External vs. Internal Focus During Abdominal Bracing in Low Back Pain

Chronic non-specific low back pain (CLBP) is a common musculoskeletal condition associated with reduced physical function, movement limitations, and disability. Exercise-based physiotherapy is widely used in its management, with motor control and trunk stabilization exercises frequently incorporated into rehabilitation programs. However, the effectiveness of these exercises may be influenced by how patients direct their attention during movement execution.

Attentional focus refers to the direction of an individual's attention while performing a motor task. An internal focus (IF) directs attention toward body movements or muscle activation, whereas an external focus (EF) directs attention toward the effects of movement on the environment. Previous research in motor learning has suggested that EF may promote more automatic and efficient movement control than IF. Nevertheless, limited evidence is available regarding the application of these attentional strategies specifically during abdominal bracing exercises in individuals with CLBP.

\*\*Study Objective\*\*

The aim of this pilot randomized controlled trial was to compare the effects of external versus internal attentional focus instructions during abdominal bracing exercises in adults with chronic non-specific low back pain.

The study investigated whether EF instructions would lead to greater improvements in dynamic trunk movement performance and trunk flexor endurance compared with IF instructions. Additional exploratory outcomes included pain intensity, low back pain-related disability, fear of movement, and pressure pain sensitivity.

\*\*Study Design and Participants\*\*

This study employed a two-arm, parallel-group randomized controlled design. Twelve adults with chronic non-specific low back pain were recruited from two outpatient physiotherapy clinics in Olomouc, Czech Republic, between January and December 2025.

Participants were randomly allocated to either the external focus group (n = 6) or the internal focus group (n = 6) using a computer-generated randomization sequence with a 1:1 allocation ratio.

All participants completed the assigned intervention, and no participants were lost to follow-up. The physiotherapist responsible for delivering the intervention also conducted the outcome assessments and was not blinded to group allocation.

\*\*Intervention Procedures\*\*

Both groups completed an identical motor control exercise program based on abdominal bracing. Abdominal bracing was defined as the co-contraction of the abdominal muscles without drawing the abdomen inward or pushing it outward.

The intervention consisted of eight individually supervised physiotherapy sessions over five weeks, with each session lasting approximately 30 minutes. Participants also performed one additional home-based exercise session per week.

The exercise program followed a three-stage progression:

Stage I involved static abdominal bracing exercises performed in supine, standing, and quadrupedal positions.

Stage II involved dynamic exercises performed in supine, side-lying, quadrupedal, and standing positions.

Stage III included functional exercises simulating activities of daily living.

Progression between stages depended on participants' ability to perform abdominal bracing correctly while maintaining appropriate movement quality.

Both groups received the same exercise demonstrations, descriptive instructions, and corrective feedback. The only difference between the groups was the attentional focus instruction used during abdominal bracing.

For the external focus group, small foam markers were attached to the participants' seventh ribs, and participants were instructed to concentrate on bringing the foam pieces toward their waistband.

For the internal focus group, participants were instructed to concentrate on bringing their lower ribs toward their pelvis.

Participants were instructed to activate abdominal bracing before each exercise and maintain the contraction throughout movement execution. The physiotherapist monitored exercise performance and provided corrective feedback when necessary.

\*\*Outcome Assessment\*\*

Participants underwent assessments before and immediately after the intervention period.

Dynamic trunk movement performance was assessed using the Repeated Trunk Flexion test, in which participants performed repeated trunk flexion and extension movements as quickly as possible.

Trunk flexor endurance was assessed using the Flexor Endurance Test.

Additional clinical outcomes included pain intensity measured using the Numerical Pain Rating Scale, disability measured using the Oswestry Disability Index, fear of movement measured using the Tampa Scale of Kinesiophobia, and mechanical pain sensitivity assessed using pressure pain threshold measurements over the lumbar erector spinae muscles.

Adherence to the assigned attentional focus instructions was monitored using weekly self-report questionnaires.

\*\*Data Analysis\*\*

Between-group differences in post-intervention outcomes were analyzed using analysis of covariance (ANCOVA), with baseline scores included as covariates.

Changes in repeated trunk flexion performance and trunk flexor endurance across selected intervention sessions were additionally evaluated using mixed-design analyses of variance.

Effect sizes were calculated to support interpretation of the findings, given the exploratory nature and small sample size of this pilot trial.

\*\*Study Significance\*\*

This pilot study was designed to provide preliminary evidence regarding the influence of attentional focus instructions during abdominal bracing exercises in individuals with chronic non-specific low back pain.

The findings may inform the development of physiotherapy interventions that incorporate attentional focus strategies to optimize movement performance and motor learning during rehabilitation.

Participants received physiotherapy exercises incorporating abdominal bracing with external attentional focus instructions. They were instructed to concentrate on bringing foam markers attached to their lower ribs toward their waistband. The intervention consisted of eight supervised sessions over five weeks, supplemented by one home-based exercise session per week.

Behavioral: Intervention 1 - External Focus

Participants received the same physiotherapy exercise program incorporating abdominal bracing but with internal attentional focus instructions. They were instructed to concentrate on bringing their lower ribs toward their pelvis. The intervention consisted of eight supervised sessions over five weeks, supplemented by one home-based exercise session per week.

Behavioral: Intervention 2 - Internal Focus

Intervention 1 - External Focus Abdominal Bracing Exercises With External Focus of Attention

Intervention 2 - Internal Focus Abdominal Bracing Exercises With Internal Focus of Attention

Plazo: Baseline and immediately after the 5-week intervention

Dynamic trunk movement performance was assessed using the Repeated Trunk Flexion (RTF) test. Participants performed 10 consecutive trunk flexion-extension movements from a standing position as quickly as possible, reaching their available range of motion and returning to an upright position. The test was performed twice, and the average completion time of the two trials was recorded in seconds. Lower values indicate better performance.

Plazo: Baseline and immediately after the 5-week intervention.

Trunk flexor muscle endurance was assessed using the Flexor Endurance Test (FET). Participants maintained a 60-degree trunk flexion position for as long as possible until fatigue or loss of the required position. Endurance time was recorded in seconds. Higher values indicate better trunk muscle endurance.

Plazo: Baseline and immediately after the 5-week intervention.

Low back pain-related disability was assessed using the Oswestry Disability Index (ODI), version 2.1a. The questionnaire consists of 10 sections assessing limitations in daily activities. Scores are expressed as a percentage ranging from 0% (no disability) to 100% (maximum disability). Lower scores indicate less disability

Plazo: Baseline and immediately after the 5-week intervention.

Pain intensity was assessed using the Numerical Pain Rating Scale (NPRS), an 11-point scale ranging from 0 (no pain) to 10 (worst imaginable pain). Higher scores indicate greater pain intensity.

Plazo: Baseline and immediately after the 5-week intervention.

Fear of movement and reinjury was assessed using the 17-item Tampa Scale of Kinesiophobia (TSK). Each item is rated on a 4-point Likert scale. Total scores range from 17 to 68, with higher scores indicating greater fear of movement or reinjury.

Plazo: Baseline and immediately after the 5-week intervention.

Mechanical pain sensitivity was assessed using a Wagner FPN 100 pressure algometer applied bilaterally over the lumbar erector spinae muscles, approximately 5 cm lateral to the L3 spinous process. Three measurements were obtained on each side and averaged. An overall pressure pain threshold was calculated as the mean of the left and right values. Higher values indicate lower mechanical pain sensitivity.

External Versus Internal Focus During Abdominal Bracing Exercises for Nonspecific Low Back Pain: A Pilot Randomized Control Trial