Purpose & Background. The ability to jump higher is a key factor for athletic performance and relies on many factors including spinal movement and trunk muscle activity. Manual therapy including Mulligan' Sustained Natural Apophyseal Glide (SNAG) techniques are proposed to increase spinal movement and thus function. The evidence pf the effect of manual therapy on muscle activity is limited. We aimed to determine the immediate effects of an extension SNAG on the lower lumbar spine on jump height and rectus abdominis (RA), external oblique (EO), multifidus (M) and iliocostalis Lumborum (IL) muscle activity during the flight phase of vertical jump compared to a placebo intervention (flat hand pressure). Method. Eighteen healthy participants (16 males, age 28.11±5.01 years, weight 70.58±11.9 kg, height 1.70±0.07m, body mass index 24.28±3.30)from Cardiff University were randomly allocated to either an extension SNAG or placebo intervention. Surface Electromyography was normalised to maximum voluntary contraction and was collected during the flight phase of the jump and jump height was measured using jump and reach test. Results. There was a significant increase (p=0.01) in jump height for the SNAG group. No significant differences in RA, EO, M, IL muscle activity was noted between SNAG and placebo interventions In EO, LES and M descriptive analysis showed a decrease in muscle activity in on average 14 of the subjects. Conclusion. SNAG mobilisation can produce an immediate increase in jump height but no significant changes in muscle activity in healthy subjects. Further work is warranted in subjects with low back pain. No Conflict of Interests. No funding was obtained

Background:. We have recently shown, using transcranial magnetic stimulation (TMS) to assess voluntary activation (VA), that neural drive to back muscles is reduced in subjects with chronic low back pain. There is also evidence that central nervous system drive to abdominal muscles is altered in these subjects, however VA has not yet been assessed for these muscles in healthy subjects; this is the purpose of the present study. Methods:. Twenty one healthy subjects (10M:11F) participated. Electromyographic activity was recorded from back and abdominal muscles and flexor torque was measured using a dynamometer. Subjects performed a series of isometric voluntary contractions (10%–100% MVC) of rectus abdominis during which TMS was applied to the motor cortex. The resulting superimposed twitches (SIT) were measured and VA was derived. Results:. There was a linear relationship between voluntary torque (50–100% MVC) and SIT amplitude and between voluntary torque (50–100% MVC) and VA. VA at a target torque of 100% MVC was less than maximal (∼86%). Time-to-peak amplitude of SITs displayed a linear relationship with voluntary torque between 10%–100% MVC. Discussion:. This study has shown that it is possible to assess VA of abdominal muscles using TMS. Further, it appears that VA is submaximal during maximum voluntary contractions, similar to that observed in back muscles. This may reflect the function of trunk muscles in general, which are routinely used for maintenance of posture. Whether imbalances of abdominal and back muscle strength observed in low back pain are reflected in imbalances of neural drive to these muscles remains to be investigated

Introduction. Changes in the central nervous system (CNS) pathways controlling trunk and leg muscles in patients with low back pain and radiculopathy have been observed and this study investigated whether surgery impacts upon these changes. Methods. Parameters of corticospinal control were examined on 3 occasions in 22 patients prior to, at 6 and 26 weeks following lumbar decompression surgery and in 14 control subjects at the same intervals. Electromyographic activity was recorded from tibialis anterior (TA), soleus (SOL), rectus abdominis (RA), external oblique (EO) and erector spinae (ES) muscles at the T12 & L4 levels in response to transcranial magnetic stimulation of the motor cortex. Results. In the surgical group, asymmetries in the size of motor evoked potentials (MEPs) in TA (P=0.001) and in the cortical silent periods (cSP) were found between the left and right sides in SOL (P=0.005) and ES at L4 (P=0.014) prior to surgery. This was not observed at 6 or 26 weeks. Abdominal responses could be evoked in 12 patients and there was a significant reduction in the cSP contralateral to the pain in EO (P=0.034) and RA (P=0.041) at 6 weeks. These parameters remained stable in controls over time. Discussion. The fact that changes appear to stabilise at 6 weeks is of interest as this parallels clinical outcome studies. Current work is ongoing to examine these excitability changes in both inhibitory and excitatory cortical pathways in these patients, and to what extent they may be related to clinical outcome