Introduction
Morphological and functional changes in the paraspinal muscles (e.g., atrophy, fatty infiltrations, strength impairments) are well documented in chronic, specific, and neuropathic low back pain (CLBP) [1]. A growing body of evidence underlines the potential of conservative treatment approaches including exercise for patient rehabilitation [2]. Machine-based isolated lumbar extension resistance exercise (ILEX) recently attracted new research interest as a promising tool for muscle reconditioning [3,4,5]. However, studies analysing morphological adaptations of the M. multifidus (MF) during ILEX-based rehabilitation are scarce [3].
Methods
In this ongoing comparative study, 46 CLBP patients were assigned into two groups: I) 24 patients (14 m / 10 w, Ø age: 42.29) underwent an ILEX-based protocol consisting of 25 sessions 1–2x times per week combined with additional exercise (e.g. lat pull down, abdominal crunch) and manual therapy (group ILEX+). 22 patients (9 m / 13 w, Ø age: 37.95) underwent a program consisting of 25 ILEX sessions alone (ILEX alone). All patients were diagnosed with specific lumbar spine pathologies including disc herniations, spondylolisthesis and other degenerative conditions (pain duration > 3 months). One exercise set was performed in a diagnose-based range of motion complimented by a software (Alflexus). A Logic S7 Expert (GE Healthcare, Munich, GER) device was used for ultrasound imaging to assess MF cross-sectional area (CSA), muscle thickness (MT), and echogenicity (EI). Isometric strength was tested with the POWERSPINE Back device (PSB) (Wuerzburg, GER). Pain and disability levels were documented with the Visual Analogue Scale (VAS) and the Oswestry Disability Index (ODI). Measures were taken at baseline (t1) and post-interventional after 16 weeks (t2).
Results
A significant decrease in mean pain levels and disability was documented for both groups (ILEX+: t1 VAS: 38.19 ±25.51, t2 VAS: 18.46 ±15.50, p<0.05 ; t1 ODI: 18%, t2 ODI: 9%, p<0.05; ILEX alone: t1 VAS: 44.98 ±20.23, t2 VAS: 20.61 ±19.19, p<0.05; t1 ODI: 22%, t2 ODI: 7%, p<0.05). Mean isometric strength increased significantly in both groups (ILEX+: t1 176.86 Nm ±60.99, t2 267.96 Nm ±84.94, p<0.05; ILEX alone: t1 153.34 Nm ±62.89, t2 257.60 Nm ±89.86, p<0.05). For morphological changes, MT increased significantly in the ILEX+ group (t1 3.10 cm ±0.47, t2 3.22 cm ±0.53, p<0.05) but non-significantly in ILEX alone (t1 3.00 cm ±0.49, t2 3.10 cm ±0.53, p=0.128). CSA increased significantly in both groups (ILEX+ t1 7.71 cm2 ±1.45, t2 8.52 cm2 ±1.65, p<0.05; ILEX alone: t1 7.46 cm2 ±1.61, t2 8.52 cm2 ±1.84, p<0.05; see example Fig.1). No changes were found for EI. Intergroup comparisons revealed no significant difference for any of the parameters at t2.
DISCUSSION
The results underline the clinical potential of ILEX-based rehabilitation programs. In line with earlier research, isometric strength and quantitative measures of the MF (MT, CSA) can be increased with ILEX [3,6]. More research needs to be done to analyse effects on muscle quality (EI). To the best of our knowledge, this is the first study showing that clinical improvements and morphological adaptations in an ILEX only approach may be comparable to more holistic conservative ILEX-based treatments.