Written by: Adam Tzur

Posted: February 2, 2017

Last updated: March 29, 2018

Table of Contents

Summary

This article contains 31 videos, 42 studies, + articles about anatomy, biomechanics, individualization, physics, and exercise technique. You can read or watch the videos, it's up to you!

The article is structured as follows: (1) intro to anatomy and biomechanics, (2) Practical application of strength training biomechanics , (3) other exercises, biomechanical models, discussion, and (4) scientific studies on biomechanics for humans.

, (3) other exercises, biomechanical models, discussion, and (4) scientific studies on biomechanics for humans. Several of the videos discuss how your anatomy affects lifting technique (it's not just about muscle tightness and mobility)

There is no cookie-cutter technique that is ideal for everyone - See McGill's, Henoch's, and Purvis' videos for details.

Moment arms change throughout the exercise (i.e. the squat at the top vs. in the hole). This affect when an exercise becomes difficult and also how difficult it becomes. When we hit the position we are least biomechanically efficient in, we tend to hit the "sticking point". Improving the sticking point is particularly important for 1RMs and competitive lifting.

Overcome the sticking point with ROM-specific training (partials), momentum training, technique alteration, isolation training, and accommodating resistance (i.e. bands):

"If the momentum is supplied to the load at a point in the lift at which the target muscles are in a biomechanically inferior position to exert effective force, this weakness may be overcome" (Arandjelovic, 2012)

"If the momentum is supplied to the load at a point in the lift at which the target muscles are in a biomechanically inferior position to exert effective force, this weakness may be overcome" (Arandjelovic, 2012) Cheating can be useful in some exercises and for some purposes, but should we always use momentum to cheat? What about isolation exercises? (see Purvis videos)

Free weights/cable exercises/machines do not provide constant resistance due to inertia, technique, "momentum cheating", and moment arms: "even a linear resistance has a variable resistance" (Purvis, 2015)

Range of motion can be joint-specific, or exercise-specific (i.e. you can do a full ROM bench without utilizing full shoulder and pectoral ROM)

Check the Customizable exercise simulations -section to play around with a deadlift/bench/squat biomechanics model (change limb length, ROM, etc.)

-section to play around with a deadlift/bench/squat biomechanics model (change limb length, ROM, etc.) There are 39 biomechanics studies in the studies-section (footwear, technique comparisons, strength-curves, etc.)

Introduction

This is a collection of biomechanics resources you might find helpful. The resources presented here could help you improve your squat, bench, deadlift, etc. and improve your understanding of why you need to use certain techniques.

Note that some of the arguments made in some of the videos are actively debated in the literature so this isn't the undisputed end-all-be-all of biomechanics.

Anatomy and Kinesiology

Explains the following:

Skeletal system : joints, girdles, bones, levers, range of movement, etc.

: joints, girdles, bones, levers, range of movement, etc. Muscular system: muscle types, motor units, tendons, muscle insertions and origins, lever system of muscles, agonists, antagonists, types of movement, +++

"Muscle insertions are so frequently found close to the joints they move, therefore the effort is located between the pivot and the resistance (...) the levers of the human body are adapted for range, speed, and precision of movement rather than for handling weight"

Most skeletal muscles of the body act in third-class lever systems (...) In a third-class lever, the effort is applied between the load and the fulcrum. These levers are speedy and always operate at a mechanical disadvantage (...) An example is the activity of the biceps muscle of the arm, lifting the distal forearm and anything carried in the hand. Third-class lever systems permit a muscle to be inserted very close to the joint across which movement occurs, which allows rapid, extensive movements (as in throwing) with relatively little shortening of the muscle. Muscles involved in third-class levers tend to be thicker and more powerful."

Example of human lever:

Source (illustration is edited for clarity)

Basics of Biomechanics

This is a simplified introduction to leverages, moment arms, and individualized anatomy.



1:36 - 10 lbs of weight is not necessarily 10 lbs of resistance

3:40 - "five lbs is different when it's sitting still and you try to move it, and five lbs moving becomes a different thing when you try to stop it" (...) "it's about changes in speed: acceleration and deceleration"

5:47 - "the way I choose to move [the weight] makes it zero [lbs] at some parts of the range, and 20 at other parts of the range"

6:10 - "did you know that the speed, or more importantly the acceleration and deceleration rate of your client's movement, of your movement, changes the load"

6:50 - "if your [movement] is always accompanied by a weight that is flying to zero, you're never training that end of the motion" (...) "you're using your (...) own inertia, your own mass to overcome that mass"

7:31 - "we're looking for the most weight moved, with the least amount of effect (...) because that acceleration and deceleration reduces the stimulation from the load"

A moment arm (MA) determines the degree of effectiveness or influence of a force to produce or prevent the rotation of an object around an axis. Moment arm is the most vital mechanical factor that is consistently ignored by the exercise industry, experts and consumers alike. When presented in formal study it is with such poor examples and lack of reverence that one must assume that the professors themselves don’t really understand its importance in exercise. Below are just a few of the numerous examples of moment arm neglect or misunderstanding. The only free weight that is constant resistance is one that is not moving. A weight that is moving will be a variable resistance due to the potentially dramatic influence of inertial effects, and a weight moving around an axis will always be a variable resistance due to the constantly changing moment arms to each involved joint.

the external moment arms at the hip and knee are very long at the start of a lift like the barbell back squat when the weight is closer to the ground, and they get smaller very quickly as you lift the weight. This means that even though the weight of the barbell does not change, the hip and knee joint torques produced by the barbell are greatest at the start of the lift, and reduce as you rise upwards.

(...)

Partial and full range of motion training are not as different as you might think from isometric training at short and long muscle lengths. Many exercises with free weights are like squats and have external moment arms that are long at the bottom of the movement, and short at the top. So the total range of motion of the exercise (partial or full) determines the muscle length at which the peak contraction occurs.

On limb length:

The further away a weight is from a joint, the more force is required to lift it. People with long limbs therefore must produce more force to lift the same weight as a person with much shorter limbs (i.e. doing biceps curls with really long vs. short forearms)

A secondary effect of this is that longer limbs mean that any given weight has to be lifted through a longer total distance. Long-armed people have to move the weight further in a flat bench and move through a longer distance when they squat for example.

On muscle length and attachments:

Muscles attach to bones via tendons and these tendons can attach at difference places along the bone in different people. Some people have longer muscles and others have shorter muscles or longer or shorter tendons. For example, common to African Americans are calves that insert very high on the bone; this is fantastic for jumping (for reasons I won’t get into) but terrible for calf growth. You can find people with pecs that simply don’t meet that close together (they lack cleavage), people with shorter or longer biceps, etc. And the end effect of this is that shorter muscles generate less force around a joint (thought they generate it faster) than longer muscles.

What should people with mechanical disadvantages do?

Sumo DL is often superior for people with a very long torso since their low back often gets beaten up or is limiting in the movement: the length of their spine means their low back muscles have to generate more force for the same weight lifted. By making the torso more upright, Sumo eliminates this particular weakness (and the wider stance may additionally benefit long legged folks).

Biomechanical implications of skeletal muscle hypertrophy and atrophy: a musculoskeletal model (Vigotsky et al., 2015)

Force-length relationships (3 studies)

Misc (18 studies)