Does Power Output or Cadence Affect Muscle Recruitment Patterns?

Photo by Simon Connellan

Two interesting studies attempted to understand the relationship between power output or cadence and the origin of that power in the body. The first study, “Joint-Specific Power-Pedaling Rate Relationship During Maximal Cycling” by McDaniel and colleagues looks at three second maximal efforts at cadences of 60, 90, 120, 150, 180. Using a few kinematic and kinetic techniques, the authors determined the contributions of each joint to the total power of the pedal stroke.

To summarize the results, total power was highest and about the same for cadences of 120 and 150 with 180 and 90 being slightly less and 60 cadence producing significantly less power. The 180 cadence test generally produced a negative pedal force on the backside of the pedal stroke, likely due to the rider’s inability to unweight the pedal at such a high cadence. For joint-specific power, the two big differences were an increase in hip extension power (41% to 59%) and knee flexion power (34% to 49%) at higher cadences. The percentage values represent the percent contribution of the motor pattern compared to the total force production in that part of the pedal stroke. So, the hip extension movement produced 59% of the downstroke power at higher cadences.

The second study, “Joint-Specific Power Production during Submaximal and Maximal Cycling” by Elmer and colleagues looks at the power each joint produces at a variety of powers, but with constant cadence. There was one maximal trial at 120 cadence, but it will not be discussed here. The trials of interest were the 250w, 400w, 550w, 700w, 850w and maximum watts, all at 90 rpm. In this study, as in the one before, three seconds of data was collected.

Summarizing the results of the paper: total pedal power, of course, increased, but essentially of that increase came from the downstroke. Between the 250w and 850w tests, power at 90 degrees (3 o’clock) increased from ~450w to ~1200w while maximal upstroke power increased from about -100w to about 100w. A negative wattage indicates the pedal was not lifted on the backside of the pedal stroke.

Other interesting findings include increases in knee flexion power as total power increased, specifically between 250w and 850w an increase in maximal upstroke knee joint power increased from ~80w to ~250w. Lastly and possibly most importantly, hip power production saw dramatic increases in power production with ~120w and ~650w for the 250w and 850w tests, respectively.

Conclusions – What does it mean?

These two studies are fascinating because they reveal the differences in demands of moderate intensity exercise and full-gas efforts. This information can potentially help riders or coaches understand why they feel great on endurance rides, but fail to ramp up the power when necessary.

To start, it appears cadences of 120 to 150 are optimal for seated maximal efforts and this is likely due to increases in hip extension power production. Observing sprint track cyclists, they generally race at this cadence range although the prevailing idea is to maximize knee extension power through a high seat height and a focus on smashing down the pedals. It may be worthwhile for track cyclists to focus more on their glute max recruitment and power production to eek out a bit more power.

Regarding the rest of the cycling population, it appears that at high intensities there is a greater emphasis on the downstroke. When producing a lot of power, the focus should be on maximizing the power production in the first half of the pedal stroke, peaking at around 90 degrees (3 o’clock). With that being said, there is some evidence that hamstring utilization (knee flexion) is increased at higher powers. It could be prudent to work on hamstring activation and strength in the weight room to support this knee flexion activity. With that being said, knee flexion produces approximately 1/3 of the power production of hip extension (glute max) at higher powers. Thus, if there is one area to focus on in the weight room, it is getting your glute max to be powerful.

And the first study regarding maximal seat sprints also supports this idea of focusing on your glutes. Dramatic increases in hip extension power were shown as cadence and power production increased for the maximal three second efforts. While there are at least a few interesting conclusions from these papers, it appears the biggest area to work on if the goal is to push higher watts is to PUMP UP THOSE GLUTES.

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