Effectiveness and Durability of Training Program Dynamic Neuromuscular Stabilization on Strength, Endurance, and Flexibility of Adults with intellectual disabilities

doi:10.21203/rs.3.rs-4963722/v1

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Effectiveness and Durability of Training Program Dynamic Neuromuscular Stabilization on Strength, Endurance, and Flexibility of Adults with intellectual disabilities

https://doi.org/10.21203/rs.3.rs-4963722/v1

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Individuals with intellectual disabilities (ID) often exhibit lower levels of physical fitness compared to the general population, including reduced strength, endurance, flexibility, and coordination. Dynamic neuromuscular stabilization (DNS) training has been proposed as a potential intervention to improve physical fitness in this population, but the effectiveness and durability of DNS training on specific fitness components have not been well-established. This study employed a randomized controlled trial design to investigate the effects of an 8-week DNS training program on the strength, endurance, and flexibility of adults with ID. A total of 31 participants were randomly assigned to either an intervention group (n=16) or a control group (n=15). Muscular strength, endurance, and flexibility were assessed at baseline (pre-test), immediately after the intervention (post-test), and 2 months following the intervention (follow-up) using the 30-second chair stand (30sCS) test, sit-ups test, trunk lift test, and chair sit-and-reach test. Participants in the intervention group engaged in the DNS training program for 8 weeks, with 3 sessions per week, while the control group maintained their usual activities. The analysis of the outcome measures revealed significant time, group, and time-group interaction effects. Post-hoc analyses indicated that the DNS group exhibited significantly greater improvements in 30sCS, sit-ups, trunk lift, and chair sit-and-reach compared to the control group (p<0.01). These improvements were maintained at the 2-month follow-up assessment in the DNS group. This randomized controlled trial demonstrates that an 8-week DNS training program significantly improves muscular strength, endurance, and flexibility in adults with ID, with benefits maintained at a 2 month follow-up. Further research is needed to replicate these findings and investigate underlying mechanisms, but the study highlights the potential of DNS training to promote physical fitness and well-being in individuals with ID.

Biological sciences/Neuroscience

Health sciences/Health care

Intellectual Disability

Adult

Exercise

Dynamic Neuromuscular Stabilization

The global prevalence of intellectual disabilities (ID) is estimated to be approximately 3% ¹. This neurodevelopmental disorder is characterized by significant limitations in intellectual functioning and adaptive behavior, manifesting in conceptual, social, and practical skills ². Individuals with ID often experience challenges across various domains, including cognitive processing, communication, self-care, and social interaction ³. Research has consistently demonstrated that adults with ID frequently exhibit deficits in physical fitness components, such as muscle strength, endurance, flexibility, and coordination ⁴. These limitations can be attributed to a combination of factors, including impaired cognitive abilities, decreased attention span, reduced motivation to engage in age-appropriate physical activities, poor motor coordination and performance, and underlying issues in motor development^5–8. To effectively address the multifaceted needs of individuals with ID, a comprehensive approach is required. This approach should involve targeted interventions that address both the physical and cognitive-behavioral aspects of the condition, with the ultimate goal of improving overall functioning, enhancing quality of life, and promoting social inclusion and participation ^9–10.

The importance of improving the physical performance of individuals with a shorter life expectancy cannot be overstated. However, a lack of physical activity can lead to various adverse health consequences, including muscle and bone deterioration, type 2 diabetes, obesity, hypertension, and neuromuscular disorders ⁹. Engaging in physical activity, on the other hand, can have a positive impact on brain function and help mitigate health issues such as hypertension and abnormal brain lipid profiles, potentially contributing to a lower mortality rate ¹⁰. Enhancing muscle strength and endurance can facilitate a more active lifestyle, which may in turn reduce health problems and foster greater self-confidence and social interaction for individuals with disabilities ¹¹.

Research has demonstrated that well-designed exercise interventions can effectively improve factors such as strength and muscle balance in human populations ¹². However, a gap exists in the literature regarding the most effective training approaches for significantly improving the physical performance of individuals with disabilities. To address this gap, research is needed to identify and evaluate the most impactful training interventions that can enhance the physical fitness and overall health outcomes of individuals with reduced life expectancy.

Individuals with ID often struggle with the performance of motor skills, particularly more complex ones, due to underlying issues with muscle function ¹³. To enable these individuals to lead more independent lives and maintain appropriate levels of muscle strength and endurance, it is crucial to focus on the development of their motor skills ¹⁴. In this context, the implementation of training programs specifically tailored to the individual's needs is of paramount importance. One approach that has shown promise in improving muscle strength and endurance is dynamic neuromuscular stabilization (DNS) exercises ¹⁵, which aim to enhance the coordination and integration of the neuromuscular system.

DNS is a rehabilitation concept proposed by Pavel Kolar, which was influenced by Vaclav Vojta's work on reflex locomotion therapy ¹⁵. The DNS approach focuses on posture, breathing patterns, and joint centration (the position in which a joint is most congruent), emphasizing the importance of core stability provided primarily by the neck flexors and extensors, diaphragm, transverse abdominis, and multifidus muscles ¹⁶.

