Lean angle and g-force (nerd alert)

[Bill_S]

Because I missed the last day of skating today, I was thinking about why my legs have been so tired for this past week. I've been skating everyday until today.

I found some video footage showing a lean into a turn, and did a frame grab. I took this into a drawing program to mark up the illustration to get an idea of how much g-force is acting on my body. (See what I'm doing here? Looking for a way to explain my tired legs!)

Here's the photo...



I apologize for the fuzziness of the video frame-grab, but it is sufficient for a quicky analysis.

My legs support 1g (influence of gravity acting on mass) when I'm standing up straight. On a bathroom scale, the action of one g on my body mass reads out in pounds.

When skating with the lean angle shown in the photo (30 degrees, give-or-take), centrifugal force wants to force me outside of the lobe that I'm skating on. I must lean into the turn and press more into the ice to maintain the arc. The tangent of the lean angle for a skater represents how many gs I must endure. The total is represented by the diagonal line shown. Use simple geometric math (sum the squares the weight vector and the centrifugal vector, then take the square root) to find the value.

For this lean, I'm experiencing 1.15 times my normal weight, or in my case, about 25 pounds extra.

If I lean 45 degrees, I would experience 1.4 times my normal weight. I'd probably be contacting the side of my figure skating boot by then.

No wonder my legs get tired!

[lutefisk]

Bill:  Several questions spring to mind--If you walked around, during your off-ice hours, with a 25 lb back pack to simulate the added weight of the g-force, I wonder if your legs would adapt and feel less tired when you skate hammer and tongs at an estimated angle 30 degrees? 

Meaningless statics dept question: I only skate 3 or so times per week rather than your 6 in a row and that effort makes my legs tired.  If we calculate an index of tiredness does that make my legs 50% more efficient? 

Final observation:  That wedge shaped 30 degree angle in your figure reminds me that I haven't had any pie in a while--no wonder my legs feel stale! 

[Bill_S]

If I walked around with a 25 pound pack, I'm sure that I'd develop some extra muscle which would help. Also if I did, I'd want part of that 25 pounds to be a liquid refreshment. 

I like your index of tiredness. I can relate in a similar way by noting my own high-performance kidneys becoming even more efficient as I age.

I didn't use π in my calculations, but a slice does sound appealing.

[lutefisk]

If I walked around with a 25 pound pack, I'm sure that I'd develop some extra muscle which would help. Also if I did, I'd want part of that 25 pounds to be a liquid refreshment. 

I like your index of tiredness. I can relate in a similar way by noting my own high-performance kidneys becoming even more efficient as I age.

I didn't use π in my calculations, but a slice does sound appealing.

Plus GOE!  I vote for rhubarb.