The purpose of pelvic floor muscle training is to improve the strength and timing of contraction of the pelvic floor muscles under abdominal pressure by strengthening the pelvic floor muscles. However, during voluntary contraction of the pelvic floor, it often fails to do so spontaneously, even in healthy individuals.
 While training the pelvic floor muscles, it is recommended to avoid excessive contraction of the surrounding muscles (abdominal muscles, hip adductor muscles, psoas muscles, etc.) and to begin training in the supine position with the pelvic organs unweighted. During the 2021 conference, we reported that when the supine-to-standing inclination angles were varied between 0–70º, the pelvic floor muscle elevation was significantly greater at an inclination angle of 20º. Therefore, it was predicted that increasing the head-up angle, which involves flexion of the individual’s hip joints and raising the upper body, might increase the degree of elevation of the pelvic floor muscles.
 Therefore, the purpose of this study was to clarify whether the same change in the degree of elevation of the pelvic floor muscle group occurs in the head-up posture with hip flexion.

Thirty-two healthy women without orthopedic disease in the lumbar region, pelvic girdle area, or lower extremities were included in the study with their consent. The mean and standard deviation of age, height, weight, and BMI of the participants were 21.2 ± 0.9 years, 161.5 ± 6.0 cm, 53.6 ± 6.7 kg, and 20.5 ± 1.9 kg/m2, respectively. 
 An ultrasound system (SONIMAGE MX1 Konica Minolta) was used to measure pelvic floor elevation (length of pelvic floor moved headward from rest) using a 3.5 MHz convex-type probe.
 The participants drank 500 mL of water 1h before the measurement to allow the bladder to fill with urine. The probe was placed on the suprapubic margin to measure the bladder floor and tilted 60 degrees cephalad. The depth was adjusted so that the entire bladder could be observed. After drawing a transverse section of the bladder and confirming the position of the pelvic floor muscles, three measurements were acquired per position, with 3 seconds of contraction and 10 seconds of relaxation as a set. We checked whether the pelvic floor muscles were appropriately contracted by measuring the cephalad movement of the bladder floor. The length from the abdominal wall to the bladder floor was measured when the head-up angle was 0º, 10º, and 20º (Figure). The order of measurement positions was randomized.
 Statistical analysis was performed using SPSS 26.0 (IBM). The significance level was set to 5%. One-way analysis of variance was used to compare pelvic floor elevation in the three limb positions. This study was approved by the Research Safety and Ethics Committee (Approval No. 21036)

The mean (standard deviation) pelvic floor elevation at 0º, 10º, and 20° head-up angles were 7.5 (5.9), 6.9 (5.8), and 7.8 (6.4) mm, respectively.
 There was no significant difference noted between the three groups (F (2,93) =0.217, p=0.806).

In this study, we hypothesized that the degree of elevation of the pelvic floor muscles would be greater at a 20º head-up angle with hip flexion. However, our results showed that the mean degree of elevation of the pelvic floor muscles did not change between 0º, 10º, and 20º.
 When the pelvic girdle is tilted posteriorly, the pelvic floor is easily loaded and the pelvic floor muscle groups are less active. Conversely, when the pelvic girdle is excessively tilted anteriorly and the abdominal muscle groups are weakly supported, abdominal pressure may be applied forward in the pelvic region.
 As the pelvic tilt angle affects the degree of elevation of the pelvic floor musculature, it can be inferred that changing the gap-up angle does not make a difference in the pelvic tilt angle relative to the spinal column. Thus, it does not make a difference in the contractile activity of the pelvic floor musculature.

Although their upper body was moved by having the participants move their head up, no consideration was given to the anterior, posterior, or intermediate position of the pelvic girdle. It was speculated that the contraction activity of the pelvic floor muscles may have differed due to the different positions of the pelvic girdle in each individual. It is necessary to measure the activity of the pelvic floor muscles at positions that highlight the relationship between the spinal column and pelvic girdle, not just the angle of the upper body.