DNS has been successfully used for the rehabilitation of various neurological, musculoskeletal, and sports injury cases ¹⁶. By stimulating specific areas derived from balance and stabilizing points during an individual's development, DNS aims to activate the neural circuits that guide complex movement patterns ¹⁶. This method can potentially improve the performance of adults with ID caused by weak motor skills due to a lack of desirable nerve growth during childhood and before puberty ¹³.

The effectiveness of DNS has been demonstrated in several studies. A case study by Oppelt et al. showed significant improvements in sleep pattern, mobility, body mechanics, and emotional outlook in a stroke patient after a 32-week DNS intervention ^{15, 17}. Another study by Son et al. concluded that DNS is a promising intervention for facilitating deep core muscle activation, thereby improving age-appropriate functional activities in participants with ID ^{15, 18}.

The purpose of this study was to determine the effects and durability of a DNS training program on measures of strength, endurance, and flexibility in adults with ID. Adequate physical fitness in these domains is crucial for maintaining independence and quality of life among this population. By targeting core stability, breathing, and movement patterns, the DNS approach may facilitate improved muscle function, endurance, and flexibility - all of which are critical for supporting independent living and community participation in adults with ID ¹⁹.

Ethics statement

The current study was conducted in full compliance with the ethical guidelines established by the Ethics Committee of Shahroud University of Medical Sciences in Semnan, Iran (protocol code: IR.SHAHROODUT.REC.1402.031). The ethical procedures followed the principles outlined in the Declaration of Helsinki, as well as additional criteria specific to sport and exercise science research. Prior to participation, all individuals provided written informed consent, ensuring their voluntary involvement in the study.

Study design and participants

Participants were recruited from Hekmat Rasht for the Disabled, an organization affiliated with the Rasht Welfare Association, through direct contact with the administrator by the principal investigator. The purpose of the study, including the procedures involved and the potential benefits of participating in the training program, was clearly communicated to all prospective participants. To be considered for inclusion, individuals had to meet specific eligibility criteria, such as being between 30 and 55 years of age, having a diagnosed ID with an IQ score ranging from 50 to 70, and demonstrating the ability to participate independently in an exercise program. Exclusion criteria were also established, which included a diagnosis of Down syndrome, participation in a structured exercise program within the past 6 months, current smoking status, and/or ongoing medication use. The implementation of these inclusion and exclusion criteria aimed to ensure the homogeneity of the study population and minimize potential confounding factors that could influence the outcomes of the exercise intervention.

Experimental Design and Study Procedures

The study protocol consisted of three distinct phases: an initial assessment, an 8-week intervention, and a 2-month follow-up evaluation. During the initial assessment, participants completed an informed consent form and underwent a series of anthropometric and physical fitness measurements, including assessments of height, weight, muscle strength, and mobility using the chair sit-and-reach test. In a separate session, muscular endurance was evaluated through sit-up and 30-second chair stand tests. To mitigate the risk of participant fatigue, a 15-minute rest period was provided between each test. Each field test was performed twice, with the most favorable result recorded for each individual.

A total of 31 individuals underwent the screening procedure and were selected to participate in either the control group (n = 15) or the DNS intervention group (n = 16). The sample size was estimated using the G*Power program, with a sample size of 16 individuals per group using the repeated measures statistical test with an alpha value of 0.05 and a beta value of 0.23. This sample size was chosen to achieve a statistical power of 0.80, which is considered appropriate for experimental studies. The control group participated in center-based activities, while the DNS intervention group engaged in targeted training exercises at the center from 8:00 am to 1:30 pm. Participants who did not opt for the DNS interventions or had an attendance rate below 60% were excluded from the data analysis (Fig. 1).

During the 8-week intervention phase, eligible participants in the DNS group took part in 25–30 minutes of supervised DNS exercises at the center. The DNS program focused on posture, breathing patterns, and core stability, emphasizing the proper activation of the diaphragm and deep abdominal muscles prior to any targeted movement.

The implementation of a comprehensive assessment protocol, structured DNS exercise intervention, and follow-up evaluation aligns with the methodological rigor expected in high-quality exercise science research. The exclusion of participants who did not meet the eligibility criteria or adhere to the intervention further strengthens the internal validity of the study, allowing for a more homogeneous sample and an accurate evaluation of the DNS intervention's effects.

Muscle endurance: 30 s chair stand test

The 30-second chair stand (30sCS) test was utilized to assess the muscular endurance in the study participants. Participants were instructed to perform the 30sCS test by sitting and standing on a chair for 30 seconds without using their hands. The test result was determined by the total number of successful repetitions completed within the given time frame. At the beginning of the test, participants were instructed to sit on a chair with their feet flat on the floor and their knees bent at a 90-degree angle ²⁰.

