Comparison of core stabilization techniques on ultrasound imaging of the diaphragm,and core muscle thickness and external abdominal oblique muscle electromyography activity

Abstract

BACKGROUND:

To restore core stability, abdominal drawing-in maneuver (ADIM), abdominal bracing (AB), and dynamic neuromuscular stabilization (DNS) have been employed but outcome measures varied and one intervention was not superior over another.

OBJECTIVE:

The purpose of this study was to compare the differential effects of ADIM, AB, and DNS on diaphragm movement, abdominal muscle thickness difference, and external abdominal oblique (EO) electromyography (EMG) amplitude.

METHODS:

Forty-one participants with core instability participated in this study. The subjects performed ADIM, AB, and DNS in random order. A Simi Aktisys and Pressure Biofeedback Unit (PBU) were utilized to measure core stability, an ultrasound was utilized to measure diaphragm movement and measure abdominal muscles thickness and EMG was utilized to measure EO amplitude. Analysis of variance (ANOVA) was conducted at $P<$ 0.05.

RESULTS:

Diaphragm descending movement and transverse abdominis (TrA) and internal abdominal oblique (IO) thickness differences were significantly increased in DNS compared to ADIM and AB ( $P<$ 0.05). EO amplitude was significantly increased in AB compared to ADIM, and DNS.

CONCLUSIONS:

DNS was the best technique to provide balanced co-activation of the diaphragm and TrA with relatively less contraction of EO and subsequently producing motor control for efficient core stabilization.

Keywords

Abdominal bracing abdominal drawing-in maneuver dynamic neuromuscular stabilization electromyography ultrasound

1. Introduction

Core instability is the most common pathomarker for low back pain (LBP) which is often implicated with movement impairment and sports performance worldwide [1, 2, 3]. Recent clinical evidence showed that core instability in low back patients was closely linked with impaired motor control in deep core muscles such as diaphragm and transverse abdominis (TrA) [4, 5]. Specifically in LBP patients, the diaphragm was inhibited and remained ascended during inspiration with isometric shoulder and hip flexion [4, 6], and delayed TrA activation during shoulder movement was also observed [7]. The coordination of the diaphragm and core muscles could be important for dynamic neuromuscular stabilization (DNS) to mitigate individuals with core instability and associated LBP.

Neuromechanically, in non-symptomatic subjects, the synkinetic activation of the inner core muscular chain of TrA, the pelvic floor, and the diaphragm regulates intra-abdominal pressure (IAP), providing anterior stabilization of the lumbopelvic region [8, 9, 10]. In coordination with IAP, this local muscular chain provides spinal stiffness, which serves to provide dynamic core stability of the spine [8, 11]. This dynamic spinal stabilization modulates deep core stabilization via the automatic and subconscious ‘feed-forward control mechanism,’ which precedes any cortical, purposeful movement [8].

Pathologically, core instability is a common pathomarker for LBP [7, 12]. Recently, local muscle motor control deficit was proven to be crucial for core instability [4, 13]. Diaphragm movement was significantly decreased during upper and lower extremity isometric flexion against resistance [4] and TrA activation was delayed during shoulder movement in low back patients [13]. These findings suggest that synkinetic dynamic neuromuscular stabilization is essential for effective management of the LBP population with core instability.

Contemporary core stabilization techniques including the abdominal drawing-in maneuver (ADIM), abdominal bracing (AB), and DNS have been employed to optimize spinal stability and reduce associated LBP [8, 14, 15, 16, 17], but outcome measures varied and one intervention was not superior over another [11, 13, 18, 19]. ADIM has shown to be effective in ‘segmental’ lumbar spinal instability and associated LBP because it selectively activates TrA and creates a ‘sandglass-like cylinder,’ thereby providing the localized segmental stabilization to the ventral region of the lower lumbar spinal column [11, 19, 20].

