This post is the second in a 2-part series that was written by Neal Henderson of Apex Coaching. In part 1 of this case study, Neal used the LEOMO Type-R in a 3-stage race in Colorado that started with a climbing time-trial (which we like to call a climb-trial), a flat time-trial and finished with a road race.
In reviewing the movement data, Neal saw a few of interesting findings:
- Neal’s DSS was significantly different left to right in the TT compared to two other races.
- Neal also saw major differences in Pelvic Tilt angle comparing road to TT bikes.
Neal then setup a test:
Since the climb trial had about 8 km of riding in the clip-on TT aerobars, I compared the Pelvic Tilt of that portion of the race, compared to the final 4 km of climbing. On the 8 km flatter out and back section, the Pelvic Tilt average was 42.1 degrees at an average of 259 watts (12 watts higher than the TT average power, but at 1000 meters greater elevation). The final 4 km of climbing was at 56.8 degrees at 283 watts average.
Based on the 6-degree difference in Pelvic Tilt average angle in the climb trial aerobar position and the TT position, I decided to evaluate the effects of decreasing the crank length on the TT bike — going from 172.5mm down to 170mm. My goal was to improve DSS on the left leg, and to increase the height of the aerobar pads on my TT bike by adding a 1 cm spacer.
To compare the effects, I first looked at power production and heart rate without the LEOMO Type-R motion sensors to see if there were any changes in power production.
- I first rode my old TT position with 172.5mm cranks and low aerobar pads on the Old Stage climb in Boulder, Colorado.
- The climb is 2.6km long with 6% grade, which I rode at 258w with average heart rate of 150 bpm for 10 minutes and 21 seconds.
- My PR on this climb is 8 minutes and 40 seconds at 281w.
I then switched to the new TT setup with 170mm cranks and +1cm aerobar pads and rode another similar climb — NCAR in South Boulder. This climb is 2.7km long and also has a 6% grade.
- In this position, I rode my 2nd fastest time up NCAR in 9 minutes and 11 seconds at an average wattage of 322, and average heart rate of 158 bpm.
- During the NCAR interval, the outside temperature was 28 degrees celsius, vs 18 degrees celsius on the previous Old Stage interval. This may explain some of the difference in heart rate and power.
Based on this data, it’s clear that the new TT position (shorter cranks, +1cm aerobar height) allowed me to do a lot more work. The files for these two efforts can be seen on Strava: Old Stage and NCAR.
Finally, I used the LEOMO Type-R for two flat TT intervals in the new TT position to compare the effects of the changes on my motion and power output. This file can be viewed here.
First, the power output during the two intervals in the new TT position indicate that the ability to produce power is increased considerably: 288 vs. 296 watts average, respectively for 6:27 and 5:03 segment times. This is compared to 248 watts from the TT).
- The average heart rate for the two efforts was 148 and 155 bpm, with 94 and 96 rpm average cadence.
- The motion analysis provided by the Type-R show that average pelvic tilt was 41.4 and 40.5 degrees, and DSS on left/right was 0.2/0.2 and 0.5/0.2 which is considerably less and more balanced than the TT race showing DSS of 2.1/0.4.
The graphic below shows the two interval averages from the new TT position with 170mm cranks and + 1cm aerobar pad height.
Based on the motion analysis data collected from the LEOMO Type-R during the stage race, there was a marked difference in both output and motion on the TT bike. Making changes to the TT bike crank length and aerobar pads resulted in measurable improvements in power production and improved motion with respect to reduced DSS with increased pelvic tilt.