The validity and reliability of the 30sCS test have been well-established in the general population. The psychometric properties of the 30sCS were further examined in older adults with ID, demonstrating moderate to high feasibility and test-retest reliability. Specifically, the intraclass correlation coefficients (ICCs) for a same-day interval and a two-week interval were 0.72 (95% CI 0.32–0.91) and 0.65 (95% CI 0.19–0.87), respectively ^21–22. Moreover, longitudinal studies have shown the potential of the 30sCS to predict deterioration in the performance of instrumental and basic activities of daily living, as well as mobility, in older individuals with ID over a 3-year follow-up period ^23–24.

The inclusion of the well-validated 30sCS test in the assessment protocol aligns with the recommended practices for evaluating physical fitness in individuals with ID. The robust psychometric properties of this measure, as demonstrated in previous research, further strengthen the methodological rigor of the current study.

Core muscle endurance: Sit-ups test

The sit-up test was utilized to assess the muscular endurance of the abdominal muscles. During this test, participants were instructed to lie on their backs with their knees bent and the soles of their feet flat on the floor. Participants were then required to perform as many correctly executed sit-ups as possible within a 30-second time frame, with their arms reaching towards their knees during the movement.

The sit-up test is a well-established measure of core muscular endurance that has been widely used in both clinical and research settings. The scoring of this test is based on the total number of properly completed sit-ups within the 30-second time limit, providing a quantitative assessment of abdominal muscle strength and fatigue resistance. The inclusion of the sit-up test in the assessment protocol aligns with the recommended practices for evaluating physical fitness components, particularly muscular endurance, in individuals with ID. This measure has been extensively validated and has demonstrated reliability in various populations, making it a suitable choice for the current study ²⁵.

Trunk muscle strength: Trunk lift test

The trunk lift test was utilized to assess trunk muscle strength in the study participants. During this assessment, participants were instructed to lie in a prone position with their hands placed under their thighs. They were then asked to lift their chin as high as possible off the mat by pushing through their back. The distance from the mat to the bottom of the lower jaw was measured twice using a tape measure, with the best result recorded.

The test-retest reliability of the trunk lift test has been well-established in the literature. A previous study conducted by the researchers found the test to have adequate reliability, with an intraclass correlation coefficient (ICC) of 0.89 when assessed at two-week intervals in adolescents with intellectual impairment. Additionally, studies have demonstrated the logical validity of this test, as well as its ability to discriminate between different age groups (18–25, 26–35, 36–45, and > 45 years) in adults with Down syndrome ²⁶.

The inclusion of the trunk lift test in the assessment protocol aligns with the recommended practices for evaluating physical fitness components, particularly trunk muscle strength, in individuals with ID. The robust psychometric properties of this measure, as reported in the existing literature, further strengthen the methodological rigor of the current study and its applicability to the target population.

Flexibility: Chair sit and reach test

The mobility of the study participants was assessed using an extended version of the modified back-saver sit-and-reach test. This test involved the participant sitting on a chair, bending forward, and extending one leg onto a second chair. The distance between the distal tip of the middle finger and the lateral malleolus was measured as the participant leaned forward ²⁷. The test was performed on both legs, and to align with previous research, 6 cm was added to the measured distance to standardize the findings ²⁸.

The modified back-saver sit-and-reach test has demonstrated a high degree of validity and test-retest reliability in the general population. For males, the correlation coefficients for the low back and hamstring criteria ranged from 0.47 to 0.67, while for females, the coefficients ranged from 0.23 to 0.54 (3). Additionally, the intraclass correlation coefficients (ICCs) for test-retest reliability were 0.96 for men and 0.97 for women, indicating excellent reproducibility ²².

Previous research has also examined the psychometric properties of this test in older individuals with ID. The ICC values for the left leg were 0.96 and 0.63 for the same day and 2-week intervals, respectively, while the right leg had values of 0.95 and 0.71 for the same day and 2-week intervals, respectively. These findings suggest that the modified back-saver sit-and-reach test is a reliable measure of mobility in this population.

The inclusion of this well-validated assessment of flexibility and range of motion aligns with the recommended practices for evaluating physical fitness components in individuals with ID. The robust psychometric properties of the modified back-saver sit-and-reach test, as demonstrated in the existing literature, further strengthen the methodological rigor of the current study.

DNS exercise program

The DNS exercise intervention was implemented by the researchers over an 8-week period. The program consisted of three supervised sessions per week, each lasting 25 to 30 minutes. Participants in the DNS training group completed their sessions from 8:30 am to 1:30 pm and were paired to allow for close monitoring of exercise execution accuracy.

The pairing of participants during the DNS sessions was a strategic decision to address the potential difficulties in learning and executing the exercises, which can be common in individuals with ID ^29–30. By providing close supervision and individualized support, the researchers aimed to ensure the successful performance of the DNS exercises by each participant.

Furthermore, the DNS exercises were adapted to the specific abilities of each participant to facilitate proper technique and engagement. This personalized approach is crucial when implementing exercise interventions for populations with ID, as it allows for the tailoring of the program to individual needs and capabilities.

