In this blog I will tell you more about the Peak Height Velocity. Especially how to apply and use it in practice.
Formula for peak high velocity
To measure the Peak Height Velocity, you need a special formula. There is a separate formula for boys and for girls.
The following formulas are used to calculate the PHV:
-9.236 + (0.0002708*(BL*ZL)) + (0.001663*(LT*BL)) + (0.007216*(LT*ZL)) + (0.02292*(KG/LL*100))
-9.376 + (0.0001882*(BL+ZL)) = (0.0022*(LT*BL)) + (0.005841*(LT*ZL)) + (-0.002658*(LT*KG)) + (0.07693*(KG/LL)*100)
BL = leg length (cm), which you can calculate by the difference in length and seat heightZL
= seat height (cm)
LT = age (years)
LL = body length (cm)
KG = weight (in kg)
In order to be able to use and apply this formula, it is useful to be able to represent the particles of the formula in an Excel file. It is quite difficult to put together and create such an Excel file. Fortunately, there are a number of existing Excel files that already use this formula. So you only have to fill in a few things and the result of the formula is already there. So that is super handy!
Should you wish to have one, you can always ask for it through Gymnastics Tools.
To be able to fill in the formula and to be able to put your data into Excel, you will of course need some data. You choose an athlete of whom you want to calculate the Peak Height Velocity. The first thing you have to do is to check the date of birth. So that you know what age this athlete is. Because that age has to be entered in the Excel file.
The next thing you need to do to calculate the formula is to measure the length. That in itself does not sound very difficult, and in fact it is not. However, it is a useful tip to use a correct and reliable length gauge. If you have a ruler or tape measure against the wall, you have to look with your hand above the turner's head. That can sometimes be a bit tricky. You also have mobile length gauges where you can move the top. You can put this against the head and then you can measure how tall someone is from the side. These are just a bit more reliable than a tape measure. But then again, you have to look at what you have in the room or what you have available at all.
In addition to the length, you also need to measure the seat height. To do this, you put someone on a chair so that their feet can reach the floor and their back can sit against the wall. So you have to see which chair he/she needs. Then how you do the same thing you do when you measure the length. You measure with a mobile length gauge against the head of the athlete. Or you look at the tape or ruler how high the athlete is when he/she is sitting.
Thirdly, you need the weight of the athlete. It is important that you have a relationship of trust with the athlete because the weight can be a personal matter for some athletes. In any case, make sure you are open about it. That someone may not be ashamed of his/her weight. And that he/she can share it with you from safety.
Tip: use the same scales every time because you probably also know that not every scale is calibrated in the same way, so not every scale reads the same weight.
In the existing Excel file I used, it is customary to measure length, seat height and weight twice because sometimes - especially with the length - there can be a difference if you measure it again. The Excel file takes the average, so we can be sure that we arrive at the correct length we use for the formula.
Reliability of measurement results
When do you measure and how long should you measure for a reliable Peak Height Velocity? The longer you measure, i.e. the more years you measure, the more reliable the Peak Height Velocity becomes. If you think today, "I'd like to measure my 14-year-old gymnast and see when she has or has not had her Peak Height Velocity," you are already too late. So start measuring on time.
For girls, it is a good idea to start measuring from about the age of seven, i.e. the year in which they turn seven or are seven to start measuring Peak Height Velocity. For boys, it is convenient to start measuring from about age nine because their Peak Height Velocity is often later than a girl's Peak Height Velocity.
Starting to measure
If you start measuring when they are seven or nine years old, or perhaps a little older, how often should you measure? To make the Peak Height Velocity even more reliable, it is useful to measure a little more often as you move towards the Peak Height Velocity age.
For example, you start measuring your gymnast at the age of 7. Then you don't really need to measure her weight and height every week; you can do this about every two months. As she gets older and older and moves closer to Peak Height Velocity or the age of Peak Height Velocity, it is a good idea to measure her more frequently, about two years before Peak Height Velocity, because you will already know more or less which age she is. It is not very reliable, but you have already measured it according to the formula. Then you might start measuring every other month or every fortnight.
Frequency of measurements
When do you calculate the entire Peak Height Velocity? If you have created or are using an existing Excel file, the Peak Height Velocity will automatically come out of it. The literature indicates that it is fine and convenient to measure or at least calculate the Peak Height Velocity between 2-4 times a year. So you measure height and weight more often, but the Peak Height Velocity calculation only needs to be done 2-4 times a year. So it is based on all those small measurements. In an existing Excel file, the Peak Height Velocity is already calculated more often than the 2-4 times per year.
What does the formula give you in terms of data? That is not the age of the Peak Height Velocity but a maturity offset. When the maturity offset is in the plus, so for example +2.5, that means you have already had your Peak Height Velocity. For example, you are 17 years old and your maturity offset is 2.5. You have to subtract that 2.5 from the age of 17, so that is 14.5. That means that you have had your Peak Height Velocity at the age of 14.5. This does not mean that it is impossible that you are no longer growing, but the period in which you were growing fastest was when you were 14.5 years old.
When the maturity offset is in the minus, for example -1.0, that means it is still to come. You have not yet had your Peak Height Velocity. For example, are you 11 years old and do you have a maturity offset from that formula of 1.0? This means that you will have your fastest growth at about the age of 12. It does not mean that at the age of 11 you are not already growing. But you will grow fastest at the age of 12.
I hope that this information has made you a little wiser. And now you know how to calculate and use Peak Height Velocity in practice. If you need help to start calculating Peak Height Velocity, please let me know again. Gymnastics Tools can help you!