Improving core stability: Targeting success with core strengthening programs

Abstract

Introduction: Poor dynamic core stability is implicated in the development of low back pain and lower limb injuries. Core strengtheningprograms are used to treat these conditions however the therapeutic outcomes are unpredictable. Sources of variability may be the method of program delivery (supervised or homebased), adherence and type of exercises (static endurance versus dynamic stability). The aim of this study was to investigate the contribution of method of delivery, adherence and exercise selection on static endurance and dynamic stability outcomes of a core -strengthening program. Methods: This was a randomised controlled trial with participants allocated to one of three groups: 8-week supervised core-strengthening program, an identical program delivered as a home-based program or a control group. Primary outcomes weremeasures of lumbo-pelvic dynamic stability (Sahrmann test), dynamic postural stability (Star Excursion Balance Test [SEBT] in posterior-lateral [PL], posterior-medial [PM] and anterior directions) and static core stability (side-bridge, flexor endurance and Sorensen tests). Secondary outcomes included measures of adherence to the program and perceived difficulty of exercises. Analysis of covariancewasperformedon the change frombaseline formeasures of static and dynamic core stability. In the home-based group regression analysis was used to determine the effect of adherence to specific exercises on core stability outcomes. Results: Seventy-eight participants were recruited (n=26 per group). The supervised program produced superior results to other groups on all measures of static and dynamic stability, with greatest improvement in the flexor endurance and Sahrmann tests (ES 2.35, p=0.0001 and ES 2.06, p=0.0001). The home-based program produced significant improvements compared to the control group in all static tests, but not in most dynamic tests (Sahrmann: ES 0.34, p=0.09, SEBT PL: ES 0.24, p=0.08, SEBT PM: ES 0.36). Overall adherence was similar in both intervention groups (∼80%) however strong correlations with improvements in dynamic stability occurred in the supervised group only. In the home-based group greater perceived difficulty of dynamic stability exercises was strongly negatively correlated to adherence to those exercises (r=−0.50, p=0.01). Hierarchical regression analysis demonstrated completion of dynamic stability exercises predicted 52%of the variance in measures of dynamic stability (beta =0.80, p=0.0001). Discussion: Supervised programs provide greater improvements in static endurance anddynamic core strength than the same program delivered in a home-based environment. Home-based programs produce poorer outcomes particularly for measures of dynamic core stability and this is related to poor adherence to, and greater perceived difficulty of, exercises targeting dynamic stability.