V̇O2 and muscle deoxygenation kinetics during skating: comparison between slide board
and treadmill skating
Post-print as accepted for publication.
Abstract
Purpose: this study aimed to compare the oxygen uptake (V̇O2) kinetics during skating on a
treadmill and skating on a slide board and discuss potential mechanisms that might control
the V̇O2 kinetics responses during skating. Methods: breath-by-breath pulmonary V̇O2 and
near-infrared spectroscopy-derived muscle deoxygenation ([HHbMb]) were monitored
continuously in 12 well-trained young long track speed skaters. On-transient V̇O2 and
[HHbMb] responses to skating on a treadmill and skating on a slide board at 80% of the
estimated gas exchange threshold were fitted as mono-exponential function. The signals were
time aligned, and the individual [HHbMb]-to-V̇O2 ratio was calculated as the average value
from 20–120 s after exercise starts. Results: the time constants for the adjustment of phase
II V̇O2 (τ V̇O2) and [HHbMb] (τ[HHbMb]) were low and similar between slide board vs.
treadmill skating (18.1 ± 3.4 vs. 18.9 ± 3.6 for τ V̇O2 and 12.6 ± 4.0 vs. 12.4 ± 4.0 s for
τ[HHbMb]). The [HHbMb]/V̇O2 ratio was not different from 1.0 (p > 0.05) in both
conditions. Conclusion: the fast V̇O2 kinetics during skating suggest that chronical
adaptation to skating might overcome any possible restriction in leg blood flow during low
intensity exercise. The [HHbMb]/V̇O2 ratio values also suggest a good matching of O2
delivery to O2 utilization in trained speed skaters. The similar τ V̇O2 and τ [HHbMb] values
between slide board and treadmill further reinforce the validity of using a slide board for
skating testing and training purposes.
Keywords: muscle deoxygenation, skating, slide board, V̇O2 kinetics.

Introduction

The speed of adjustment of oxidative phosphorylation during the on-transient of
exercise, i.e. V̇O2 kinetics, provides valuable information in relation to the instantaneous rate
of aerobic and anaerobic energy transfer1,2. A faster V̇O2 kinetics response implies a smaller
oxygen deficit and a consequent reduction in metabolites accumulation and sparing of
anaerobic substrates, which could possibly lead to a reduction in fatigue and improved
exercise performance3.
In speed skating, although the relative contribution from different energy pathways
depends on the distance in competition, both aerobic and anaerobic energy sources are crucial
for performance4. In this context, a rapid adjustment of the oxidative metabolism presents an
advantage, as non-oxidative sources can be spared and then used during the end-spurt. It is
noteworthy that, when performing, skaters adopt low posture and long cycles of isometric
contractions, which are associated to restriction of muscle blood flow to the lower limbs and
high intramuscular forces5,6 that could impair oxygen delivery. Indeed, these specific
characteristics have been indicated to be responsible for a lower maximal oxygen uptake
(V̇O2max) and higher muscle oxygen desaturation during skating exercise when compared to
cycling7,5,4. However, whether or not these hemodynamic limitations that occur at higher
intensities of exercise play a role in determining the speed of adjustment of oxidative
phosphorylation in response to submaximal skating exercise is still unclear.
A reason why measurements of V̇O2 kinetics have not been performed during skating
could be the challenges associated with performing physiological measurements on the track.
To overcome this limitation, researchers have performed physiological evaluations of skating
on instrumented motorized treadmills5,6. However, even though these evaluations mimic
physiological responses to skating, the access to this type of equipment is limited and
expensive. As an alternative and inexpensive method that simulates speed skating conditions,
slide board skating platforms have gained attention for both training and testing protocols8,9.
Our group recently compared physiological responses during a maximal incremental skating
performed on a treadmill vs. a slide board and demonstrated that aerobic performance (i.e.,
V̇O2 responses associated to peak exercise as well as gas exchange threshold and the
respiratory compensation point) was similar between the two conditions10. However, it is not
known whether V̇O2 kinetics responses are also comparable between treadmill and slide
board skating, which is important to further validate the use of a slide board as a
physiologically valid option to skating on a motorized treadmill.
Thus, the goals of this study were to: 1) compare the V̇O2 kinetics responses during
treadmill vs. slide board skating; 2) discuss potential mechanisms that might control the V̇O2
kinetics responses. We hypothesized that: 1) given the similarities previously reported for
treadmill and slide board skating at submaximal and peak intensities of exercise10, the V̇O2
kinetics response would be similar in both conditions; 2) well-trained speed skaters would
have a fast (~20 s)11 V̇O2 kinetics and a good matching of O2 delivery to O2 utilization,
despite some potential restrictions in muscle blood flow associated to the posture during
skating.
Methods
Participants
Twelve competitive trained long track speed skaters (8 females and 4 males), age 18.0
± 0.9 years; body mass 65.0 ± 6.8 kg; height, 173.0 ± 8.8 cm - volunteered and gave written
consent to participate in the study. The speed skaters were participating in a systematic