However, such a sandglass-like cylinder may inhibit natural descending movement of the diaphragm and can interfere with both IAP regulation and integrated dynamic spinal stabilization as is evident in LBP [21, 22]. AB is another core stabilization exercise which is presumably to co-activate deep core muscles (diaphragm, internal abdominal oblique; IO, TrA) and superficial core muscles (external abdominal oblique; EO, rectus abdominis) in order to produce a greater IAP and stabilize the spine [18, 23]. However, individuals with LBP and core instability are incapable of co-activating the deep and superficial muscles because of inherent core muscle imbalance between the deep and superficial muscles [8, 24]. Specifically, the core muscle imbalance between the overactive external oblique muscle and the underactive diaphragm, transverse abdominis, and internal oblique muscles can result in mechanical stress and strain on the lumbar spine and further accentuate LBP [8, 25, 26]. To restore such core muscle imbalance effectively, DNS was designed to create optimal IAP and generate lumbopelvic stabilization. Unlike other core stabilization techniques, DNS generates core stability by involving subconscious co-activation of deep abdominal muscles (TrA, IO) in coordination with diaphragm while inhibiting activation of superficial core muscles (rectus abdominis, EO) [8]. A recent study by Kolar et al demonstrated altered postural core activation of the diaphragm when isometric resistance was applied to the upper and lower extremities [4]. This abnormal activation of the diaphragm might serve as an underlying mechanism of chronic low back pain because such diaphragm dysfunction may result in a greater strain on the ventral region of the spinal column [4, 20, 26].

Despite the important clinical and therapeutic ramifications of the contemporary core stabilization techniques, coordination of the diaphragm and core muscles during these core stabilization techniques is unknown in participants with core instability. Therefore, the purpose of this study was to compare the effects of ADIM, AB, and DNS on diaphragm movement, abdominal muscle thickness difference, and EO electromyography (EMG) amplitude in core instability in non-symptomatic subjects. It was hypothesized that DNS would show superior coordinated neuromuscular activation of the diaphragm and TrA muscle than other techniques.

2. Methods

2.1 Subjects

Forty-one subjects with non-symptomatic core instability (female $=$ 7; mean age $\pm$ standard deviation $=$ 21.1 $\pm$ 2.3) were recruited from a university to participate in this cross-sectional study (Table 1). Inclusion criterion entailed: (1) participants with core instability who were unable to perform the bilateral lower extremity sliding (BLES) test while maintaining the target pressure level (40 $\pm$ 10 mmHg) recorded from the pressure biofeedback unit (PBU) (Chattanooga Group, Hixon, TN, USA), (2) absence of symptoms and age 19–25 years, (3) moderate and high activity level of participants, and (4) body mass index (BMI) $<$ 25 [12, 27, 28]. Exclusion criteria included musculoskeletal, neurological and cardiopulmonary disease, surgery, and pain or injury to the low back or lower extremities, and medications that may interfere with the experiment.

Table 1
Demographical characteristics of the subjects ( $N=$ 41)

Parameters	Subject ( $n=$ 41)
Age (years)	21.1 $\pm$ 2.4 ${}^{\text{a}}$
Height	173.0 $\pm$ 6.5
Weight	64.6 $\pm$ 10.7
BMI (kg/m ${}^{2}$ )	21.6 $\pm$ 1.2

${}^{\text{a}}$ Mean $\pm$ standard deviation; ${}^{\text{b}}$ Body mass index.

2.2 Experimental procedures

The present study is a randomized experimental design where the participants were randomly assigned to either ADIM, AB, or DNS by a random allocation sequence method. To reduce or eliminate experimental biases associated with participants’ expectations, experimental information which may affect the participants of the experiment is masked until after the experiment is completed. A consistent experimental procedure was followed using the intervention and standardized tests, including diaphragm movement, abdominal muscle thickness difference, and EO EMG amplitude. The tests were used throughout the pre-test and post-test conditions. All tests and interventions were consistently conducted by the same investigators to improve internal validity of the measurements. All participants underwent baseline or pre-BLES, intervention (ADIM, AB, and DNS), and the post-BLES, ultrasound and EMG measurements. The BLES test was performed using PBU and Simi Aktisys (Simi Reality Motion Systems GmbH, Unterschleissheim, Germany); abdominal muscles thickness difference and diaphragm movement using a 10 MHz linear ultrasound (X8, Medison Co., Ltd, Korea) and a 3.5 MHz curvilinear ultrasound (6000, Medison Co., Ltd, Korea); and EO activity using EMG (Laxtha Inc., Daejeon, Korea) during baseline, ADIM, AB, and DNS conditions.

Figure 1.

Flowchart of the study.

2.3 Core instability test

The BLES test was used to determine baseline core instability before the intervention, followed by the retest after the intervention [27]. For the test, the participant was instructed to lie in the hook-lying position with approximately 70 ${}^{\circ}$ of hip flexion. A PBU with a built-in pressure sensor was placed under the lumbar spine at L5 and inflated to the target pressure range (40 mmHg) which then detects the target pressure changes associated core instability during the test [27]. The participant was asked to contract his or her navel posteriorly toward the spine to activate TrA and then gradually slide out or extend both lower extremities while maintaining the target pressure range and neutral lumbopelvic alignment. Those participants who were unable to complete the test were classified as core instability and included in the present studies [7, 29]. To ensure the measurement consistency, we performed the test-retest for the BLES test and confirmed a good reliability, $r=$ 0.933, $P<$ 0.001.

