Biomechanics in Strength Training - BodyGNTX | Institute of Biomechanics & Movement Performance

INTRODUCTION TO MOVEMENT SCIENCE

Welcome to this comprehensive guide on the biomechanics of strength training. This presentation is designed to help physical therapists, trainers, and movement professionals understand the underlying physics and proper mechanics of common strength exercises.

By understanding the biomechanical principles that govern human movement, you can:

Teach proper form more effectively
Identify and correct movement errors
Understand the “why” behind exercise recommendations
Optimize exercise selection for specific goals
Reduce injury risk through proper mechanics

This guide includes detailed explanations of the physics involved in each movement pattern, with space for you to add your own video demonstrations.

FUNDAMENTAL BIOMECHANICS PRINCIPLES

Force Production & Distribution

How forces are generated by muscles and distributed through the kinetic chain, including concepts like ground reaction force and force vectors.

Torque & Moment Arms

How rotational forces affect joints, and how the distance between the force application and the axis of rotation impacts exercise difficulty and joint stress.

Center of Mass & Balance

How the body’s center of mass affects stability during exercises, and strategies for maintaining balance during complex movements.

Lever Systems

How the body creates mechanical advantage through different classes of levers, and how lever length affects force requirements.

Kinematic Analysis

The study of motion without regard to forces, including joint angles, ranges of motion, velocity, and acceleration during exercises.

Kinetic Analysis

The study of forces that cause motion, including muscle activation patterns, energy systems, and work/power relationships.

STRENGTH TRAINING EXERCISES

Select an exercise below to view detailed biomechanical analysis and add your own videos.

Squat

A fundamental lower body compound movement that primarily targets the quadriceps, hamstrings, and glutes.

Proper Form for Squat

Stand with feet slightly wider than hip-width apart
Lower hips into a squat as you bend knees and keep back flat
Continue to lower until thighs are parallel to the floor
Push into the floor through heels to return to start
Keep heels flat and knees aligned with second toe

Muscles Worked: Glutes, quads, and core muscles

Squat muscles worked

Basic Biomechanical Principles

The squat demonstrates several key biomechanical principles:

Force Production and Distribution

During a squat, the body must generate force to overcome gravity and the weight of the body. This force is primarily produced by the quadriceps, hamstrings, and gluteal muscles.

When performing a squat, the force applied by the feet against the ground results in an equal and opposite reaction force (Newton’s Third Law). This Ground Reaction Force (GRF) travels up through the kinetic chain.

Torque and Moment Arms

Torque is calculated as the product of force and the perpendicular distance from the line of force to the axis of rotation (moment arm).

The position of the torso and knees affects the moment arms at each joint. A more vertical shin reduces the knee moment arm, while a more forward lean increases the hip moment arm.

Center of Mass and Balance

For stability during a squat, the Center of Mass (COM) must remain over the base of support (the feet). As the body descends, the COM shifts, requiring adjustments in posture to maintain balance.

Common Errors and Their Physical Consequences

Knee Valgus (Knees Collapsing Inward)

Physics Issue: Creates rotational torque at the knee joint
Consequence: Increases stress on the medial collateral ligament (MCL) and anterior cruciate ligament (ACL)

Excessive Forward Lean

Physics Issue: Shifts center of mass forward, increasing shear forces on the lumbar spine
Consequence: Greater compressive and shear forces on the intervertebral discs

Heels Rising

Physics Issue: Reduces base of support and shifts weight distribution
Consequence: Decreases stability and increases knee torque relative to hip torque

Insufficient Depth

Physics Issue: Limits range of motion and muscle activation
Consequence: Reduces work done and limits training stimulus

ABOUT THIS PRESENTATION

This educational resource was developed to provide biomechanics professionals and physical therapists with a comprehensive tool for teaching movement science in strength training.

The content focuses on:

Accurate representation of proper movement mechanics
Clear explanation of common errors
Scientific explanation of the physics principles involved
Practical applications for teaching and correction

For questions or additional information, please contact the developer.

Created By

Dr. Neeraj Mehta

PhD in Biomechanics and Alternative Medicine

30+ years of experience in the field