Kieran O'Sullivan

Effect of different upright sitting postures on spinal-pelvic curvature and trunk muscle activation in a pain-free population

Study Design. A normative within-subjects single-group study. Objective. To compare spinal-pelvic curvature and trunk muscle activation in 2 upright sitting postures (“thoracic” and “lumbo-pelvic”) and slump sitting in a pain-free population. Summary of Background Data. Clinical observations suggest that both upright and slump sitting postures can exacerbate low back pain. Little research has investigated the effects of different upright sitting postures on trunk muscle activation. Methods. Spinal-pelvic curvature and surface electromyography of 6 trunk muscles were measured bilaterally in 2 upright (thoracic and lumbo-pelvic) sitting postures and slump sitting in 22 subjects. Results. Thoracic, compared to lumbo-pelvic, upright sitting showed significantly greater thoracic extension (P < 0.001), with significantly less lumbar extension (P < 0.001) and anterior pelvic tilt (P = 0.03). Furthermore, there was significantly less superficial lumbar multifidus (P < 0.001) and internal oblique (P = 0.03) activity, with significantly higher thoracic erector spinae (P < 0.001) and external oblique (P = 0.04) activity in thoracic upright sitting. There was no significant difference in superficial lumbar multifidus activity between thoracic upright and slump sitting. Conclusions. Different upright sitting postures resulted in altered trunk muscle activation. Thoracic when compared to lumbo-pelvic upright sitting involved less coactivation of the local spinal muscles, with greater coactivation of the global muscles. These results highlight the importance of postural training specificity when the aim is to activate the lumbo-pelvic stabilizing muscles in subjects with back pain.

The effect of warm-up, static stretching and dynamic stretching on hamstring flexibility in previously injured subjects

BackgroundWarm-up and stretching are suggested to increase hamstring flexibility and reduce the risk of injury. This study examined the short-term effects of warm-up, static stretching and dynamic stretching on hamstring flexibility in individuals with previous hamstring injury and uninjured controls.MethodsA randomised crossover study design, over 2 separate days. Hamstring flexibility was assessed using passive knee extension range of motion (PKE ROM). 18 previously injured individuals and 18 uninjured controls participated. On both days, four measurements of PKE ROM were recorded: (1) at baseline; (2) after warm-up; (3) after stretch (static or dynamic) and (4) after a 15-minute rest. Participants carried out both static and dynamic stretches, but on different days. Data were analysed using Anova.ResultsAcross both groups, there was a significant main effect for time (p < 0.001). PKE ROM significantly increased with warm-up (p < 0.001). From warm-up, PKE ROM further increased with static stretching (p = 0.04) but significantly decreased after dynamic stretching (p = 0.013). The increased flexibility after warm-up and static stretching reduced significantly (p < 0.001) after 15 minutes of rest, but remained significantly greater than at baseline (p < 0.001). Between groups, there was no main effect for group (p = 0.462), with no difference in mean PKE ROM values at any individual stage of the protocol (p > 0.05). Using ANCOVA to adjust for the non-significant (p = 0.141) baseline difference between groups, the previously injured group demonstrated a greater response to warm-up and static stretching, however this was not statistically significant (p = 0.05).ConclusionWarm-up significantly increased hamstring flexibility. Static stretching also increased hamstring flexibility, whereas dynamic did not, in agreement with previous findings on uninjured controls. The effect of warm-up and static stretching on flexibility was greater in those with reduced flexibility post-injury, but this did not reach statistical significance. Further prospective research is required to validate the hypothesis that increased flexibility improves outcomes.Trial RegistrationACTRN12608000638336

What do physiotherapists consider to be the best sitting spinal posture

While sitting is a common aggravating factor in low back pain (LBP), the best sitting posture remains unclear. This study investigated the perceptions of 295 physiotherapists in four different European countries on sitting posture. Physiotherapists selected their perceived best sitting posture from a sample of nine options that ranged from slumped to upright sitting, as well as completing the back beliefs questionnaire (BBQ). 85% of physiotherapists selected one of two postures as best, with one posture being selected significantly more frequently than the remainder (p < 0.05). Interestingly, these two most frequently selected postures were very different from each other. Those who selected the more upright sitting posture had more negative LBP beliefs on the BBQ (p < 0.05). The choice of best sitting posture also varied between countries (p < 0.05). Overall, disagreement remains on what constitutes a neutral spine posture, and what is the best sitting posture. Qualitative comments indicated that sitting postures which matched the natural shape of the spine, and appeared comfortable and/or relaxed without excessive muscle tone were often deemed advantageous. Further research on the perceptions of people with LBP on sitting posture are indicated.