2.4 Intervention

All participants underwent approximately a standardized 2-hour practical training protocol (each technique: 5 times $\times$ 10 sets with a 5-minute resting interval) for all ADIM, AB, and DNS core stabilization techniques. Abdominal muscle thickness difference and diaphragm movement using ultrasound and EO activity using EMG during each core stabilization technique were concomitantly used to provide accurate real-time feedback about muscle activation to help achieve the successful performance. As with the core instability, the initial position for the intervention was consistently implemented in the hook-lying position with approximately 70 ${}^{\circ}$ of hip flexion. For ADIM, the participant was asked to pull his or her navel up and toward the spine without any compensatory motion in the lumboplevic area [30, 31]. The successful performance of ADIM was ensured by proving accurate feedback about a selective activation of TrA with a minimal activity of superficial rectus abdominals (RA) and external oblique (EO) muscles. For AB, the participant was instructed to swell out his or her abdomen gradually without pulling the abdomen inwards to co-activate or co-contract deep (TrA/IO) and superficial (RA and EO) abdominal muscles. Participants were instructed to emphasize activation with the TrA, while less emphasize the superficial muscles without the need to pull the navel [32, 33]. The successful performance of AB was ensured by proving accurate feedback about balanced co-activation of TrA/IO and EO and RA muscles. For DNS, the investigator (a DNS certified therapist) first neutralized the thorax and rib cage in a caudal position if abnormally aligned (e.g., flared rib cage) to allow a proper descending movement of the diaphragm. He or she was instructed to inhale and expand the ribcage and chest anterior-posteriorly and posterior-laterally such that it reflexively co-activates the diaphragm-TrA/IO-pelvic floor muscles to generate the IAP. The successful performance of DNS was ensured by proving accurate feedback about a proper descending movement of the diaphragm and TrA/IO co-activation with a minimal activity of superficial RA and EO muscles. In addition, the other investigator palpated anterior expansion of the xiphoid process landmark; lateral expansion of the 10 $\sim$ 12 ribs (e.g., corpus costae); and posterior expansion of the angulus costae which optimally constitutes a symmetrical, cylinder-like chest expansion movement. The corrective movement involves caudal movement and widening of the intercostal spaces, and relatively stable rib motion (no cranial motion) in a transverse plane [34] (Fig. 1).

2.5 Experimental testing

The experimental tests included the BLES test using PBU and Simi Aktisys, bilateral abdominal muscles thickness difference and diaphragm movement using ultrasound, and bilateral EO activity using EMG during baseline, ADIM, AB, and DNS conditions in a randomized sequence to avoid the ordering effects after the intervention.

2.5.1 Ultrasound imaging measurement of diaphragm movement and abdominal muscle thickness difference

The participant was positioned in the crook lying position with 70 ${}^{\circ}$ of hip flexion and the four test conditions were performed in a random sequence. Two ultrasounds were concomitantly employed to determine diaphragm movement and abdominal muscle thickness during baseline, ADIM, AB, and DNS conditions. One ultrasound with a 3.5 MHz curved transducer was used to measure diaphragm movement. The transducer was placed between the midclavicular and anterior axillary lines in the subcostal area, and applied to the medial, cranial, and dorsal direction. As illustrated in Fig. 1, the clearest image of the diaphragm inspiratory amplitudes (excursions) was immediately recorded by M mode and measured with an onscreen caliper. Specifically, baseline diaphragm excursion and abdominal muscle thickness measurement were assessed at the end of the inspiration phase for 3 seconds whereas the core stabilization activity-related diaphragm excursion and abdominal muscle thickness measurement were determined after the participant inhaled and correctly performed each core stabilization task and maintained it for 5 seconds.

For the diaphragm excursion movement analysis, the first caliper was placed at the foot of the expiration slope on the diaphragm echoic line and recorded at the tidal breathing (rest) condition and the second caliper was placed at the apex of this slope and recorded at each ADIM, AB, and DNS condition. The amplitude of excursion was measured on the vertical axis of the tracing from the baseline to the point of maximum height of inspiration on the graph. Three times of cycles were recorded, and measurements were averaged. The first reference line was placed at the rest condition slope and the second reference line was placed at the core stabilization technique condition slope on the diaphragm echoic line (Fig. 2) (Fig. 3) [35].

Figure 2.