training program with a volume of 2 hours/day, 5 days per week, for at least 3 years, and
their best time for the 1500 m distance was 2.13 ± 0.14 min during competition. All
procedures were approved by the Ethics Committee of Human Research where the study was
conducted (REB15-2537).
Experimental protocol
In separated days, each participant performed two incremental skating tests to fatigue, one
on an oversized treadmill (2.5 × 3.5 m, Athletic Republic, Salt Lake City, UT) and the other on a
slide board (2.0 x 0.6 m, Athletic Innovation, Inc, Rochester, NY) fixed to the ground with
double sided tape. One the treadmill, participants used their own inline skates while on the
slide board, participants wore a pair of nylon socks over their sport shoes. The maximal
incremental tests on a slide board and on a treadmill are described elsewhere10. The gas
exchange threshold (GET) was defined as the V̇O2 at which carbon dioxide production
(V̇CO2) began to increase out of proportion in relation to V̇O2 with a systematic rise in minute
ventilation-to-V̇O2 ratio and end-tidal PO2, whereas minute ventilation-to-V̇CO2 ratio and
end-tidal PCO2 were stable12. A moderate-intensity speed and cadence was selected from the
treadmill and slide board skating tests respectively, to elicit a V̇O2 equivalent to ~80% of the
V̇O2 at GET. All participants were familiarized with the treadmill skating protocols at least
twice, for a minimum of 30 min total, 2 to 5 days before the data collection. Participants were
familiar with the slide board skating movement as they used it regularly for training. In the
subsequent days, participants performed three-step transitions of 6 min of moderateintensities preceded by a 6-min baseline (BL) of 8 km∙h-1 and 15 push-offs per minutes (ppm)
on the treadmill and on the slide board, respectively. The skating cadence on a slide board
was controlled by optical sensors, connected to a software specially developed for that
purpose9. The three transitions were performed consecutively in a single session based on the
recommendations of Spencer et al.13.
Measurements
Throughout each exercise trial ventilation (V̇E), V̇O2 and V̇CO2 were measured
breath-by-breath using a portable gas analyzer (K4b2 Cosmed®, Rome, Italy), calibrated
according to manufacturer’s instructions prior to each test. V̇O2peak was considered to be the
highest value averaged over a 15-s period during the last stage of the test. Heart rate (HR)
data were collected using radiotelemetry (SP0180 Polar Transmitter; Polar Electro Inc.,
Kempele, Finland). GET was identified by two blinded experts. If a discrepancy of more than
200 mL∙min-1 was detected, a third expert was involved and the average of the two closest
values was used.
Local muscle deoxygenation profiles of the quadriceps vastus lateralis (VL) muscle
of the right leg were measured using a wireless near-infrared spectroscopy (NIRS) system
(Moxy Muscle Oxygen Sensor, Hutchinson, Minnesota USA) that functions by sequentially
sending light waves (630–850 nm) from four light emitting diodes into the tissue beneath it
and recording the amount of returned scattered light at two detectors positioned 12.5 and 25
mm from the light source. This allows the system to estimate oxygenation status of the
muscle with a penetration depth of about 12 mm. Data support the validity of the Moxy to
measure local oxygen saturation, with statistical analyses showing a strong or excellent
correlation between trials for all participants (SROC: r = 0.842–0.993, ICC: r = 0.773–0.992,
p < .01)14. The system was inserted into a dark rubber shield and then placed on the belly of
the medial belly of VL muscle, midway from the greater trochanter, using double side tape