The structured and supervised nature of the DNS intervention, along with the adaptations made to accommodate the participants' learning needs, aligns with the recommended best practices for exercise programming in individuals with ID. This methodological rigor enhances the internal validity of the study and increases the likelihood of observing meaningful improvements in the targeted physical fitness outcomes (Table 1).

Table 1

Detailed description of the DNS training Program
Sessions 1–4	Sets/reps-seconds	Sessions 5–8	Sets/reps-seconds
Learning and practicing diaphragmatic breathing in the supine position	3*10 s	Breathing exercises in the prone position by pressing both forearms to the ground	3*10 s
Learning and practicing diaphragmatic breathing in the prone position	3*10 s	Simultaneous flexion/extension of both arms at shoulder and elbow joints in Baby Rock position	3*8 r
Maintaining static movement and focusing on diaphragmatic breathing in Baby Rock position	3*10 s	Being fixed in rolling sideways with short range (three diaphragmatic breathing)	3*6 r
Breathing exercise while on side lying	3*10 s	Arm movement in different planes of motion in side lying position (left/right)	3*6 r
Breathing exercises in a sitting position	3*10 s	Arm movement in different planes of motion in the Oblique Sit position (left/right)	3*6 r
Breathing exercise in a standing position	3*10 s	Arm movement in different planes of motion in the Tripod position (flexed knees)	3*8 r
Breathing exercises in the kneeling position	3*10 s	Arm movement in different planes of motion in kneeling position (left/right)	3*6 r
Breathing exercise in the Tripod position	3*10 s	Performing short-range squats and focusing on diaphragmatic breathing (parallel hands on the horizontal plane)	3*8 r
Sessions 9–12	Sets/reps-seconds	Sessions 13–16	Sets/reps-seconds
Transferring weight by bending the leg in a prone position by pressing both forearms to the ground	3*6 r	Lifting the upper trunk in a prone position by pressing both forearms to the ground	3*10 s
Moving both hands at the elbow and shoulder joints in different planes of motion with a dumbbell in the Baby Rock position	3*6 r	Flexion/extension of one arm and one leg (diagonal) simultaneously in the Baby Rock position	3*8 r
Being fixed in rolling sideways with short range (for the length of time required for five diaphragmatic breaths)	3*4 r	Movement of one arm and one leg (on the same or opposite side of the body) simultaneously in different planes of motion in the rolling position	3*8 r
Arm movement in different planes of motion in side lying position (left/right)	1*8 r	Moving arm/leg in different planes of motion in side lying position (left/right)	3*6 r
leg movement in different planes of motion in side lying position (left/right)	3*6 r	Moving arm/leg in different planes of motion simultaneously in the Oblique sitting position (left/right)	3*6 r
Arm movement in different planes of motion in the Oblique Sit position (left/right)	1*8 r	opposite leg/arm movement in different planes of motion in the Tripod position (flexed knees)	3*8 r
Leg movement in different planes of motion + knee/hip flexion/extension in Oblique Sit position (left/right)	3*6 r	Arm movement in different planes of motion with Thera band in kneeling position (left/right)	3*6 r
Arm movement in different planes of motion in the Tripod position (flexed knees)	1*8 r	Maintaining static squat movement and focusing on diaphragmatic breathing (parallel hands next to the ear on the frontal plane)	3*10 s
leg movement (hip/knee joint) in different planes of motion in the Tripod position (flexed knees)	3*8 r
Arm movement in different planes of motion with a dumbbell in the kneeling position (left/right)	3*6 r
Maintaining static squat movement and focusing on diaphragmatic breathing (parallel hands on the horizontal plane)	3*10 s
Sessions 17–20	Sets/reps-seconds	Sessions 21–24	Sets/reps-seconds
Simultaneous lifting of arms and legs in the prone position	3*8 r	Pressing two hands on the ground while simultaneously lifting the trunk and thighs from the ground to keep weight on the knees and palms	3*8 r
Flexion/extension of one arm and one leg (diagonal) simultaneously with a dumbbell in Baby Rock position	3*6 r	Pressing the Pilates ball between both thighs and Moving both hands in different planes of motion in the Baby Rock position	3*8 r
Static pressure on Pilates ball between both hands for 10 seconds + stretching Thera band loop around the thighs (long range rolling)	3*6 r	stretching Thera band loop Around the thighs and wrists (long range rolling to the opposite side)	3*6 r
Moving arm/leg in different planes of motion with a dumbbell in side lying position (left/right)	3*6 r	Lifting the torso from the ground by pushing the lower hand on the ground (left/right)	3*6 r
Moving arm/leg in different planes of motion simultaneously with Thera band in Oblique sitting position (left/right)	3*6 r	Moving arm/leg in different planes of motion simultaneously + lifting the hip and holding it about two inches above the ground in the Oblique sitting position	3*6 r
opposite leg/arm movement in different planes of motion in the Tripod position (stretching Thera band loop Around the thighs)	3*6 r	opposite leg/arm movement in different planes of motion in the Tripod position (stretching Thera band loop Around the thighs and Dumbbell in hand)	3*6 r
Arm movement in different planes of motion with dumbbells in kneeling position with Knee extension in short range (left/right)	3*6 r	Combining kneeling and squatting with a Dumbbell	3*6 r
Maintaining static squat movement and focusing on diaphragmatic breathing (parallel hands next to the ear on the frontal plane with a dumbbell)	3*8 r	Arm movement in different planes of motion with Thera band in the static squat position	3*8 r
r: repetitions, s: seconds, rest between sets: 45 seconds, end-set rest: 60 seconds

