EQUINE VETERINARY EDUCATION / AE / SEPTEMBER 2017


493


Original Article


Whole body vibration affects the cross-sectional area and symmetry of the m. multifidus of the thoracolumbar spine in the horse


B. T. Halsberghe†*, P. Gordon-Ross‡ and R. Peterson†


†Peninsula Equine Medical Center, Menlo Park; and ‡Western University of Health Sciences College of Veterinary Medicine, Pomona, California, USA. *Corresponding author email: bhalsber@gmail.com


Keywords: horse; back pain; hypertrophy; ultrasonography; static dynamic exercise; paraspinal muscles


Summary Whole body vibration (WBV) has been used as an adjunctive therapy to improve the strength and size of paraspinal muscles as well as postural control in people with lower back pain. It has been proposed that activation of the m. multifidus plays a key role. As the function and anatomy of the m. multifidus in the horse is comparable to that in man, the authors investigated whether WBV might also be a valuable physiotherapeutic modality in horses. The effects of WBV on the cross-sectional area (CSA) and left to right symmetry of the m. multifidus at various locations of the thoracolumbar spine of the horse was evaluated in a single-subject quasi- experimental time-series design with repeated measure. Nine horses were subject to WBV, 30 min, twice daily, 5 days a week, for 60 days in addition to their regular exercise routine. The CSA of the left and right m. multifidus was measured ultrasonographically at four levels (T15–T16, T16–T17, T18–L1


and L1–L2) along the thoracolumbar spine at Days 30, 0, 30 and 60 of the study. Changes in the CSA and CSA symmetry (left to right) of the m. multifidus were analysed using nonparametric, repeated measures, comparison of mean ranks with post-hoc analysis as necessary. A significant increase (P<0.05) in m. multifidus CSA was found at all spinal levels after 30 and 60 days of WBV and a statistically significant improvement in m. multifidus symmetry (becoming more symmetrical) was found after 60 days of WBV, indicating that WBV may be a valuable alternative to dynamic mobilisation exercises when an increase in size and improvement in left to right symmetry of the m. multifidus is sought.


Introduction


Dynamic mobilisation exercises in horses, targeting preparative activation and strengthening of the m. multifidus and other core muscles, can increase cross-sectional area (CSA) and improve symmetry of m. multifidus (Stubbs et al. 2011). Based on these results and research in man on the role of the m. multifidus in spine stability (Freeman et al. 2010), Stubbs et al. (2011) suggest that these exercises might be potentially beneficial in improving or restoring spinal function and stability leading to reduced back pain; however, these exercises are labour intensive, time-consuming and require some practice to ensure they are performed correctly. Whole body vibration (WBV), by contrast, is an alternative method of neuromuscular training that exposes the whole


body to vertical mechanical sinusoidal oscillations in a controlled manner by the selection of preset intensities, amplitudes and frequencies. Research in man indicates that WBV is capable of increasing muscle activity (Marın et al. 2015), muscle strength (Machado et al. 2009; Osawa and Oguma 2013), inducing muscle hypertrophy (Gilsanz et al. 2006), improving postural balance and reducing chronic back pain (del Pozo-Cruz et al. 2011). The aim of this study was to conduct a preliminary


exploration of the effects of WBV on the m. multifidus. The authors hypothesised that daily WBV over a 60-day period will result in an overall increase CSA and improved symmetry (left to right) of the m. multifidus in the horse.


Materials and methods


Study design The study was a single-subject quasi-experimental time-series design with repeated measure. Attribute independent variables included breed, age, gender, primary use, exercise level and AAEP lameness score; the active independent variable was WBV treatment. Of the nine participants, five (B1, B2, B3, B4 and B5; Table 1) were selected to assess the stability of the CSA of the m. multifidus prior to WBV treatment


(from Days 30 to 0). All participants received WBV treatment from Days 0 to 60 and the dependent variable consisted of m. multifidus CSA measurements taken at Days 0, 30 and 60. All inferential statistics were evaluated within subject differences.


Participants Of the theoretical population horses with clinical signs for back pain and associated lameness, nine horses (age


10.2 4.2 years) (Table 1) were selected via convenience sampling from an accessible population of 1651 horses owned by clients of Peninsula Equine Medical Center, Menlo Park, California. Inclusion criteria were as follows: a gradable lameness before the start of the study not exceeding a lameness score of 4/5 on an AAEP scale (Stashak 2002), a previous lameness history indicative of a chronic or recurring lameness issue, no treatments or any other therapies within the last 6 months prior and during the study and signed informed client consent form before the start of the study. All horses (n = 9) were required to be housed in a stall (4 9 4m) with daily turnout in a small paddock (8 9 16 m) and exercised 6 days a week. A specific type and duration of


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