and wrapped with an elastic bandage. Changes in light intensities were recorded continuously
at 2 Hz. Given the uncertainty of the optical path length in the VL at rest and during exercise,
NIRS data are presented as delta concentration changes expressed in arbitrary units (AU).
Data analysis
Individual breath-by-breath V̇O2 data were edited by removing the outlier data that laid 3 SD
from the local mean. The data for each moderate transition were linearly interpolated secondby-second and time aligned such that time “zero” represented the onset of the transition. Data
from each transition were ensemble-averaged into 5-s bins to provide a single profile for each
participant. The on-transient response for V̇O2 was fitted using a mono-exponential function
(Eq 1):
V̇O2 (t) = V̇O2BL + AP (1 – e – (t – TD) / τ)
where V̇O2 (t) represents V̇O2 at any time (t), V̇O2BL is the baseline value, AP is the steadystate increase in V̇O2 above the baseline value, τ is the time constant defined as the duration
of time for V̇O2 to increase to 63% of the steady-state increase, and TD is the time delay of
the model. The initial 20 s of data where excluded to avoid inclusion of data points from
phase I of the V̇O2 response in the fitting of phase II V̇O2 - since including data from the
phase I in the mono-exponential model results in overestimation of the actual time constant
(i.e., τ) of the increase in V̇O2 - while still allowing TD to vary freely to optimize accuracy of
parameter estimates11. V̇O2 data were modeled from 20 s to 4 min (240 s) of the step
transition, but always ensuring that each participant had attained a V̇O2 steady-state within
this time frame11. The model parameters were estimated by least-squares nonlinear regression
(Origin, OriginLab, Northampton, MA). The 95% confidence interval (CI) for the estimated
τ was determined after preliminary fitting of the data and with baseline, AP and TD fixed to
the best-fit values and τ allowed to vary.
The calculated TD (CTD) for the NIRS-derived deoxyhemoglobin [HHbMb]
response (reflecting a physiological TD before the [HHbMb] begins to increase) was visually
determined using second-by-second data and corresponded to the time, after the onset of
exercise, at which the [HHbMb] signal began a systematic increase from its nadir value11.
Following the time alignment and ensemble averaging, the [HHbMb] data were averaged
into 5 s bins as described above for V̇O2. The [HHbMb] data were modeled from the end of
the CTD-[HHbMb] to 90 s of the transition using an exponential model as described in Eq.1.
Different fitting strategies (i.e., 90–180 s) resulted in minimal differences in [HHbMb]
kinetics parameters previously explained15. Whereas the τ [HHbMb] described the time
course for the increase in [HHbMb], the overall change of muscle deoxygenation was
described by the effective [HHbMb] response (τ’ [HHbMb] = TD-[HHbMb] + τ’ [HHbMb])
from the onset of exercise to provide a description of the overall time course for muscle
deoxygenation.
The second-by-second [HHbMb] and V̇O2 data modelled from the parameter
estimates derived from the kinetics analysis were normalized for each participant from 0%,
corresponding to the baseline, to 100% reflecting the steady-state response. The V̇O2 data
were time-aligned with the onset of exercise left-shifted by 20 s to account for the phase I
duration11. Data were further averaged into 5-s bins for statistical comparison of the rate of
adjustment for [HHbMb] and V̇O2. Additionally, an overall [HHbMb]/V̇O2 ratio for the
adjustment during the exercise on-transient was derived for each individual as the average
value from 20–120 s into the transition. To analyze the [HHbMb] response in relation to the
V̇O2 the data were modelled based on the calculated BL, AP, TD and τ parameter estimates16.

