BIOMECHANICAL ANALYSIS
Sit to stand movement is one of the most important human activities.
1. Sit to stand Analysis
We can divide this movement in three phases. Each phase is differentiated in terms of momentum and stability characteristics.
Phase 1: Inititation or Acceleration phase
In this phase, the center of gravity is accelerated onto the horizontal direction until to acquire its maximum speed, Some scientist also call it, acceleration phase.
Is a flexion-momentum phase used to generate the initial momentum for rising.
Phase 2 or Transition phase.
This phase begins when the center of gravity is in its maximal horizontal speed, and ends when CG reachs its maximal vertical speed.
Begins as the individual leaves the chair seat and ends at maximal ankle dorsiflexion. Forward momentum of the upper body is transferred to forward and upward momentum of the total body.
Phase 3 or Descceleration or Stabilitation phase
It begins when CoG is on its maximal speed and the full body begins to elevate itself, moving vertically its center of gravity until to stabilize its base of sustentation rising its full upright position. As speed is decreasing in this phase, it's also normally called desacceleration phase.
2 Muscles actions at standing
The extensor muscles that support erect posture are called posturals or antigravitatores. Theses muscles have red fibers that are highly resistent to fatigue, Its energy comsumption is low and show a kind of contractions that's called tonic contraction.
3 Antigravitatories muscles at erect posture
· Neck Extensor muscles
· Erector spinae muscles
· Gluteal muscles
· Quadriceps muscles.
· Tríceps sureal muscle (gemellus y soleus).
