Immediate changes in chest mobility and trunk muscle activity during pelvic tilt following different trunk muscle exercises

Abstract

BACKGROUND:

Given the characteristics of the superficial trunk muscles that cross the chest and pelvis, their excessive contraction might limit chest mobility.

OBJECTIVE:

To examine the immediate effects of two types of trunk muscle exercises on chest mobility and trunk muscle activities.

METHODS:

Fourteen healthy men (age: 21.1 $\pm$ 1.0 years, height: 172.7 $\pm$ 5.6 cm, weight: 61.0 $\pm$ 7.1 kg, body mass index: 20.4 $\pm$ 1.7 kg/m ${}^{2}$ ; mean $\pm$ SD) randomly performed trunk side flexion and draw-in exercises using a cross-over design. The chest kinematic data and trunk muscle activities were measured before and after each intervention during the following tasks: maximum inspiration/expiration and maximum pelvic anterior/posterior tilt while standing. Two-way repeated measures analysis of variance was used for statistical analysis ( $P<$ 0.05).

RESULTS:

After the side flexion, upper and lower chest mobility significantly decreased, and superficial trunk muscle activity significantly increased during the maximum pelvic anterior tilt ( $P<$ 0.05). Additionally, after the draw-in, upper chest mobility significantly increased during the maximum pelvic anterior tilt ( $P<$ 0.05).

CONCLUSIONS:

Increased activity of the superficial abdominal muscles might limit chest mobility during maximum pelvic anterior tilt. Conversely, the facilitation of deep trunk muscles might increase upper chest mobility during the maximum pelvic anterior tilt.

Keywords

Electromyography thorax thoracic wall rib cage torso kinematics

1. Introduction

Various functions of the trunk muscles have been reported, including those involved in breathing, spinal conditions, and chest conditions [1, 2, 3, 4, 5], for which clinicians have traditionally focused on trunk muscle exercises. In this context, Ninane et al. [1, 2] reported that transverse abdominis activity increases during the expiration of patients with chronic obstructive pulmonary disease. Hodges et al. [3] reported that the diaphragm and abdominal muscles are relatively involved in the respiratory function and regulated the intra-abdominal pressure (IAP), i.e., increased IAP indicates increased spinal rigidity [4]. Additionally, Lanza et al. [5] suggested that the maximal inspiratory pressure and forced vital capacity are closely related to the respiratory muscles, and the most common factor that influences chest shape changes is respiratory muscles [5]. Thus, the muscles of the trunk, which involves the respiratory muscles, are associated with respiratory conditions, chest mobility, and spinal rigidity. Furthermore, Suzuki et al. [6] reported that chest extension may contribute to reduced mechanical demand in the glenohumeral joint during throwing, which can potentially reduce shoulder injuries. Considering these reports, the deterioration of trunk muscle functions might negatively influence chest mobility during physical performance.

The trunk muscles have been divided into superficial trunk muscles (originated from and inserted in the chest and pelvis) and deep trunk muscles (i.e., the lumbar intervertebral region) [7]. Exercises that improve trunk function include conventional exercise, which repeats the trunk movement, and core exercise, which facilitates deep muscle functions [8, 9, 10, 11, 12, 13]. A study has suggested that various trunk muscle exercises improve pain, physical function, and muscle strength [14]. The draw-in maneuver is a core exercise in which contraction of the lower abdomen is performed without changing the pelvic or spinal alignment; this exercise facilitates the activity of the transverse abdominis while suppressing the trunk global muscle activity. It has also been reported to improve the stability of the lumbar intervertebral region during postural control, decrease chronic low back pain, and improve the feedforward function [8, 9, 10, 11]. Conversely, conventional trunk exercises comprise trunk flexion, extension, side bending, and rotation repetition. Their effects have been reported to promote the development of global muscle strength, improve muscle endurance [12], and regulate the trunk muscles, which is important for spinal stability [13]. Although such findings have been commonly reported, considering the characteristics of the superficial trunk muscles that cross the chest and pelvis, excessive contraction of the superficial trunk muscles might limit the chest mobility. Therefore, the null hypothesis states that global muscle-dominant exercises do not limit the chest and pelvic mobility, whereas the alternative hypothesis states that the global muscle-dominant exercises limit the chest and pelvic mobility. The purpose of this study was to examine immediate changes following two types of trunk muscle exercises on the chest and pelvic mobility and trunk muscle activity.