Statistical analysis
Data are presented as mean ± SD. Normality of the data was assessed using the
Shapiro-Wilk test. Two-tailed pairwise t-tests were used to determine statistical significance
between the variables studied during skating on the treadmill and on the slide board. Pearson
product-moment correlation coefficients were used to determine the degree of association of
V̇O2 and [HHbMb] kinetics parameters between the two skating protocols. All statistical
analyses were performed using Graph Prism (v. 5.0 GraphPad Prism Software Inc, San
Diego, CA). Statistical significance was accepted at an alpha level less than 0.05.
Results

The V̇O2peak values for the skaters during the maximal incremental skating test on the
treadmill and on the slide board were 46.7 ± 6.1 mL·kg-1·min-1 and 46.4 ± 4.4 mL·kg-1·min1
, respectively. These data were published and discussed elsewhere10. The moderate intensity
exercise bouts, performed at 80% GET, required workloads of 15.2 ± 0.3 km∙h-1 on the
treadmill and 34.8 ± 0.3 ppm on the slide board.
The V̇O2 and [HHbMb] kinetics parameter estimates are described in Table 1. No
differences were observed between the two experimental conditions for V̇O2BL, V̇O2Ap,
V̇O2TD, τ V̇O2 and CI τ V̇O2. Similarly, no differences were observed in [HHbMb]BL,
[HHbMb]Ap, [HHbMb]TD, τ [HHbMb], [HHbMb]CTD, and τ’ [HHbMb] when parameters
were derived from treadmill or slide board skating protocols. The 95% CI for the estimated
[HHbMb] was smaller when skating on treadmill compared to slide board (p = 0.03). Figure
1 displays the V̇O2 and [HHbMb] kinetics during skating of a representative participant
during moderate transitions on the treadmill and on the slide board.
The [HHbMb]/V̇O2 ratio was not different from 1.0 during treadmill skating (1.007
± 0.007) and slide board (1.003 ± 0.005) skating, and it was similar in both conditions. The
normalized responses for the [HHbMb] and V̇O2 signal as well as the normalized
[HHbMb]/V̇O2 ratio are presented in Figure 2.
Discussion
The main goal of this study was to examine the V̇O2 kinetics responses observed
during treadmill compared to slide board skating. The main findings were that: (i) welltrained speed skaters demonstrated τ V̇O2 values that were similar during treadmill and slide
board skating; (ii) the pattern of O2 extraction (reflected by the dynamic adjustment of the
[HHbMb]) and the matching of O2 provision to O2 utilization (represented by the
[HHbMb]/V̇O2 ratio) during skating on treadmill and slide board were similar; (iii) The τ
V̇O2 values were ~20 s, which is comparable to results from other sports modalities when
trained athletes are tested 17,18.
In agreement with our hypothesis, the average time-constant of the V̇O2 kinetics
found for the well-trained speed skating group (18.9 ± 3.6 on the treadmill and 18.1 ± 3.4 on
the slide board) were similar to values obtained for endurance trained athletes in cycling and
running17,18. These results suggest that, despite the previously reported leg blood flow
restriction and increased O2 muscle desaturation that occur during skating, even during
moderate intensity, due to low skating position5,6 , the rate of adjustment of V̇O2 was not
impaired. This might be surprising as adequate delivery of O2 to the active muscles has been
considered by some authors as a limiting factor for the kinetics of V̇O219. Different
explanations can be proposed for this fast adjustment of V̇O2. First, the large amount of