Statistical Analysis

In the study, the demographic data of the study participants were recorded and the Levene test was used to determine the homogeneity of variance. The data included the mean, standard deviation, and 95% confidence interval. A 2 × 3 mixed model analysis of variance (ANOVA) was performed to examine the effects of therapy at different intervals. The study consisted of an experimental and a control group and specific time intervals (baseline, eight weeks, and follow-up). A post-hoc Bonferroni analysis was performed to determine significant differences between the intervals. In addition, a repeated measures ANOVA was used to compare differences between groups. Independent t-tests were used to compare the groups. A statistical significance threshold of p < 0.05 was set. All statistical analyses were performed using SPSS software (version 26.0; SPSS Inc., Chicago, IL, USA).

Basic Characteristics of Participants

A total thirty-one participants with mild ID with the ages range of 30 and 55 agreed to take part in the study. The intervention and control groups were similar in terms of gender, age, height, weight, BMI, and IQ. There were no significant differences (p > 0.05) in demographic characteristics between the two groups at baseline. Table 2 shows the results of the data.

Table 2

Baseline demographic characteristics of study participants: mean (SD)
Characteristics	Intervention group (n = 16)	Control Group (n = 15)	p value
Age (years)	41.12 (± 9.01)	41.26 (± 8.15)	0.96
Height (m)	1.65 (± 0.09)	1.65 (± 0.10)	0.93
Weight (kg)	67.81 (± 18.80)	66.13 (± 13.49)	0.77
BMI(Kg/m²)	24.59 (± 5.79)	24.03 (± 4.22)	0.75
IQ	50–70	50–70	-

-Data are presented as mean and standard deviation

p-value: p-value of independent sample t-test between groups.

BMI: Body Mass Index

IQ: Intelligence Quotient

Outcome measures

Table 3 shows the mean and standard deviation (SD) of the variables for both groups in three time intervals. The baseline data for the 30sCS, sit-ups, trunk lifts, and chair sit and reach tests between the experimental and control groups showed no statistical differences (p ≥ 0.05).

30 s chair stand

Table 3 shows the results of the tests of the intervention program. The 30sCS scores showed significant differences by time point (F = 31.19, p = 0.001, ηp² = 0.51) and group (F = 48.81, p = 0.001, ηp² = 0.63). The interaction effect of group × time was also significant (F = 25.27, p = 0.001, ηp² = 0.46). In the post hoc analysis, the follow-up test (T3) showed an increase of 7.50 points in the intervention group compared to the pre-test (T1) (Fig. 2). In contrast, the control group showed an increase of 0.27 points, indicating a statistically significant difference between the groups (p = 0.001). The intervention group showed a clear increase of 6.69 points after the test (T2) compared to the pre-test, while the control group showed a smaller increase of 0.53 points. This difference between the two groups was significant (p = 0.001) and large, with a Cohen's d of 2.26. Table 3 provides further details on the within-group comparison.

Sit-ups

Sit-up scores differed significantly by time (F = 79.07, p = .001, ηp² = 0.73) and by group (F = 44.26, p = .001, ηp² = 0.72). In addition, the interaction effects of group × time were also statistically significant (F = 51.81, p = .001, ηp² = 0.64). In the posttest analysis, the intervention group showed an increase of 11.94 points compared to the pretest. In contrast, the control group showed an increase of 1.07 points, which differed significantly from that of the intervention group (p = .001). The intervention group showed a significant increase of 10.87 points in the follow-up test (T3) compared to the pre-test (T1) (Fig. 2). In contrast, the control group showed a decrease of 1.40 points, indicating a significant difference between the two groups (p = .001). Table 3 contains additional information on the comparison within the groups.

Trunk lift

The values for trunk lifting showed significant differences by time (F = 9.95, p = .001, ηp² = 0.25) and group (F = 18.36, p = .001, ηp² = 0.38). In addition, the interaction effects of group × time were also statistically significant (F = 14.15, p = .001, ηp² = 0.32). In the post hoc analysis, the intervention group showed an increase of 1.75 points in the post-test (T2) compared to the pre-test (T1). In contrast, the control group showed a slight increase of 0.07 points, which differed significantly from that of the intervention group (p = .001). The intervention group, on the other hand, showed a significant increase of 2.87 points in the follow-up test (T3) compared to the pre-test (T1) (see Fig. 1). The control group, on the other hand, showed a decrease of 0.27 points, indicating a significant difference between the two groups (p = .001). This was a large effect with a Cohen's d of 1.55. Further details on the comparison within the groups can be found in Table 3.

