Senior Principal Research Fellow, NeuRA
Principal Research Fellow, NHMRC
Conjoint Professor, School of Medical Sciences, UNSW
Honorary Professorial Fellow, The George Institute for Global Health
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Professor Rob Herbert initially trained as a physiotherapist. He completed a PhD under the supervision of Professor Simon Gandevia. Subsequently Rob and Simon have collaborated on research projects investigating fundamental physiological mechanisms and mechanisms of motor impairment for over 15 years. Rob also has an interest in clinical research and conducts randomised trials investigating the effects of physical interventions for motor impairment. He was a founding Director of the Centre for Evidence-Based Physiotherapy, which maintains the PEDro database (www.pedro.org.au), a unique database of randomised trials, systematic reviews and clinical practice guidelines in physiotherapy.
Our recent studies of the control of breathing muscles have shown a strong link between neural drive and mechanical action of the muscle. We showed that for a number of breathing muscles, the neural drive is directed to the muscles with the best mechanical effect for breathing. We termed this link between mechanics and neural drive ‘neuromechanical matching’. It is a new principle of muscle activation that allows for metabolically efficient activation of the muscles. This basic research finding is now leading to further studies in patients with respiratory disorders where muscle mechanics have changed. Chronic obstructive pulmonary disease is one such disease, where muscle mechanics are known to change. Our new studies will look at whether these patients have “adapted” to the changed muscle mechanics or whether their muscles may be activated inefficiently.
DR MARTIN HEROUX Research Officer
DR PETER STUBBS Research Officer
ARKIEV D’SOUZA PhD student
In vivo measurements of muscle architecture provide insight into inter-individual differences in muscle function and could be used to personalise musculoskeletal models. When muscle architecture is measured from ultrasound images, as is frequently done, it is assumed that fascicles are oriented in the image plane and, for some measurements, that the image plane is perpendicular to the aponeurosis at the intersection of fascicle and aponeurosis. This study presents an in vivo validation of these assumptions by comparing ultrasound image plane orientation to three-dimensional reconstructions of muscle fascicles and aponeuroses obtained with diffusion tensor imaging (DTI) and high-resolution anatomical MRI scans. It was found that muscle fascicles were oriented on average at 5.5±4.1° to the ultrasound image plane. On average, ultrasound yielded similar measurements of fascicle lengths to DTI (difference <3mm), suggesting that the measurements were unbiased. The absolute difference in length between any pair of measurements made with ultrasound and DTI was substantial (10mm or 20% of the mean), indicating that the measurements were imprecise. Pennation angles measured with ultrasound were significantly smaller than those measured with DTI (mean difference 6°). This difference was apparent only at the superficial insertion of the muscle fascicles so it was probably due to pressure on the skin applied by the ultrasound probes. It is concluded that ultrasound measurements of deep pennation angles and fascicle lengths in the medial gastrocnemius are unbiased but have a low precision and that superficial pennation angles are underestimated by approximately 10°. The low precision limits the use of ultrasound to personalise fascicle length in musculoskeletal models.
The length and pennation of muscle fascicles are frequently measured using ultrasonography. Conventional ultrasonography imaging methods only provide two-dimensional images of muscles, but muscles have complex three-dimensional arrangements. The most accurate measurements will be obtained when the ultrasound transducer is oriented so that endpoints of a fascicle lie on the ultrasound image plane and the image plane is oriented perpendicular to the aponeurosis, but little is known about how to find this optimal transducer orientation in the frequently-studied medial gastrocnemius muscle. In the current study, we determined the optimal transducer orientation at 9 sites in the medial gastrocnemius muscle of 8 human subjects by calculating the angle of misalignment between three-dimensional muscle fascicles, reconstructed from diffusion tensor images, and the plane of a virtual ultrasound image. The misalignment angle was calculated for a range of tilts and rotations of the ultrasound transducer relative to a reference orientation that was perpendicular to the skin and parallel to the tibia. With the transducer in the reference orientation, the misalignment was substantial (mean across sites and subjects of 6.5°, range 1.4 to 20.2°). However for all sites and subjects a near-optimal alignment (on average 2.6°, range 0.5° to 6.0°) could be achieved by maintaining 0° tilt and applying a small rotation (typically less than 10°). On the basis of these data we recommend that ultrasonographic measurements of medial gastrocnemius muscle fascicle architecture be obtained, at least for relaxed muscles under static conditions, with the transducer oriented perpendicular to the skin and nearly parallel to the tibia.
There is no shortage of treatment approaches offered to people with pain. The maze of options presents patients and clinicians with difficult choices. Key to making those choices is evidence of treatment effectiveness provided by clinical trials and systematic reviews. Recent growth in the number of clinical trials and systematic reviews, of both high and low quality, makes it vital that users of this evidence-clinicians, researchers, patients, and policy makers-have the skills and knowledge to critically interpret these studies. In this review, we discuss some contemporary issues regarding evidence of effectiveness derived from clinical trials and systematic reviews-issues that we think are critical to understanding the field. We focus on evidence of treatment effectiveness in pain, although many of these issues are relevant to and transferable across the spectrum of evidence-based practice.