Kinesiology note 1
Proximal-Distal Orientation, Core Stability, and the Kinetic Chain
Core as the proximal stabilizer is essential to generate and transfer force to distal segments (limbs).
Proximal-to-distal perspective: generate force within the core first, then transfer it to the extremities for actions like kicking, throwing, swinging, lifting.
Kinetic chain concept: energy/force transfer through linked segments; movement typically starts ground up (proximal visceral/inferior to superior pattern).
Practical note: a lag in the kinetic chain can be detrimental, particularly in complex tasks like throwing (concept revisited later in the course).
Core stability and force transfer underpin many functional tasks and athletic movements.
Open vs Closed Kinetic Chain: Definitions and Implications
Open kinetic chain (OKC): distal segment is not fixed and can move independently; joints can move in isolation.
Definition: the distal segment is not fixed, allowing movement of the distal segment and potential isolation of a single joint.
Example: elbow flexion/extension during a dumbbell tricep extension; shoulder and trunk can remain relatively stable while the elbow moves.
Common plane and axis in OKC elbow flexion/extension: sagittal plane with axis of rotation approximately medial-to-lateral.
Advantages: greater range of motion (ROM) and ability to isolate a muscle or muscle group.
Disadvantages: less joint stability due to fewer co-contractions across joints.
Closed kinetic chain (CKC): distal segment is fixed; joints within the chain move in a coordinated fashion around a fixed distal segment.
Definition: the distal segment is fixed, so multiple joints are linked and must move in concert.
Example: push-ups, where the hands/wrists are fixed to the surface and the body moves around this fixed distal point.
In CKC, proximal joints rotate about the fixed distal segment.
A note on classification:
Not every movement fits neatly into OKC or CKC; some tasks combine elements of both, or can be upper-extremity OKC with lower-extremity CKC, etc.
Clinically, categorization helps understanding muscle/joint function and guiding exercise prescription, but beware exceptions.
Key Differences Between OKC and CKC
Distal segment:
OKC: movable/distal segment not fixed.
CKC: distal segment fixed.
Joint isolation and force transfer:
OKC: allows isolation of a single joint and targeted muscle activation.
CKC: results in multi-joint co-contraction and joint stability through proximal–distal synergy.
ROM considerations:
OKC generally offers a larger ROM and less constraint from proximal joints.
CKC may have restricted ROM due to fixed distal segment and multi-joint coordination.
Equipment-related movement patterns:
Free weights typically enable OKC movement with high variability in direction and pattern.
Cables/pulleys can constrain movement to specific planes, reducing pattern variability.
Functional relevance and injury considerations:
OKC may be advantageous for isolating weak muscle groups or retraining specific joints.
CKC often enhances joint stability through cocontraction of agonists/antagonists, especially in weight-bearing tasks.
Practical Examples and Implications for Exercise Prescription
OKC example recap (upper extremity):
Tricep extension with a dumbbell: OKC; primary moving joint is the elbow; distal segment (hand/wrist) is not fixed.
Primary muscle: triceps brachii (elbow extension). Plane: sagittal; axis: medial-lateral.
CKC example recap (upper extremity):
Push-up: CKC; distal segment (wrist/hand) is fixed to the ground; requires shoulder extension and elbow flexion with trunk stability.
Multi-muscle involvement makes it harder to isolate triceps; increased co-contraction across shoulder, trunk, and arm.
Special case: biceps tendonitis and push-ups
CKC push-ups may involve the biceps due to shoulder and elbow mechanics; therefore, they can be problematic when trying to avoid overloading the biceps.
Functional considerations:
OKC is often more appropriate for tasks requiring distal mobility and joint isolation (e.g., specific strengthening for a weakened muscle group).
CKC tends to be more functional for weight-bearing, joint stability, and tasks requiring integrated multi-joint control.
Upper vs lower extremity tendencies:
CKC tends to be more functional for lower extremity activities (e.g., squats, lunges) due to weight-bearing and multi-joint stabilization.
OKC is often more functional for the upper extremity where precise, isolated force generation is needed.
Movement variability and control:
OKC allows greater ROM and movement variability, which can be beneficial or detrimental depending on the athlete’s skill level and goals.
CKC increases joint stability via cocontraction but reduces movement variability; can be protective in rehab and functional scenarios.
Diagonal and multi-planar movements:
Diagonal patterns are common in functional tasks and rely on core involvement and the kinetic chain to transfer energy across the body.
Core integration includes abdomen, trunk extensors, deep spinal stabilizers, and hip/pelvis muscles; diagonal patterns leverage these muscles for efficient movement.
Diagonal Patterns and Core Involvement in Functional Movement
Diagonal patterns tend to be functional because they require coordinated multi-joint, multi-muscle activation and core stabilization.
Core involvement supports both generation and transfer of force from lower to upper extremities (and vice versa).
Diagonal movement often reflects real-world tasks (e.g., reaching across the body, stepping diagonally in daily activities, or sports movements).
Core and knee–hip–spine integration support stable base while the limbs move through diagonal patterns.
Coordination and Movement Quality
Coordinated movement vs. uncoordinated movement (examples discussed):
Michael Jackson-style moves: appear controlled, smooth, and efficient; timing between joints is well orchestrated; stable core with fluid limb movement.