Chair sit and reach

Chair sit and reach scores showed significant differences by time point (F = 24.47, p = .001, ηp² = 0.45) and group (F = 17.47, p = .001, ηp² = 0.37). In addition, the interaction effects of group × time were also statistically significant (F = 14.88, p = .001, ηp² = 0.33). In the post hoc analysis, the intervention group showed an increase of 8.62 points in the post-test (T2) compared to the pre-test (T1). In contrast, the control group showed an increase of 1.40 points, which differed significantly from that of the intervention group (p = .001). The intervention group showed a significant increase of 9.50 points in the follow-up test (T3) compared to the pre-test (T1) (Fig. 1). In contrast, the control group showed a decrease of 0.93 points, indicating a significant difference between the groups (p = .001). These findings indicate a large effect, with a Cohen's d of 1.51. Further details on the comparison within the groups can be found in Table 3.

Table 3

Pre- and post-primary and secondary outcome measures analysis between the experimental and control groups. mean (SD)
						Difference ^b
Variables	Intervention group(N = 16) Mean (SD)	Control Group (N = 15) Mean (SD)	Group ^a F(p)	Time ^a F(p) ƞ2	Group × Time ^a F(p)	Time difference	Intervention group Mean (SD)	Control Group Mean	p	d_{intervention−control}
30sCS
T1	9.37(± 1.93)	7.93(± 2.25)	F = 48.81 p = 0.001 ƞ²=0.63	F = 31.19 p = 0.001 ƞ²=0.51	F = 25.27 p = 0.001 ƞ²=0.46	T1-T2	-6.69(2.63)	-0.53(2.82)	0.001	2.26
T2	16.06(± 2.91)	8.47(± 3.04)				T1-T3	-7.50(3.30)	-0.27(4.49)	0.001	1.83
T3	16.87(± 3.50)	8.20(± 3.63)				T2-T3	-0.81(1.28)	0.27(2.99)	0.49	0.47
sit-ups
T1	8.00(± 2.63)	6.40(± 2.69)	F = 44.26 p = 0.001 ƞ²=0.72	F = 79.07 p = 0.001 ƞ²=0.73	F = 51.81 p = 0.001 ƞ²=0.64	T1-T2	-11.94(4.23)	-1.07(2.05)	0.001	3.27
T2	19.94(± 5.38)	7.47(± 2.64)				T1-T3	-10.87(4.92)	-1.40(2.56)	0.001	2.41
T3	18.87(± 6.16)	7.80(± 3.71)				T2-T3	1.06(2.32)	-0.33(1.80)	0.33	0.67
Trunk lift
T1	10.44(± 4.57)	8.87(± 3.96)	F = 18.36 p = 0.001 ƞ²=0.38	F = 9.95 p = 0.001 ƞ²=0.25	F = 14.15 p = 0.001 ƞ²=0.32	T1-T2	-1.75(1.94)	0.07(0.70)	0.009	1.25
T2	12.19(± 4.53)	8.80(± 4.00)				T1-T3	-2.87(2.33)	0.27(1.67)	0.006	1.55
T3	13.31(± 4.13)	8.60(± 3.72)				T2-T3	-1.12(1.31)	0.20(1.37)	0.08	0.98
Chair Sit and Reach
T1	-11.75(± 4.96)	-16.10(± 6.93)	F = 17.47 p = 0.001 ƞ²=0.37	F = 24.47 p = 0.001 ƞ²=0.45	F = 14.88 p = 0.001 ƞ²=0.33	T1-T2	-8.62(6.25)	-1.40(3.98)	0.001	1.38
T2	-3.12(± 5.11)	-14(± 7.14)				T1-T3	-9.50(6.44)	-0.93(4.79)	0.001	1.51
T3	-2.25(± 5.13)	-15(± 6.68)				T2-T3	-0.87(2.89)	0.47(1.81)	0.62	0.55
Note: Intervention-control effect size for intervention group improvement corrected for control group improvement. d = Cohen d effect size (0.2 ~ small size, 0.5 ~ medium size, 0.8 ~ large size). Abbreviation: SD, standard deviation. 30Scs, 30-Second Chair Stand. T1, Pre-intervention. T2, Post-intervention. T3, Follow-up

^a Analysed by repeated measures ANOVA.

^b Analysed by Bonferroni correction.

The primary objective of this study was to evaluate the impact of a DNS training program on the strength, endurance, and flexibility of individuals diagnosed with ID. Individuals with ID often experience challenges in physical fitness and motor function, which can negatively impact their overall health and quality of life. DNS techniques have emerged as a promising approach to address these issues, as they focus on enhancing neuromuscular control and core stability. However, the empirical evidence regarding the efficacy of DNS training for individuals with ID remains limited.

