Odour-mediated Interactions Between an Apex Reptilian Predator and its Mammalian Prey.

An important but understudied modality for eavesdropping between predators and prey is olfaction, especially between non-mammalian vertebrate predators and their prey. Here we test three olfactory eavesdropping predictions involving an apex reptilian predator, the sand goanna Varanus gouldii, and several species of its small mammalian prey in arid central Australia: 1) small mammals will recognize and avoid the odour of V. gouldii; 2) V. gouldii will be attracted to the odour of small mammals, especially of species that maximize its energetic returns; and 3) small mammals will be less mobile and will show higher burrow fidelity where V. gouldii is absent compared with where it is present. As expected, we found that small mammals recognized and avoided faecal odour of this goanna, feeding less intensively at food patches where the odour of V. gouldii was present than at patches with no odour or a pungency control odour. Varanus gouldii also was attracted to the odour of small mammals in artificial burrows and dug more frequently at burrows containing the odour of species that were energetically profitable than at those of species likely to yield diminishing returns. Our third prediction received mixed support. Rates of movement of three species of small mammals were no different where V. gouldii was present or absent, but burrow fidelity in two of these species increased as expected where V. gouldii had been removed. We conclude that olfaction plays a key role in the dynamic interaction between V. gouldii and its mammalian prey, with the interactants using olfaction to balance their respective costs of foraging and reducing predation risk. We speculate that the risk of predation from this apex reptilian predator drives the highly unusual burrow-shifting behaviour that characterizes many of Australia's small desert mammals.

The acute effects of targeted abdominal muscle activation training on spine stability and neuromuscular control.

BACKGROUND: Targeted activation of the transversus abdominis (TrA) muscle through the abdominal drawing-in maneuver (ADIM) is a frequently prescribed exercise for the prevention and rehabilitation of low back pain. However, there is still debate over the role the ADIM plays in maintaining a stable spine during movement. Thus, a single cohort pre/post-intervention protocol was used to examine whether 5 min of ADIM training prior to a dynamic movement task alters dynamic spine stability and control. METHODS: Thirteen healthy participants performed a repetitive spine flexion task twice, once before and once after they received biofeedback training on how to correctly perform the ADIM in standing. Abdominal and back muscle activation (indwelling and surface electromyography, EMG) and 3D kinematic data were recorded during all trials. EMG activation (percent maximum) and local dynamic stability of spine movement [maximum finite-time Lyapunov exponent (λmax)] were compared before and after the training using Friedman's rank test and repeated-measures ANOVA, respectively. To assess the moderating effects of absolute changes in EMG (∆EMG) of each muscle after training on changes in stability, the ∆EMG (peak and mean) were added to the ANOVA as separate covariates (ANCOVA). RESULTS: Following ADIM training, there were greater peak and mean levels of activation in all tested abdominal muscles, including TrA, (p < 0.05), but not in the back muscles. The ANOVA showed no significant change in λmax following training (p = 0.633). However, after considering the moderating effects of the ∆EMG seen in each muscle with training, it was found that only changes in TrA EMG significantly influenced stability. The ANCOVA revealed a significant main effect of training on stability as well as a significant interaction effect between training and ∆EMG recorded from TrA (p < 0.05); those with larger increases in TrA activation demonstrated larger improvements in stability. CONCLUSION: As a group, 5 min of ADIM training did not change spine stability during dynamic movement. However, those who were most successful in improving TrA activation with a 5-min ADIM training session showed the greatest improvements in local dynamic spine stability after training. As such, dynamic spine stability in some individuals may benefit from ADIM training.

Influence of Ultrasound Transducer Tilt in the Cranial and Caudal Directions on Measurements of Inter-Rectus Distance in Parous Women.

Purpose: An increased inter-rectus distance (IRD) can persist after a pregnancy and may be associated with lumbopelvic dysfunction. Ultrasound imaging (USI) is currently the gold standard for measuring IRD; however, no study has explored the need to standardize the transducer angle during these evaluations. The purpose of this study was to determine whether the angle of the ultrasound transducer relative to the underlying abdominal wall has an effect on measurements of IRD in parous women. Method: Ultrasound images of the linea alba (LA) were captured from 15 women, at rest and during a head lift, beginning with images acquired perpendicular to the LA at the midline, then tilted in 5° increments to 15° in both the cranial and the caudal directions. Repeated-measures analyses of variance were used to test for systematic differences in IRD measurements among the transducer angles in both the rest and the head-lift conditions. An α of 0.05 was used for all tests. Results: No significant effect of transducer angle was found in IRD measurements acquired with participants at rest (F2.24,31.3=1.814; p=0.18) or during a head lift (F3.15,44.1=1.315; p=0.28). Conclusion: When using USI, cranial or caudal tilt errors in transducer angle do not appear to pose a problem when measuring IRD.

Objectif : une diastase des grands droits (DGD) peut persister après la grossesse et s'associer à une dysfonction lombo-pelvienne. L'échographie est actuellement la norme pour mesurer la DGD, mais aucune étude n'a porté sur la standardisation de l'angle du transducteur pendant ces évaluations. La présente étude visait à déterminer si l'angle du transducteur échographique par rapport à la paroi abdominale sous-jacente influe sur les mesures de la DGD chez les femmes primipares. Méthodologie : les chercheurs ont utilisé les images échographiques de la ligne blanche (LB) de 15 femmes, au repos et pendant qu'elles soulevaient la tête, à commencer par des images acquises perpendiculairement à la ligne médiane de la LB, puis inclinées par incréments de cinq degrés jusqu'à concurrence de 15 degrés dans une orientation crânienne, puis caudale. Ils ont utilisé les analyses de mesures de variance répétées pour vérifier les différences systématiques entre les mesures de DGD selon les divers angles du transducteur, à la fois au repos et au moment de soulever la tête. Ils ont privilégié un taux alpha de 0,05 pour tous les tests. Résultats : l'angle du transducteur n'avait pas d'effet significatif sur les mesures de la DGD prises chez des participantes au repos (F2,24,31,3=1,814; p=0,18) ou qui soulevaient la tête (F3,15,44,1=1,315; p=0,28). Conclusion : à l'échographie, les erreurs d'inclinaison de l'orientation crânienne ou caudale de l'angle du transducteur ne semblent pas poser problème lors de la mesure de la DGD.

