Allen Lim: power and heart rate

tunney

Heart Rate's Role in Training with Power
With the advent of power meters, heart rate can and should still play an
important role in training. In fact, power and heart rate are really
complimentary to one another. Here's why:
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The most basic training paradigm is a simple dose-response one. There's some
dose, stress, or cause which creates some sort of response, strain, or
effect. Like, popping corn, you need to apply some amount of "heat" or
"power" to unleash the genetic potential of each of your kernel into a nice
fluffy piece of popped corn. In a perfect world, you'd pop as many kernels
as possible without burning any to optimize performance. In the real world,
it's usually just the individuals who are born with the most kernels and who
can stand the most heat that become the elite performers.
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At its simplest, training dose can be measured as the duration, frequency,
type, and intensity of training. Of these, intensity, or how hard a workout
is, can often be the most obscure or difficult to measure. The reason is
that we can measure intensity as either the actual power or speed of an
activity or as our response to that activity (e.g., heart rate, perception
of effort, lactate, core temp etc...). For many sports like running on a
track or swimming where the resistance is constant, speed is a great measure
of intensity, and pace is the primary way that coaches and athletes track
and measure training and race performance or load. In cycling, where
resistance is not constant due to variations in things like drafting, wind,
and terrain, speed is not always a good measure of the actual intensity.
Since there is a strong and almost perfect relationship between heart rate
and power in laboratory settings, heart rate became an extremely popular way
of measure intensity in cycling before power meters became widely available.
But when cyclists started using power meters in the field, they found that
there wasn't always a good relationship between their power output and heart
rate. More importantly, when using heart rate alone, athletes were operating
under an inherent response-response paradox rather than a standard
dose-response paradigm. Because of this, many have abandoned heart rate as
an inaccurate measure of training intensity and use power only.
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The real issue though is not if power and heart rate correlate perfectly
with one another, it's that power and heart rate are measuring two
fundamentally different things. Power is a measure of your actual dose.
Heart rate is a measure of your response. Not only are they distinct, they
are both a critical aspect of a basic training paradigm. That is, power
measures the heat while heart rate tells you how fast the kernels are
burning. Add time, and you get the total energy that goes into a system
(power x time) as well as the total number of kernels popped (heart rate x
time). So the inherent value of measuring both power and heart rate is that
you can track the fundamental relationship between your training dose or
load and your response or adaptation. You can see, chronically or acutely,
if you are getting better or worse. In many ways, the process of training
and adaptation isn't too different from a growing tree blowing in the wind.
Initially, the young tree bends quite a bit to a gust of wind, but as it
grows and gets stronger, the same wind barely causes any flex in that tree's
trunk. In this scenario, power is that gust of wind and heart rate is how
much that tree bends. In theory, as we get stronger over time, we should be
able to produce more power at a given heart rate. Likewise, within a ride,
as we fatigue, dehydrate, or over heat, our heart rate drifts high at any
given power output. Understanding the relationship between the two and being
aware of the factors that can affect both are important to optimizing one's
training.
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In the end, power and heart rate are just two distinct tools for measuring
dose and response. Because power is the most inherently accurate way to
measure intensity, it will always be king as a measure of training and
racing dose. And since heart rate is such an easy response variable to
measure, it will always have a place as a measure of the effect of a given
training or racing dose. That said, there are other ways to measure
intensity, and there are many other response variables than heart rate.
Speed, terrain, environmental features, and tactics all dictate power.
Likewise, our perception of effort, body temperature, blood lactate,
substrate utilization, cardiac output, and ultimately our performance
relative to our peers are important responses. In a perfect world you'd
measure everything. In the real world, you just throw a bag in the
microwave, hit play on the DVD, and hope you don't burn any corn.