Less coordinated moves: movements appear less controlled; transitions between joints are粗 more jumbled and less efficient; timing is off.
What makes movement coordinated?
Proper timing of muscle contractions between segments; smooth transitions; anticipatory vs. reactive control; efficient flow of movement.
Spastic or uncoordinated movement:
In some pathologies, muscles may contract at inappropriate times, leading to unpredictable, spastic patterns.
Neuromuscular control is disrupted when timing and magnitude of contractions are not properly coordinated.
Neuromuscular Control: Proprioception and Kinesthesia
Definitions:
Proprioception: awareness of body position in space (external environment and internal body segments).
Kinesthesia: awareness of joint motion or acceleration (direction and velocity of movement).
Neuromuscular control: the integrated function of the nervous system and muscular system to plan, interpret, and execute movements.
Involves appropriate timing and magnitude of muscle contractions in response to sensory input.
Examples include planning a movement (preprogramming) or responding to environment (reactive adjustments).
Proprioceptors and kinesthetic sensors:
Located in joints, ligaments, tendons, muscles, and skin; provide constant information to the CNS about position and movement.
CNS integrates this information to generate appropriate motor output.
Everyday examples of proprioceptive/kinesthetic processing:
Brushing teeth without looking in a mirror; placing items into a grocery cart; subtle adjustments during reaching tasks.
Neuromuscular control outcomes:
Timing, magnitude, and coordination of muscle contractions depend on sensory input from proprioception and kinesthesia.
Preplanned activities rely on anticipated force/motion; reactive adjustments depend on real-time sensory feedback.
Afferent and Efferent Pathways in Neural Control
Afferent (sensory) pathway:
Definition: ascending pathway from periphery to central nervous system (CNS).
Example: proprioceptive input from the ankle joint travels via afferent nerves to the spinal cord and possibly the brain for processing.
Notation: "Afferent = ascending to CNS."
Efferent (motor) pathway:
Definition: motor output from CNS to muscles to elicit a response.
Example: after processing, the CNS sends signals to peroneal muscles to eccentrically or concentrically contract to correct ankle position.
Notation: "Efferent = descending from CNS to muscles."
In the ankle inversion example (man who sprains an ankle):
Inversion stretches lateral structures (peroneal tendons like peroneus longus/brevis, etc.) and joint capsule on the lateral side.
Proprioceptors in ligaments and muscles detect length changes and inform the CNS via afferent pathways.
CNS integrates input; reflexive or planned motor response via efferent pathways activates peroneal muscles to evert/stand the ankle back toward neutral.
Timescale: responses occur in milliseconds.
Question prompts for Wednesday's session:
How might delaying or altering this neuromuscular response affect injury risk or stability?
What factors influence the speed and effectiveness of the afferent/efferent response in dynamic tasks?
Practical and Ethical Considerations for Training and Rehabilitation
When choosing OKC vs CKC in practice:
Consider goals: isolation and strengthening of a specific muscle group (OKC) vs functional, weight-bearing stability (CKC).
Consider joint health and existing injuries: CKC can enhance joint stability via cocontraction but may limit ROM; OKC can target specific deficits with greater ROM.
For upper extremity rehab, OKC may be more appropriate initially to avoid excessive co-contraction and help isolate healing structures; CKC can be gradually introduced to restore functional multi-joint control.
For lower extremity rehab, CKC exercises often provide robust functional outcomes due to weight-bearing and multi-joint stabilization.
Risk and safety considerations:
Excessive ROM with poor control can decrease joint stability; ensure proper technique and progression.
Diagonal and multi-planar movements should progress gradually to avoid instability and injury risk.
Real-world relevance and ethics:
Respect patient/athlete goals, sport demands, and daily living activities when designing programs.
Provide clear cues about movement quality, avoid forcing uncontrolled ranges, and monitor for pain or unusual joint sounds.
Emphasize gradual progression and individualization based on neuromuscular control, proprioception, and kinesthetic feedback.
Quick Recap: Core Takeaways for Exam Preparedness
The kinetic chain emphasizes proximal-to-distal energy transfer; the core is foundational for generating and transferring force.
OKC vs CKC define distinct movement patterns with different implications for isolation, ROM, joint stability, and functional applicability.
Functionally, diagonal movement and multi-joint coordination rely on a stable core and well-timed, well-modulated muscle activations.
Proprioception and kinesthesia are essential components of neuromuscular control, enabling the CNS to interpret body position and movement, and to generate appropriate motor responses.
Afferent pathways convey sensory information to the CNS, while efferent pathways deliver motor commands to the muscles; both are essential for dynamic, coordinated movement.
Practical exercise prescription should balance CKC/OKC based on goals, injury status, and functional demands, always prioritizing proper technique and progression.
ext{Axis of rotation in the sagittal plane} = ext{medial-to-lateral (mediolateral)}
ext{Open Kinetic Chain (OKC)} ext{: distal segment not fixed}
ext{Closed Kinetic Chain (CKC)} ext{: distal segment fixed}
ext{Afferent (ascending)}
ightarrow ext{CNS} o ext{Efferent (descending)}