Clinical Effects of Early Intensive Motor Intervention on Gross Motor Development in Infants and Toddlers with Developmental Delay

Summary

This protocol describes an early intensive motor intervention that integrates mesh suspension training. These exercises enhance core strength and balance coordination, thereby improving gross motor function and activities of daily living in infants with developmental delay.

Abstract

Early intensive motor intervention is one of the most important rehabilitation tools to improve gross motor development in infants and toddlers with developmental delay. The combination of conventional rehabilitation training and mesh-intensive suspension training aims to improve core muscle strength, motor control, and balance coordination, and thus improve gross motor function. However, there is no comprehensive clinical evidence on the effects of early intensive exercise intervention combined with conventional rehabilitation on gross motor development and activities of daily living (ADL) in infants and children with developmental delay. The purpose of this study was to investigate the safety and efficacy of early intensive exercise intervention combined with conventional rehabilitation training for gross motor development in infants and toddlers with developmental delay. In the study, the treatment group implemented an early intensive exercise intervention on top of conventional rehabilitation training. The effectiveness of the treatment was evaluated based on the changes in scores on the Alberta Infant Motor Scale (AIMS), Peabody Gross Motor Development Scale (PDMS-GM), and Infant and Toddler Activities of Daily Living score. The results showed that all the indicators improved significantly in both groups after the intervention, and the treatment group showed significantly greater improvement compared to the control group (P<0.05). In the treatment group, the AIMS score increased from (36.80 ± 11.38) to (53.12 ± 7.48), the PDMS-GM standardized total score increased from (18.65 ± 2.33) to (28.03 ± 2.51), and the ADL score increased from (32.89 ± 7.02) to (58.92 ± 6.34). These findings highlight the effectiveness of early intensive motor intervention combined with conventional rehabilitation in improving gross motor function and ADL in infants and children with developmental delay.

Introduction

Developmental delay is a common neurodevelopmental disorder affecting approximately 10%-15% of infants globally, with incidence rates rising annually¹. Gross motor delays, in particular, significantly hinder physical growth and the acquisition of daily living skills. Without timely intervention, these delays can lead to lifelong motor dysfunction, diminishing quality of life, and social integration^2,3,4. Therefore, it is crucial to find effective rehabilitation interventions to promote gross motor development in infants and children with developmental delay.

Early intensive motor intervention has recently gained attention as a proactive rehabilitation tool⁶. This approach leverages neural plasticity to stimulate neuromuscular development through targeted exercise⁵. Protocols are typically tailored for children aged 6-36 months, involving frequent, moderate-duration sessions (e.g., 30-60 min multiple times per week). Clinically, this method applies to medically stable children but is unsuitable for those with unmanaged epilepsy or recent orthopedic surgery⁵. While conventional rehabilitation (e.g., physical therapy) improves motor function to a certain extent⁶, mesh-intensive suspension training offers distinct advantages. By utilizing a unique suspension device to alter the support surface and center of gravity, it increases training difficulty and engagement, thereby better enhancing core muscle strength, motor control, and balance^7,8.

However, conclusive evidence regarding the combined effects of early intensive intervention and conventional rehabilitation on gross motor development and daily living skills remains limited. This study aims to investigate the safety and efficacy of this combined approach, specifically assessing its impact on the Alberta Infant Motor Scale (AIMS), Peabody Developmental Motor Scales-Gross Motor (PDMS-GM), and Activities of Daily Living (ADL) in infants and toddlers with developmental delay⁹.

Protocol

This study complied with the guidelines of the institutional human research ethics committee and received approval from the Institutional Review Board of The Affiliated Hospital of Xuzhou Medical University (Project Number: XYFY2022-JS020-01). All patients or their legal representatives have provided written informed consent to participate in the study, including the use and publication of anonymized data, in strict compliance with the ethical guidelines outlined in the approved protocol. The consumables and the equipment used are listed in the Table of Materials.

1. Recruitment and sample size

Participants were infants and toddlers with developmental delay from the pediatric rehabilitation outpatient and inpatient departments. In total, 56 participants were included in the study. All research activities involving minors adhered to applicable ethical standards.

