The kettlebell handles are holders similar to kettlebells that are loaded with dumbbells. The kettlebell handles are not suitable for the exercises popular with kettlebells, such as swings, cleans and snatches. However, they are excellent variation options for exercises such as curls and rows.
The big advantage of the VA7 kettlebell handles over other variants is that they are loaded with dumbbells instead of discs, which makes it much more efficient to increase or decrease weight.
Here is a video of the kettlebell handles in 45° incline bench curls:
The primary effect on muscle overload in kettlebell handle curls comes from modifying the overload of the strength curve.
Definition: The strength curve determines the sum of all muscularly generated forces to be produced for a body movement as a function of the movement amplitude and the joint angle. The strength curve is inherently movement specific, depends to a small extent on the speed of movement, and tends to vary slightly from person to person based on anatomy.
In the context of strength training, it is crucial to modify the overload of the strength curve through various exercises, methods and tools in order to enable and accelerate progress. There are several ways to modify the strength curve or overload of the movement in strength training
Three of these ways are:
Chains & Ribbons (accommodating resistance)
Chains and bands modify resistance so that the resistance curve is ascending, thereby overloading the movement more at the top as resistance increases gradually or exponentially during the concentric contraction.
Modification of horizontal distance from pivot point to center of mass
In this case, the resistance remains the same, only the horizontal distance is changed. A simple example is raising a sledgehammer with your arm straight in front of your body - this means fronting with a sledgehammer. If you grip the sledgehammer directly in front of the handle so that your fingers touch the hammer head, a front raise is relatively easy. However, if you grab the handle at the very back, front lifting is hardly possible. In both cases, the resistance of the sledgehammer is identical, but the overload of the movement changes significantly due to the modification of the horizontal distance from the pivot point to the center of mass. Technically, this is the change in leverage. An example from strength training is a power curl bar where the resistance in the top position is far in front of your hand, which overloads the top position significantly more. A picture of the Power Curl Bar here.
Modification of vertical distance from pivot point to center of mass
In this case, too, the resistance remains the same, only the vertical distance is changed. If you were to do an exercise that was completely vertical, this change in vertical distance would have no effect on muscle overload. In the example of curls, however, the movement is not vertical but bell-shaped and in such horizontal-vertical movements this vertical distance from pivot point to center of mass plays a large role in the acceleration of the weight and therefore the moment of inertia.
The technically detailed explanation of the mechanics of kettlebell handles
The kettlebell handles increase the vertical distance between the pivot point (elbow) and the force of the weight (gravity mg). The kettlebell handles therefore have no effect on the moment generated, since the handle can rotate freely in the hand. This means that there is no change in the horizontal distance, the weight is always under your hand. In other words, the kettlebell handles have no effect on leverage and torque. However, with the kettlebell handles, there is a greater load on the bicep muscles due to the moment of inertia.
Figure 1: Simplified drawing of arm with kettlebell handle in lowest position
In Figure 1 we see the kettlebell handles in action in the bottom position of the curl. Where L O is the length of the upper arm, L U is the length of the forearm and L P is the (vertical) length of the kettlebell handles. The pivot point (elbow) is fixed for completeness of the figure. This should also be the case in practice for optimal movement execution. In this model it is assumed that the arms have no mass and that there is no friction at the handle or pivot, and that there is no oscillation, so alpha and beta are always equal. However, all of these factors amplify the effect in reality, but would give this theoretical model too much mathematical depth for the purposes of this explanation.
Figure 2: Simplified drawing of arm with kettlebell handle in top position
Figure 2 shows the top position of the curl. Where α defines the angle between the upper arm and the forearm and β as the angle between the forearm and the acting force (the weight). Likewise, r is defined as the distance between the pivot point and the application of the force, and τ as the moment generated by contraction of the biceps. We can see that the force is parallel to the upper arm and thus there is no difference in the moment generated by a vertical change in the application of the force.
To find out what causes the higher load, we solve for the moment about the pivot point:
Where I is defined as the mass inertia and as the angular acceleration. We see that LP does not appear in this equation. As expected, the kettlebell handle has no effect on the moment. Only the mass, the length of the forearm and the angle between the forearm and upper arm affect the moment. In order to explain the higher load, i.e. a larger number for τ, we have to take a closer look at the last term.
I, the mass inertia is defined as follows:
Now we solve for our system:
Here we can see that the vertical length of the kettlebell handles, L P , has an effect on the inertia, or moment of inertia.
Now we have the following equation for the moment at the pivot point τ, which is generated by loading the biceps waste:
Also, the oscillation of the kettlebell handles plays a small role in overloading the strength curve.
In summary, this means that the horizontal modification of the center of mass to the pivot primarily affects the torque. And the vertical modification of the center of mass to the pivot primarily affects the moment of inertia.
The different effects of the three modifications are also clearly noticeable in practice. Again, as with everything in training, practice beats theory every day. All three modifications are excellent options to overcome plateaus.
Thus, the Kettlebells Handles are an excellent tool for variation and progression in training!
The kettlebell handles were developed in cooperation with Wolfgang Unsöld from YPSI Stuttgart. YPSI A-License trainer Philip Schmieder had the idea for this at the YPSI Invitation-Only Seminar in September 2017, which is why they are also known as pettlebells.
Many thanks for the technical explanation and formula as well as the drawings to YPSI athlete and master student of aerospace engineering Frederick Lüthcke as well as to YPSI coach and mechanical engineer Dr. Bastian Jörißen for initial discussions about the mechanics of kettlebell handles a few years ago.
For all trainers who have attended YPSI seminars, a discount for the kettlebell handles and all other VA7 products is available, more information directly in the YPSI forum .
Image: The kettlebell handles, with and without dumbbells.