Our analysis revealed a remarkable correlation between changes in core strength, lower extremity muscle resistance, and flexibility (P < 0.05), emphasizing the beneficial results of DNS exercises. Furthermore, subsequent observations indicated the sustained effect of DNS exercises on these parameters (P < 0.05). By examining the changes in these key physical attributes, the researchers aimed to provide valuable insights into the potential benefits of DNS interventions for this population.

The findings of the present study align with previous research demonstrating the beneficial effects of structured physical training programs on the physical fitness of individuals with intellectual ID. Asonitou et al. (2018) conducted a study that showed a 4-month physical exercise program, which included strength and endurance exercises, improved muscle flexibility, strength, and endurance in adults with mild ID ³. Similarly, Gutiérrez et al. (2023) emphasized the effectiveness of resistance exercises using one's own body weight and external loads to increase physical performance in adults with mild to moderate disability ³¹.

The current study's results are also consistent with the findings of Dehghani and Qasemi (2021), who investigated the effects of DNS exercises on improving trunk muscle strength and endurance in mentally disabled students ²⁹. The present research extends these previous findings by demonstrating the positive impact of a DNS training program on the core strength, lower extremity muscle endurance, and flexibility of individuals diagnosed with ID.

The observed improvements in these key physical attributes underscore the potential benefits of incorporating DNS techniques into the rehabilitation and fitness regimens of the ID population. The enhanced neuromuscular control and core stability developed through DNS exercises may contribute to the observed gains in strength, endurance, and flexibility, which can subsequently improve overall physical function and quality of life for individuals with ID.

These findings highlight the importance of tailoring physical activity programs to the specific needs and capabilities of individuals with ID, as opposed to a one-size-fits-all approach. The development and implementation of adapted physical activity programs, such as the DNS training program utilized in this study, can play a crucial role in promoting an active lifestyle and improving the physical well-being of this population.

Muscle strength and endurance typically decline with age, a phenomenon commonly attributed to the aging process and the associated reduction in muscle mass ³² .However, it is primarily exacerbated by the reduced physical activity characteristic of older people. Similar to the general population, there is a positive correlation between the level of physical activity and muscle strength, endurance, and flexibility in adults with ID. This means that increasing the level of physical activity and mitigating the degree of disability can improve these parameters. These observations are consistent with the results of an intervention study conducted in adults with ID, which found the positive effects of physical activity on physical fitness ³³. Previous research has shown that people with ID who exercise less have poorer physical fitness and sedentary lifestyles compared to their non-disabled peers ³². Consequently, increasing the level of physical activity, regardless of its duration or intensity, is promising to improve the physical fitness of people with ID and promote their overall health ³⁴.

The DNS technique strives to cultivate dynamic muscular stability by adhering to the DNS paradigm ³⁵. Each joint position within the kinetic chain aims to achieve a central or neutral alignment supported by coordinated muscular contractions of the local and global muscles to stabilize the joints ³⁶. The mechanics and stiffness of the spine are subject to various influences, particularly intra-abdominal pressure (IAP). Kolar assumes that stabilization of the spine requires harmonious activation of the spinal extensor muscles and the deep flexor muscles in the cervical and upper thoracic spine as well as activation of the diaphragm, the pelvic floor, the abdominal wall, and the spinal extensor muscles in the lower thoracic spine ³⁷.

The intrinsic stabilizing muscles of the spine play a central role in promoting dynamic spinal stability by generating stiffness in response to intra-abdominal pressure (IAP) ³⁸. There is also empirical evidence that exercises targeting the abdominal muscles can improve flexibility by allowing controlled contraction and relaxation ³⁹. The results of the study suggest that neuromuscular stabilization exercises performed in different positions and contexts have the potential to improve flexibility. This observation is in line with previous studies that investigated the effects of stability exercises with external loads on physiological parameters ⁴⁰.

In this study, the goal of the DNS exercises was to improve strength, endurance, and flexibility by positioning the patient in various developmental postures while ensuring optimal support and alignment of the joint structures. Participants were first given verbal and manual instructions to differentiate between the various postural configurations. They were then instructed to maintain the ideal alignment during different activities. Given the close relationship between postural positions and breathing patterns, the DNS assessment also included an evaluation of respiratory mechanics. Both stability and respiratory function were considered during the exercise programs ⁴⁰. The overall goal of DNS is to teach people how to integrate appropriate breathing patterns and stability into their daily activities. In general, DNS exercises rely on the unconscious activation of specific muscle groups to modulate diaphragmatic reflexes and engage other central muscles, making them particularly beneficial for individuals with impaired proprioceptive awareness or motor control ⁴¹.

People with ID often face limitations in central nervous system development, leading to a more isolated lifestyle with fewer opportunities for social and economic engagement compared to neurotypical individuals. The DNS exercises aim to address these challenges by focusing on establishing stability of the cranial column, activating the upper centers of the central nervous system, and promoting the emotional-motor pathways (41).

