Effect of Two Core Stability Training Programs of Different Intensity on Trunk Function, Postural Control and Functional Mobility in Older Adults: a Randomized Controlled Trial

Fifty-seven physically active older adults (22 men and 35 women) participated in the study. All participants were assessed on two occasions prior to the intervention (pre-test 1 and pre-test 2), and two after the intervention (post-test 1 and post-test 2) using the same outcome measures to assess training effects. The testing sessions included: (i) core stability assessment using an unstable sitting test with force platforms; (ii) evaluation of core stabilization exercises-later used in the training program-via smartphone accelerometry; (iii) assessment of postural control and gait under multiple conditions using force platforms and smartphone accelerometry; and (iv) functional mobility testing.

Participants were randomly assigned to one of three groups: two experimental groups (low-intensity and high-intensity core stability training) and a control group. The intervention consisted of a 6-week core stability training program performed twice per week. Each training session included four sets of one variation of four commonly used stabilization exercises targeting the core musculature: frontal bridge, back bridge, lateral bridge, and bird-dog. The two experimental training programs differed in exercise intensity, which was quantified using lumbopelvic accelerations measured via smartphone accelerometers. Participants in the low-intensity group performed exercise variations that elicited oscillation ranges of 0.20-0.30 m/s² for the frontal bridge and 0.15-0.25 m/s² for the lateral bridge, back bridge, and bird-dog exercises during pre-testing. Participants in the high-intensity group performed exercise variations corresponding to oscillation ranges of 0.30-0.40 m/s² for the frontal bridge and 0.25-0.35 m/s² for the lateral bridge, back bridge, and bird-dog exercises. Exercise duration was standardized to 25 seconds for both experimental groups. Training loads were reassessed and adjusted every two weeks throughout the intervention period.

For statistical analysis, means and standard deviations were calculated for all outcomes using both intention-to-treat and per-protocol approaches. Data normality and homogeneity of variance were assessed using the Shapiro-Wilk and Levene's tests, respectively. Two-way mixed-design ANOVAs were conducted with time (pre- vs. post-intervention) as the within-subject factor and group (low intensity, high intensity, control) as the between-subject factor to examine differences in trunk stability, postural control, gait, and functional mobility. Effect sizes were calculated using partial eta squared (η²p). Paired t-tests were performed to examine pre-post changes within each group. All statistical analyses were conducted using JASP software (version 0.18.3; University of Amsterdam, The Netherlands), with statistical significance set at p < 0.05.