3.1 Biomechanical principles and their application to strength and conditioning

Biomechanics is crucial for strength and conditioning, applying physics to human movement. It helps us understand how forces affect the body during exercise, informing proper technique and program design. By grasping these principles, we can optimize performance and reduce injury risk.

Key concepts include Newton's laws, lever systems, and force-velocity relationships. These fundamentals guide exercise selection, technique analysis, and loading strategies. Mastering biomechanics allows trainers to create effective, safe programs tailored to individual needs and goals.

Biomechanics for Strength and Conditioning

Fundamental Principles

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• Biomechanics studies the structure, function, and motion of the human body, applying principles from mechanics and engineering
• Key biomechanical principles include force, torque, momentum, impulse, work, power, and energy which govern human movement and interaction with external forces
• Newton's laws of motion (inertia, acceleration, action-reaction) form the foundation for understanding how forces affect the human body during exercise and sports performance
  • Law of inertia: An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force
  • Law of acceleration: The acceleration of an object depends on the net force acting on it and the object's mass ($F = ma$)
  • Law of action-reaction: For every action, there is an equal and opposite reaction

Musculoskeletal System and Forces

• The musculoskeletal system, comprised of bones, joints, muscles, and connective tissues, functions as a system of levers to produce movement
  • Lever systems (first, second, third class) affect force production and range of motion
  • Example: The elbow joint functions as a third-class lever during biceps curls
• Muscle contraction generates internal forces to produce movement, while external forces like gravity, friction, and air/water resistance oppose motion
  • The balance and magnitude of these forces determine movement outcomes
  • Example: Gravity provides resistance during exercises like squats and push-ups

Applying Biomechanics to Exercise

Technique Analysis and Optimization

• Proper exercise technique involves optimal body positioning, joint angles, and movement patterns to efficiently produce and transfer forces while minimizing injury risk
• Analyzing movement using kinematic (motion description) and kinetic (force) variables helps identify technique strengths and weaknesses
  • Key variables include displacement, velocity, acceleration, force application, and joint torques
  • Example: Analyzing barbell velocity during a bench press can indicate power output and fatigue
• The force-velocity relationship states that muscles produce less force at higher contraction velocities
  • This affects exercise selection and loading parameters for power vs. strength training
  • Example: Olympic weightlifting exercises (snatch, clean and jerk) require high velocities and moderate loads to develop power

Resistance Manipulation and Exercise Difficulty

• Mechanical advantage relates to the positioning of resistance relative to joint axes of rotation
  • Modifying body and equipment positioning can alter the resistance curve and muscular demands of an exercise
  • Example: Performing a biceps curl with the elbow in front of the body increases the moment arm and resistance
• Stability, balance, and coordination are influenced by the body's base of support, center of gravity, and interaction with external forces
  • Manipulating these factors can increase or decrease exercise difficulty and specificity
  • Example: Performing a single-leg squat on an unstable surface challenges balance and coordination

Biomechanics and Performance Optimization

Athletic Performance Determinants

• Muscular strength, rate of force development, and power output are key biomechanical determinants of athletic performance across various sports
  • Enhancing these qualities is a primary goal of strength and conditioning programs
  • Example: Improving vertical jump height through plyometric training and weightlifting exercises
• Movement efficiency relates to the optimization of force production and minimization of energy expenditure
  • Efficient movement patterns are associated with improved performance and reduced injury risk
  • Example: Proper running mechanics minimize energy cost and improve running economy

Injury Prevention Considerations

• Overuse injuries can result from repetitive sub-optimal movement patterns that cause excessive stress on tissues over time
  • Identifying and correcting biomechanical inefficiencies is crucial for injury prevention
  • Example: Addressing muscle imbalances and movement asymmetries to prevent knee injuries in athletes
• Acute injuries often occur when external forces exceed the tissue's loading capacity
  • Understanding the mechanisms of common injuries informs exercise progressions and technique modifications to mitigate risk
  • Example: Teaching proper landing mechanics during plyometric exercises to reduce ACL injury risk
• Equipment factors such as footwear, surfaces, and implements can alter force application and movement patterns
  • Considering these interactions is important for optimizing performance and safety
  • Example: Selecting appropriate footwear for specific sports and training activities

Integrating Biomechanics in Program Design

Exercise Selection and Loading Strategies

• Exercise selection should consider the specific movement patterns, force-velocity demands, and joint angles that are relevant to the athlete's sport and individual needs
• Resistance training programs can be designed to target specific force-velocity characteristics by manipulating loading parameters and exercise tempo
  • High-force/low-velocity exercises develop strength (heavy squats, deadlifts)
  • Low-force/high-velocity exercises develop speed (medicine ball throws, sprints)
• Plyometric and ballistic exercises utilize the stretch-shortening cycle to develop explosive power
  • Proper technique and progressions based on biomechanical principles are essential for effectiveness and safety
  • Example: Depth jumps and box jumps to improve lower body power

Periodization and Monitoring

• Periodization strategies manipulate training variables (volume, intensity, frequency) to optimize specific adaptations while managing fatigue and injury risk
  • Biomechanical considerations inform exercise selection and loading progressions within periodized plans
  • Example: Progressing from strength-focused exercises to power-focused exercises during a training cycle
• Regular biomechanical assessments can be used to monitor training adaptations, identify areas for improvement, and adjust programming based on individual responses
  • Movement screens assess functional movement patterns and identify limitations
  • Jump testing (countermovement jump, drop jump) evaluates lower body power and reactive strength
  • This iterative process helps ensure the program remains effective and relevant to the athlete's evolving needs