Dynamic Variable Resistance Training

Dynamic Variable Resistance Training

Josh Henkin


Sandbags are an underappreciated tool for helping people achieve improvements in their stability, strength, and overall movement patterns. While the idea of sandbags might be an ancient one, some tracing back to Egyptian times, the modern evolution and thought of the use of the tool is very new. The value of training with sandbags appears to be for those athletes wanting functional strength, agility, and reactive ability.

Old-time strongmen, wrestlers, and martial artists came to the use of sandbags through different means. One of the great curators of physical culture, Brooks Kubik, summed up the unique benefits of sandbags, “You feel sore as you do because the bags (sandbags) worked your body in ways you could not approach with a barbell alone. You got into the muscle areas you normally don’t work. You worked the ‘heck’ out of the stabilizers.”1

This chapter focuses on the sandbag as an essential and unique tool in the rehabilitation and training armamentarium of clinicians and trainers.


On a foundational level, training with a sandbag functions the same as many other strength training mediums using variables such as load, volume, density, etc. However, using the sandbag like a barbell or other free weights poses problems and doesn’t allow us to maximize the unique attributes of the sandbag.

Most pronounced is the fact that the sandbag is not going to micro load. Placing a heavy emphasis on the load variable is going to limit progress and building progression in training. What the sandbag doesn’t allow for in micro loading, it more than makes up for in expanding our ability to use a wider array of training variables.

The most prominent of these training variables is instability. The primary focus of sandbags in history has been their ability to challenge stability in several different mediums. While some may think the instability of the sandbag only comes in the form of the sand shifting itself, the sandbag actually allows us to expand the concept of instability into four primary concepts.

  • Body Position

  • Holding Position

  • Plane of Motion

  • Dimension of Implement

These four concepts help us create an environment where we can have instability be as progressive as load, volume, and density. It also allows us to address one of the major, but missed, goals of instability training: movement accuracy. While it is true that instability training does improve the neurological system and trains the smaller stabilizers of the joints, what may be one of the most profound benefits of instability training is challenging movement accuracy.

These are elements that reflect varying levels of instability, strength, and challenging of our natural kinetic chains that create efficient movement. While recent research has demonstrated that unstable surface training may not provide any benefit to strength or core development,2 there is very strong evidence that unstable implements and body positions can achieve these goals.3

Why doesn’t unstable surface training create the changes in core and overall body strength and stability that we once believed? One reasonable conclusion is that unstable surfaces are not incremental and therefore cause the body spending more time in trying to maintain posture than producing force. In fact, in a review of unstable surface training literature, Behm and Colado stated, “ground-based free-weight exercises with moderate levels of instability should form the foundation of exercises to train the core musculature.”4 The key in this description is “moderate.” Too much instability can result in the individual using the startle reflex in response and retarding movement education.

Creating Efficiency Through Movement Accuracy

Movement accuracy is the ability to maintain the qualities of the movement patterns of an exercise under varying conditions. The variables include load position, body position, plane of motion, and instability of implement. These concepts should apply to all training tools, but sandbags best optimize these variables.

Our goal in dynamic variable resistance training (DVRT) is to first establish great proficiency in the fundamental movement patterns. The sandbag provides us the ability to improve these foundational patterns in a very short amount of time. As Dr. Stuart McGill describes, this includes:

  • Squat/lift

  • Push/pull

  • Lunge

  • Gait

  • Twist

  • Balance

Once we establish the pattern, then we want to challenge the pattern. While most strength training programs will do so predominantly through load or repetition, DVRT sandbag training uses the four training concepts to create much more well-rounded means challenging the movement pattern.

As physical therapist, Gray Cook, discusses the role of strength, “We want adaptable strength that can work in changing environments. Adaptable strength is developed though complex movement patterns, not over-rehearsed, over-coached lifts in a never-changing environment. The athlete, warrior, outdoor enthusiast or physical adventurer embraces change and challenge, while the gym rat needs comfort and consistency for a happy workout.”5

Such a progression can be demonstrated in how we build and then challenge the squat pattern. When first screening one’s squat, many coaches assume issues in muscular imbalances and flexibility issues. However, when we use load not to challenge, but help to direct movement, we find that the individual can move in the squat pattern quite well. This leads us to the conclusion that many movement issues are not an issue of either muscle imbalances or flexibility deficiency, but poor motor engrams.

The sandbag provides us a powerful tool to accomplish these goals. Due to the ability to alter load position, we can work from using specific placement of load to establish good movement skills to challenging our ability to maintain the pattern under stresses of load and instability.

Foundational Methods

The Squat Press Out (Fig. 24.1) teaches the client not only how to move in the squat pattern but also how to create appropriate tension. Greater core activation and the use of the latissimus dorsi help create better movement through greater core stability. The concepts of proprioceptive neuromuscular facilitation teach us “proximal stability creates distal mobility.”

The pressing out motion is rather specific to the sandbag; having experimented with other implements, the effects are not the same. This is due to the shape, weight distribution, and leverage the sandbag creates. We will discuss the deliberate creation of the right tool shortly.

Once good squatting patterns are developed through the Press Out Squat, we can change holding position and change to the Bear Hug position to apply
more load and not rely on the counterbalance of the weight as greatly. As the client can perform five repetitions of the Bear Hug Squat (Fig. 24.2) with half of their body weight, they have developed enough full body strength to move to the Front Load position.

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Apr 17, 2020 | Posted by in PHYSICAL MEDICINE & REHABILITATION | Comments Off on Dynamic Variable Resistance Training

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