Thursday, May 10, 2018

Fatigue and How It Impacts Range of Motion in the Foot

By PCG Master Coach Hunter Allen

This past month, I was able to gather motion data on many of the cyclists that came to our 21st annual cycling camp here in the beautiful Blue Ridge Mountains. The main goal was to be able to identify when a rider fatigues based on a change in their motion. This could be the motion in their foot angular range (how far the foot moves up and down), or in their torso movement, which includes rotation, angle, and rock. Fatigue and movement are fickle things, and sometimes hard to identify. Some riders will change the way their feet move when they become tired in a ride, and others will move their upper body more.  The calf muscles (gastrocnemius) hold their foot in place when pedaling, and for many riders, when they fatigue, they are no longer able to hold the foot within the previous range of motion.  For some riders, this means reducing their range of motion, for others, it means increasing it. Many riders will also change their upper body movements when they become fatigued, and 99% of the time, they will increase their torso rotation, or rock, and even change the angle of their torso. With this in mind, we looked at all of the riders using a LEOMO TYPE-R at the camp to see if we could identify fatigue from a big picture view.

Our first rider completed the “long” day at camp, which is 95 miles over two mountains, each mountain stretch being about 35 minutes long. He had no change in his foot angular range throughout the entire ride. However, when I compared the ride after the first climb (while he was still fresh) to the ride after the second climb, then there were some big changes in his torso data. First off, he was no longer able (or willing) to keep his upper body as low as he could when fresh, so he was less aerodynamic at the end of the ride than at the beginning. Second, he rotated his body more in the second half of the ride versus the first half, which is a well-known indicator that a rider is fatigued and needs to use their upper body more to help with the pedaling motion.  

In our second rider, we see an increase in the FAR, foot angular range, near the end of the ride as he fatigued. This rider’s feet moved more once he became fatigued. I believe the reason for this is that his calf muscles were so tired that he could no longer hold his foot in it’s normal position, and could no longer hold his foot stable. 

Our next example is yours truly. In our long ride, we have two mountains that we must climb up and over. On the first climb, I was relatively fresh and felt good the entire way up the climb, but, from Figure 3, you’ll notice that my FAR became larger and larger near the end of the climb. I attribute this to accumulated muscular fatigue over the week of riding. For the second climb, you’ll notice, also in figure 3, that the opposite happens, and my FAR becomes smaller over the climb. Even though I was more fatigued on this second climb, the climb itself also becomes less steep the closer you get to the top. I believe that I was climbing very steadily during this time, and that reduced my FAR. The two long green dashed lines in Figure 3 show that the overall FAR continued to increase throughout the entire ride, which demonstrates increasing fatigue and how it impacts motion.

Why is this so important to be able to see fatigue? If we can see where fatigue occurs, then that gives us more insight into the endurance and stamina of the athlete. This will allow the rider or coach to make important decisions about the upcoming type of training needed for the athlete. (More on how and what decisions to make will come later in another article.)