Change in levator ani muscle stiffness and active force during pregnancy and post-partum.

INTRODUCTION AND HYPOTHESIS: It is assumed changes occur to the biomechanics and viscoelastic response of the levator ani muscle during pregnancy; however, there is limited evidence of this. This study used instrumentation and clinical measures to determine the stiffness and active force capacity of levator ani muscle during pregnancy and post-partum, investigated any associations with delivery outcomes, and explored the biomechanical properties associated with symptoms of pelvic floor dysfunction. METHODS: This was a prospective observational study, with nulliparous women with a singleton low-risk pregnancy. Data were collected at two stages during pregnancy and post-partum. Measurements included the Australian Pelvic Floor Questionnaire, palpation of active force, and elastometry measurements. Post-partum, 3D/4D ultrasound measurements were included. Repeated measures ANOVAs, pairwise comparisons, Pearson correlation coefficients, and Student's t-tests were used as appropriate. RESULTS: Fifty-nine women took part in the study. Active force was significantly different over the pregnancy and post-partum, measured with instrumentation (p = 0.002) and palpation (p = 0.006 right, p = 0.029 left). There was no significant change in muscle stiffness during pregnancy. Post-partum muscle stiffness was significantly different between women who gave birth vaginally vs. caesarean section (p = 0.002). Post-partum there were differences in levator hiatal area, symptoms of bladder dysfunction, prolapse symptoms, and sexual dysfunction symptoms. CONCLUSIONS: Active force of the levator ani muscle was significantly reduced during pregnancy and in the post-partum period, while muscle stiffness reduced only in those who had vaginal deliveries.

Is it time to rethink using digital palpation for assessment of muscle stiffness?

AIM: Physiotherapists typically use digital palpation to determine residual tension in a muscle, referred to as muscle stiffness or tone. These assessments are subjective, and little is known about their accuracy or repeatability. Despite this, it is standard practice to base clinical treatment on these findings. The aim of this study was to assess physiotherapists' ability to assign a seven-point palpation scale to quantitative stiffness values generated by a novel device. METHODS: Prospective observational study involving 125 musculoskeletal and pelvic floor physiotherapists. A novel device was developed that replicates the haptic feedback that clinicians assess as muscle stiffness. Measurements of displacement, force, and stiffness were recorded. RESULTS: There was wide overlap between each scale category assigned to the stiffness values, from low stiffness at -3 (119 [106, 132] N/m) to moderate stiffness at 0 (462 [435,489] N/m); to high stiffness at +3 (897 [881,913] N/m). Consistency in applying the scale was poor, and the probability of a similar value of stiffness being assigned to the same scale category by different participants was low. CONCLUSIONS: While palpation is used globally by physiotherapists as a readily available and low-cost method of assessing muscle stiffness, these results indicate that it should be used with caution in diagnosing and defining patient care. Clinical assessment of muscle stiffness requires a validated and reliable palpation scale if this metric is to be used to diagnose pathology and develop treatment protocols. Training in this scale should then be recommended to improve reliability in patient assessment.

Myotonometry Reliably Measures Muscle Stiffness in the Thenar and Perineal Muscles.

Purpose: The authors investigated the reliability of myotonometry-measured muscle tone in the thenar and perineal muscles. Methods: Participants were women aged 18-50 years who were asymptomatic for thumb and pelvic floor dysfunction (interrater study n=20; intrarater study n=43) or who were symptomatic for vulvodynia (interrater study n=14; intrarater study n=32). Mechanical properties (stiffness, frequency, decrement, relaxation time, and creep) of the muscles were measured using a myotonometer (MyotonPRO) while the muscles were in a relaxed state. Measures were performed twice by two assessors. Intra- and interrater reliability were determined using intra-class correlation coefficients (ICCs) and absolute reliability using the standard error of measurement and a minimum detectable change. Results: The primary property of interest, muscle stiffness, showed very good interrater (ICC 0.85-0.86) and intrarater (ICC 0.82-0.88) reliability in the thenar eminence. In the perineal muscles, reliability results ranged from good to very good for interrater (ICC 0.70-0.86) and intrarater (ICC 0.80-0.91) reliability for muscle stiffness. Absolute reliability was confirmed, with all measures showing minimal variance. Conclusions: Muscle stiffness of the smaller muscles of the body can be reliably measured using the MyotonPRO. The device could be used as a reference standard in the development of a digital palpation scale that would facilitate accurate diagnosis of muscle tone.

Objectif : étudier la fiabilité de la raideur musculaire mesurée par myotonométrie dans les muscles de l'éminence thénar et du périnée. Méthodologie : Les participantes étaient des femmes âgées de 18 à 50 ans ne présentant aucun symptôme de dysfonctionnement du pouce ni du plancher pelvien (étude interévaluateur n=20; étude intra-évaluateur n=43) ou présentant des symptômes de vulvodynie (étude interévaluateur n=14; étude intra-évaluateur n=32). Les propriétés mécaniques (raideur, fréquence, décrément, temps de relaxation et fluage) des muscles au repos ont été mesurées à l'aide d'un myotonomètre (MyotonPRO). Les mesures ont été prises deux fois par deux évaluateurs. La fiabilité intra-évaluateur et interévaluateur a été déterminée à l'aide des coefficients de corrélation intraclasse (CCI) et la fiabilité absolue à l'aide de l'écart type de mesure et du changement minimal détectable. Résultats : la propriété d'intérêt principal, la raideur musculaire, a montré une très bonne fiabilité interévaluateur (CCI 0,85-0,86) et intra-évaluateur (CCI 0,82-0,88) pour l'éminence thénar. Concernant les muscles du périnée, les résultats de fiabilité variaient de bons à très bons pour la fiabilité interévaluateur (CCI 0,70-0,86) et intra-évaluateur (CCI 0,80-0,91) pour la raideur musculaire. La fiabilité absolue a été confirmée, toutes les mesures montrant une variabilité minimale. Conclusions : la raideur musculaire des plus petits muscles du corps peut être mesurée de manière fiable à l'aide du MyotonPRO. L'appareil pourrait être utilisé comme norme de référence dans la conception d'une échelle numérique de palpation qui faciliterait le diagnostic exact du tonus musculaire.