Aside from looking really cool, applying chains to your strength training has some even cooler benefits. The same could be said with the use of resistance bands. Most commonly seen around the knees of “Yeah, She Squats” Instagram models, just like chains, bands can actually be used to accomodate resistance. The use of chains in strength training has long existed in powerlifting and has made a transition to sports performance facilities over the last decade or so.
It is important to note that the use of chains and resistance bands in this style of training possesses a degree of difficulty and expertise required. While athletes are still relatively new to strength training, the variable resistance and instability created by the chains or bands may limit their ability to improve force production. This suggests that a strength and stability pre-requisite may be required before introducing such methods.
So what are the benefits of lifting with chains and bands? Training with chains and bands, when applied properly, has the potential to improve the velocity on the bar by enhancing the force-velocity relationship. This will improve your stability under the bar and your ability to overcome sticking points on certain lifts.
A common excuse made by athletes for avoiding weight training is the misconception that weights will make them big, bulky, and slow. This statement is neither true or false, its just missing a lot of relevant information. Following a strictly hypertrophy program that sees 200 bicep curl and tricep extension movements performed each week will have little benefit to ones athletic performance and yes, may in fact slow down a fighters punch for example. However, a properly constructed strength program with the inclusion of chains and bands where applicable, will actually increase force production and barbell acceleration and therefore, have transferable application to the sport and create a faster and more powerful strike.
Strength Curves
A strength curve is a mathematical model that represents how much force can be produced at specific joint angles. In other words, its the amount of force produced over a range of motion. Strength curves are further broken down into ascending strength curves and descending strength curves.
Ascending Strength Curve:
Generally pressing movements and exercises that create force through extension represent an ascending strength curve. These movements include squats, deadlifts, bench press, military press etc. and are often easiest in the top ranges of motion (ROM). It is not uncommon to meet someone who brags of their squat 1RM, yet to only discover their misconception as to how much they can actually lift given their squat never threatens to even get close to parallel. With too much weight, the Central Nervous System (CNS) detects weakness and governs ROM and will prevent entire squat depths being reached to protect the individual from injury. This 1/4 squat form etc. is commonly referred to as ego lifting.
Descending Strength Curve: 
Generally pulling movements and exercises that create force through flexion represent a descending strength curve. These movements include pull ups, bicep curls, lateral raise, hamstring curls etc. and are often hardest at the top ranges of motion. Muscle become their weakest when at the shortest point of contraction. Pair that with an ascending strength curve its no wonder that a few reps into a set of pull ups, fatigue sets in heavily and your ability to bring your chest to the bar becomes non existent, unless you’re into dry humping the air, kipping cross fit style. Excluding the use of bands to assist pull ups, the use of chains and bands in exercises of this category, does not enhance your strength throughout a full ROM. Instead, they act solely as a heavier load.
In summary, exercises that have an ascending strength curve limit your strength potential in the top ranges of motion. If your goal is to get the most benefit out of every rep, you should be looking to accomodate resistance. Accomodating resistance means that the load on the bar accommodates the varying strengths of your body throughout the entire range of motion rather than at a certain point. The use of bands and chains will create a varying load on the bar that allows to overload in the top half of the range while still maintaining overload in the weaker bottom half of the range.
Example: Placing resistance bands around the hack squat machine. At the bottom half of the range (deep part of the squat), the bands relax while your body is in its weakest position. As you progress through the squat, the bands pull tighter adding more resistance matching the increasing strength curve in the top parts of the range.
Accomodating resistance (using bands and chains) places a larger emphasis on the concentric phase of the lift rather than the eccentric phase. This means that the antagonist muscles and those responsible for decelerating aren’t trained to the same extent. Being able to decelerate properly and efficiently will save you from injury.
Therefore, its important for someone who is training lots with bands and chains, to balance their work with plenty of focus on the external rotators of the shoulder joint. The same could be said in regard to the glutes, hip flexors, and lower abs for safety of the lumbar spine and lower extremities. Without this symmetry and support of muscles responsible for deceleration, again the CNS detects weakness and may actually prevent full acceleration during throwing, punching and kicking in sports, to save you from injury. The equivalent could be examined if we were to put Honda Jazz break pads on a Lamborghini and watched tried stopping quickly from 280km/h. You’re asking for trouble.
Bands and chains are awesome to use on exercises with ascending strength curves. The benefits to be found are more power, explosive strength, speed, acceleration, hypertrophy, and stability. By utilising the concept of accomodating resistance, programming must also include work for antagonistic muscles and those responsible for deceleration, in order to make these new strength gains functional, while managing to avoid injury.