Question

Please explain sitting on a chair to standing up how biomechanically the following phases work (anatomy)

Flexion momentum (start sitting)-

Momentum transfer (lift off)-

Extension (Max dorsiflexion)-

Stabilization ( End Hip Extension)-

How does sitting on a chair to standing up work Mechanical and Anatomical? (use anatomy parts)

Answer 1

Ans :

Phase I (flexion-momentum phase) starts with initiation of the movement and ends just before the buttocks are lifted from the seat of the chair.

The primary event in the flexion- momentum phase of rising was the trunk and pelvis rotation forward into flexion. For seven of the nine sub- jects, the trunk flexed on the pelvis an average of 16 degrees and reached a point of maximum flexion relative to the pelvis during this phase . For two subjects, there was no trunk motion relative to the pelvis; that is, the trunk and pelvis moved into flex- ion together. Characteristic timing of events for the subjects is depicted in . Because of the relationship between angular momentum and angular velocity, maximum angular velocity can be used to determine maximum angular momentum and thus to iden tify aspects of the propulsion phases during a movement. Maximum trunk- flexion angular velocity, hip-flexion angular velocity, and head-extension angular velocity were reached during the flexion-momentum phase and occurred almost simultaneously,. Head extension and flexion are referenced to the trunk. (Phase I = flex- ion momentum; phase II = momentum transfer; phase III = extension.) Full Hip Extension - Full Knee Extension - Maximum Ankle Dorsiflexion Maximum Head . Extension Maximum Trunk .

Phase II (momentum-transfer phase) begins as the buttocks are lifted and ends when maximal ankle dorsiflexion is achieved.

The momentum-transfer phase began when the buttocks lifted off from the chair and was completed on attain- ment of the maximally forward-flexed position . In this phase, maxi- mum ankle dorsiflexion, trunk flex- ion, hip flexion, and head extension were reached. There was almost no difference between right and left sides for maximum hip flexion, maximum ankle dorsiflexion, and total knee extension . Differences between the right and left sides were not significant at the hip, knee, or ankle. In the momentum-transfer phase, the order of events was invariant for eight of the nine subjects.

The sequence of events for these eight subjects was maximum hip flexion, maximum trunk flexion, maximum head exten- sion, and finally maximum ankle dor- siflexion. For one subject, maximum head extension was achieved after the

Phase III (extension phase) is initiated just after maximum ankle dorsiflexion and ends when the hips first cease to extend; including leg and trunk extension

the extension phase of rising, maxi- mum hip, trunk-, and knee-extension velocities and maximum head-flexion velocity were reached . Elapsed time between the first and last events was 0.13 second. In phase 1 of rising, there was more variability in the order in which events occurred than in phase I. The time at which maximum head extension occurred showed the greatest variability.

Phase IV (stabilization phase) begins after hip extension is reached and ends when all motion associated with stabilization is completed.