Fundamental Positions in Exercise Therapy

Starting Position - Definition

"Posture follows movement like a shadow. Every movement begins in posture and ends in posture." - Sherrington

1. Fundamental (Starting) Positions
2. Derived Positions

The 5 Fundamental Starting Positions

1. STANDING (St)

• Heels together and on the same line; toes slightly apart
• Knees together and straight
• Hips extended and slightly laterally rotated
• Pelvis balanced on the femoral heads
• Spine stretched to maximum length
• Vertex thrust upward, eyes level, looking straight forward
• Shoulders down and back
• Arms hang loosely to sides, palms facing inward toward the body

• Plantar flexors/dorsiflexors of ankle: balance tibia on the ankle
• Flexors/extensors of knee: keep the knee straight
• Hip extensors and abductors: maintain erect posture
• Trunk extensors + abdominals: stabilize the spine
• Neck muscles: maintain head position

• Maximum anti-gravity muscle work
• Best for weight-bearing and balance training
• Promotes proprioception

• Gait training
• Balance exercises
• Strengthening lower limb muscles
• Patient feels joy and efficiency during standing exercises

• Walk standing (one foot in front)
• Step standing (one foot on a step)
• Toe standing
• Stride standing (feet apart)
• Lunge position

2. KNEELING (Kn)

• Body supported on the knees (together or slightly apart)
• Lower leg rests on the floor, feet plantar flexed
• Hips extended
• Pelvis balanced on femoral heads
• Spine stretched to maximum length
• Vertex thrust upward, eyes level
• Shoulders down and back
• Arms hang loosely to the sides, palms inward

• Flexors and extensors of knees: balance the femur vertically on the knee
• Hip extensors
• Trunk and spinal muscles

• Reduces base of support vs. standing
• Eliminates foot and ankle involvement
• Challenges balance and hip stability

• Hip and knee disorders where standing is not possible
• Core stability training
• Strengthening hip extensors and abductors
• When foot/ankle must be protected

• Half kneeling (one knee on ground, one foot flat)
• Crook kneeling (sitting back on heels)
• Prone kneeling (on all fours / quadruped)
• Knee lean forward

3. SITTING (Sitt)

• Weight borne on the ischial tuberosities and thighs
• Hips and knees at approximately 90 degrees
• Feet flat on floor
• Spine erect
• Shoulders down and back
• Eyes level

• Hip flexors: maintain flexion
• Trunk extensors and flexors: stabilize the spine
• Less anti-gravity work than standing

• Good stability (wide base of support)
• Reduced demand on lower limb anti-gravity muscles
• Allows free movement of upper and lower limbs

• Upper limb exercises
• Trunk exercises
• Patients who cannot stand
• Elderly and debilitated patients

• Long sitting (legs extended, 90° hip flexion)
• Cross sitting / tailor sitting
• Side sitting
• Forward lean sitting
• Crook sitting (feet on floor, knees bent)
• Ride sitting (astride a stool)

4. LYING (Ly)

• Crook lying (supine, knees bent, feet flat) - most common
• Prone lying (face down)
• Side lying

• Entire body supported by a surface
• Spine in neutral
• Arms at sides

• Minimal anti-gravity work
• Trunk muscles work isometrically to stabilize

• Minimum muscle effort required
• Maximum relaxation
• Complete elimination of gravity effects (in horizontal)
• Good for passive movements, relaxation, acute conditions

• Acute injuries and early post-operative phase
• Relaxation techniques
• Passive and assisted exercises
• Breathing exercises
• Spinal traction
• Patients with poor tolerance for upright posture

• Prone lying
• Side lying
• Crook lying
• Half lying (head and trunk elevated)
• Prone kneeling

5. HANGING (Hg)

• Body suspended by the hands (or feet in inverted hanging)
• Shoulders fully elevated and flexed
• Arms overhead gripping a bar/rings
• Spine elongated under traction effect
• Lower limbs hang freely

• Shoulder girdle muscles (especially shoulder elevators and depressors)
• Grip strength muscles
• Trunk muscles (to prevent excessive swing)

• Spinal elongation / decompression
• Shoulder girdle strengthening
• Traction effect on the spine and hips
• Develops grip strength and shoulder stability

• Spinal conditions (scoliosis, disc problems)
• Shoulder girdle strengthening
• Gymnastic and remedial exercises
• Grip strength development