Measurement of diaphragm movement. A: B-mode for detecting diaphragm, B: M-mode for measuring diaphragm movement.

Figure 3.

Representative composite illustration of diaphragm movement during three core stabilization techniques (Res: Resting, ADIM: Abdominal drawing-in maneuver, AB: Abdominal bracing, DNS: Dynamic neuromuscular stabilization).

The other ultrasound with 10 MHz linear transducer was used to measure abdominal muscle thickness between the core stabilization conditions and rest condition. The transducer was placed on the anterolateral abdominal wall between the 12th rib and the iliac crest. The clearest images were captured immediately on B mode and measured the muscle thickness determined with an onscreen caliper. The TrA, IO, and EO muscles were measured along the horizontal reference line located 1 cm from the medial boundary of the TrA myofascial junction (Fig. 3) [36].

Table 2

Diaphragm movement during the three test conditions

	Conditions
	ADIM ${}^{\text{b}}$	AB ${}^{\text{c}}$	DNS ${}^{\text{d}}$	$F$	$p$
Diaphragm movement ${}^{\text{a}}$ (mm)	$-$ 1.54 $\pm$ 3.55 ${}^{\text{e}}$	8.17 $\pm$ 5.99	10.80 $\pm$ 6.65	91.953	$p<$ 0.01
Minimum	$-$ 5.09	2.18	4.15
Maximum (mm)	2.01	14.16	17.45

${}^{\text{a}}$ Diaphragm movement: Diaphragm position during core stabilization technique, – Diaphragm position during rest; ${}^{\text{b}}$ ADIM: Abdominal drawing-in maneuver; ${}^{\text{c}}$ AB: Abdominal bracing; ${}^{\text{d}}$ DNS: Dynamic neuromuscular stabilization; ${}^{\text{e}}$ Mean $\pm$ standard deviation.

Table 3

Abdominal muscle thickness during the three conditions

Conditions				$F$	$p$
	ADIM ${}^{\text{a}}$	AB ${}^{\text{b}}$	DNS ${}^{\text{c}}$
TrA ${}^{\text{d}}$ (mm)	6.44 $\pm$ 1.85 ${}^{\text{g}}$	5.18 $\pm$ 1.74	6.35 $\pm$ 1.96	56.370	$p<$ 0.01
Minimum	4.59	3.44	4.39
Maximum (mm)	8.29	6.92	8.31
IO ${}^{\text{e}}$ (mm)	11.06 $\pm$ 2.60	9.63 $\pm$ 2.99	10.83 $\pm$ 3.01	69.733	$p<$ 0.01
Minimum	8.46	6.64	7.82
Maximum (mm)	13.66	12.62	13.84
EO ${}^{\text{f}}$ (mm)	7.97 $\pm$ 3.53	6.67 $\pm$ 2.23	6.93 $\pm$ 2.20	5.590	$p<$ 0.01
Minimum	4.44	4.44	4.73
Maximum (mm)	11.50	8.90	9.13

${}^{\text{a}}$ ADIM: Abdominal drawing-in maneuver; ${}^{\text{b}}$ AB: Abdominal bracing; ${}^{\text{c}}$ DNS: Dynamic neuromuscular stabilization; ${}^{\text{d}}$ TrA: Transversus abdominis; ${}^{\text{e}}$ IO: Internal oblique; ${}^{\text{f}}$ EO: External oblique; ${}^{\text{g}}$ Mean $\pm$ standard deviation.

Diaphragm movement and TrA, IO, and EO thicknesses were measured three consecutive times and the relative difference data from the baseline measurement were used for further statistical analysis. Unacceptable data due to movement artefact were discarded, and the scan was then repeated. Please note that we have previously established the test-retest reliability and validity of our ultrasound measurement, which yielded intraclass correlation coefficient (ICC) values ( $r=$ 0.78–0.83) [37].

2.5.2 Electromyography amplitude measurement of external oblique

A surface EMG was used to measure the EO amplitude at a sampling rate of 1024 Hz along with the 60 Hz notch filter; the band-pass filtered was between 20 and 450 Hz and analyzed using Telescan 3.06 software. The EMG data was expressed as a percentage of maximum voluntary isometric contraction (MVIC). Before the data collection, the skin sites for electrode attachment were prepared to reduce skin impedance by dry shaving, abrading with 70% ethyl alcohol. A pair of active electrodes with a 2 cm-interelectrode distance was attached on the muscle zone in parallel, which is laterally located to the rectus abdominis and directly above the ASIS. A reference electrode was attached on the anterior superior iliac spine (ASIS) [38]. As with the ultrasound measurement, the testing position was identically done in the crook lying position [39]. The root mean-square (RMS) of the EMG amplitude was calculated and, then normalized based on maximum voluntary isometric contraction (%MVIC).

