1. health and fitness
2. exercise

WHITE PAPER: EPOC
Validation of the LifeQ solution for estimating EPOC
April 2015
WHITE PAPER: EPOC
Introduction
Excess post-exercise oxygen consumption
(EPOC) is the additional oxygen consumption
required by the body after activity to return
the body to its resting state and is measured
in ml oxygen consumed per kg of body
weight.
The excess oxygen consumed during this
recovery period is used in several processes
aimed at returning the body to resting state
homeostasis. For example, physiological
variables such as hemoglobin re-oxygenation,
phosphagen store replenishment, lactate
removal, restoration of muscle glycogen
stores, hormone balancing, and cellular repair
are all EPOC dependent. EPOC therefore
serves to repay the oxygen debt incurred
during exercise.
assessing and modulating an individual’s
training routine as well as the response to
varying exercise regimes.
Furthermore,
variations from normative EPOC values may
indicate illness or overtraining and therefore
the negative physiological impact of training
under these conditions may be prevented.
Traditionally, EPOC is measured by analyzing
respiratory gas exchange in a laboratory setup.
To do this, the area between resting VO2 and
the VO2 recovery period is quantified (Fig. 1A).
This measurement is used at the “gold
standard” benchmark for this white paper for
the comparison of estimated values.
EPOC is useful in assessing the following, for
all types of exercise:
•
•
•
•
•
The body’s rest requirements.
Recovery
status
from
previous
workout sessions.
The physical effect of an entire
training routine.
Exercise
and
recovery
energy
expenditure.
Balancing the level of effort to
increase fitness without overtaxing the
system.
Given the above-mentioned applications,
EPOC can be used as a tool to assess the
achievement of workout goals. For example,
an individual performing the same type of
exercise at the same intensity for the same
amount of time each day should observe a
decrease in their EPOC, as well as a faster
recovery time, as their cardiorespiratory
fitness increases.
Additionally, because individuals respond
differently to exercise, EPOC is useful for
Figure 1: Measured EPOC (area under VO2 recovery
period) in ml/kg from a typical increasing intensity
exercise period and subsequent rest period. The red dot
depicts peak EPOC values.
A disadvantage of this is that EPOC can only
be assessed upon completing the exercise
routine and therefore does not allow for
continuous monitoring of the training effect.
For example, in Figure 1A, with the traditional
WHITE PAPER: EPOC
Methods
The LifeQ EPOC solution was evaluated by
comparing LifeQ predicted EPOC values (using
heart rate measurements) to that of EPOC
values, as determined by respiratory gas
exchange analysis. For this evaluation, due to
experimental constraints, the LifeQ EPOC
solution was only evaluated from the point of
exhaustion (Fig.1A, point C).
The validity of LifeQ’s EPOC solution was
evaluated with 24 healthy individuals who
each completed a VO2max test. For this test,
each participant began walking on a treadmill
at a speed of 1km/h, which was incrementally
increased by 1km/h each minute until 8km/h
after which the speed increased every three
minutes, until the participant reached
exhaustion. After the test, the participants
were asked to sit quietly for a resting period
of 25 minutes. In addition, before the VO2max
test was performed, resting heart rate and
respiratory gases were also measured.
The LifeQ EPOC solution has an average
expected error of 21.9% and a SD of 14.4%, at
the point of exhaustion, when compared with
traditional
gold
standard
EPOC
measurements (Fig. 2 Top graph).
Furthermore, for comparison, EPOC was
estimated by a commercially available EPOC
estimation application solution that is utilized
by the Suunto Movescount application
(http://www.movescount.com/apps/app10017
721-EPOC_estimation) and validated against
the same gold standard This had an average
expected error of 31.2% and a SD of 23.4%
(Fig. 2 Bottom graph).
250 EPOC as predicted by the LifeQ solu8on (ml/kg). As an alternative to the traditional method of
determining EPOC, the LifeQ solution is able
to predict EPOC from heart rate derived
information as the LifeQ solution can estimate
VO2max
values
from
heart
rate
measurements with 93.3% accuracy (LifeQ
White Paper, Validation of the LifeQ solution
for measuring VO2max, February 2015). Using
heart rate information the LifeQ solution is
able to provide EPOC predictions for points A,
B, and C without disrupting the exercise
routine and thus the EPOC estimation can be
monitored in real time (Fig. 1B).
Key findings
r2 = 0.5678 200 150 100 50 0 0 250 EPOC a per Movescount solu8on (ml/kg). method of measuring EPOC it would not be
possible to measure EPOC at points A and B
without disrupting the entire exercise routine.
Therefore it is only possible to determine
EPOC at point C.
EPOC as measured by respiratory gas 50 exchange 100 (ml/kg). 150 200 250 r2 = 0.4252 200 150 100 50 0 0 EPOC as measured by respiratory gas 50 exchange 100 (ml/kg). 150 200 250 Figure 2: Correlation between EPOC values as determined
by the LifeQ (Top) and Movescount (Bottom) EPOC
solutions and by means of respiratory gas exchange.
WHITE PAPER: EPOC
At this point we cannot yet test the error
levels continuously as there is no laboratory
test available and as such the the accuracy of
the LifeQ solution is assumed for EPOC
estimations at any point during the exercise
routine to be similar to the exhaustion point
measure validating here.
In addition, the LifeQ EPOC solution also
allows for the monitoring of EPOC during
exercise recovery, (Fig. 3) allowing an
individual to ensure full recovery before their
next exercise routine. Figure 3A illustrates the
decline in EPOC after maximum exhaustion as
determined by respiratory gas exchange and
figure 3B shows the corresponding EPOC
decline as estimated by the LifeQ EPOC
solution.
Figure 3: Comparison of the decline in EPOC following
the point of maximum exhaustion (red dot) as
determined by (A) respiratory gas exchange and (B) the
LIfeQ EPOC solution.
In conclusion, the LifeQ EPOC solution
provides the only viable solution for
quantifying an individual’s continuous EPOC in
real time.