Neutral lumbar spine sitting posture in pain-free subjects

Sitting is a common aggravating factor in low back pain (LBP), and re-education of sitting posture is a common aspect of LBP management. However, there is debate regarding what is an optimal sitting posture. This pilot study had 2 aims; to investigate whether pain-free subjects can be reliably positioned in a neutral sitting posture (slight lumbar lordosis and relaxed thorax); and to compare perceptions of neutral sitting posture to habitual sitting posture (HSP). The lower lumbar spine HSP of seventeen pain-free subjects was initially recorded. Subjects then assumed their own subjectively perceived ideal posture (SPIP). Finally, 2 testers independently positioned the subjects into a tester perceived neutral posture (TPNP). The inter-tester reliability of positioning in TPNP was very good (intraclass correlation coefficient (ICC) = 0.91, mean difference = 3% of range of motion). A repeated measures ANOVA revealed that HSP was significantly more flexed than both SPIP and TPNP (p <0.05). There was no significant difference between SPIP and TPNP (p > 0.05). HSP was more kyphotic than all other postures. This study suggests that pain-free subjects can be reliably positioned in a neutral lumbar sitting posture. Further investigation into the role of neutral sitting posture in LBP subjects is warranted.

Electromyographic analysis of the three subdivisions of gluteus medius during weight-bearing exercises

BackgroundGluteus medius (GM) dysfunction is associated with many musculoskeletal disorders. Rehabilitation exercises aimed at strengthening GM appear to improve lower limb kinematics and reduce pain. However, there is a lack of evidence to identify which exercises best activate GM. In particular, as GM consists of three distinct subdivisions, it is unclear if GM activation is consistent across these subdivisions during exercise. The aim of this study was to determine the activation of the anterior, middle and posterior subdivisions of GM during weight-bearing exercises.MethodsA single session, repeated-measures design. The activity of each GM subdivision was measured in 15 pain-free subjects using surface electromyography (sEMG) during three weight-bearing exercises; wall squat (WS), pelvic drop (PD) and wall press (WP). Muscle activity was expressed relative to maximum voluntary isometric contraction (MVIC). Differences in muscle activation were determined using one-way repeated measures ANOVA with post-hoc Bonferroni analysis.ResultsThe activation of each GM subdivision during the exercises was significantly different (interaction effect; p < 0.001). There were also significant main effects for muscle subdivision (p < 0.001) and for exercise (p < 0.001). The exercises were progressively more demanding from WS to PD to WP. The exercises caused significantly greater activation of the middle and posterior subdivisions than the anterior subdivision, with the WP significantly increasing the activation of the posterior subdivision (all p < 0.05).DiscussionPosterior GM displayed higher activation across all three exercises than both anterior and middle GM. The WP produced the highest %MVIC activation for all GM subdivisions, and this was most pronounced for posterior GM. Clinicians may use these results to effectively progress strengthening exercises for GM in the rehabilitation of lower extremity injuries.

The effect of low-dye taping on rearfoot motion and plantar pressure during the stance phase of gait

BackgroundLow-dye (LD) taping is commonly used to reduce rearfoot pronation. No studies have previously investigated the effectiveness of LD taping using both plantar pressure distribution (F-Scan) and 3-D (CODA) analysis of rearfoot motion.Methods20 healthy subjects with a navicular drop test exceeding 10 mm participated in the study. T tests were used to determine whether significant (p < 0.05) differences in plantar pressure and rearfoot motion occurred with LD taping.ResultsLD taping resulted in statistically significant increases in peak plantar pressure in the lateral midfoot (p = 0.000), along with significant decreases in pressure in the medial forefoot (p = 0.014), and the medial (p = 0.000) and lateral hindfoot (p = 0.007). No significant changes occurred in the medial midfoot (p = 0.794) or lateral forefoot (p = 0.654). When assessed using motion analysis, taping resulted in a statistically significant decrease in rearfoot pronation (p = 0.006), supination (p = 0.025) and total rearfoot range of motion (p = 0.000). The mean rearfoot position during stance was not significantly different however (p = 0.188).ConclusionLD taping is associated with alterations in peak plantar pressure in the midfoot and forefoot that indicate reduced pronation with LD taping. However, LD taping appears to reduce both pronation and supination in the rearfoot, rather than simply reducing pronation, when assessed using 3D motion analysis. Therefore, it would appear that LD taping does indeed reduce pronation, by restricting rearfoot motion in general, rather than pronation specifically. The degree of change observed with LD taping was however very small, and further research is needed to clarify the clinical significance of these initial findings.