training at a low skating position likely induces chronic peripheral and central adaptations
that might help overcoming a possible interference in the dynamics of adjustment of leg
blood flow, and thus a greater τ V̇O2. For example, increased stroke volume20, increased
microvascular filtration capacity a greater number of capillaries per fiber21 and intracellular
adaptations associated to a higher sensitivity to changes in partial pressure of oxygen and
oxygen metabolism activation22 have been found as consequences of different blood flow
restriction or ischemic training regimes. Additionally, blood flow restriction training has
been associated to increased muscle glycogen content23, higher percentage of type-I fibers
and a lower percentage of IIb fibers and higher citrate synthase activity24. These specific
adaptations to skating training regimens in conditions of partial blood flow occlusion would
be expected to result in improved oxygen transport and utilization that are likely to speed the
V̇O2 kinetics response at moderate intensities of exercise. A direct association between V̇O2
kinetics and muscle fiber properties has previously been reported25, where in-vitro V̇O2
kinetics of single muscle fibers, obtained across fiber types, was strongly related to the
oxidative capacity of the muscle fiber.
Despite some indications that blood flow to the legs might be compromised during
skating at moderate intensity 5,6, chronic exposure to skating results in adaptation in oxygen
delivery and utilization as described above. The relationship between O2 extraction and O2
utilization during the exercise on-transient (represented by the ([HHbMb]/V̇O2 ratio), allows
to make inferences on the dynamic behavior of microvascular delivery of O2 during the ontransient of exercise2. The [HHbMb]/V̇O2 ratio values during the exercise on-transient were
1.0 for both skating-treadmill and skating on a slide board (Figure 2). The indication of a
well-matched O2 delivery to a given O2 utilization during the transition from lower to higher
metabolic demands supports the idea that, for moderate intensities of skating exercise on a
slide board and on a treadmill, blood flow provision to the muscle was not a limiting factor
determining the speed of the V̇O2 response. In relation to this, a recent review proposed that
when τ V̇O2 is smaller than ~20 s, O2 delivery to the active tissues is likely sufficient (i.e.,
not a rate limiting factor) and that intracellular mechanisms of control are presumably
determining how fast the dynamic adjustment of V̇O2 is2.
From a practical perspective, a fast V̇O2 kinetics is associated to less muscle fatigue,
delayed anaerobic substrate depletion and enhanced tolerance to high-intensity exercise
independent of the overall fitness levels or V̇O2max3. However, although having a faster V̇O2
kinetics may be connected to performance in different type of events, no study has previously
investigated V̇O2 kinetics parameters on inline or ice speed skating. Only two studies26,27
reported a very fast rate constant for the increase in V̇O2 of 0.153 s-1 and 0.125 s-1 during
simulated skating competitions based on 1500 m time-trial. This value could be equated to a
τ V̇O2 value of 15.2 s from the start of the exercise26. However, proper analysis of V̇O2
kinetics parameters during skating is challenging due to difficulties to mimic the skating
movement in a laboratory environment where all variables can be controlled. On the track,
the main limitations are related to difficulties to control the skating intensities for the
moderate intensities transitions28,29, as well as the difficulties related to the relative long time
needed for the athlete to reach a pace corresponding to the moderate skating intensity
workload (i.e., a true square-wave rest to exercise transitions is not possible and thus the
increase in metabolic demand, and thus V̇O2 is delayed). A delay in the rest to exercise
transitions will increase the time constant of V̇O2 kinetics leading to underestimation of the
real kinetic speed values.

