I have just put out a video to explain how to use the force curve comparison analysis in-app purchase with my app Remote Rowing Coach. The feedback I was getting was that folks wanted to know how to use this functionality effectively, so here is a video with some explanation on what you are looking for and how to analyze your comparison graphs.
For more information on my app Remote Rowing Coach, please visit the app page here.
For information on real-time data transmission to facilitate online remote coaching and real-time data transmission visit this article here.
For a full discussion on the history of force curves with detailed explanations of the force application strategies contained within this post, I recommend reading Peter Mallory’s work in The Sport Of Rowing which you can find on worldrowing.org at this link. The chapter in question starts at page 376 in volume 1. Additionally, a discussion of force application strategy can be found in Volume 4 and starts on page 2438.
Force Curve Analysis With Remote Rowing Coach
One type of force application is the front-loaded drive. This force application is generally accepted by the biomechanics community as the most effective force application approach. It is characterized by a rapid increase in force generated by an explosive leg drive with the aim to reach max peak force as early as possible during the drive.
As you can see from the image below (simulated force curve not actually taken from an athlete) the curve leans left.
Another type of force curve is a more even force curve. This is generally achieved with concurrent activation of legs, body, and arms. It results in a more symmetrical application of force. It does generally result in a lower peak force compared to the front-loaded drive as mentioned above.
I provide an image below to show a hypothetical comparison between the two force application approaches. The time that peak force is reached in the front-loaded drive is earlier than the approach that results from a sharp beginning and a continued thrust through to the end of the stroke. The area under the curve is the impulse imparted to the machine during the course of one stroke. Therefore, it makes sense that the larger this area the faster the wheel will spin.
I like to think of a painting analogy when describing force application approaches. If the amount of paint in a can is the amount of work supplied during the drive (the area under the curve), then the way in which the brush is used to apply this work provides the SHAPE of the curve.
It is also worth noting that there is a continuum between front-loaded force application and the more progressive “thrust stroke”.
I am also not showing any force curves that demonstrate late acceleration in the stroke because this application strategy has not been shown to be effective at generating boat speed.
An effective force curve will have a rounded convex look to it. If the force curve goes concave at any point on the curve this demonstrates an acceleration discontinuity in the stroke. If there is an interruption in acceleration, the curve begins to go inward, and then after a period of time, it will begin the curve back as an athlete “recovers or rebounds” from the discontinuity in force application. These concavities help to pinpoint sections of the drive mechanics where there is a disconnection and improvements can be made in coordination, activation, and force application.
In the graphic below, I have shown the areas of potential improvement that can be made between the symmetric force application and a hypothetical athlete force curve where there are discontinuities in force application.
As mentioned above, my app Remote Rowing Coach provides an in-app purchase feature that allows you to compare the average force curve at a particular rate on the same graph. I am unaware of any other app that provides this functionality at the time of writing. As you can see from my image, my force curves are not perfect and that is to be expected because of the general “noise” inherent in movement and force application in athlete activity. However, you can see from the image below that on this particular 8km steady state row, peak force is reached earlier in the stroke at higher rates than at lower rates. The Concept2 PM5 v2 and v3 derives a force point every 0.015 seconds. As a result, the width of the base becomes less as stroke rate increases.
From a coaching standpoint in order to improve the force curve of the athlete it is appropriate to teach correct stroke mechanics, connection and acceleration and then see how the curve responds. The graph itself does not help instruct a rower how to row effectively.