In popular fitness modalities, the participants often perform abdominal breathing while maintaining stable or rather unstable as well as inverted body stances that may challenge the respiratory muscles’ activation. This study aimed to examine the abdominal breathing effect on postural stability and the respiratory muscles’ activation during four body stances: the Upright Stance, the Quadrupled Inverted V, the Elbow Side-Bridge, and the Headstand. Participants (n = 29) maintained (40 s) the body stances under regular and abdominal breathing (the latter verified through visual inspection and 3D inertial sensing of the abdominal wall angular displacements, LORD-MicroStrain®, 100 Hz, MicroStrain, Inc., Williston, VT, USA). The trajectory of the center of pressure (CoP) (Kistler force plate, 100 Hz, Kistler Group, Winterthur, Switzerland) was recorded in synchronization with the respiratory muscles’ (sternocleidomastoid, external intercostals, diaphragm, rectus abdominis) vibromyographic activation (Biopac VMG sensors, 2000 Hz, Biopac Systems, Inc., Santa Barbara, CA, USA). Abdominal breathing had a significant (p ≤ 0.05) deteriorating effect on postural stability and an increasing one on the respiratory muscles’ activation; however, this was not consistent across body stances. The body stance specificity of the abdominal breathing effect justifies the purpose of the present study. Thus, before the request for abdominal breathing in popular fitness modalities, one should acknowledge the postural and the breathing demands of each particular stance, particularly for the inverted ones.

Purpose. this study aimed to verify the reliability of estimating ballet dancers' postural stability during the unshod and the en pointe relevé position with a smartphone application Methods. the participants (13 ballet dancers, 22.4 ± 2.5 years of age) were tested in the unshod and the en pointe relevé position (YMED Balance test application, smartphone secured at the L5 level for centre of mass approximation, 10 trials for each condition, 10 seconds per trial, 2-minute intertrial break, arms relaxed at bodyside, gaze fixated at an eye-level target, preferred feet width and orientation). Paired t-tests examined the inter-condition differences. relative (intraclass correlation coefficient, Icc) and absolute (standard error of measurement, SEM, SEM%) reliability indices (for accumulated and paired trials) were computed for each condition (SPSS software v. 26.0, p < 0.05). Results. the total balance score and all centre of mass spatial measures indicated worse postural stability in the en pointe condition (p < 0.05), with no significant temporal differences (p > 0.05). the total body balance score was the most reliable measure (good to excellent Iccs, low to moderate SEM%) with a minimum of 8 trials ensuring reliability in both the unshod and the en pointe relevé positions. Conclusions. taken a minimum of 8 trials and the measure of total balance score, we may obtain a reliable estimation of ballet dancers' postural stability in the unshod and the en pointe relevé position by using the YMED Balance test smartphone application.

Barefoot, BS: Base of support, COM: Center of mass. Methods ParticipantsEleven young women (Age: 22.14 ± 2.93yrs, Height: 1.63 ± 0.04 m, Weight: 52.44 ± 6.94 kg, BMI: 19.85 ± 2.99 kg/m 2 ) participated in the study. The age of the young women was within the age range (20 to 29 years old) that the highest rate of injuries due to the use of high heel shoes is reported (34.2% of cases from 2002 to 2012 [15], and 33.4% of cases from 2006 to 2010 [16]). Their anthropometric characteristics

<b><i>Introduction:</i></b> The effect of rhythmic acoustic stimuli on body sway is of increasing interest due to their positive contribution when training or restoring the control of movement. Inertial sensors show promise as a portable, easier, and more affordable method compared to the force plate “gold standard” concerning the evaluation of postural sway. This study examined the concurrent validity of inertially sensed measures of voluntary body sway against those obtained with a force plate, in silence and while exposed to a rhythmic acoustic stimulus. <b><i>Methods:</i></b> Temporal (sway duration and variability) and spatial (trajectory length, variability, range, velocity, and area) body sway variables were extracted using an inertial sensor (at L5) in synchronization with a force plate, during anteroposterior body sway in silence and while exposed to a rhythmic acoustic stimulus (<i>n</i> = 18 young women; two 70-s trials in each condition). Statistics included bivariate correlations between the inertially sensed and the force plate measures, separately, in silence and with a rhythmic acoustic stimulus, as well as for the effect of the rhythmic acoustic stimulus (percentage difference from silence) (<i>p</i> ≤ 0.05, SPSS v25.0). <b><i>Results:</i></b> The inertially sensed measures demonstrated good-to-excellent concurrent validity for all temporal and almost all spatial variables, both in silence and with rhythmic acoustic stimulus (<i>r</i> &#x3e; 0.75, <i>p</i> = 0.000), as well as for the rhythmic acoustic-stimulus effect (<i>r</i> &#x3e; 0.75, <i>p</i> ≤ 0.05). <b><i>Conclusion:</i></b> The inertially sensed measures of the voluntary anteroposterior body sway demonstrated an overall good-to-excellent concurrent validity against those obtained with the force plate “gold standard,” both in the silence and the rhythmic acoustic stimulus conditions, as well as for the rhythmic acoustic-stimulus effect. The findings of this pilot study allow the recommendation of inertial sensing for the evaluation of postural control alterations when exposed to rhythmic acoustic stimuli, a condition of increasing interest due to the positive contribution of such stimuli when training or restoring the control of movement.

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