2.6 Statistical analysis

Predictive analytics software (PASW) Statistics ver. 25.0 software (SPSS, Inc., Chicago, IL, USA) was used for all statistical analyses. The descriptive statistics include the mean $\pm$ standard deviation (SD). A one-way repeated measures analysis of variance (ANOVA) was used to determine the statistical significance in the changes of diaphragm movement, abdominal muscle thickness difference and EO EMG amplitude during three core stabilization technique conditions (ADIM, AB, DNS). If any statistical significance was found for the main effect, Fisher’s least-significant-difference (LSD) was applied as a post hoc test. The level of statistical significance was set at $P<$ 0.05.

Table 4
EMG amplitude during the four exercise conditions

	ADIM ${}^{\text{a}}$	AB ${}^{\text{b}}$	DNS ${}^{\text{c}}$	$F$	$p$
	Exercise
EO ${}^{\text{d}}$ (%MVIC)	4.77 $\pm$ 2.08 ${}^{\text{e}}$	8.57 $\pm$ 4.76	6.07 $\pm$ 3.33	37.711	$p<$ 0.01
Minimum	2.69	3.81	2.74
Maximum (%MVIC)	6.85	13.33	9.40

${}^{\text{a}}$ ADIM: Abdominal drawing-in maneuver; ${}^{\text{b}}$ AB: Abdominal bracing; ${}^{\text{c}}$ DNS: Dynamic neuromuscular stabilization; ${}^{\text{d}}$ EO: External abdominal oblique; ${}^{\text{e}}$ Mean $\pm$ standard deviation.

3. Results

3.1 Diaphragm movement

Repeated measures ANOVA revealed a significant difference in diaphragm movement across the three conditions: ADIM (95% confidence interval (CI): $-$ 2.63 to $-$ 0.45), AB 95% CI: 6.34 to 10), and DNS (95% CI: 8.76 to 12.8) ( $P<$ 0.05) (Table 2). The LSD post-hoc comparison confirmed that DNS (10.8 mm, descending) showed a significantly greater increase in diaphragm descending movement than AB (8.17 mm, descending) and ADIM ( $-$ 1.54 mm, ascending) ( $P<$ 0.05). AB showed a relatively greater diaphragm descending movement than ADIM ( $P<$ 0.05).

3.2 Abdominal muscle thickness difference

Repeated measures ANOVA showed a significant difference in TrA and IO thickness across three core exercise conditions: ADIM (95% CI: 5.87 to 7.01; 10.30 to 11.90), AB (95% CI: 4.63 to 5.71; 8.71 to 10.5), DNS (95% CI: 5.75 to 6.95; 9.91 to 11.8) ( $P<$ 0.05) (Table 3). The LSD post hoc comparison indicated that DNS and ADIM were greater than AB (Fig. 4) ( $P<$ 0.05).

Figure 4.

Measurement of abdominal muscle thickness (Res: Resting, ADIM: Abdominal drawing-in maneuver, AB: Abdominal bracing, DNS: Dynamic neuromuscular stabilization, EO: External abdominal oblique, IO: Internal abdominal oblique, TrA: Transversus abdominis, D1: Horizontal reference line, D2: TrA thickness, D3: IO thickness, D4: EO thickness).

3.3 EMG amplitude

Repeated measures ANOVA revealed a significant difference in EO activity amplitude across three conditions: ADIM (95% CI: 4.13 to 5.41), AB (95% CI: 7.11 to 10), DNS (95% CI: 5.05 to 7.09) ( $P<$ 0.05) (Table 4). A LSD post hoc comparison confirmed higher amplitude during AB (6.23 %MVIC) than during ADIM (2.42 %MVIC) and DNS (3.72 %MVIC) ( $P<$ 0.05). DNS showed significantly higher amplitude than ADIM ( $P<$ 0.05).

4. Discussion

The current investigation is the first study highlighting the differential effects of ADIM, AB, and DNS on core stability, diaphragm movement, abdominal muscles thickness, and EO EMG amplitude in individuals with core instability. As anticipated, DNS produced the most effective neuromuscular coordination for core stabilization by means of synchronous activation of the diaphragm and TrA while inhibiting excessive EO when compared with AB and ADIM techniques. Most importantly, this finding suggests that DNS is beneficial for improving core stabilization in adults with core instability. It was difficult to compare our novel findings with previous studies because no current core stability data related with DNS, AB, and ADIM are available.

