Peak Power is cool

This is a continuation of yesterday's post.

The only output from jumping that related to Time to Peak Force (TPF) is peak power production. Check it out;

- The Pearson Product Correlation between Time to Peak Force and Peak Power is 0.513
- The data is divided into 2 main groups, based on high TPF or low TPF
- high TPF group generally had higher peak power values than the low TPF group

The high TPF group has higher peak power values because power is a product of force and velocity. Upward velocity is always less at the beginning of the concentric phase than at the end. The same vertical force output at the start and at the end of the concentric phase would result in different power outputs due to velocity being small at the beginning and larger at the end.

I'll work on showign a graphical representation of this. I also want to post about what type of athlete's are in the high TPF and low TPF groups.

Time to Peak Force

Here is some information from my bank of roughly 600 counter-movement jump tests. I wanted to compare time to peak force (TPF) and time to peak power (TPP) for each jump to see how they related (see bottom of post for definitions).

Intuitively, TPF should be smaller than TPP due to the velocity component of power. Here are the results;- There is a high TPF group
- There is a low TPF group (as noted by poorly drawn paint circles)
- Wow, TPF was not always smaller than TPP
- My guess would be that the explosive performers would fall into the low TPF group because they would be changing their velocity the fastest around the bottom of their preload.

I want to investigate this more to see if any one aspect of jumping performance is associated with lower TPF percentages, initially I thought that push-off time (concentric contraction time) would be correlated, but as you can see in the following graph, it is not;
Clearly, push-off times are similar for the low TPF group and the high TPF group.

TPF - Time to Peak Force - is the time from the bottom of the athlete's pre-load until they achive their peak upward force. This is being shown as a percentage of total push off time, which is time from bottom of preload until the athlete's feet leave the ground.

TPP - Time to Peak Power - this is similar to TPF, the only difference being that instead of vertical force production this represents vertical power production (which is a product of force and velocity).

Sprinting Validation

Did some preliminary validation work with the Optojump system today...

Push-Off Time and Skate Speed

Oops, in yesterday's post I over-looked the strongest correlation between skating speed and jumping, it was push-off time. Push-off time is the concentric force generation phase of the jump, it begins when the athlete is at their bottom most preload and ends once the athlete's foot has left the ground.

The Pearson Product for push-off time and skate speed was 0.857.

Players who had a faster push-off for their jump also had faster skating speeds. Does this mean that max skate speed depends a lot on an athlete's ability to move fast? Force generation or peak power were not correlated with skate speed, should hockey players do more training focusing on speed of movement?

CMJ as predictor of skate performance

Could a hockey coach use jump tests before a game or practice to see how ready a player is to perform at their peak? This could be a useful tool to prevent over-training and to maximize training benefit by knowing when the athlete is ready to work hard.

- 9 Junior B Hockey players were tested
- Counter-movement jumps performed in shoe's before practice
- 25m sprints on ice after warm up
- A-Pod used as measurement tool for both tests
- Is there any correlation between jump performance and skate speed?

Most correlated: Time to Peak Power (r squared = 0.723)
- TPP is the time (in sec) it takes the athlete to go from the bottom of their preload until they reach peak power. Put another way, it is what time into their concentric contraction do they achieve peak power.
Athletes who achieved their peak power later in the concentric phase of their jump tended to have slower skating speeds.