1. Participant inclusion criteria
   Inclusion criteria were: (1) age between 6-36 months at the time of enrollment; (2) diagnosis of developmental delay or high-risk for developmental delay by a pediatric neurologist or rehabilitation physician, meeting the World Health Organization (WHO) diagnostic criteria for infant and toddler developmental delays; (3) gross motor function score at least two standard deviations below the age-appropriate mean on the PDMS-GM¹⁰; and (4) medically stable to participate in rehabilitation training as confirmed by the attending physician.
2. Participant exclusion criteria
   Exclusion criteria were: (1) confirmed genetic syndromes or progressive neuromuscular diseases (e.g., trisomy 21, Rett syndrome, spinal muscular atrophy) or unmanaged epilepsy; (2) severe, uncorrected visual or auditory impairments; (3) orthopedic surgery within the past 6 months or severe joint contractures that would prevent the execution of motor tasks; and (4) receiving other structured, experimental motor interventions concurrently.

2. Study design

1. Randomization, allocation concealment, and blinding
   This parallel-group study randomized eligible participants in a 1:1 ratio to either a treatment group (early intensive exercise plus conventional rehabilitation) or a control group (conventional rehabilitation alone), with 28 patients per group. The randomization sequence was generated using SAS and implemented with allocation concealment via sealed, opaque envelopes. Due to the nature of interventions, therapists and caregivers were not blinded; however, outcome assessments were performed by assessors blinded to group assignment to minimize measurement bias.

3. Control group: Conventional rehabilitation training

1. Physical therapy
   1. Neurodevelopmental therapy
      ​Neurodevelopmental therapy involves total body relaxation, where the therapist performs gentle rhythmic shaking of the child's limbs and trunk to induce relaxation of the whole body. It also utilizes Reflex Inhibition Modalities to correct abnormal postures (e.g., rostral protrusion, upper extremity flexion, lower extremity extension), with each movement lasting 3-5 min and performed 3-5 times per session. This therapy incorporates the Bobath technique¹¹, which inhibits abnormal muscle tone and reflex patterns and promotes normal movement patterns by controlling key points in the body such as the head, scapular girdle, and pelvis. Additionally, the Vojta technique is applied to improve children's motor function by inducing reflexive movement; for each training session, 2-3 evoked bands are selected, with each band being stimulated 3-5 times for 5-10 s each time.
   2. Joint mobility training
      ​Joint mobility training is tailored to the children's limited joint mobility (e.g., shoulder flexion, extension, abduction, and adduction; hip flexion, extension, abduction, adduction, and rotation). The therapist fixes the proximal end of the joint with one hand and moves the distal end with the other, performing gentle and slow movements 10-15 times in each direction for each joint. Each training session lasts 15-20 min.
   3. Muscle strength training
      ​Muscle strength training combines passive, assisted, and active training for weak muscle groups, with each session lasting 15-20 min. Specifically, lower limb passive strength training involves the therapist helping the child lift the lower limb slowly, maintaining each lift for 3-5 s for 10-15 repetitions. For assistance training, the therapist provides a certain amount of help while allowing the child to lift the lower extremity on their own for 10-15 times. In active training, the child is encouraged to perform straight leg raising independently.
2. Occupational therapy
   1. Basic movement training
      ​Basic movement training focuses on fundamental motor skills tailored to the child's progress. For sitting training, children sit on a chair with a backrest, and the support is gradually reduced to enhance balance. Turning training guides the child to turn over from a supine position to a lateral and then prone position, with the therapist facilitating movement at the pelvic and shoulder girdles. To encourage crawling, interesting toys are placed on the floor to attract children to move forward. Standing training progresses from standing against a wall to independent standing. Typically, 2-3 of these movements (e.g., sitting, rolling, crawling, or standing) are selected per session, with each movement trained for 10-15 min.
   2. Hand-eye coordination training
      1. Hand-eye coordination training: Toys of different sizes, colors, and shapes (e.g., blocks, balls) are used for children to grasp, place, and throw for 10-15 min per session.
         ​NOTE: Training time is 60 min, 5 times per week, for 12 months.