2. Methods

2.1 Participants

The present study was conducted in the laboratory of the Saitama Medical University from July to August 2018. A prior power analysis by G*power 3.1.9.6 (Heinrich Heine Universität Düsseldorf, Düsseldorf, Germany) was used to determine the sample size for the two-way repeated measures analysis of variance (ANOVA) at the beginning of the study. The sample size was estimated at fourteen to be conducted via the two-way repeated ANOVA (effect size of 0.4, $\alpha$ level of 0.05, and power level of 0.8). Fourteen healthy men (age: 21.1 $\pm$ 1.0 years, height: 172.7 $\pm$ 5.6 cm, weight: 61.0 $\pm$ 7.1 kg, body mass index: 20.4 $\pm$ 1.7 kg/m ${}^{2}$ ; mean $\pm$ SD) volunteered to participate in this study. All of them provided written informed consent after receiving a detailed explanation on the purpose, potential benefits, and risks associated with participation. Inclusion criteria for this study included healthy individuals without history of any orthopedics, musculoskeletal, or neurological disorders. Moreover, those with respiratory diseases and a history of smoking were excluded. Prior to study participation, all participants were verbally asked about their medical history and smoking history. This study followed the Declaration of Helsinki and was approved by the Ethics Committee at Saitama Medical University, Saitama, Japan (IRB number 163, approved on 25 June 2018).

2.2 Protocol

The study protocol was defined in the order of tasks, including pre-measurements, interventions, and post-measurements. The study protocol was explained to all participants prior to their participation in the study to confirm if they could perform the tasks and interventions. All participants randomly performed two types of interventions following a cross-over design and were provided a resting period of ${>}$ 1 week based on a previous study [15]. All tasks were performed before and after each intervention. The intervention methods and precautions were confirmed after the pre-measurement. Verbal instructions were given to prevent compensatory movements during each intervention. Post-measurements were performed within 10-min post-intervention. The kinematic data of the chest and lower extremity and the muscle activity in the trunk and cervical were evaluated during all tasks. Each intervention and task was practiced before the measurement.

Figure 1.

Two types of interventions: side flexion (A) and draw-in (B).

2.3 Interventions

The study participants were instructed to perform trunk side flexion while side-lying down (Fig. 1A) and abdominal draw-in (Fig. 1B). The trunk side flexion was performed with the participants in a side-lying position with the iliac crest positioned outside from the bedside as the start position. Participants repeated concentric contraction to the maximum side flexion position and eccentric contraction to a line parallel to the bed for 2 s each while two examiners supported the lower limbs of the participants. During this intervention, all participants held both palms on their heads to prevent compensatory movements of the upper extremities. Additionally, examiners verbally instructed participants to maintain a slightly rotated position in the direction of the floor and to place their palms at the back of their head in order to prevent compensatory flexion in the hip and trunk. Two sets of 10 repetitions were performed for each bilateral side. If the participants were unable to perform this intervention in our designated posture, the intervention was terminated.

For the abdominal draw-in intervention, participants were placed in a supine position with their upper limbs on their body sides and their hip and knees in mild flexion. Participants slowly pulled in their stomachs while breathing, repeating the cycle of 4-s contraction and 4-s relaxation, and performed this 10 times for two sets. The examiner palpated the anterior superior iliac spine to confirm contractions of the internal oblique/transversus abdominis (IO/TrA) and instructed participants not to perform compensatory motions of the pelvis or spine. For participants who could not perceive their contractions or who performed compensated contractions using other abdominal muscles during confirmation of the intervention after pre-measurement, the muscle activity pattern was monitored using electromyography (EMG) and feedback was provided to help them understand their contractions.

Figure 2.

Four types of tasks before and after each intervention: maximum inspiration (A), maximum expiration (B), maximum pelvic anterior tilt (C), and maximum pelvic posterior tilt (D).

2.4 Tasks

All participants performed four types of tasks before and after each intervention: maximum inspiration, maximum expiration, maximum pelvic anterior tilt, and maximum pelvic posterior tilt (Fig. 2). All tasks were defined as follows: the maximum inspiration was the maximum expansion of the chest while breathing in, maximum expiration was the maximum narrowing down of the chest while breathing out; maximum pelvic anterior tilt was maximum anterior tilting of the pelvis in the closed-glottis condition at the end of the resting expiration phase; and the maximum pelvic posterior tilt was the maximum posterior pelvic tilt in the closed-glottis condition at the end of the resting expiration phase. A previous study reported that sustained activity of the diaphragm to maintain lung volume in the open-glottis condition contributed to increase spine stiffness [4]. Therefore, the posture with the closed-glottis condition at the end point was maintained during the tasks of maximum inspiration and maximum expiration. All tasks were only performed once before and after each intervention.