• Reach grasp hanging (wider grip)
• Inverted hanging
• Arm swing hanging

Factors for Selecting a Starting Position

1. Patient's ability - Can they maintain the position?
2. Need for stabilization - How much support is required?
3. Use of gravity - Is gravity to be assisted, resisted, or eliminated?
4. Pain levels - Does the position aggravate or relieve symptoms?
5. Intended effects - What therapeutic goal is to be achieved?
6. Base of support - Stability vs. challenge
7. Muscle work required - Active vs. passive

Summary Comparison Table (Exam-Focused)

Key Principles to Remember for Exam

• The 5 fundamentals can be remembered as: S-K-S-L-H (Standing, Kneeling, Sitting, Lying, Hanging)
• Derived positions are modifications of the fundamental five to improve stability, alter leverage, promote relaxation, or isolate muscle groups
• As you progress from Lying → Sitting → Kneeling → Standing: anti-gravity muscle work increases progressively
• Hanging is unique - it uses the body's own weight for traction and overhead muscle work
• Sherrington's principle: every movement starts and ends in posture

Assignment - Biomechanics of the Shoulder Complex

Question 1: Biomechanics of Shoulder Abduction (0° to 180°) [10 Marks]

(a) Phases of Shoulder Abduction (2 marks)

• Movement occurs almost entirely at the glenohumeral (GH) joint.
• The scapula is "setting" - it either remains stationary or rotates very slightly to find a stable position on the thorax.
• Deltoid and supraspinatus are the primary movers.
• The humeral head is kept centered in the glenoid by rotator cuff compressive force.

• Both GH and scapulothoracic (ST) joints contribute.
• For every 3° of total abduction: 2° occurs at GH + 1° at ST (scapulohumeral rhythm begins).
• The scapula rotates upward on the thorax.
• Supraspinatus and deltoid continue to work. Upper and lower trapezius and serratus anterior rotate the scapula.

• From 90° to 120°: continued GH and scapular upward rotation.
• From 120° to 180°: spinal lateral flexion to the opposite side, plus GH external rotation (to clear the greater tuberosity from the acromion).
• The scapula rotates a total of 60° during full elevation.
• At 180°, the GH joint contributes 120° and the scapulothoracic joint contributes 60°.

(b) Contribution of GH Joint and Scapulothoracic Joint (2 marks)

• A ball-and-socket synovial joint with the greatest range of motion in the body.
• The large spherical head of the humerus articulates with the small, shallow glenoid cavity, allowing wide ROM at the cost of intrinsic bony stability.
• Stability is instead provided by the rotator cuff muscles, glenoid labrum, and joint capsule.
• During abduction, the GH joint allows the humeral head to roll superiorly while simultaneously gliding inferiorly to remain in the glenoid cavity (roll-glide mechanism).

• A physiological (not true synovial) joint - the scapula glides over the posterior thorax.
• Upward rotation of the scapula elevates the glenoid fossa, keeping it "under" the humeral head during abduction.
• Without scapular rotation, the greater tuberosity would impinge the acromion above 90°.
• The scapula also tips posteriorly and rotates externally on the thorax during elevation.

(c) Scapulohumeral Rhythm and the 2:1 Ratio (2 marks)

• For every 3° of shoulder abduction, 2° occurs at the GH joint and 1° occurs at the ST joint.
• This gives a GH:ST ratio of 2:1.
• Over the full 180°:
  • GH contributes: 2/3 × 180° = 120°
  • ST contributes: 1/3 × 180° = 60°

• Maintains the optimal length-tension relationship of the deltoid throughout the range.
• Keeps the glenoid positioned under the humeral head to prevent superior subluxation.
• Prevents subacromial impingement by continuously elevating and rotating the acromion away from the greater tuberosity.

Total Abduction = GH (2 parts) + ST (1 part)
0°  ──►  30°  : GH only (scapula setting)
30° ──►  90°  : GH 2° : ST 1° (rhythm begins)
90° ──► 180°  : Continued 2:1 ratio + lateral spinal flexion
Final: GH = 120°, ST = 60°, Total = 180°

(d) Movements at Sternoclavicular and Acromioclavicular Joints (2 marks)

• Elevation of the clavicle (25-30°) - occurs during the first 90° of abduction.
• Posterior rotation of the clavicle (up to 50°) - occurs mainly between 90° and 180°, driven by the pull of the coracoclavicular ligament.
• Protraction and retraction of the clavicle during horizontal movements.

