size 0.5, signi cance level α = .05, and the power 80%. So, 30 people were recruited. The selection criteria were selected as students who do not exercise regularly and who can continue to participate in the program. After receiving the approval of the research committee of Chungnam National University Hospital(No.2015-10-035-005), the subjects were recruited by announcing the explanation of the exercise program. The participants were excluded from the study if they could not perform chest compression due to health reasons or if they did not agree to participate in the experiment. The duration of this study was a schedule of applying a six-week programmed plank exercise based on previous studies [11]. After six weeks of plank exercise, a total of twelve weeks were conducted on a schedule of no exercise, including plank exercise. In order to prevent the participants from feeling uncomfortable, the indoor environment of the test and test sites was maintained at the comfort index to make the surrounding environment comfortable by setting the room temperature to 26 degrees and the humidity to 40% [12].

Research tools and methods
The muscle mass of the study participants was measured using Avis 333® (Jawon medical, Korea), a body composition measurement tool. A total of 13th measurements were recorded. Noraxon Clinical DTS 546® (Noraxon Inc., ARIZONA, USA) was used to determine the muscle activity of the erector spinae, pectoralis major, rectus abdominis and measured using four radiochannel surface electromyograms. The collected EMG digital signal was ltered and other signal processing on the computer using MR-XP Master program (Noraxon Inc., Arizona, USA). The electrode attachment point is Erector Spinae is 6 cm later from L1 spinous process, Pectoralis Major is (sternal portion) horizontally on the chest-wall over the muscle mass that arises (approximately 2 cm out from the axillary fold), Rectus Abdominis is 3 cm later from the umbilicus. Plank exercise was performed in a single posture, maintaining the shoulder angle at 90 degrees based on previous study and no other postural changes were performed. The abdominal drawing-in maneuver was performed after maintaining the lumbar neutral posture. Three sets of one set at 10 times were performed by 30 seconds of exercise and 20 seconds of rest. Performed rest after each set of exercise to prevent fatigue. Chest compression was determined by a single rescuer performing continuous chest compressions only on a mannequin(Resusci Anne simulator®, Laerdal® PC skill reporting system, Stavanger, Norway) for 8 minutes without arti cial respiration. Effective chest compression was de ned as the number of chest compressions between 100 ~ 120 times per minute, chest compression depth of at least 50 ~ 60 mm, and chest compression recoil of the chest to 20 mm. During the experiment, no feedback was provided to the participants.

Statistical analysis
SPSS 21.0 for Windows was used for statistical analysis. The mean and standard deviation was used to analyze con dence in percent error values and bleeding estimation accuracy before and after simulation training. One-way ANOVA was used to analyze subjects' grade differences. If p value is less than 0.05, it is de ned as statistically signi cant.

General Characteristics of Subjects
Thirty participants 16 males(53.33%) and 14 females(46.66%) participated in this study. The average age was 23.33 ± 1.68 years, the average height was 168.00 ± 6.74 cm, and the average weight was 68.53 ± 12.81 kg.

Relation between Muscle Mass, High Quality Depth, Compression Maintenance Time
The correlation coe cient between muscle mass and effective compression depth was .79, which was very high. In other words, the greater the muscle mass, the deeper the depth of effective compression. The correlation coe cient between muscle mass and effective chest compression time was .61. In other words, the more muscle mass, the longer the effective chest compression time (Table 3).

Relation between High Quality Depth, Compression Maintenance Time
The correlation coe cient between effective chest compression depth and effective chest compression maintenance time was .58, which was high. In other words, the maintenance time to compression the chest to the effective depth is increased (Table 4).

