I bought
a new mountain bike this summer. I already had two perfectly good bicycles
chained up in the garage, but there’s nothing like a new toy to get you
motivated. Hitting the trails these days involves monitoring my data. I’m
interested to test myself using Personalised Activity Intelligence (PAI),
a health score that measures cardiorespiratory fitness (CRF).
PAI draws
heart rate activity from wearables, such as Fitbit and Apple Watch. It uses
that information, along with personal self-reported data, to guide me towards
the most beneficial amount of exercise for my body. Using all that data, the
weekly effort I put in to physical activity is translated into a single PAI
score. Maintaining 100 PAI reduces my risk of cardiovascular disease and
early death. I might like to live longer now that I’ve spent EUR2500 on this
new bike…
PAI takes
account of my resting and maximum heart rate over a seven-day rolling period,
adjusted for exercise intensity to reflect my VO2 max, a measure of CRF.
Cycling should increase my heart rate above a threshold, and into the CRF
training zone, generating PAI points. Consistently maintaining 100 PAI
will derive the health benefits.
PAI
requires several weeks of activity data to properly attune to my VO2 max,
but my first five rides provide an indication of what’s to come (see Figure
below). PAI uses the first ride data to begin calibrating the algorithm to me -
the score is irrelevant. My second ride ends abruptly with a puncture and a
fall but by ride four I’m back in the zone and by ride five back in
the woods.

My average heart rate dropped over the first four rides, which
suggests my fitness reserve was decent and that I’ve quickly added some heart
health to the equation. Although my average speed was consistent, the effort
involved measured by heart rate and, ultimately, the points earned, trend
downwards.
It’s
clear that longer duration coupled with higher attained heart rate scores more
points. I must up my game since the algorithm calibrates to my personal heart
effort. With PAI, very low intensity exercise doesn’t contribute to increased
levels of CRF, while fitter people with higher heart rate reserve face a tougher
threshold to accumulate PAI points.
Now the
PAI algorithm is adjusting to my profile, and I’m discovering the effort
required to earn a protective score. I go back out on the bike for ride 5
and earn 75 points; the maximum possible in one day. This isn’t a
surprise. The route is longer, more challenging and I ride harder because I’m
already feeling fitter (see Figure below).

The algorithm will continue to adjust to my exercise behaviour
over the next few months. As my CRF increases, I will discover that running on
a treadmill for 30 minutes is less fun and nets me fewer points. I will
find that my daily brisk walking and average of 6000 steps contribute but
do not raise my heart effort enough to strongly influence my CRF. Running and
walking will supplement my PAI score, but to score 100 - enough to impact
my long-term health and get good value out of this bike - well, that simply
requires greater effort. For further background read my blog Heart Health - Why Linking It to Insurance Is a Winning Formula.
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