By Dr. Brent Smale, Director of Human Performance and Biomechanics
Arguably the most basic skill in skating is starting from a static position and accelerating forwards, oftentimes with maximum effort. The two most common techniques are the open hip start, where the skater’s pelvis is facing the line of progression and rapid hip extension initiates the movement, and the crossover, where the skater is perpendicular to the line of progression and a rapid hip adduction brings the outside leg up and across the inside leg. Coaches have long had their preferences but here, we are going to provide evidence to support our Apex Skating Method of coaching the open hip start opposed to the crossover technique.
Skating starts research appears to begin with Ronald Naud and Laurence Holt with their seminal paper in 1979 testing the acceleration produced by different types of starts. Here they found the crossover to be the slowest and they attributed this to the centre of mass having to go up so that the outside leg can get enough clearance to cross over the inside leg. With this raise in centre of mass, it becomes suspended in air for a short period of time meaning the player is losing valuable milliseconds before being able to generate the next push. They also found that the key to maximizing the thrust produced by the initial push is to get the skate blade as close to 90° as possible. If the blade is positioned at lower angles, the skater loses some of their energy to a lateral thrust.
Another important study concerning skating acceleration was performed by Wayne Marino in 1983. Here he determined what characteristics were most related to faster acceleration. The first characteristic he noted was stride rate. Simple enough that the more strides the skater can complete within a certain distance, the faster they will accelerate. The second distinction was a short single support period. This means that once the faster skaters completed their power strike with their pushing limb, they got it back to its recovery position faster than the slower skaters, i.e. they didn’t waste any time in the recovery phase. The third characteristic was that the faster skaters had significant forward trunk lean at the point of touchdown. This is another basic principle as just think how far one can step forwards when leaning forwards, as opposed to leaning backwards. Finally, the last distinction Marino made was that the placement of the recovery foot was below the hip of the recovery limb in faster skaters. A skater can only generate a thrusting force forwards if their foot is behind the centre of mass. Thus, if the skater’s recovery foot is too far ahead of the hip joint, they cannot produce a backwards push until their hip has moved in front of the foot, i.e. they lose time to make this transition. In conclusion, combining these characteristics with the open hip start appears to be the best method, but now let’s put it into practice with a purpose.
At Apex Skating, we have been extremely interested in the starting technique debate so we decided to use our state-of-the-art inertial measurement unit (IMU) system to conduct 3D motion capture of the open hip and crossover starts. We had one of our test subjects start at the blue line and accelerate to the red line as fast as they could with each type of starting technique. When using the crossover method, he was able to reach the centre line in 2.17 seconds, which equates to an acceleration of 1.67 m/s2. When he used the open hip technique, he reached the centre line in 2.04 seconds (acceleration of 1.83 m/s2), which is a whole 0.13 seconds faster. This may not seem like a lot, but in a tight, high-quality match-up, 130 milliseconds is likely the difference between you getting to the puck before your opponent.
Figure 1) the beginning of the initial push with the right leg (top) and recovery after the initial push with the right leg (bottom) during a cross-over start.
Now that we’ve established which technique is faster, let’s dive into the biomechanical principles behind the methods to help explain the difference. In the figure above, you can see the beginning of the initial push (top) and recovery of the initial push (bottom) during a crossover start. As mentioned earlier, the crossover is dominated by hip adduction, which is the motion of bringing the outside (right) leg across the midline of the body and in front of the inside (left) leg. Here, the skater has a hip adduction range of motion of approximately 17°. This is not a lot of space to produce a powerful push-off, especially considering that the hip is going from an extended position (18°) at push-off to a more flexed position (30°) at recovery. This hip flexion means that this motion is not generating any power as a push-off involves hip extension (i.e. higher to lower angles) and not flexion. Finally, attention needs to be drawn to the lower body positioning at the end of the initial push of the right leg (bottom right). This is clearly not a useful body position to be in as 1) the legs are still crossed, causing the second upcoming push to occur on the outside edge of the left skate, which is less efficient than an inside edge push; 2) there is a small base of support making balance control more difficult; and 3) the pelvis is still not aligned with the line of progression, meaning energy must be used to rotate the body to that forward-facing position instead of being spent in forward acceleration.
Figure 2) the beginning of the initial push with the right leg (top) and recovery after the initial push with the right leg (bottom) during an open-hip start.
In the second figure we have the 3D motion capture outputs during the open hip starting technique. Here, the largest contributor to forward progression is hip extension, which is beneficial due to the large range of motion providing ample opportunity for force generation. During the initial push on the right leg, this skater had a large range of motion of approximately 75°, which is massive compared to the relatively small hip adduction and hip flexion observed during the cross-over technique. A second benefit of the open hip technique is that since the pelvis begins facing the line of progression, the second push (coming from the left leg) is in an optimal position to get a strong thrust from that inside edge. Finally, the base of support is nice and wide providing the skater with greater balance and the ability to react to their surrounding environment such as a change in puck possession. Overall, the open hip keeps the skater on their most powerful edges and does not place the skater in awkward, unathletic body positions.
Even though we’ve established an evidence-based approach to our open hip coaching strategy, we acknowledge that this presentation was of a single skater. Check back here in early 2019 for the extensive results of our rigorous research study.
Marino, G.W., 1983. Selected Mechanical Factors Associated with Acceleration in Ice Skating. Res. Q. Exerc. Sport 54, 234–238. https://doi.org/10.1080/02701367.1983.10605301
Naud, R.L., Hold, L.E., 1979. A comparison of selected hockey skating starts. Can. J. Appl. Sport Sci. J. Can. Sci. Appl. Au Sport 4, 8–10.