2.5 Kinematics data

Twenty-one reflective markers were placed on specific anatomical landmarks (bilateral superior angelus, and bilateral acromion, following the intersection: the horizontal line of the 4/10th rib and perpendicular to the angelus superior, midclavicular line, anterior axillary line, xiphoid process, bilateral anterior inferior iliac spine, bilateral posterior superior iliac spine) to measure each segment of the kinematic data. The placement of the reflective markers and measurement position of the chest was determined using a modified method from previous studies [16, 17]. Three high-speed cameras (EXILIM EX-100F, Casio Computer Co., Ltd., Tokyo, Japan) were used to capture images for the measurement of kinematic data before and after each intervention during static and maximum positions of all tasks. These cameras were adjusted to a height of 121-cm from the ground, set 3-m away from the front, back, and right sides of participants, and synchronized verbally due to the capture of static image data. Image J software was used to calculate the upper and lower elevation distances, anteroposterior and lateral diameters, and anteroposterior tilt angles using the reflective markers affixed on the body. A 10-cm reference was provided on images for each direction to calibrate the length. Elevation distances were calculated from the level of the fourth or tenth rib to the anterior inferior iliac spine. The anteroposterior diameters were calculated as the line connecting the front and back markers at the fourth or tenth rib levels. Lateral diameters were calculated as the line connecting the anterior axillary markers at each selected rib level on both sides. Anteroposterior tilt angles were calculated by tilting each chest line level relative to the pelvic line. A previous study reported that chest mobility is indicated by the difference in circumference between the maximum inspiration and maximum expiration [18]. Based on this study, all kinematic data obtained during tasks of maximum inspiration and expiration were calculated as the differences between each data as a scale of chest mobility.

Figure 3.

The time change graph in one cycle of all muscles during each intervention: side flexion (A) and draw-in (B).

Figure 4.

Results of the muscle activity during each intervention: side flexion (A) and draw-in (B). RA: rectus abdominis, EO: external oblique, IO: internal oblique, LES: lumbar erector spinae, TES: thoracic erector spinae, SCM: Sternocleidomastoid, SL: Scalene. ${}^{*}$ : %MVC of the EO in the side flexion was significantly higher than that in RA, LES, SCM, and SL ( $P<$ 0.01). ${}^{**}$ : %MVC of the IO in draw-in was significantly higher than that of other muscles ( $P<$ 0.01).

2.6 Muscle activity

The EMG (MQ Air; Kissei Comtec Co., Ltd., Nagano, Japan) synchronized with the video was used to record the muscle activity during each intervention and task. A pair of surface electrodes (BlueSensor N-00-S, METS Co., Japan) was attached to the rectus abdominis (RA, 3 cm lateral to the umbilicus) [13, 19], external oblique (EO, 15 cm lateral to the umbilicus) [13, 19], internal oblique/transversus abdominis (IO/TrA, downward inside the anterior superior iliac spine) [20], lumbar erector spinae (LES, 3 cm lateral to the L3 spinous process) [19], thoracic erector spinae (TES, 3 cm lateral to the T8 spinous process) [21], sternocleidomastoid (SCM, 1/3 position from the sternal notch on the line connecting the sternal notch and the mastoid process) [22], and scalene (SL, muscle belly on the vertical line drawn from the 1/3 mark) [22] on the right side. The attached position of the surface electrodes was applied in accordance with previous studies [13, 19, 20, 21, 22] and marked before being attached to each muscle in parallel to the muscle fiber. The distance between the surface electrodes was 20 mm. The measurement of the surface EMG was performed before and after each intervention during the experimental tasks of maximum inspiration/expiration and maximum pelvic anterior/posterior tilt while standing. The surface electrodes were not removed before and after each procedure. Additionally, a surface EMG was used to monitor trunk and cervical muscle activity during each intervention (Fig. 3). The sampling frequency of all EMG signals was 1,000 Hz. Raw data were band-pass filtered between 20 and 500 Hz and were full-wave rectified using analysis software (BIMUTAS-Video; Kissei Comtec CO., Ltd., Nagano, Japan). The root mean square was calculated for 1 s during each intervention and task and was normalized as a percentage of the greatest root mean square obtained over a 1-s period during the maximum voluntary contraction (MVC) test (%MVC). The MVC test for RA was conducted by performing a partial sit-up in the knee flexion position, holding both palms behind the head, and applying a manual resistance to the shoulder toward trunk extension [19]. For the EO and IO/TrA, the participants performed bilateral oblique sit-ups while holding both palms behind their heads and applying a manual resistance to the shoulder that attempted to move toward the opposite flexed knee [19]. For the LES and TES, the participants performed trunk extension in the prone position and held both palms behind their head with manual resistance applied to the upper chest [19]. For the SCM and SL, the participants underwent forward flexion of the cervical spine in the supine position with manual resistance applied to the forehead [22]. Manual resistance was applied gradually until maximum effort was reached, which was then maintained for 3 s. Analysis of the side flexion was decided at 1 s of the maximum muscle activity during the concentric phase. Analysis of the draw-in was decided at the last 1 s during the 4-s contraction. Moreover, the analysis of tasks was determined for 1 s between the camera flash, as confirmed on the video image synchronized with EMG. All average values were calculated using the value of three random times, excluding the first times.

