This is an excerpt from Kettlebell Training-2nd Edition by Steven Cotter.
Circular Strength Principle
A key distinction of the manner of kettlebell training when compared to training with other “bells” (e.g., barbells and dumbbells) is the nonlinear emphasis (i.e., circular strength) rather than the more common linear emphasis. The distinction is centered around both the selection of exercises and the philosophy of movement training.
A linear approach to training values movements in a single plane, like a straight line, as the building blocks of the training program. Common examples are the deadlift, bench press, bent-over row, and similar fundamental strength-building exercises. A nonlinear or circular strength approach to training values multiplanar movements that incorporate a rotational component. Common examples of nonlinear exercises are the kettlebell snatch, Turkish get-up, and clean and press.
The most common tools for training linear strength are the barbell and dumbbell. Most exercises move from point A to point B in a straight line. The kettlebell is the most notable tool for nonlinear training and can be placed at the center of an unconventional training model. Because of the use of inertia, the so-called pendulum swing mechanics, the kettlebell movements facilitate rhythmic, cyclical patterns. These cyclical patterns are by nature nonlinear.
A kettlebell lifter does not train exclusively nonlinear movements and also values developing linear strength. Heavy kettlebell presses, for example, are a common exercise for developing upper-body strength and move in a more linear trajectory. However, because of the kettlebell’s distance between the load and the handle, the kettlebell facilitates a nonlinear, or swinging, way of moving and extends the range of motion that the kettlebell travels during a given exercise. This swinging motion present in most kettlebell exercises creates the circular nature of the patterns and incorporates force development through multiple planes (frontal, sagittal, and transverse).
With the proliferation of the unique “unconventional” training equipment sparked by the popularity of kettlebells over the last 20 years, more personal trainers, gyms, and programs follow primarily an unconventional training matrix. Often these unconventional tools are paired with barbells, dumbbells, and other more traditional tools to develop more comprehensive movement systems, which incorporate both linear and nonlinear strength development. Figure 3.1 demonstrates how an unconventional training model might look.