Discussion
Six weeks of plank exercise had an effect on muscle mass and muscle activity. In particular, 4 weeks after the start of the plank exercise showed a signi cant effect, and even after stopping the plank exercise showed a signi cant result until 2 weeks. In addition, the pectoralis major, erector spinae and rectus abdominis which are mainly used for chest compressions, had a signi cant effect from 3 weeks after the start of the plank exercise and even after stopping the plank exercise showed a signi cant result until 4 weeks. These results showed the same results as the present study showing the increase in muscle activity in the major muscles including the abdominal muscle in a previously published study of muscle activity during plank exercise [13].
Analyzing the depth of chest compressions of the study participants, it showed a signi cant increase after 5 weeks of starting the plank exercise, and after 3 weeks of stopping the plank exercise, it did not become effective chest compression and continued to decrease afterwards. Although chest compression pro ciency increases with increasing rate of chest compressions, the decrease in chest compression depth after stopping plank exercise is considered to be due to the change of muscle mass following plank exercise. As the activity of trunk muscles, which is mainly used for chest compression, increases the chest compression depth, which is a high level of force, through the plank exercise. In addition, the previous study showed a rapid increase rate from 4 weeks to 6 weeks after the start of exercise. Since then, there is no signi cant change in the increase rate. According to these results, in order to achieve effective chest compression depth through plank exercise, plank exercise should be continued for at least 5 weeks, and should not have a break period of at least 2 weeks. As a result of analyzing the change in the rate of chest compressions, there was no signi cant result about the number of chest compressions by the plank exercise. This is because the depth of chest compression decreases signi cantly over time in several published studies, but the number of chest compressions is relatively free from problems such as physical consumption compared to chest compression. Incomplete chest compression recoil showed the highest duration of exercise in the effect of chest compression through plank exercise. However, 5 weeks after stopping the plank exercise, the incomplete recoil of chest compressions increases again, and it is thought that the plan should be continued for at least 4 weeks for effective chest compressions and there should be no break of at least 4 weeks. As a result of analyzing the chest compression maintenance time, as shown in the result of analyzing the incomplete chest compression rate, the plank exercise seems to be a result of the signi cant improvement of muscle endurance. In addition, the effective chest compression success rate increased signi cantly after 5 weeks of starting exercise, and signi cantly increased after until 2 weeks of stopping exercise. This means that the maintenance time to chest compression has been increased to the chest compression depth recommended by the 2015 AHA Guidelines. The plank exercise not only increased the maintenance time for chest compression, but also increased the maintenance time for effective chest compressions, which is practically helpful for cardiac arrest patients.
The results of this study showed that for effective chest compressions, plank exercise was effective in increasing proper chest compression depth and muscle endurance for chest compressions. Through this, plank exercise is expected to be effective for longterm chest compression, and furthermore, it can reduce muscle fatigue by centering the trunk muscle.
The limitations of this study are rst, the number of study participants is di cult to generalize to 30, and secondly, the use of educational mannequins, it did not accurately re ect the anatomy of the chest. Third, it was that the laboratory was familiar to the participants, not the actual emergency. Fourth, the condition regarding diet that could affect muscles was not considered. Fifth, there is a possibility that psychological factors that subjects can speculate and control the results of research due to continuous experiments. Sixth, the study participants were composed of college students in their twenties and did not re ect the change according to age.
In conclusion, it was found that there was a positive effect on effective chest compressions when the chest compression was performed after training trunk muscles using plank exercise. It is recommended to perform 3 sets of one set(every 10 times for 30 seconds exercise and 20 seconds rest) for 5 weeks as a plank exercise. Unless you have a period of up to two weeks of inactivity, it may be helpful in out-of-hospital cardiac arrest situations where mechanical chest compressions are not available. The study was approved by the ethical committee of Chungnam National University Hospital with ethical code number 2015-10-035-005. The written informed consent was obtained from all participants. In the form, the participants had given their consent for publishing the study data. They were informed that their names and characteristics will not be published.

Consent for publication
Not applicable.

Availability of data and material
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Competing interests
The authors declare that they have no competing interests.

Funding
This research received no external funding.
Authors' contributions YHM participated in the design of the study, acquisition and analysis of the data and writing of the manuscript. KGY contributed in writing the manuscript. KJW and KYS veri ed the analytical methods and contributed to the interpretation of the results. All authors read and approved the nal version of the submitted manuscript.