Long-Term Mechanical Low-Back Pain (LMLBP) is a growing public health concern characterized by exacerbated nociceptive sensations, decreased physical performance, impaired psychosocial functioning and work disability. LMLBP has remained resistant to most therapeutic approaches and constitutes a challenge to clinicians and researchers worldwide. This study evaluated the effects of static and dynamic back extensors endurance exercises on physiological and psychosocial variables in patients with LMLBP treated with McKenzie Protocol (McKP).

            A single-blind controlled trial was carried out. Eighty four patients who met the eligibility criteria were consecutively recruited from the Physiotherapy Department, Obafemi Awolowo University (OAU) Teaching Hospital and the OAU Health Centre, Ile-Ife respectively and were randomly assigned to one of three groups; the McKP Group (MPG), McKP and Static Endurance Exercise Group (MPSEEG) and McKP and Dynamic Endurance Exercise Group (MPDEEG). Treatment was applied thrice weekly for eight weeks and outcomes were measured in terms of physiological variables of: pain intensity, static and dynamic muscle endurance, and muscle fatigue; and psychosocial variables of activity limitation, participation restriction, fear-avoidance behaviour, pain self-efficacy belief, belief of consequence of back pain and general health status at the end of 4th and 8th week of study, using Quadruple Visual Analogue Scale (QVAS), Biering-Sorensen test, repetitive arch-up test, Borg scale, Roland – Morris Back Pain Questionnaire (RMBPQ), Oswestry Low-back Disability Questionnaire (OLBDQ), Fear-avoidance Beliefs Questionnaire (FABQ), Pain Self-Efficacy Questionnaire (PSEQ), Back Belief Questionnaire (BBQ) and SF-36 questionnaire. Data were analyzed using descriptive and inferential statistics of One-way analysis of variance (ANOVA), repeated measures of ANOVA, Friedman’s ANOVA, Kruskal-Wallis test and multiple comparisons post-hoc tests at 0.05 alpha level. 

            Sixty seven participants aged 51.8 ± 7.35 years completed the study comprising of 25, 22 and 20 in MPG, MPSEEG and MPDEEG respectively. The groups were comparable in age, physical characteristics and baseline outcome measures (p>0.05). Within-group comparison across the 3 time-points of the study revealed that the different treatment regimens had significant effects on the physiological and psychosocial variables (p < 0.05). The different regimens were comparable in their Mean Change (MC) scores on QVAS (p=0.579), OLBDQ (p=0.755), BBQ (p=0.176), FABQ – physical (p=0.627) and FABQ-work (p=0.077) at week four; and QVAS (p=0.883), RMBPQ (p=0.129), OLBDQ (p=0.630), BBQ (p=0.904), FABQ – physical (p=0.785) and work (p=0.154) at week eight respectively. Post-hoc analysis showed that MPSEEG had significantly higher MC in static (60.7 ± 17.1 seconds; p = 0.001) and dynamic endurance (18.1 ± 10.1 repetitions; p = 0.001) scores respectively, while MPDEEG had higher MC in PSEQ (43.5; p=0.001) and in all domains of SF-36 scores (p = 0.001).  

            All the treatment regimens were effective at improving physiological and psychosocial variables in patients with Long-Term Mechanical Low-Back Pain. McKenzie protocol and static endurance exercise led to increased back extensors endurance capability while Mckenzie protocol and dynamic endurance exercise led to higher improvement on pain self-efficacy and general health status. It is recommended that static and dynamic endurance exercise be combined with McKenzie protocol in patients with long-term mechanical low-back pain to derive maximum benefit.