The primary goal of the DNS exercises is to improve neuromuscular coordination, thereby promoting proper muscle function and reducing muscle tension, which in turn can improve strength and endurance. By practicing and reinforcing the correct breathing patterns as well as the movement patterns seen in typical child development, the DNS exercises stimulate the brain to automatically perform movements correctly and efficiently. The automatic integration of correct movement patterns into daily activities leads to improved functioning in people with ID ⁴¹.

Previous research has demonstrated the effectiveness of various exercise modalities, including sports and resistance training, in improving muscle strength, endurance, and flexibility in people with ID. Simultaneous activation of the diaphragm, abdominal, and lumbar muscles increases intra-abdominal pressure, helping to stabilize the trunk. Training plans should therefore focus on activities that promote stability without placing excessive strain on the superficial muscles ⁴¹.

The DNS exercises not only focus on localized muscle strengthening but also emphasize neuromuscular coordination and spinal integrity. By performing them in different positions that mirror everyday movement patterns, these exercises represent a novel approach to maintaining core stability without being overly challenging ⁴². In this regard, functional and muscular rehabilitation exercises should emphasize the stabilizing role of muscles in addition to dynamic anatomical function. Accordingly, the DNS technique used in this study appears to be a valuable tool for the assessment and training of muscles in all aspects of their physiological function ¹⁹.

Improved strength, endurance, and flexibility achieved through DNS exercises can significantly contribute to maintaining independence in daily life for people with ID (41). The comprehensive approach of the DNS technique, focusing on both neuromuscular coordination and spinal stability, makes it a promising intervention for enhancing the physical and functional abilities of individuals with intellectual disabilitiy.

The findings of this study suggest that the DNS technique represents a promising approach for improving muscle strength, endurance, and flexibility in individuals with ID. By emphasizing neuromuscular coordination and spinal integrity, the DNS exercises aim to enhance overall muscle function and reduce tension, leading to better physical fitness. Previous research has demonstrated the effectiveness of various exercise modalities in this population, but training plans should focus on activities that promote stability without excessive strain on the superficial muscles. The simultaneous activation of the diaphragm, abdominal, and lumbar muscles during the DNS exercises increases intra-abdominal pressure, helping to stabilize the trunk. Functional and muscular rehabilitation exercises should emphasize the stabilizing role of muscles, and the comprehensive approach of the DNS technique, focusing on both neuromuscular coordination and spinal stability, makes it a valuable intervention for enhancing the physical and functional abilities of individuals with ID.

Limitations include the small sample size and difficulty controlling for factors influencing educational practices. Further research is warranted. The study focused exclusively on adults with a disability, and the results may not be applicable to other related syndromes characterized by different pathophysiological features.

The results of the current study support the use of appropriate and targeted standardized exercises that improve the physical abilities of people with ID. We advocate the introduction of a specific DNS training program tailored for people with mild ID. This 8-week program has been shown to effectively improve muscle strength, endurance, and flexibility, with durable effects up to 2 months.

The DNS exercises focus on establishing stability of the cranial column, activating the upper centers of the central nervous system, and promoting the emotional-motor pathways. By emphasizing neuromuscular coordination and spinal integrity, the DNS exercises aim to enhance overall muscle function and reduce tension, leading to better physical fitness. The simultaneous activation of the diaphragm, abdominal, and lumbar muscles during the DNS exercises increases intra-abdominal pressure, helping to stabilize the trunk. The comprehensive approach of the DNS technique makes it a valuable intervention for enhancing the physical and functional abilities of individuals with ID.

Acknowledgments

The authors would like to express their gratitude to all the study participants.

Author contributions

H.B-S and S.B conceived, designed, and helped write and revise the manuscript; H.B-S, and B.A were responsible for coordinating the study, contributed to the intellectual content, and reviewed the manuscript. H.B-S, S.B and B.A helped write and revise the manuscript. All authors contributed to the study design, critically reviewed the manuscript, and approved the final version.

Data availability statement

The data that support the findings of this study are available on request from the corresponding author.

Ethics approval

Shahroud University of Medical Sciences, Semnan, Iran. code: IR.SHAHROODUT.REC.1402.031

Funding

None

Competing interests

The author(s) declare no competing interests.

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No competing interests reported.

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Effectiveness and Durability of Training Program Dynamic Neuromuscular Stabilization on Strength, Endurance, and Flexibility of Adults with intellectual disabilities

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Abstract

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Introduction

Materials and Methods

Ethics statement

Study design and participants

Experimental Design and Study Procedures

Muscle endurance: 30 s chair stand test

Core muscle endurance: Sit-ups test

Trunk muscle strength: Trunk lift test

Flexibility: Chair sit and reach test

DNS exercise program

Statistical Analysis

Results

Basic Characteristics of Participants

Outcome measures

30 s chair stand

Sit-ups

Trunk lift

Chair sit and reach

Discussion

Conclusion

Declarations

References

Additional Declarations

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