Thinking Physics and Skating
Introduction
There's sort of two things I want to get out of the way before beginning this piece.
- When it comes to skateboarding the whole Bruce Lee "I fear not the man who has practiced 10,000 kicks once, but I fear the man who has practiced one kick 10,000 times" is extremely true for skateboarding. So to that end I really only feal comfortable with ollies and 180s but they're repeatable and have that magical board-sticking-to-your-feet quality.
- My knowledge of biomechanics comes from jumping in volleyball, but luckily you jump off of two feet when skateboarding so a lot of the principles transfer directly. With that in mind I hope this is an interesting piece that can help any beginner wrap their head around how to get the board off the ground in conjunction with your feet. In particular, I will focus on ollie's and frontside 180s but these ideas carry over to other tricks (flip tricks to a lesser extent) also.
What is a Skateboard?
Balancing on a skateboard is really hard but after enough time pushing around and attempting tricks, you develop a base ability to balance and manipulate the board under your feet. For this reason, I find that kickturns and tic-tacs are an exceptional exercise for understanding how to get your front trucks in the air and more importantly what a skateboard actually is.
A skateboard is basically a lever with two fulcra (the fulcra being the wheel-axl-truck part of the board). Due to the convexivity of the board (longwise in this instance) applying greater pressure to either the tail or the nose will cause the otherwise to rise if the load on the rest of the board is sufficiently small. This is one of three primary properties that allows skaters to do crazy things; the other two being elasticity and friction.
Energy Transfer in the Skateboard
In skateboarding, pop refers to the elastic quality of the tail (or nose) wooden deck to bounce off the ground after lifting the nose (or tail) into the air with the lever property. When jumping off the skateboard, you apply downward kinetic energy to the tail which hits the ground and transfers the kinetic energy to elastic potential energy. The expression of the potential energy against the normal force is what allows the board to spring up into the air in an ollie like motion.
The deck itself acts like a spring, storing elastic potential energy depending on the distribution of weight and foot-placement before the jump. In a frontside 180 for example, the the front foot is placed slightly more forward than in an ollie with the back foot placed slightly more behind. This footplacement allows you to stay balanced over the long-axis of the board while also applying more forward pressure to the backfoot. This twists the deck slightly down and to the left which then rebounds upon the jump to spin frontside along with your body.
Then of course, friction between the grip tape and shoe plays a huge role in keeping the board under you and manipulating it in the air whether or not you're flipping. High friction between the shoe and grip tape allows skaters to "catch" the board with their front foot and guide it higher into the air, onto a rail, or over a curb while the backfoot catches up and becomes equally involved in stabilizing the landing with its own contact point.
A Good Jump Does The Timing
Timing a good pop is one of the hardest things to learn when learning to skate. I struggle with ollieing straight and not turning frontside. For months I tried different foot positions, balance points, techniques for kicking the board back to get a straight pop. Then I realized my jump wasn't really a jump. In any two-foot jumping sport, height and power and achieved by engaging the ankle, knee and hips in triple extension. I realized I wasn't triple extending through my hips or knees in my ollies! On my next attempt, I did a "real" jump where my back leg was parallel with my torso in full triple extension. The pop was tremendous and I found the grip tape meeting both feet perfectly at the apex of my jump. When committing to an ollie, it's key to commit to the triple extension as well.
One problem persisted though. My board was still turning about 20 degrees frontside when I really tried to ollie high. Again, I thought about what constitues a good jump in volleyball or basketball. A good jump comes from a good approach which stretches the tendons, storing elastic potential energy. Then amortization of the posterior chain, quads, calves, etc. releases that elastic potential energy in perfect triple extension during the jump. Most importantly, the timing of triple extension happens on instinct.
If you watch a lot of good skateboarders, you'll notice many of them do a mini hop before squatting down to ollie. This
- resets foot position but also
- allows them to gain full ankle flexion before jumping. This last part is crucial for ollieing properly. Without a running approach the only way to stretch the achilles and patella is with gravitational potential energy in a good crouch over your center of gravity.
After experimenting with this mini hop, I redistributed my weight from being so focused on the ball of my back foot to being more evenly spread over the ball and beginning of the arch like how it felt in a volleyball jump. Then like magic, I couched down biased toward my heel side rail, jumped, landed and rolled away. By relying on my body's natural jumping cues I cut out many of the major painpoints with my ollies. They're still not perfect, but this motion relies less on intense focus with more emphasis on instinct and intuition from practice.
Applying the "real" jump took my frontside 180 to a whole other level. Keeping my foot placement and weight distribution largely the same, applying more ankle flexion to stretch the achilles led to more consistent 2-foot board control in the air and stable landings as a result.