Effects of the posterior pelvic tilt sitting posture on thoracic morphology and respiratory function

Influence of chair seat forward tilt angle on upper limb dexterity improvement in seated tasks: a pilot study

[Purpose] This study aimed to investigate the influence of seat-forward tilt angles on improving upper limb dexterity in seated tasks and to contribute to the development of seating strategies. [Participants and Methods] Seventeen healthy men (age, 20.0 ± 0.5 years; height, 175.1 ± 4.9 cm; and body weight, 63.8 ± 6.7 kg) participated in this study. The forward tilt angles of the seat were set at 0°, 15°, and 30°, with knee pads used in all conditions. The Purdue Pegboard task was used to assess upper limb dexterity, with participants inserting pins into holes in the board for 60 s. Additionally, a visual analog scale was used to evaluate the perceived ease of the task. [Results] The Purdue Pegboard task scores were 30.0 ± 2.5, 30.6 ± 2.7, and 32.5 ± 2.9 for the 0°, 15°, and 30° conditions, respectively. The visual analog scale scores were 75.3 ± 9.8, 76.4 ± 14.6, and 84.1 ± 11.1 for the 0°, 15°, and 30° conditions, respectively. Both measurements showed significantly higher values under the 30° condition than under the other two conditions. [Conclusion] These results suggest that a tilt angle of 30° provides the most significant ease and upper limb dexterity.

Relationship between the bilateral ratios of the thoracic shape and electromyographic activity of the thoracic and lumbar iliocostalis muscles during thoracic lateral translation

[Purpose] This study aimed to determine the relationship between thoracic lateral deviation, the bilateral ratio of the thoracic shape, and the bilateral ratio of the thoracic and lumbar iliocostalis muscles during resting sitting and thoracic lateral translation. [Participants and Methods] We included 23 healthy adult males in the study. The measurement tasks were resting sitting and thoracic lateral translation relative to the pelvis. The thoracic lateral deviation and bilateral ratio of the upper and lower thoracic shapes were measured using three-dimensional motion capture. The bilateral ratio of the thoracic and lumbar iliocostalis muscles were measured using the surface electromyographic recording. [Results] The bilateral ratio of the lower thoracic shape was significantly positively correlated with the thoracic translation distance and the bilateral ratio of the thoracic and iliocostalis muscles. In addition, the bilateral ratio of the thoracic iliocostalis muscles was significantly negatively correlated with the bilateral ratios of the lower thoracic shape and lumbar iliocostalis muscles. [Conclusion] Our findings showed that the asymmetry of the lower thoracic shape is associated with left lateral deviation of the thorax at rest and thoracic translation distance. In addition, the thoracic and lumbar iliocostalis muscle activity differed between the left and right translations.

Analysis of the asymmetry of thoracic shape at rest: relationship with lateral thoracic deviation

[Purpose] We analyzed the relationship between the degree of asymmetry in the shape of the thorax and postural changes in the frontal plane, and examined the mechanism that creates an asymmetry in the thoracic shape. [Participants and Methods] The participants included 19 healthy young males. We calculated the thoracic volume and lateral deviation from the amount of displacement of reflective markers attached to the thoracic area using the Vicon MX 3D-analysis system. [Results] Left-right differences were shown in each area of the thorax, and positive and negative correlations were found with the amount of lateral deviation of the thorax, which captured postural changes in the frontal plane. [Conclusion] The results of this study suggest that postural changes in the frontal plane are factors involved in the mechanism of left-right asymmetry formation in the thoracic shape.