More Aerobic Intervals

Some more aerobic intervals today with a female soccer player. She did 3 sets of 6 reps, 80% sprint the length of a soccer field.

The graph to the left shows the strong correlation between her sprint time and mean ground contact time (pearson = 0.725). Sprint time is generally faster with a longer mean ground contact time.

From this information it looks like this athlete has a tendency to 'jump' up into the air too much while sprinting. Next session I will cue her to try to not move up so high during her air times.

How does weight relate to force / power in a jump?

Extra weight will increase force because force = acceleration x mass, BUT more weight is harder to accelerate. What is the relationship between weight and actual force production? This gets even more confusing when considering power (power = force x velcoity).

The following two graphs show how mass related to mean force and power development in a single counter-movement jump, for roughly 500 tests in our database;According to our database of tests and the pearson product correlation, athlete weight is somewhat related to force and power output in a jump.

I think that the relationship that is seen here is mostly due to the wide variety of groups in our testing database. We have tested a lot of high level athletes as well as some younger athletes, I see two main groups by looking at the above graphs and I'm not convinced that weight makes much difference within them - weight only makes a difference between them.

It would be more interesting to see this type of information with a homogenous group of athlete's. I'll work on that for another day.

GC Time during aerobic intervals

This morning I ran an aerobic interval session and had one athlete wearing the A-Pod System. The workout was
- 2 sets of
- 6 x 100m run
- at 80% max speed
- 45 sec walk/jog between intervals
- 5min rest between sets


The graph on the left shows the athlete's 100m times for each interval.






This graph shows how average ground contact time related to running speed for each interval. Clearly, he ran faster with shorter ground contact times.

What does this mean? Do shorter contact times mean faster runs? Up to a point I'm sure, but this athlete was not sprinting at 100%.

Perhaps he was just lazy on his slow runs, but this athlete does run faster with shorter ground contact times. Maybe he should be trained to focus on high running cadence.

One of the main reasons for performing an aerobic interval workout is so athlete's can focus on maintaining proper form. In our next session I will be more diligent in cueing him to maintain good running form, I will post what the results look like.




Definition: Average ground contact time is the average amount of time that the athlete's foot was on the ground for each step in the sprint.

High Speed Camera

Tonnes of fun this week playing with our new high speed camera. Difficult to use, but amazing what can be seen when recording human movement.

Forward-Upward Training?

Perhaps results from our sprinting analysis could result in coaches training athlete's performance in certain planes and on left or right feet to correct imbalances.

The following graph shows forward force production on each step;

Clearly, this athlete is generating more forward force with his left foot than his right foot.

This discrepancy is not true when viewing this athlete's vertical force production on each step;
Does this mean that this athlete should train his left foot in the horizontal direction? Maybe, but maybe that will mess up other factors of the left-right forward-upward force production generation. Trainers have not had access to this type of information before, these questions are being addressed for the first time ever.

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).