In our last blog, we had a simple lesson plan for younger students. In it was a promise to begin with some biomechanical measurement. And we will, just after we review how to measure PHV, which was introduced in our first blog. There are two methods that can be used: one using a chair for sitting height and the other sitting directly on the scale. The following measurements are needed: height, sitting height, weight, gender and date of birth. It is important to get the measurables accurate.
Here is the site we use for the calculation: https://www.usask.ca/kin-growthutility/phv_ui.php
They have a good document for their method of measurement which you are referred to it by clicking the link on the site just above the data entry area on page 1. They use the chair method to get sitting height. We have the athlete sit on the scale in the same posture with their back right against the vertical measurement post. If your scale has the capability of measurement on the lower portion of the post, then use that.
Okay, now we have the PHV measurement. Now we can determine the optimal training periods for stamina and strength which is based on the onset of puberty. Skill, speed and flexibility are based on chronological age.
Now we have shown some exercises for Agility, Balance and Coordination, but we want to measure them in order to track progress. Here’s some suggestions.
• Make sure the drill is done the same way each time-apples to apples.
• Better to video and compare repetitions over time. Also, easier to measure. Put camera in the same relative position each time
• Make sure you measure the same way. E.g. agility is a bit harder to do with hard measurement
• Determine how many agility movements exist in the drill
• If around objects, how much clearance is defined as successful?
• How much control is defined as success?
– Maybe consider following centre of gravity or distance between feet. This can work for balance measurement, as well.
• For balance, consider standing on one leg and observe deflection in front to back or side to side
• Decide if the standing leg can bend and, if so, how much
• Have the athlete abduct a straight arm and or leg laterally and observe any loss of balance
• Also, have them move the extended arm and or leg forward or backward
• Use time as a measure
• Use either standing leg arm and lifted leg arm as different measures
– If you have access to a two-axis force plate, you can look at normal and parallel forces during the exercise. Set up the drill with the foot lined up with the way the scale measures parallel force.
• For coordination, consider the combination or all arm and leg movements during the drill and body posture. Drills like skater hops, bounding, crossover steps (karaoke in our gym), ladder movements. Side by side of video is helpful. Look for consistent location of the limbs at the same point of the exercise repetitions.
Having now set up some tracking measurements for basic movements, we can extend this to any sport specific movement using similar methods. Measurement of the key performance factors can be made using visual means or biometrical measurement technology.
Keep in mind that if a movement is new to the athlete, the first phase is learning, so it is critical to make sure that the correct technique is taught. Once the technique is fully learned, then performance improvements will be based on refinement.
Many coaches err on the side of demonstrating what not to do. This is a serious error. It is confusing and detracts from the goal of performing the desired task correctly. Only show the correct technique.
All of the basic sports movements depend on control of the athlete’s centre of gravity. What is that? Our weight is the force of gravity acting on our body’s mass-the sum of the atomic weight of every atom in or attached to our body. The net effect is that every atom is pulled by the net gravitational force of the centre of the earth (in proper terms mass is in kilograms). At any instant, when more than half the mass is off centre, you have to counteract that force, or you move in that direction. So, all movement is based on motion of some portion of the body that takes mass away from the centre of your body. Gravity is a force which is defined as mass multiplied by acceleration. Mass was defined above, but acceleration is the rate of change of velocity, which is defined as speed in a specific direction. In the case of gravity, that is in a downward direction and the value is 9.81 metres per second per second. Without turning this into a physics course, this means that a falling object starts at 0 metres per second and in 9.81 metres is now travelling at 9.81 metres per second in a downward direction. Although we should be measuring weight in Newtons which is mass x the acceleration due to gravity, we typically stick with Kgs. So, if I have a mass of 100 Kgs, my weight at sea level on earth is 981 Newtons.
One of the things we need to remember that links directly to this is the forces at work when we jump on and off boxes or other objects. If a 50 Kg athlete jumps up to a 0.25 metre box and clears the edge of the box by 0.03 metres, she has needed to apply a force that exceeds gravity, but lands on the box with only a force of just under 15 newtons. When jumping down, if she used the same force to jump up and then off the box, she would be landing with a force of nearly 19 times greater because she would reach 0.56 metres above the ground and thus be accelerated by gravity over a longer distance and will apply landing force of about 275 newtons.
Measurement tells us where we are, but unless we know where we want to be, the measurement may not give us everything we need. If your goal is to be the best in the world, you must measure the best in world creating what is being called the Gold Medal Profile by our national sports strategy team who have created excellent documents to present this. The difference between the measurable skills and attributes of the gold medalist in your sport or division within that sport and your skills and attributes is called the gap. You do gap analysis on each skill and attribute, set intermediate goals, design programs to meet those goals and track the progress. This is easy to say, but not really that easy to do. In our next blog, we will address ways to do this.