2.7 Statistical analysis

The SPSS Statics version 20 for Windows (IBM Corp., Armonk, NY, USA) was used for data analysis in this study. Two-way repeated measure ANOVA was used to measure kinematic data and muscle activity during all tasks between the intervention and period ( $P<$ 0.05). The Bonferroni test was used to compare the outcomes that showed interaction between the intervention and period ( $P<$ 0.05). Furthermore, %MVC during each intervention was analyzed using one-way ANOVA to compare between muscles ( $P<$ 0.05).

3. Results

3.1 Muscle activity

With regard to the results of muscle activities during each intervention, the muscle activity of the EO (160.3 $\pm$ 100.9%MVC) during trunk side flexion was significantly greater than that of the other muscle activities (Fig. 4A). Moreover, the muscle activity of the IO/TrA (44.7 $\pm$ 25.2%MVC) during draw-in was significantly greater than that of the other muscle activities (Fig. 4B).

Figure 5.

Results of the muscle activity during four types of tasks: maximum inspiration (A), maximum expiration (B), maximum pelvic anterior tilt (C), and maximum pelvic posterior tilt (D). RA: rectus abdominis, EO: external oblique, IO: internal oblique, LES: lumbar erector spinae, TES: thoracic erector spinae, SCM: Sternocleidomastoid, SL: Scalene. ${}^{\dagger}$ : Indicates interaction between before and after the side flexion ( $P<$ 0.05). ${}^{\$}$ : Indicates interaction between before and after the draw-in ( $P<$ 0.05).

Results of muscle activities between each intervention are shown in Fig. 5. Significant interactions were observed in the RA and EO activities during the maximum pelvic anterior tilt (RA: $P=$ 0.04, Partial $\eta^{2}=$ 0.29, EO: $P=$ 0.01, Partial $\eta^{2}=$ 0.40), and a significant increase was observed after trunk side flexion (RA: pre $=$ 2.9 $\pm$ 2.1%MVC, post $=$ 4.1 $\pm$ 2.6%MVC, EO: pre $=$ 4.2 $\pm$ 3.7%MVC, post $=$ 5.6 $\pm$ 4.1%MVC). Moreover, a significant interaction in EO activity was observed during the maximum expiration ( $P=$ 0.04, Partial $\eta^{2}=$ 0.28), with significantly increased EO activity during maximum expiration after the draw-in.

Figure 6.

Results of the kinematics data of the upper chest: elevation distance (A), lateral diameter (B), anteroposterior diameter (C), and anteroposterior tilt angle (D). ${}^{\dagger}$ : Indicates interaction between before and after the side flexion ( $P<$ 0.05). ${}^{\$}$ : Indicates interaction between before and after the draw-in ( $P<$ 0.05).

Figure 7.

Results of the kinematics data of the lower chest: elevation distance (A), lateral diameter (B), anteroposterior diameter (C), and anteroposterior tilt angle (D). ${}^{\dagger}$ : Indicates interaction between before and after the side flexion ( $P<$ 0.05). ${}^{\ddagger}$ : Indicates interaction between after the side flexion and draw-in ( $P<$ 0.05).

Figure 8.

Results of the kinematics data difference between the maximum inspiration and maximum expiration: elevation distance (A), lateral diameter (B), anteroposterior diameter (C), and anteroposterior tilt angle (D). ${}^{\dagger}$ : Indicates interaction between before and after the side flexion ( $P<$ 0.05). ${}^{\ddagger}$ : Indicates interaction between after the side flexion and after the draw-in ( $P<$ 0.05).

