It might be the MOST annoying saying in all of fitness. I have even heard some of the smartest and most accomplished strength coaches fall prey to it:

"Weight is just weight, the body doesn’t know the difference."

At first glance, it makes a lot of sense! It reminds me of an old joke, "What weighs more, 1000 pounds of feathers or 1000 pounds of rocks?" Does science and the real world tell us anything otherwise?

I can remember my first time flipping tires, lifting atlas stones, and lifting strongman logs—holy cow! I had lifted barbells for ten years and had some good lifts, but all this stuff was totally humbling. I was strong, and thought that just couldn’t be right! But, the truth is we all have had a similar experience when trying different types of weights—many of you have noticed this effect when first using a kettlebell.

The kettlebell’s offset handle makes lifting it very different from lifting a dumbbell or even a barbell. Many more people can clean over 200 pounds with a barbell than can double clean two 48kg (106lb) kettlebells.

Why?

Our tools are all made differently. Leverage and dimension all play a role in how differently constructed weights can feel, and more importantly create an entirely NEW stress on the body. If we understand the differences in our tools, then we can develop BETTER exercises, progressions, and programs.

All of this sounds good, but other than how these experiences feel, is there any real science to back up these claims?

Last year I had the honor to work with researchers from the University of Wisconsin-Milwaukee and put our DVRT Ultimate Sandbag Training to the test. I was nervous because I would find out whether or not much of what I’ve said about DVRT and Ultimate Sandbags was or wasn’t true. This research could be the end of many great "theories".

The researchers’ test would be relatively simple. The energy expenditure of eighteen college students would be evaluated. The goal was to see if dumbbells or our Ultimate Sandbags would create a significant difference in energy expenditure while performing lunges.

These eighteen students completed two randomly ordered 60 second dumbbell and Ultimate Sandbag lunge trials. They had to lunge at a cadence of 60 beats per minute for a total of 30 lunges completed in each trial.

The participants used weights which were 25% of their bodyweight for both dumbbells and Ultimate Sandbags. For consistency in testing, they held the dumbbells in a neutral grip position by their shoulders, or held the Ultimate Sandbags on their fists in a very similar position.

In the study, the students performed the same volume of work with the same amount of weight held in essentially the same position.

At this point, if we are led to believe that "weight is just weight", we could assume that there should be NO difference between the dumbbell and Ultimate Sandbag trials.

What did the researchers find?

"The estimated energy expenditure of the Ultimate Sandbag trial was significantly greater than the dumbbell trial." What?! How can that be?

Unfortunately, the purpose of this initial study wasn’t to find out why, but to be honest, I was pretty shocked at how big of a difference there was between the two trial groups. The difference was over eight beats per minute—HUGE considering how equal everything in the trials appeared on paper. But eight beats per minute can be a rather large change in intensity when considering heart rate percentages.

While we don’t know for sure why there was such a big difference between the dumbbell and Ultimate Sandbag trials, we can make some educated guesses.

Some people will say that the Ultimate Sandbag is unstable, and that instability would cause the difference. However, that isn’t the case here . The holding position for the Ultimate Sandbag in the study ensured that there wasn’t any unstable movement with the implement. The difference was likely to be the compressive forces acting on the body. These forces possibly stimulated more muscles through the upper body and trunk, increasing the amount of energy used to complete the lunges with an Ultimate Sandbag.

This is the FIRST time that we have started to see that our tools are not all the same. We don’t just use Ultimate Sandbags because they are just different, or we feel the need for some variety. Instead, our tools can create very different results if we realize the unique attributes they can bring to our training. Once we know those attributes, we can really get an edge with our own fitness and with our clients’ training.

Being a better fitness professional also means appreciating the power of our tools!

***Note: Researchers were also supposed to test the Ultimate Sandbag Rotational Lunge, but the participants became too tired too quickly for accurate testing. This study is still unpublished, but will be published once the additional materials on EMG activity are completed.