The relationship between previous hamstring injury and the concentric isokinetic knee muscle strength of irish gaelic footballers

BackgroundHamstring injury is one of the most common injuries affecting gaelic footballers, similar to other field sports. Research in other sports on whether residual hamstring weakness is present after hamstring injury is inconsistent, and no study has examined this factor in irish gaelic footballers. The aim of this study was to examine whether significant knee muscle weakness is present in male Irish gaelic footballers who have returned to full activity after hamstring injury.MethodsThe concentric isokinetic knee flexion and extension strength of 44 members of a university gaelic football team was assessed at 60, 180 and 300 degrees per second using a Contrex dynamometer.ResultsFifteen players (34%) reported a history of hamstring strain, with 68% of injuries affecting the dominant (kicking) limb. The hamstrings were significantly stronger (p < 0.05) on the dominant limb in all uninjured subjects. The previously injured limbs had a significantly lower (p < 0.05) hamstrings to quadriceps (HQ) strength ratio than all other non-injured limbs, but neither their hamstrings nor quadriceps were significantly weaker (p > 0.05) using this comparison. The previously unilaterally injured hamstrings were significantly weaker (p < 0.05) than uninjured limbs however, when matched for dominance. The hamstring to opposite hamstring (H:oppH) strength ratio of the previously injured players was also found to be significantly lower (p < 0.05) than that of the uninjured players.ConclusionHamstring muscle weakness was observed in male Irish gaelic footballers with a history of hamstring injury. This weakness is most evident when comparisons are made to multiple control populations, both within and between subjects. The increased strength of the dominant limb should be considered as a potential confounding variable in future trials. The study design does not allow interpretation of whether these changes in strength were present before or after injury.

The effect of dynamic sitting on the prevention and management of low back pain and low back discomfort: a systematic review

Dynamic sitting has been proposed to reduce low back pain (LBP) and/or low back discomfort (LBD) while sitting. This is supported by studies suggesting that subjects with LBP assume more static, sustained postures while sitting. This systematic review investigated the effect of dynamic sitting on LBP among subjects with LBP and the development of LBD among pain-free subjects. Electronic databases were searched by two independent assessors. All prospective studies which compared the effect of a dynamic sitting condition on LBP or LBD to another sitting condition were eligible, with no minimum follow-up period applied. The quality of the included studies was assessed using the PEDro scale. Seven high-quality studies were eligible, including five crossover studies and two randomised controlled trials. The results suggest there is currently no evidence to support the use of dynamic sitting as a stand-alone approach in the management of LBP. Practitioner Summary: This systematic review investigated the effect of dynamic sitting on LBP or LBD. Seven high-quality studies met the inclusion and exclusion criteria. Overall, the evidence suggests that dynamic sitting approaches are not effective as a stand-alone management approach for LBP.

Lumbar posture and trunk muscle activation during a typing task when sitting on a novel dynamic ergonomic chair

Low back pain (LBP) is a common musculoskeletal disorder and prolonged sitting often aggravates LBP. A novel dynamic ergonomic chair (‘Back App’), which facilitates less hip flexion while sitting on an unstable base has been developed. This study compared lumbar posture and trunk muscle activation on this novel chair with a standard backless office chair. Twelve painfree participants completed a typing task on both chairs. Lumbar posture and trunk muscle activation were collected simultaneously and were analysed using paired t-tests. Sitting on the novel dynamic chair significantly (p < 0.05) reduced both lumbar flexion and the activation of one back muscle (Iliocostalis Lumborum pars Thoracis). The discomfort experienced was mild and was similar (p > 0.05) between chairs. Maintaining lordosis with less muscle activation during prolonged sitting could reduce the fatigue associated with upright sitting postures. Studies with longer sitting durations, and in people with LBP, are required. Practitioner Summary: Sitting on a novel dynamic chair resulted in less lumbar flexion and less back muscle activation than sitting on a standard backless office chair during a typing task among pain-free participants. Facilitating lordotic sitting with less muscle activation may reduce the fatigue and discomfort often associated with lordotic sitting postures.

The between-day and inter-rater reliability of a novel wireless system to analyse lumbar spine posture

Lumbar posture is commonly assessed in non-specific chronic low back pain (NSCLBP), although quantitative measures have mostly been limited to laboratory environments. The BodyGuard™ is a spinal position monitoring device that can monitor posture in real time, both inside and outside the laboratory. The reliability of this wireless device was examined in 18 healthy participants during usual sitting and forward bending, two tasks that are commonly provocative in NSCLBP. Reliability was determined using intraclass correlation coefficients (ICC), the standard error of measurement (SEM), the mean difference and the minimal detectable change (MDC90). Between-day ICC values ranged from 0.84 to 0.87, with small SEM (5%), mean difference (<9%) and MDC90 (<14%) values. Inter-rater ICC values ranged from 0.91 to 0.94, with small SEM (4%), mean difference (6%) and MDC90 (9%) values. Between-day and inter-rater reliability are essential requirements for clinical utility and were excellent in this study. Further studies into the validity of this device and its application in clinical trials in occupational settings are required. Statement of Relevance:A novel device that can analyse spinal posture exposure in occupational settings in a minimally invasive manner has been developed. This study established that the device has excellent between-day and inter-rater reliability in healthy pain-free subjects. Further studies in people with low back pain are planned.