3.2 Kinematics data

Results of the kinematic data between each intervention are shown in Figs 6 and 7. Significant interactions in the lateral diameter of the upper and lower chest were observed during the maximum inspiration (upper chest: $P=$ 0.02, Partial $\eta^{2}=$ 0.37, lower chest: $P=$ 0.02, Partial $\eta^{2}=$ 0.37), in the elevation distance of the upper and lower chest during the maximum pelvic anterior tilt (upper chest: $P=$ 0.004, Partial $\eta^{2}=$ 0.49, lower chest: $P=$ 0.02, Partial $\eta^{2}=$ 0.38), in the lateral diameter of the upper chest during the maximum pelvic anterior tilt ( $P=$ 0.02, Partial $\eta^{2}=$ 0.38), and in the anteroposterior tilt angle of the upper chest during the maximum pelvic anterior tilt ( $P=$ 0.02, Partial $\eta^{2}=$ 0.37). The lateral diameter of the upper and lower chest during maximum inspiration (upper chest: pre $=$ 31.4 $\pm$ 1.9 cm, post $=$ 30.8 $\pm$ 1.7 cm, lower chest: pre $=$ 28.4 $\pm$ 1.6 cm, post $=$ 27.8 $\pm$ 1.5 cm), the lateral diameter of the upper chest during the maximum pelvic anterior tilt (pre $=$ 30.3 $\pm$ 1.8 cm, post $=$ 30.0 $\pm$ 1.7 cm), and the elevation distance of the upper and lower chests during the maximum pelvic anterior tilt (upper chest: pre $=$ 36.4 $\pm$ 2.5 cm, post $=$ 35.5 $\pm$ 2.5 cm, lower chest: pre $=$ 16.7 $\pm$ 2.7 cm, post $=$ 16.3 $\pm$ 2.6 cm) after the trunk side flexion were significantly lower than those before the intervention. The elevation distance (pre $=$ 36.3 $\pm$ 3.3 cm, post $=$ 36.7 $\pm$ 3.4 cm) and anteroposterior tilt angle (pre $=$ 29.7 $\pm$ 8.4 ${}^{\circ}$ , post $=$ 31.4 $\pm$ 9.0 ${}^{\circ}$ ) of the upper chest during the maximum pelvic anterior tilt after draw-in were significantly greater than those before the intervention. In addition, significant interactions in the lateral diameter of the difference between the maximum inspiration and maximum expiration (upper chest: $P=$ 0.02, Partial $\eta^{2}=$ 0.20, lower chest: $P=$ 0.001, Partial $\eta^{2}=$ 0.35) were observed (Fig. 8). The difference in the lateral diameter of the upper and lower chest (upper chest: pre $=$ 2.1 $\pm$ 0.6 cm, post $=$ 1.4 $\pm$ 0.8 cm, lower chest: pre $=$ 2.4 $\pm$ 0.8 cm, post $=$ 1.7 $\pm$ 0.9 cm) after side flexion was significantly shorter than that before the intervention. However, no significant interactions were observed with other kinematic data.

4. Discussion

In this study, the null hypothesis states that global muscle-dominant exercises do not limit chest and pelvic mobility, whereas the alternative hypothesis states that global muscle-dominant exercises limit chest and pelvic mobility. Immediate changes in kinematics data were investigated around the chest and trunk muscle activities after two types of trunk exercise interventions.

Immediate kinematic data changes after side flexion during the maximum pelvic anterior tilt suggest the increased influence of superficial trunk muscles. In this study, the muscle activity of the superficial trunk muscles was greater in the intervention of side flexion, with the EO muscle especially having the greatest activity. Increased RA and EO muscle activity after the side flexion intervention means that eccentric activity has been increased to elongate the abdomen to lean forward to the pelvis during the maximum pelvic anterior tilt. A previous study that focused on activities of the superficial muscles reported that the range of motion of a frozen shoulder was limited by increased superficial shoulder muscle [23]. Thus, although site differences may be observed from the trunk, superficial muscle activities have been reported as the limiting factor for the range of motion. As the superficial trunk muscles originate extensively from the frontal and lateral sides of the chest, the significantly increased eccentric activity of the superficial trunk muscles might limit the chest mobility. Therefore, increased eccentric activity of the superficial trunk muscles after the side flexion intervention suggests that chest mobility might limit the maximum pelvic anterior tilt and maximum inspiration, the tasks that elongate the abdomen.