• Upward rotation of the scapula - the AC joint allows the scapula to rotate relative to the clavicle, contributing approximately 20° of the total 60° of scapular upward rotation.
• Posterior tipping of the scapula - the scapula tips posteriorly relative to the clavicle.
• Internal/external rotation of the scapula - scapula rotates about an axis perpendicular to the scapular plane.

(e) Role of Rotator Cuff Muscles in Shoulder Stability During Abduction (2 marks)

• The deltoid creates a large superiorly directed force on the humeral head during abduction.
• Without a counterforce, the head would translate superiorly and impinge under the acromion.
• The rotator cuff muscles (especially infraspinatus + subscapularis) create a downward-directed compressive force that keeps the humeral head centered in the glenoid - this is the force couple mechanism.
• The long head of biceps brachii also restricts superior translation of the humeral head.

Question 2: Structure and Biomechanics of the Sternoclavicular Joint (5 Marks)

Classification and Type of Joint

• Classification: Synovial joint
• Type: Saddle (sellar) joint - the articular surfaces are reciprocally concave-convex (saddle-shaped)
• It is the only true synovial joint connecting the upper limb to the axial skeleton.

Articular Surfaces

• Medially: The proximal (sternal/medial) end of the clavicle
• Laterally: The clavicular notch of the manubrium of the sternum, together with a small part of the first costal cartilage
• Both surfaces are covered by fibrocartilage (not hyaline cartilage, which is unusual for a synovial joint).
• A complete fibrocartilaginous articular disc divides the joint cavity into two separate compartments.
  • The disc prevents medial displacement of the clavicle.
  • It also acts as a shock absorber, transmitting forces from the upper limb to the sternum.

Ligaments Supporting the Joint

Available Movements

1. Elevation - Depression (vertical plane):
   • Clavicle elevates ~25-30° (shoulder shrug)
   • Clavicle depresses ~5-10°
2. Protraction - Retraction (anteroposterior plane):
   • Clavicle protracts ~15-20° (reaching forward)
   • Clavicle retracts ~15° (bracing the shoulder back)
3. Axial Rotation (posterior rotation):
   • Clavicle rotates posteriorly ~45-50° during full arm elevation
   • This rotation is passive - driven by the pull of the coracoclavicular ligament as the scapula rotates upward

Functional Importance During Upper Limb Movements

• The SC joint is the sole bony articulation between the upper limb and the thorax - all forces from the upper limb are transmitted here.
• During shoulder abduction: SC joint elevation allows the scapula to rotate upward; without this movement, full overhead elevation would be impossible.
• The posterior rotation of the clavicle at the SC joint is essential for the last 60° of arm elevation - without it, scapular upward rotation would be restricted.
• In SC joint dislocation or fracture of the clavicle medially, all shoulder girdle mechanics are severely compromised.
• The posterior sternoclavicular dislocation is a medical emergency as the posterior clavicle can compress the trachea, esophagus, and great vessels.

Question 3: Force Couple Mechanism in Shoulder Abduction (5 Marks)

Definition of Force Couple

Muscles Involved

Mechanism of Action During Shoulder Abduction

• The deltoid muscle pulls the humeral head superiorly toward the acromion.
• Simultaneously, the rotator cuff muscles (especially infraspinatus, teres minor, and subscapularis) pull the humeral head inferiorly and compress it into the glenoid.
• These two opposing forces create a net rotational moment - the humerus rotates upward (abducts) without the head translating superiorly out of the glenoid.
• This is like two hands turning a steering wheel in opposite directions - the wheel turns without moving sideways.

• Upper trapezius pulls the clavicle/acromial end of scapula upward.
• Lower trapezius pulls the spine of scapula medially and downward.
• Serratus anterior pulls the inferior angle of the scapula anterolaterally.
• Together, these three muscles create a rotational couple that upwardly rotates the scapula by 60°, aligning the glenoid upward to remain under the humeral head throughout abduction.

Importance in Maintaining Normal Shoulder Biomechanics

1. Prevents subacromial impingement - by keeping the humeral head centered, the subacromial space is preserved.
2. Maximizes power of deltoid - without the downward compressive force, deltoid would be mechanically inefficient.
3. Allows full 180° of elevation - both GH centering and scapular rotation force couples are required for full range.
4. Provides dynamic stability - the rotator cuff force couple replaces the bony stability lacking in the shallow glenoid.
5. Protects joint structures - prevents capsular, labral, and rotator cuff injury.

Clinical Significance if the Force Couple is Disrupted