The Effects of Cadence (Part 2) Cardiovascular or Muscular Emphasis

by Tom Scotto | May 12, 2011 | Master Instructor Blog

Once we understand and move past the limitations of cadence on the indoor bike, we can begin to realize how much of the focus of our class can be affected by leg speed.  I’m not just talking about cadence drills and biomechanics, but actually controlling how much stress we place on the cardiovascular system and how much stress we place on the muscular system (legs). Although little scientific study has been done on the effects of cadence, there is substantial practical evidence from years of cycling, training and competition to grasp the overall impact of cadence on the body.

Keeping in mind that there are always exceptions, it has been generally accepted that 80 RPM is the imaginary line between cardiovascular and muscular emphasis.  More specifically, a cadence of 80 RPM or higher will demand more from the cardiovascular system where a cadence less than 80 RPM will place greater focus on the musculature of the legs. Similar to how our energy systems and fuel systems work, there is not a specific “cut-over” from cardiovascular to muscular, but rather an emphasis or greater percentage of one over the other.

A more technical way to think about it is to consider the concept of force (or torque) and velocity.  The more velocity (faster cadence) for the same amount of output (such as power) the less torque or stress on the leg muscles.  Similarly, the same power with a slower leg speed will require more force (torque) and place a greater emphasis on muscle engagement.  If you have a power meter that measures torque (in newton metres – Nm), you can see the impact of cadence as you try to hold the same power output with different leg speeds.

So what does this mean for Indoor Cycling?

Well it means a lot.  An instructor can guide riders toward a certain focus by encouraging a leg speed that provokes the right physiological response.  For example pushing a rider to a perceived effort of 80-85% with a 90 RPM cadence will place a great amount of stress on their cardio system.  The rider will most-likely feel as if their ability to breath is being severely challenged.  Pushing a rider to the same 80-85% perceived effort using a 60 RPM cadence will place a tremendous load (and emphasis) on the leg muscles.  The rider will most-likely feel as if they can sustain their breathing but their legs will soon give out.  The same target intensity but a totally different response.

So think about the type of training effect you are trying to promote and what you want your riders to feel during different parts of your class and make sure the suggested cadence is appropriate.  This may also help guide those who are pedaling too fast during an effort focused on muscular endurance.  Explain both the target cadence and how their legs should feel to entice them to decrease their leg speed and increase the resistance.  Conversely, lure the pedal masher to a faster leg speed (with less resistance) to transfer the emphasis from the legs to the lungs.

Suggested Cadences:

• Warm-up: 80-90 RPM
• Aerobic Endurance: 80-100 RPM
• Muscular Endurance: 70-80 RPM
• Muscular Strength: 60-70 RPM
• Threshold Training: 90-100 RPM
• Climbing: 60-80 RPM
• Sprinting: (See Part 4)
• Cool-down: 80-90 RPM
  

Give Em a challenge: CLIMB LIKE A PRO CYCLIST

It is not uncommon for riders in an indoor cycling class to slow their cadence to 60 RPM with tons of resistance when simulating a climb.  Instead, encourage them to climb like a pro (or maybe Tour de France) rider by maintaining an 80 RPM cadence while climbing.  Many pro cyclists will climb at faster leg speeds because it produces more power (remember the force-velocity relationship).  However, the reason they can maintain this is due to their aerobic ability (or capacity).  When we climb at an 80 RPM cadence, in or out of the saddle, we feel our lungs beginning to burn and our natural response is to slow down the legs to ease the pain in our chests.  So, bring your riders to a 80 RPM cadence either through a cadence check or music that indicates the tempo.  Then have them continue to add resistance until they are barely able to maintain the leg speed.  That is the baseline for the climb.  You can give them the option to stand while climbing, but they must maintain their 80 RPM cadence even out of the saddle.  Keep the climbs short (2-5 minutes).  Ask riders if they were successful in being able to visualize the climb at the faster cadence AND if they felt the stress in their lungs even through they were climbing.  This is a great way to demonstrate the power of cadence and how we can manipulate the way our body responds to intensity.

The Effects of Cadence (Part 1) Extremes and Limitations

by Tom Scotto | May 5, 2011 | Master Instructor Blog

The cadence or speed at which we pedal has a large impact on the type of workout we will receive.  Maybe larger than we think.  Often times, the only thing that separates one workout from another is leg speed.  This 4 part series will explore different ways cadence affects the type of workout and our body’s response.

Part 1: Extremes and Limitations
Part 2: Cardiovascular or Muscular Emphasis
Part 3: Power Output or Strength Development
Part 4: Sprinting for Maximum Power

PART 1: Extremes and Limitations

There are two things to understand as we begin to explore the full range of leg speeds in cycling, (1) what is capable on a real bike, and (2) what is appropriate on an indoor bike.  Although the later may appear more to the point for the indoor cycling instructor, I’ve seen instructors lose respect from outdoor riders because of uninformed, end-all comments.  Some of these comments sound like, “there is no value in pedaling faster than 110 RPM” or, “it is unsafe to pedal slower than 60 RPM — EVER!” or, “leg speed doesn’t matter, just ride as hard as you can!”  Anyone who has hung around me long enough knows my thought on these comments is, “it depends”.

Why is the impact of cadence when riding indoors different than when riding outdoors?  It boils down to the lack of side-to-side and forward and backward movement (limitations) of the indoor bike. This limitation of movement has both mechanical and safety implications.

Natural Movement of the Bike

When we stand on a bike outdoors, it moves side-to-side (or should) as we apply pressure to the pedals. The bike may swing as little as 3-4 inches to greater than 10 inches.  What we often don’t realizes is that the bike is also surging forward and backwards as well.  The overall movement of both the side-to-side and surges results in a “Figure 8.”  Keep in mind that this movement is also present when riding seated.  We just don’t notice it as much because the bike moves less.  So simply, a bike ridden outdoors moves much more than you may think.  This “natural” movement provides leverage for power production and aligns joints to apply maximum force. The lack of natural movement of an indoor bike can limit mechanical efficiency and power.

This lack of bike movement also presents safety concerns for indoor cycling.  Because the indoor bike does not move naturally, the body often needs to compensate by moving instead.  Regardless of how much one moves their body to compensate for the lack of bike movement, an unnatural amount of stress will be placed on the muscles and joints. This is the reason why certain movements and extreme cadences should be avoided.  Quick or explosive movements from a seated to standing position should be avoided.  These include sprints that start in the saddle and then force a rider to quickly stand with heavy resistance, and jumps (Spinning®) which encourage riders to move rapidly from a seated to standing position.  These movements will place unhealthy stress on the lower (lumbar) spine, because the body must compensate (not the bike) for the force.

Similarly, leg speeds faster than 110 RPM are discouraged on an indoor bike.  The lack of any movement on an indoor bike will place unnecessary stress on joints at higher speeds. The addition of a fixed, weighted flywheel only adds to the risk.  Conversely, pedaling slower than 55 RPM (with heavy resistance) on an indoor bike can also put a rider at risk since the bike is not able to move under the workload placing unnatural stress on joints.  Understand that it is not uncommon for riders training outdoors to perform cadence drills above 120 RPM or muscular strength efforts under 50 RPM. Are these beneficial — well, it depends.  More importantly, regardless of whether you are riding indoors or outside, appropriate resistance (gearing) and proper form should be maintained at all times.

NOTE: The limitations described above can also apply to “real” bikes ridden using an indoor (stationary) trainer.