Core stabilization is orchestrated by a synergistic co-activation of the core muscle chain of deep neck flexors, spinal extensors, diaphragm, abdominal muscles, and the pelvic floor during dynamic distal segmental movement (e.g., hip flexion), which regulates IAP and stabilizes the anterior lumbopelvic system [10, 25, 40]. Particularly, in DNS, the diaphragm is the important intrinsic spinal stabilizing muscle in coordination with other deep core muscles such as TrA, IO, and multifidus that contributes to the IAP modulation and serves to maximize dynamic spinal stability [25]. In fact, the present ultrasound measurement of the diaphragm descending movement showed the greatest excursion during DNS (10.80 mm) when compared with that of ADIM ( $-$ 1.54 mm) and AB (8.17 mm). The present finding was consistent with Kolar et al.’s dynamic magnetic resonance imaging (MRI) measurement of the diaphragm descending movement excursion (27.3 mm) [4]. AB also showed more significantly increased core stability than ADIM. However, concurrent EMG and ultrasound data in the present study demonstrated that AB mitigates core stability by means of maximizing EO activation as well as the diaphragm. Specifically, the present EMG results showed significantly higher EO amplitude during AB (8.57 %MVIC) than ADIM (4.77 %MVIC) and DNS (6.07%MVIC). This finding supports a previous study which reported that AB generated more IAP for core stabilization than ADIM [41]. This finding suggests that AB may be a challenging exercise in individuals with core instability secondary to overactive EO because of inherent neuromuscular imbalance between the deep and superficial core muscles [26]. For these reasons, AB core stabilization exercise should not be prescribed for the individuals with overactive EO or superficial abdominal muscles.

A concurrent ultrasound measurement of abdominal muscles and diaphragm descending movement showed the most balanced co-activation of deep muscles (TrA, IO) and diaphragm to provide core stabilization during DNS (TrA: 6.35 mm, IO: 10.83 mm, diaphragm: 10.80 mm) when compared to ADIM (TrA: 6.44 mm, IO: 11.06 mm, diaphragm: $-$ 1.54 mm) and AB (TrA: 5.18 mm, IO: 9.63 mm, diaphragm: 8.17 mm). TrA was more significantly activated during ADIM than AB but was similar to DNS. Previous studies showed that TrA activation is more increased during ADIM than AB which involves co-contraction of overall abdominal muscles [29, 42]. ADIM may be an effective technique to provide segmental lumbar stabilization (e.g., lumbar spine segments 3–4 or 4–5) because it creates a ‘sandglass-like cylinder’ that provides the localized pressure to the lumbar spinal region [39]. However, the ‘sandglass-like cylinder’ during ADIM may be insufficient to provide overall spinal stabilization because it limits natural diaphragm movement.

Taken together with previous findings, DNS provides the most effective motor control strategy for core stabilization via synchronous activation of TrA and the diaphragm when compared to ADIM and AB. DNS is a new promising approach that should be incorporated into the current core stabilization exercises for prevention and intervention of individuals with core instability. Several limitations should be taken into consideration in future research. First, the current study examined the effects of core stabilization exercises in non-symptomatic individuals. A careful interpretation should be made when generalizing our present results to symptomatic patients. Second, core stabilization involves a complex and dynamic lumbo-pelvic-hip system comprising the diaphragm, pelvic floor muscles, TrA/IO, multifidus, and kinetic chain muscles, which synchronously regulate IAP to provide stability. The influence of the pelvic floor and other core muscle activation on core stabilization was not evaluated in the present study. It may be of interest to concurrently measure the lumbo-pelvic-hip region using the motion magnetic resonance imaging (MRI). Finally, the study demonstrated positive therapeutic evidence and hence invites future research to investigate a long-term effect of the core stabilization exercises on athletes with core instability.

5. Conclusions

We established that DNS was the best technique to provide balanced co-activation of the diaphragm and TrA with relatively less contraction of EO and subsequently producing motor control for efficient core stabilization. Clinically, this study provides important conceptual and therapeutic evidence when designing and implementing effective core stabilization in adults with core instability for the prevention, intervention as well as optimal performance in elite sports activities.

Footnotes

Acknowledgments

This research was partially supported by a Brain Korea 21 PLUS Project grant (NO. 2019-51-0018) of the Korean Research Foundation.

Conflict of interest

None to report.

References

Hammill

Beazell

Hart

. Neuromuscular consequences of low back pain and core dysfunction. Clin Sports Med. 2008; 27(3): 449-462.