4. Treatment group: Early intensive exercise intervention

1. Mesh intensive suspension training
   NOTE: Specialized mesh suspension training equipment is used to adjust the height and tension of the suspension net according to the child's age, weight, and physical condition. The net is suspended approximately 20-30 cm above the floor (safety buffer), with tension adjusted to support the child's weight without sinking more than 50% of the net depth. The suspension net was used under therapist supervision with no adverse events observed, indicating a favorable safety profile (Figure 1).
2. Core muscle group training
   ​Core muscle group training involves specific exercises performed on the suspension net. In prone elbow support training, the child is placed in a prone position with elbows supported on the net; the therapist assists in maintaining correct posture while the child lifts their head and keeps the torso straight for 30-60 s per set, for 3-5 sets. Additionally, supine knee bending and abdominal contraction training involves the child lying supine on the net with knees bent and hands holding the head. The child slowly lifts the upper body to contract the abdominal muscles, performing 10-15 repetitions for 3-5 sets.
3. Balance coordination training
   1. Obstacle setting and training on suspension net: Obstacles of different heights (5-15 cm) and shapes (e.g., soft balls, stakes) are set on the suspension net, and children are guided to perform crossing and grasping movements (e.g., crawling across the obstacles, grasping toys in different positions). 3-5 obstacles are set up for each training session, and each movement is repeated 5-10 times, with training lasting 15-20 min.
      NOTE: Balance and coordination are trained in an unstable environment.
4. Motor control training
   1. Suspension net rocking and swinging training: The child is allowed to move in unstable environments (e.g., sitting on a wobbly net for balance training) by rocking and swinging a suspension net. The therapist manually pushes or pulls the net to oscillate it, controlling the amplitude (approximately 30 degrees) and frequency of the net's rocking, which should be at a rate of 10-15 times/min for 3-5 min, with 3-5 sets performed.
      NOTE: Each session lasts 30 min, 5 times per week.
5. Large motor games
   Large motor games incorporate specific play-based activities to enhance gross motor skills. In the "Push the ball" exercise, children sit on the ground and push a ball to a designated target at an ability-adjusted distance (generally 1-2 m), performing 10-15 repetitions for 3-5 sets. Kicking games involve children standing or crawling to kick a soft ball to various locations, repeating the action 10-15 times in 3-5 sets. Additionally, jumping games guide children through simple jumping maneuvers on soft mats, completing 10-15 jumps in 3-5 sets.
6. Sensory integration training
   Sensory integration training combines tactile and vestibular stimulation techniques. For tactile stimulation using a tactile brush, firm and deep pressure (sufficient to bend bristles) is applied in a rhythmic, longitudinal motion across the arms, back, and legs, strictly excluding the stomach, face, and groin, for 1-2 min, 3-5 times per area. Similarly, a tactile ball is rolled and pressed on the child's body for 1-2 min, 3-5 times. Vestibular sensory training includes placing the child on a merry-go-round and slowly rotating them for 3-5 revolutions, repeated 3-5 times. Additionally, balance beam training involves the child walking on a beam with therapist protection, completing 1-2 round trips at a time for 3-5 times.
7. Intervention dosage and progression
   Training time is 30 min, 5 times per week, for 12 months. The progression of intervention difficulty was gradually adjusted based on the child's progress over the 12-month training period. This was achieved by following principles such as moving from static to dynamic tasks, increasing instability and range of motion, and transitioning from assisted to active movements.

5. Outcome measures

1. Assessment timeline and procedures
   Within one week prior to intervention, all participants completed a standardized baseline battery comprising the AIMS¹², PDMS-GM⁹ (reflexes, stationary control, locomotion, object manipulation), and a validated pediatric ADL Scale.
2. Assessment battery
   After the 12-month intervention, the full battery of assessments (AIMS, PDMS-GM, and ADL Scale) was repeated for all participants by the same blinded assessor to ensure consistency. All data were recorded on standardized case report forms.

6. Statistical analysis

Statistical analysis included an independent samples t-test or Mann-Whitney U test for baseline characteristics, and a two-way mixed analysis of variance (ANOVA) for primary and secondary outcomes. The statistical significance was set at P<0.05.

Results

Fifty-six infants and toddlers with developmental delay attending our rehabilitation department from May 2022 to May 2024 were selected for the study. The screening, randomization, and intervention processes are illustrated in Figure 2. The children who met the inclusion criteria were randomly divided into a treatment group and a control group, 28 cases in each group. The differences between the two groups in terms of age (t=0.221, P=0.826), gender (χ²=0.048, P=0.842), dise...

Discussion

This study investigated the clinical effects of early intensive motor intervention combined with conventional rehabilitation training on gross motor development and ADL ability in infants and children with developmental delay through a randomized controlled trial. The results of the study showed that the treatment group significantly outperformed the control group in terms of improvement in AIMS score (from 36.80 ± 11.38 to 53.12 ± 7.48), PDMS-GM standardized total score (from 18.65 ± 2.33 to 28.03 ± ...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Balance beam	Runkang Rehabilitation Equipment	8545	800*600*150 (mm)
Dillon ball	Inot	5466	Diameter: 1000 (mm)
Grid suspension device	Sunjava/Guangzhou Class-A Medical Information Industry Co., Ltd.	1950*1000*500
Merry-go-round	Bai Zhuo	BZ-3210	1900*600 (mm)
Tactile brush	GREMED	90*70*30