Comparison of Trunk Muscle Function Between Women With and Without Diastasis Recti Abdominis at 1 Year Postpartum.

Background: A separation of the abdominal muscles at the linea alba, known as diastasis recti abdominis (DRA), can occur after childbirth. However, the impact of DRA on abdominal muscle function is not clear. Objective: The objective was to determine if differences exist in trunk muscle function and self-reported pain and low back dysfunction between women with and without DRA at 12 to 14 months postpartum and if differences that emerge from the data are associated with the magnitude of the interrectus distance (IRD). Design: This study was a prospective, observational, case-control study. Methods: Women with (IRD ≥ 2.2 cm; n = 18) and without DRA (IRD < 2.2 cm; n = 22) participated. Maximal trunk flexion, extension, and rotation torque-generating capacity (Newton-meters), the Sit-Up test (0 to 3 points), and the Sitting-Rising Test (0 to 10 points), and trunk flexion, extension, and lateral flexion endurance (seconds) were measured. Pain and disability were assessed using numerical pain rating scales (0 to 100) and the Roland Morris Low Back Pain Questionnaire (0 to 24 points). Women were compared using independent t tests and Mann-Whitney U Tests. Pearson product-moment and Spearman rank correlation coefficients were used to determine associations; a = .05 was used for all tests. Results: Women with DRA demonstrated significantly lower trunk muscle rotation torque and scored lower on the sit-up test than those without DRA. IRD was negatively correlated with both trunk rotation torque (rho = -0.367) and sit-up test score (rho = -0.514). Limitations: The results of this study should not be generalized to women who present with moderate-to-severe IRDs or to multiparous women. Conclusion: The presence of DRA in primiparous women at 1 year postpartum is associated with trunk rotation strength and ability to perform a sit-up.

Inter-Rectus Distance Measurement Using Ultrasound Imaging: Does the Rater Matter?

Purpose: To investigate the interrater reliability of inter-rectus distance (IRD) measured from ultrasound images acquired at rest and during a head-lift task in parous women and to establish the standard error of measurement (SEM) and minimal detectable change (MDC) between two raters. Methods: Two physiotherapists independently acquired ultrasound images of the anterior abdominal wall from 17 parous women and measured IRD at four locations along the linea alba: at the superior border of the umbilicus, at 3 cm and 5 cm above the superior border of the umbilicus, and at 3 cm below the inferior border of the umbilicus. The interrater reliability of the IRD measurements was determined using intra-class correlation coefficients (ICCs). Bland-Altman analyses were used to detect bias between the raters, and SEM and MDC values were established for each measurement site. Results: When the two raters performed their own image acquisition and processing, ICCs(3,5) ranged from 0.72 to 0.91 at rest and from 0.63 to 0.96 during head lift, depending on the anatomical measurement site. Bland-Altman analyses revealed no systematic bias between the raters. SEM values ranged from 0.23 cm to 0.71 cm, and MDC values ranged from 0.64 cm to 1.97 cm. Conclusion: When using ultrasound imaging to measure IRD in women, it is acceptable for different therapists to compare IRDs between patients and within patients over time if IRD is measured above or below the umbilicus. Interrater reliability of IRD measurement is poorest at the level of the superior border of the umbilicus.

Objectif : examiner la fiabilité interévaluateurs de la mesure de la distance entre les deux faisceaux du grand droit, au repos et en contraction, à partir d'échographies prises chez des femmes qui ont eu un enfant, et établir l'erreur type de mesure (ETM) et le changement minimal détectable (CMD) entre deux évaluateurs. Méthodes : deux physiothérapeutes ont obtenu indépendamment des échographies de la paroi abdominale antérieure de 17 femmes et mesuré la distance sur quatre sites le long de la ligne blanche : au bord supérieur de l'ombilic, à 3 cm et à 5 cm au-dessus du bord supérieur de l'ombilic et 3 cm sous le bord inférieur de l'ombilic. La fiabilité interévaluateurs des mesures a été déterminée à l'aide de coefficients de corrélation intraclasse (CCI). Des analyses Bland-Altman ont été réalisées afin de détecter le biais entre les évaluateurs et les valeurs ETM et CMD ont été calculées pour chaque site de mesure. Résultats : lorsque les deux évaluateurs ont obtenu et traité eux-mêmes les images, les CCI(3,5) allaient de 0,72 à 0,91 au repos et de 0,63 à 0,96 en contraction, selon le site de mesure. Les analyses Bland-Altman n'ont révélé aucun biais systématique entre les évaluateurs. Les valeurs ETM allaient de 0,23 cm à 0,71 cm, les valeurs CMD de 0,64 cm à 1,97 cm. Conclusion : lorsqu'on mesure la distance entre les faisceaux du grand droit à partir d'échographies, il est acceptable pour différents thérapeutes de comparer la distance entre patients et au fil du temps pour un même patient si la distance est mesurée au-dessus ou en dessous de l'ombilic. La fiabilité interévaluateurs de la mesure est la plus faible au niveau du bord supérieur du nombril.