Data That Matters, Part Three

posted Feb 28, 2010, 5:51 PM by Donald Vescio   [ updated Sep 12, 2011, 8:11 AM ]

Data Patterns
Most athletes who have downloadable powermeters and heartrate monitors never take full advantages of the data that they collect during their workouts.  While powermeters and heartrate monitors can provide useful instantaneous data (for instance, whether your power output or heartrate is approaching anaerobic threshold, which is can be used for pacing), the real value of the data collected is its utility in quantifying what happened during a training session and how environmental factors may have impacted performance.

Within the context of cycling, a powermeter measures the amount of work being done on the bike, while a heartrate monitor measures the impact that the work has on our physiology.  Both forms of data are important in maximizing our performance; but because bicycle powermeters are still relatively expensive, the following examples will be keyed to heartrate.

Cardiac Drift
One of the most important environmental factors that impacts athletic performance is heat.  As an athlete's body temperature increases, the overall load on his/her physiology also increases; this is frequently manifested as a gradual rise of heartrate over time.

The graph above tracks heartrate during a two hour steady-paced spinning class.  The session took place in a room that was poorly ventilated and poorly cooled; as the class progressed, the heat generated by 24 participants raised the room's ambient temperature by almost ten degrees.  While every attempt was made to keep the perceived effort the same throughout the entire session, the rise in room temperature resulted in a gradually increasing heartrate.  Take away: adequate cooling is critical for optimal athletic performance.

Stochastic Variables and Outdoor Training
Before you put your trainers away in anticipate of warm, dry spring days, consider that riding outside involves a number of variables outside of your control that may impact your ability to complete a training session as planned. Hills, wind, traffic, temperature, and humidity all can have a deleterious impact on athletic performance; what is important is understanding how such environmental variables can make structured sessions difficult to complete.

In the example above, note the significant variations in heartrate for the two hour session.  The intent for this session was to ride at a steady aerobic pace for two hours. Due to the ride's terrain and a gusty wind, it was impossible to ride without spikes in heartrate.  As a result, what should have been a simple zone three ride actually became a ride with a series of unstructured intervals: a significant portion of this ride was completed in zone four and five.  Because this ride was much more intense than planned, the following day's session was not effective due to the fatigue generated by the prior session.

The term "stochastic" means "random."  The randomness of the hills and wind associated with the session above outweighed the session's planned intent.  Perhaps the easiest way to limit environmental variables is to ride an indoor trainer or ergometer, which completely eliminates the influence of wind and hills.

The plan for the session above was to complete three intervals at AT threshold.  Note the clearly defined curves in the heartrate graph that marks warm-up, interval, recovery, and warm-down efforts.  By performing this session on an ergometer, effort and intensity could be carefully controlled to yield maximum benefit for the athlete.

What to Take Away?
Download your heartrate and/or powermeter data after every session to better assess whether your actual performance for the session matched your planned intent.  Use this data to review the impact that environmental variables might have had on your performance and refine future training sessions based on the information that you have gained.  For maximum efficiency, consider doing your most structure training sessions indoors on a trainer or ergometer to minimize variables that can have a negative impact.