CALCULATE YOUR LEANING FORCE
How much vertical force can you place through your broom and into the ice?
Using a bathroom scale, it is simple to gain a rough idea of this value, and also how altering your position affects vertical force. However, it is more useful to know what this value is when you are on the ice, having to actually sweep or lean in front of a moving stone. So how can we measure your vertical force production, even without a SmartBroom?
This simple five-step method will outline how to do just that. All you need is a video of yourself leaning in front of a stone and your Body Weight [BW].
step one
Take a screenshot of your sweeping position from the video you have recorded. Ideally, this will be directly from the side.
step two
Estimate and mark the location of your Centre of Gravity [CoG]. The CoG is a point where the total weight of your body can be thought to be concentrated. This point will be located in the centre of your body, roughly behind the belly button.
At this stage, also mark the vertical force at your broom head [F]. This is the value you are calculating.
step three
Draw a line vertically downwards from your CoG. This is called the Line of Gravity [LoG] and indicates the direction that gravity is acting upon your body.
Add your BW next to your LoG. To convert body mass [kg] to BW [N], multiply the value by 9.81, since this is the acceleration of gravity on earth:
Mass [kg] x Gravity [m/s^2] = Weight [N]
In my example, I measured my body mass = 85kg. Using the formula:
85 x 9.81 = 833.5
Therefore, my BW = 833.5N.
step four
Draw a line from your feet to your LoG [a], and measure its length.
Also, draw a line from your LoG to your broom head [b], and measure its length.
Arbitrary units can be used here, so long as they are proportional to each other.
In my example, I used a ruler and measured the lengths in mm.
step five
You now have all to the data you need to find your leaning vertical force.
Grab your calculator and use this equation:
F = [BW x a] / [a + b]
Following the calculation in my example, it can be seen that F = 532N.
Tracking this performance metric over time can inform whether your technique is improving, or your training is effective. It may also be interesting to compare the value when recorded before and after games or competitions, indicating your ability to maintain effectiveness over time.
kilograms vs newtons
Although the kilogram is a unit of mass, as opposed to force, it can be used interchangeably with newtons for our purposes. This is because the acceleration of gravity on earth is fairly constant.
Kilograms are usually easier for athletes to interpret than newtons, since most people are more familiar with using this unit.
percentage body weight
Now knowing your body weight [BW] and your leaning vertical force [F], you can also calculate the percentage of your body weight [%BW] through the broom:
%BW = [F / BW] x 100
In my example used above, F = 532N and BW = 833.5N. Using the formula:
%BW = [532 / 833.5] x 100 = 62.8
This means that when in this position, 62.8% of my body weight is being placed into the ice via the broomhead.
Over time, with training and practice, the aim should be to improve the %BW that you can place through the broom whilst sweeping. This value increasing suggests improved technique and vertical force production. Of course, increasing your bodyweight can also be beneficial to raise the ceiling for what leaning force is possible to achieve.
limitations
This method is not be perfect, since it relies on an estimates for the location of your CoM. Also, it ignores the fact that your feet will constantly be moving when sweeping down the ice. Maybe try taking a few random screenshots at different footwork stages to compare the outcome of your calculations.
Despite these limitations, you should be able to gain valuable insight regarding your leaning force and sweeping effectiveness. Plus, it is free.