To overcome such testing limitations, previous studies have used different methods
to mimic skating movement to investigate physiological and biomechanical responses in
laboratory30,31,10,8. Although a previous study has shown similar V̇O2 responses during a
maximal incremental skating test on a treadmill and on a slide board, as well as very good
agreement for V̇O2 and heart rate both at maximal intensity of performance and at different
threshold intensities10, this study was the first to characterize the dynamic adjustment of V̇O2
to two different skating modes, and shows a similar rate of adjustment of pulmonary V̇O2
and muscle O2 extraction to a given increase in work rate between skating on a slide board
and skating on a treadmill (Figure 1).
A limitation of this study is that the VL adipose tissue thickness was not considered.
It is known that scattering coefficients and absorbance are affected by adipose tissue
thickness, reducing absorbance by underlying muscle tissue32. Although it is possible that
adipose tissue thickness may influence the absolute values for the [HHbMb] in this study,
the dynamic changes in the response and normalized [HHbMb]/V̇O2 ratio, which were the
main focus of the analysis, are independent of adipose tissue thickness. Also, asymmetries
have previously been observed in oxygenation between the right and left leg of elite shorttrack speed-skaters33. Therefore, these aforementioned asymmetries between legs should also
be considered in future studies with long-track speed skaters and NIRS. Nonetheless, V̇O2
and [HHbMb] responses observed in this study have to be considered within the boundaries
of the responses predicted to occur when exercising in the moderate intensity domain. It
should be acknowledged that limitations in leg blood flow might have a more significant
impact in O2 extraction when skating at higher intensities and at a lower skating position.
Practical Applications
The similar profiles in the V̇O2 and O2 extraction kinetics and the good matching of
O2 delivery to O2 utilization during both skating modalities tested in this study adds validity
to the use of the slide board as a testing and training device. Thus, these data combined with
those from a previous study10, indicate that the slide board can be used as a practical and
feasible alternative to evaluate a large group of athletes or for different research purposes that
require a laboratory environment control.
Conclusions
In conclusion, this study demonstrated that the fast V̇O2 kinetics responses of welltrained speed skaters (~18 s) that were observed on the motorized treadmill were similar to
those observed when skating on a slide board. This fast V̇O2 kinetics might be explained by
training adaptations from skating at low posture, which have been shown to induce positive
adaptations in oxygen delivery and utilization. This study further supports the use of a slide
board as a training and testing tool that elicits similar cardiovascular response to those
observed during skating on a motorized treadmill.

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Table 1. V̇O2 and [HHbMb] kinetics calculated parameters for moderated intensity skating
transitions on treadmill and slide board. Values are presented as means ± SD.
V̇O2BL(L·min-1)
V̇O2Ap (L·min-1)
V̇O2TD (s)
τ V̇O2 (s)
CIτV̇O2 (s)
[HHbMb]BL (AU)
[HHbMb]Ap (AU)
[HHbMb]TD (s)
τ [HHbMb] (s)
CIτ[HHbMb] (s)
τ’ [HHbMb] (s)

Treadmill

Slide board

1.14±0.18
0.94±0.26
12.8±4.2
18.9±3.6
5.1±1.9
3.0±1.3
1.2±0.4
9.4±3.6
12.4±4.0
3.8±1.0
21.7±5.3

1.27±0.23
1.03±0.19
12.2±3.4
18.1±3.4
4.6±0.8
3.1±1.4
1.7±0.9
7.9±3.0
12.6±4.0
5.0±1.5 a
20.5±4.5

V̇O2BL, baseline V̇O2; V̇O2Ap, V̇O2 amplitude; τ V̇O2, V̇O2 time constant; V̇O2TD, V̇O2 time
delay; CIτ V̇O2, V̇O2confidence interval; [HHbMb]B, HHb baseline; [HHbMb]Ap, HHb
amplitude; [HHbMb]TD, HHb time delay; τ[HHbMb], HHb time constant; CIτ[HHbMb],
HHb confidence interval. a, different from treadmill.

Figure 1. Group mean V̇O2 and [HHbMb] responses to moderate-intensity (80% GET)
exercise during treadmill (panels A and C) and slide board (panels B and D) skating. Signal
at the bottom of each graph represents residual of three transitions.

Figure 2. Group mean profiles for the adjustment of [HHbMb] (squares) and V̇O2 (triangles)
during the step transition to moderate intensity (5-s averaged data) normalized from the
baseline (0%) to steady state (100%) of the amplitude in the signal on a treadmill (panel A)
and on a slide board (panel C), and [HHbMb]/V̇O2 group mean profiles for skating transitions
on treadmill (panel B) and on slide board (panel D). Dashed horizontal line indicates
[HHbMb]/V̇O2 = 1.0.