Hodges

, Core stability exercise in chronic low back pain. Orthop Clin North Am. 2003; 34(2): 245-254.

Nadler

Malanga

Bartoli

Feinberg

Prybicien

Deprince

. Hip muscle imbalance and low back pain in athletes: influence of core strengthening. Med Sci Sports Exerc. 2002; 34(1): 9-16.

Kolář

Sulc

Kyncl

Sanda

Cakrt

, Andel, et al., Postural function of the diaphragm in persons with and without chronic low back pain. J Orthop Sports Phys Ther. 2012; 42(4): 352-362.

Finta

Nagy

Bender

, The effect of diaphragm training on lumbar stabilizer muscles: a new concept for improving segmental stability in the case of low back pain. J Pain Res. 2018; 11: 3031-3045.

Vostatek

Novak

Rychnovsky

Rychnovska

. Diaphragm postural function analysis using magnetic resonance imaging. PLoS One. 2013; 8(3): e56724.

Hodges

Richardson

, Altered trunk muscle recruitment in people with low back pain with upper limb movement at different speeds. Arch Phys Med Rehabil. 1999; 80(9): pp. 1005-12.

Frank

Kobesova

Kolar

, Dynamic neuromuscular stabilization & sports rehabilitation. Int J Sports Phys Ther. 2013; 8(1): 62-73.

Gardner-Morse

Stokes

, The effects of abdominal muscle coactivation on lumbar spine stability. Spine. 1998; 23(1): 86-91.

10.

Hodges

Gandevia

, Changes in intra-abdominal pressure during postural and respiratory activation of the human diaphragm. Journal of applied Physiology. 2000; 89(3): 967-976.

11.

Hodges

Richardson

, Inefficient muscular stabilization of the lumbar spine associated with low back pain: a motor control evaluation of transversus abdominis. Spine. 1996; 21(22): 2640-2650.

12.

Ferreira

Hodges

, Changes in recruitment of the abdominal muscles in people with low back pain: ultrasound measurement of muscle activity. Spine. 2004; 29(22): 2560-2566.

13.

Faries

Greenwood

, Core training: stabilizing the confusion. Strength Cond J. 2007; 29(2): 10-25.

14.

Beazell

Grindstagff

Hart

Magrum

Cullaty

Shen

, Changes in lateral abdominal muscle thickness during an abdominal drawing-in maneuver in individuals with and without low back pain. Res Sports Med. 2011; 19(4): 271-282.

15.

Saiklang

Puntumetakul

Neubert

Boucaut

, The immediate effect of the abdominal drawing-in maneuver technique on stature change in seated sedentary workers with chronic low back pain. Ergonomics. 2021; 64(1): 55-68.

16.

McGill

, Low back stability: from formal description to issues for performance and rehabilitation. Exerc Sport Sci Rev. 2001; 29(1): 26-31.

17.

Lim

Lepsikova

Singh

. Effects of dynamic neuromuscular stabilization on lumbar flexion kinematics and posture among adults with chronic non-specific low back pain: a study protocol. in Regional Conference on Science, Technology and Social Sciences (RCSTSS 2016). 2018. Springer.

18.

Junginger

Baessler

Sapsford

Hodges

, Effect of abdominal and pelvic floor tasks on muscle activity, abdominal pressure and bladder neck. Int Urogynecol J. 2010; 21(1): 69-77.

19.

Liebenson

, Rehabilitation of the spine: a practitioner’s manual. 2007: Lippincott Williams & Wilkins.

20.

Cresswell

Oddsson

Thorstensson

, The influence of sudden perturbations on trunk muscle activity and intra-abdominal pressure while standing. Exp Brain Res. 1994; 98(2): 336-341.

21.

Hemborg

Moritz

, Intra-abdominal pressure and trunk muscle activity during lifting. II. Chronic low-back patients. Scand J Rehabil Med. 1985; 17(1): 5-13.

22.

Cholewicki

Juluru

Radebold

Panjabi

McGill

, Lumbar spine stability can be augmented with an abdominal belt and/or increased intra-abdominal pressure. Eur Spine J. 1999; 8(5): pp. 388-395.

23.

Maeo

Takahasi

Takai

Kanehisa

, Trunk muscle activities during abdominal bracing: comparison among muscles and exercises. Journal Sports Sci Med. 2013; 12(3): p. 467.

24.

Ehsani

Arab

Jaberzadeh

Salavati

, Ultrasound measurement of deep and superficial abdominal muscles thickness during standing postural tasks in participants with and without chronic low back pain. Man Ther. 2016; 23: 98-105.

25.

