Changes in MPIs with Saddle Height Adjustments

Hello, this is Saita from LEOMO. Today, I’m going to talk about how different saddle heights affect MPIs (Motion Performance Indicators) from a bike-fitting perspective. This should provide insight on how to choose an optimal saddle height based on MPIs.

For this case study we worked with a Category 2 cyclist. We referred to his normal saddle height as 00 mm and adjusted his saddle in 5 mm increments up and down for a total change of ±25 mm. The analysis was carried out using an indoor bike trainer, with the cyclist holding the hoods. The athlete was instructed to ride at 80% of his FTP with a cadence of 85 rpm for each trial.

Figure 1 displays how changes in saddle height affected each MPI.

Figure 1: Changes in MPIs with Saddle Height Adjustments

The data collected shows that saddle height had an effect on some MPIs more than others.

For example, there were no marked changes in FAR or FAR Q1, which indicate the range of foot angles during pedaling (Figure 2). However, this is not to say that there was no effect of saddle height on the movement of the foot.

Figure 2: FAR / FAR Q1 vs. Saddle Height

Looking at DSS (Dead Spot Score), which is obtained using the foot sensors (Figure 3) you can see that as saddle height increased above 00 mm so did DSS.

Figure 3: DSS vs. Saddle Height

We also noted changes in LAR (Leg Angular Range). As saddle height increased, the difference between left and right LAR became more substantial. This was mainly due to an increase in left LAR.

Figure 4: LAR vs. Saddle Height

Pelvic Angle trended lower as saddle height increased. This makes sense because as you increase saddle height- without changing handlebar height- it becomes necessary to tilt your pelvis forward to reach the handlebars.

Figure 5: Pelvic Angle vs. Saddle Height

Finally we will examine the movement of the pelvis (Figure 6). Pelvic Rotation increased as the saddle height rose above -5 mm. Conversely, there were hardly any changes in Pelvic Rock.

Figure 6: Pelvic Rotation/Pelvic Rock vs. Saddle Height

Based on his own sensations, the athlete favored a saddle height of -5 mm. Among the MPIs that were affected by saddle height, let’s pay particular attention to DSS and Pelvic Rotation.

DSS increased as saddle height increased above -5 mm, ultimately leading to a loss of pedaling smoothness. Based on DSS, the maximum saddle height at which pedaling remained smooth was -5 mm.

Pelvic Rotation increased above a threshold saddle height of -5 mm. This appears to be because hip movement was necessary to compensate for the excessive saddle height. It could be said that a saddle height of around -5 mm allowed the athlete to pedal without making any forced hip movements.

Both the MPI data and the athlete’s own sensations indicate that -5 mm may be the optimal saddle height. Lowering the saddle height a few millimeters at a time from the current height would help to determine the best height. For those who are uncertain about their saddle height, why not try looking at DSS and other MPIs with the TYPE-R?

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