🪃Principles of Strength and Conditioning Unit 3 – Biomechanics and Kinesiology

Key Concepts and Terminology

• Biomechanics studies the forces acting on and within the body and their effects on movement
• Kinesiology focuses on the study of human movement, including the physiological, mechanical, and psychological mechanisms
• Kinetics involves the study of forces that cause motion, such as force, torque, and momentum
• Kinematics describes motion without considering the forces causing it, including displacement, velocity, and acceleration
• Anatomical planes (sagittal, frontal, transverse) divide the body into sections to describe motion and joint actions
• Anatomical axes (sagittal, frontal, vertical) are imaginary lines around which motion occurs
• Center of gravity (COG) represents the point where the weight of the body is evenly distributed
  • COG location varies based on body position and movement

Anatomical Foundations

• Skeletal system provides a framework for movement and attachment points for muscles
• Joints are classified based on their structure and function (fibrous, cartilaginous, synovial)
• Synovial joints allow for a wide range of motion and are the most common type in the body
  • Examples include hinge (elbow), ball-and-socket (shoulder), and gliding (wrist) joints
• Muscles generate force through contraction, which is initiated by motor neurons
• Muscle fiber types (Type I, Type IIa, Type IIx) have different characteristics and roles in movement
• Tendons connect muscles to bones and transmit forces generated by muscle contraction
• Ligaments connect bones to bones and provide stability to joints
• Fascia is a connective tissue that surrounds and separates muscles, organs, and other structures

Biomechanical Principles

• Newton's laws of motion (inertia, acceleration, action-reaction) govern human movement
• Force-velocity relationship states that as the velocity of muscle contraction increases, the force output decreases
• Length-tension relationship describes how a muscle's force output varies depending on its length
  • Optimal force production occurs at resting length; too short or too long reduces force output
• Stretch-shortening cycle (SSC) involves a rapid eccentric contraction followed by a concentric contraction, enhancing force output
• Moment arm is the perpendicular distance from the line of force to the axis of rotation
  • Longer moment arms require less force to produce the same torque
• Mechanical advantage is the ratio of the force output to the force input in a system
• Levers (first-class, second-class, third-class) are simple machines that involve a fulcrum, effort, and resistance

Movement Analysis

• Kinematic analysis examines motion without considering the forces causing it
  • Involves measuring joint angles, velocities, and accelerations using tools like video analysis or motion capture
• Kinetic analysis investigates the forces acting on the body during movement
  • Utilizes force plates, pressure sensors, and electromyography (EMG) to measure forces and muscle activation
• Gait analysis assesses an individual's walking or running pattern to identify abnormalities or inefficiencies
• Postural analysis evaluates static and dynamic posture to identify imbalances or alignment issues
• Movement screening tools (FMS, SFMA) assess an individual's movement quality and identify limitations or asymmetries
• Biomechanical modeling uses mathematical equations and computer simulations to analyze complex movements
• Inverse dynamics calculates joint forces and moments based on kinematic and kinetic data

Kinetic Chain and Force Production

• Kinetic chain refers to the interconnected segments of the body that work together to produce movement
• Open kinetic chain (OKC) exercises involve a freely moving distal segment, such as leg extensions
• Closed kinetic chain (CKC) exercises involve a fixed distal segment, such as squats or push-ups
  • CKC exercises are generally more functional and involve multiple joints and muscle groups
• Proximal-to-distal sequencing involves the transfer of energy from larger, proximal segments to smaller, distal segments
  • Efficient sequencing is essential for generating high forces in throwing, striking, and jumping movements
• Force-couple relationships describe how muscles work together to produce motion and stability
• Joint stability is maintained by passive (ligaments, joint capsule) and active (muscles) structures
• Core stability is essential for efficient force transfer and prevention of energy leaks

Practical Applications in Strength Training

• Proper form and technique are essential for maximizing performance and minimizing injury risk
• Exercise selection should consider an individual's goals, abilities, and movement patterns
• Resistance training programs should be periodized to manage fatigue and optimize adaptations
  • Periodization involves planned variations in training volume, intensity, and specificity over time
• Progressive overload is necessary for continued strength and muscle gains
  • Achieved through increasing resistance, volume, or training frequency over time
• Specificity principle states that adaptations are specific to the demands placed on the body
  • Training should mimic the movements and energy systems used in the target activity
• Eccentric training emphasizes the lengthening phase of muscle contraction and can lead to greater strength gains
• Plyometric training involves rapid SSC movements to improve power output and reactivity

Common Errors and Corrections

• Squatting errors include knee valgus, excessive forward lean, and limited depth
  • Corrections involve cueing to maintain knee alignment, upright torso, and full range of motion
• Deadlifting errors include rounding the back, overextending the lumbar spine, and hitching
  • Corrections focus on maintaining a neutral spine, engaging the core, and smooth execution
• Bench pressing errors include flaring the elbows, bouncing the bar off the chest, and excessive arch
  • Corrections involve tucking the elbows, controlling the descent, and maintaining a stable base
• Overhead pressing errors include arching the lower back, pushing the head forward, and using momentum
  • Corrections emphasize maintaining a neutral spine, keeping the head in line, and controlled execution
• Landing mechanics errors include knee valgus, limited hip and knee flexion, and excessive ground contact time
  • Corrections focus on proper alignment, absorbing force through the hips and knees, and quick ground contact
• Gait errors include overstriding, excessive vertical oscillation, and limited hip extension
  • Corrections involve cueing shorter strides, maintaining a level head, and driving the legs back

Advanced Topics and Current Research

• Velocity-based training (VBT) uses technology to measure bar speed and provide real-time feedback
  • VBT can be used to autoregulate training loads, monitor fatigue, and optimize power output
• Flywheel training involves the use of a flywheel device to provide resistance during both concentric and eccentric phases
  • Flywheel training can lead to greater eccentric overload and enhanced muscle hypertrophy and strength
• Blood flow restriction (BFR) training involves the use of a tourniquet to restrict blood flow during low-load resistance exercise
  • BFR can stimulate muscle growth and strength gains with reduced mechanical stress on joints and connective tissues
• Wearable technology, such as accelerometers and EMG sensors, can provide insights into movement quality and muscle activation patterns
• Advanced biomechanical analysis techniques, such as principal component analysis (PCA) and machine learning, can identify key performance variables and optimize technique
• Current research is investigating the effects of different training modalities, such as variable resistance training and accentuated eccentric loading, on strength and power development
• Emerging evidence supports the use of individualized biomechanical feedback to enhance motor learning and skill acquisition in strength training