Comerford

Mottram

, Movement and stability dysfunction – contemporary developments. Man Ther. 2001; 6(1): 15-26.

26.

Page

Frank Lardner

, Assessment and treatment of muscle imbalance: the Janda approach. J Orthop Sports Phys Ther. 2011; 41(10): 799-800.

27.

Cha

Yoon

Jung

Hwang

You

JSH

. The best lumbothoracic-cervical chain stabilization exercise for longus colli activation. J Med Imaging Health Inform. 2018; 8(1): 84-87.

28.

Rangul

Holmen

Kurtze

Cuypers

Midthjell

, Reliability and validity of two frequently used self-administered physical activity questionnaires in adolescents. BMC Med Res Methodol. 2008; 8: 47.

29.

Richardson

Snijders

Hides

Damen

Pas

Storm

. The relation between the transversus abdominis muscles, sacroiliac joint mechanics, and low back pain. Spine. 2002; 27(4): 399-405.

30.

Henry

Westervelt

, The use of real-time ultrasound feedback in teaching abdominal hollowing exercises to healthy subjects. J Orthop Sports Phys Ther. 2005; 35(6): 338-345.

31.

Tayashiki

Takai

Maeo

Kanehisa

, Intra-abdominal pressure and trunk muscular activities during abdominal bracing and hollowing. Int J Sports Med. 2016; 37(2): 134-143.

32.

McGill

Karpowicz

, Exercises for spine stabilization: motion/motor patterns, stability progressions, and clinical technique. Arch phys med Rehabil. 2009; 90(1): 118-126.

33.

Kato

Murakami

Inaki

Mochizuki

Demura

Nakase

Yoshioka

, et al., Innovative exercise device for the abdominal trunk muscles: an early validation study. PLoS One. 2017; 12(2): e0172934.

34.

Cholewicki

McGill

, Mechanical stability of the in vivo lumbar spine: implications for injury and chronic low back pain. Clin Biomech. 1996; 11(1): 1-15.

35.

Ayoub

Cohendy

Dauzat

Targhetta

Coussaye

Bourgeois

, et al., Non-invasive quantification of diaphragm kinetics using m-mode sonography. Can J Anaesth, 1997; 44(7): 739-744.

36.

Whittaker

, Ultrasound imaging of the lateral abdominal wall muscles in individuals with lumbopelvic pain and signs of concurrent hypocapnia. Man Ther. 2008; 13(5): 404-410.

37.

Noh

Lee

You

JSH

. Diaphragm breathing movement measurement using ultrasound and radiographic imaging: a concurrent validity. Biomed Mater Eng. 2014; 24(1): 947-52.

38.

Criswell,

, Cram’s Introduction to Surface Electromyography. Training. 2011.

39.

Richardson

Jull

Toppenberg

Comerford

, Techniques for active lumbar stabilisation for spinal protection: A pilot study. Aust J Physiother. 1992; 38(2): 105-12.

40.

Shin

Yoon

Park

Kim

You

JSH

. Comparative Immediate Effects of Isometric Chin-tuck and Dynamic Neuromuscular Stabilization on Neck Flexor Muscle Thickness and Upright Sitting Height Posture. Phys Ther Kor. 2019; 26(4): pp. 1-9.

41.

Moghadam

Ghaffari

Noormohammadpour

Rostami

Zarei

Moosavi

, et al., Comparison of the recruitment of transverse abdominis through drawing-in and bracing in different core stability training positions. J Exerc Rehabil. 2019; 15(6): 819-825.

42.

Arab

Chehrehrazi

, Ultrasound measurement of abdominal muscles activity during abdominal hollowing and bracing in women with and without stress urinary incontinence. Man Ther. 2011; 16(6): pp. 596-601.

Comparison of core stabilization techniques on ultrasound imaging of the diaphragm,and core muscle thickness and external abdominal oblique muscle electromyography activity

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSIONS:

Keywords

1. Introduction

2. Methods

2.1 Subjects

Table 1 Demographical characteristics of the subjects ( N = 41)

2.4 Intervention

2.5 Experimental testing

2.5.1 Ultrasound imaging measurement of diaphragm movement and abdominal muscle thickness difference

2.6 Statistical analysis

Table 4 EMG amplitude during the four exercise conditions

3.1 Diaphragm movement

3.2 Abdominal muscle thickness difference

4. Discussion

5. Conclusions

Footnotes

Acknowledgments

Conflict of interest

References

Table 1
Demographical characteristics of the subjects ( $N=$ 41)

Table 4
EMG amplitude during the four exercise conditions