The Effect Of Responsive Equine Simulator Therapy Device On Biomechanics Of Sitting

Abstract

A responsive equine simulator therapy (REST) system is a sitting device replicating motions experienced during horse riding. The mild motion introduced by the REST could promote a more active sitting experience to users. Although the REST system could potentially provide the benefits associated with active sitting, the effect of a REST system on trunk motion, trunk and leg muscle activations over that of sitting on a normal chair has yet to be examined. PURPOSE: To quantify trunk motion patterns and trunk and leg muscle activity during sitting on a REST system compared to an office chair. METHODS: 20 healthy participants (22±2 yr, 75±10 kg, 1.71±7.9 m) sat on the REST device and an office chair for 20 minutes in randomized order. Electromyography (EMG) sensors were placed bilaterally on the external oblique, rectus abdominis, erector spinae, adductor longus, soleus, and tibialis anterior. 3D Motion capture was conducted while participants performed the two sitting conditions. One way repeated measures ANOVA was used to determine differences in trunk motion and root mean square (RMS) EMG between the two sitting conditions. RESULTS: For any given 10-sec sitting interval, the trunk center of mass traveled a greater distance during the REST condition (25.4±7.9 cm) over that of the Chair condition (3.6±1.5 cm) (p<0.001). Also, mean angular speeds of the trunk during sitting on the REST was greater in the sagittal plane (0.20±0.12 deg/s vs. 0.07±0.06 deg/s) (p<0.001) and in the transverse plane (0.11±0.04 deg/s vs. 0.05±0.09 deg/s) (p=0.011) than those of the Chair condition. Furthermore, average RMS EMGs of the external oblique (6.13±0.34 mv vs. 5.95±0.30 mv) (p=0.037), tibialis anterior (18.96±0.37 mv vs. 18.73±0.30 mv) (p=0.007), and soleus (9.58±0.65 mv vs. 8.70±1.10 mv) (p=0.018) were significantly higher in the REST condition than those in the Chair condition during a 10-sec interval. CONCLUSION: Using a REST device resulted in a significant increase in trunk motion. The elevated activities in trunk and leg muscles serve to maintain and control upper body posture. These biomechanical responses imply that people could assist in helping to establish an active lifestyle by using the REST device on a regular basis.