Conversely, the upper chest alignment during the maximum pelvic anterior tilt was changed after the draw-in intervention, with the IO/TrA of trunk deep muscle having the greatest activity. The IO/TrA has been reported to influence the diaphragm, pleural pressure, and lung volume in the respiration cycle [3, 24, 25]. A previous study, using a rabbit and dog, reported that increased pleural and abdominal pressures during isolated compression of the abdomen or maximal electrical stimulation of the abdominal muscles caused expansion of the rib cage and decreased the lung volume [24]. Additionally, this report similarly reported that an individual compression of the abdomen caused cranial displacement of the abdominal compartment, reducing the lung volume and expanding the rib cage to offset it [25]. Because of these reasons, the selective contraction of the deep trunk muscles in the draw-in is similar to individual compression in previous studies [24, 25], which might expand the upper chest in the human body. Additionally, TrA regulates the IAP [26], and increased IAP has been reported to generate the extension moment of the trunk [27]. Thus, the chest mobility was considered to significantly increase only at the maximum pelvic anterior tilt after the draw-in intervention. Therefore, deep trunk muscle exercises have been suggested to increase the upper chest mobility during the maximum pelvic anterior tilt.

Moreover, the EO activity during maximum expiration significantly increased after the draw-in intervention. The cervical and trunk muscles are secondarily involved in the respiratory cycle, and the muscle activity of the SCM or SL may thus change before and after the intervention of any respiratory tasks. In this study, although the interventions were only for the trunk muscles, no significant change was observed in the cervical muscles. However, after the draw-in intervention, only the EO activity changed, and there was no significant difference in the muscle activity of the SCM and SL. The draw-in maneuver is similar to the expiratory exercise for patients with respiratory diseases because it selectively activates the deep trunk muscle using an expiratory maneuver. If the EO activity as the effort expiratory muscle is deactivated during draw-in, it may affect the EO activity at maximal expiration. A previous study on the effect of the expiratory exercise reported that expiratory exercise improves the expiratory function, such as the maximum expiratory mouth pressure (Pemax) and minute ventilation [28]. Especially, the Pemax reflects the expiratory muscle strength [29], and improved expiratory function through the draw-in intervention might promote the EO muscle activity as the effort expiratory muscle without changing the cervical muscle activity.

This study clarified the difference in immediate changes in chest kinematics and trunk muscle activity patterns according to different types of trunk muscle exercises. Interestingly, limiting the chest mobility by significantly increasing the activity of the superficial trunk muscles after superficial trunk muscle exercise was a new finding; conversely, improving the chest mobility facilitated the deep trunk muscle exercise. Previous studies reported that chest mobility and trunk muscle activity affect sports injury and performance. Increased eccentric contraction of the abdominal muscles during tennis and handball has been considered a risk factor for muscle strain of the RA and EO muscles [30]. Additionally, thoracic and scapular movements and glenohumeral joint movement majorly contribute to the maximum external rotation of the shoulder complex, which may result in the occurrence of many injuries while throwing [6, 31]. Based on these reports, the trunk muscle activity pattern and chest kinematics may contribute to the occurrence of injury during sports activities. Thus, deep trunk muscle exercise should be performed as a warm-up exercise to improve chest mobility. The findings of this study are expected to contribute to the training and conditioning of individuals to prevent injuries and improve performance. Trunk muscle exercises should be performed with full understanding of their characteristics and effects. Although this study focused on superficial and deep trunk muscle exercises, there are many effective trunk muscle exercises to prevent injury and improve physical performance. In future research, it will be necessary to examine how other trunk muscle exercises affect the relationships between chest kinematics and trunk muscle activity.

5. Limitation

One limitation of this study is the method used to measure chest kinematic data. Due to the three-dimensional movement pattern of the chest, it is clinically difficult to perform chest kinematic evaluations, and a simple and detailed method used to measure chest kinematics data has not yet been established. Thus, the original method was used, which requires verification. It is considered that further verification of the measurement methods used in this study may help establish clinically simple and useful evaluation methods.

6. Conclusion

This study demonstrated changes in chest mobility and trunk muscle activity pattern following different trunk muscle exercises. After the superficial trunk muscle exercise, the mobility of the upper and lower chests became limited during the maximum pelvic anterior tilt and maximum inspiration while standing. Conversely, the deep trunk muscle exercise may increase upper chest mobility during the maximum pelvic anterior tilt while standing.

Footnotes

Acknowledgments

This study was supported by a Grant from the Faculty of Health and Medical Care, Saitama Medical University (SMU-FHMC Grant 17-026).

Conflict of interest

The authors have no conflict of interest directly relevant to the content of this article.

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