Critical skating intensity on a slide board: physiological and neuromuscular responses and
correlation with performance on ice
Tatiane Piucco1, Julia Phillips1, Jordan Finnie1, Andrew Rados1, Ricardo Dantas de Lucas2

1

Health and Physical Education Department, Mount Royal University, Calgary, AB T3E 6K6,

Canada. Mount Royal Gate SW, Calgary, AB, Canada T3E 6K6

2

Sports Center, Federal University of Santa Catarina, Florianópolis, SC 88040-900, Brazil.

UFSC Campus Trindade, Av. César Seara, Florianópolis, SC, Brazil 88040-900

Corresponding author: Tatiane Piucco
Department of Health and Physical Education. Office U241, Mount Royal University. 4825
Mount Royal Gate SW, Calgary, AB, Canada T3E 6K6
Cell phone: +1.403.702.2908 E. tatipiucco@gmail.com

Julia Phillips: jphil410@mtroyal.ca
Jordan Finnie: jfinn985@mtroyal.ca
Andrew Rados: arado370@mtroyal.ca
Ricardo Dantas de Lucas: ricardo.dantas@ufsc.br

Abstract
The aim of this study was to assess the physiological and neuromuscular responses at critical
skating intensity on a slide board and to investigate the correlations between critical cadence
(CC) and skating performances on ice. 13 well-trained speed skaters (19.8±4.2 years, 69.6±9.06
kg) performed a maximal skating incremental test (IT) on a slide board. CC was determined from
3 to 4 trials to exhaustion lasting from 3.1 ± 0.7 to 13.9 ± 3.1 min, using linear and hyperbolic
mathematical fittings. A time to exhaustion test at CC (TTE-CC) was performed. CC values
(55.3±5.0 ppm) were significantly higher than cadence at the respiratory compensation point
(RCP) (53.5±4.0 ppm). Mean duration of TTE-CC was 22.9±4.8 min. Peak values of oxygen
uptake (V̇O2peak), heart rate (HR), ventilation (VE), respiratory exchange ratio (RER) and ratings
of perceived exertion (RPE) during TTE-CC were significantly lower (p<0.05) than the peak
values reached during the IT. V̇O2, HR, VE, RER and RPE significantly increased from 25% to
100% of TTE-CC. Muscle activity (EMGi) significantly increased after 75% of TTE-CC for
vastus lateralis and gluteus maximus muscles. V̇O2 at CC was better associated to skating
performance on 500, 1000, 1500 and 5000 meters than V̇O2peak at IT and V̇O2 at RCP.
Physiological responses indicate that critical skating intensity on slide board occurred within the
heavy exercise domain where V̇O2 increases but does not reach its maximum. Critical cadence
could be used as a better indicator of performance and training prescription for long track speed
skating distances.

Keywords: power-time relationship, critical power, critical cadence, physiological responses,
slow component, EMGi, speed skating.

Introduction
During cyclic sport activities, the power-time relationship provides estimates of two
parameters: (1) the asymptote of the hyperbolic curve, called the critical power (CP); and (2) the
curvature constant, which represent the finite work that can be performed above the CP (W’)
(Hill 1993; Jones et al 2010). The concept of CP was originally proposed for use with small
muscle groups (Monod and Scherrer 1965), and later adapted for whole body exercises,
including cycling, running, and swimming (Hill 1993). It has been reported that exercise at CP
cannot typically be sustained beyond approximately 30 minutes (Brickley et al. 2002) instead of
‘for a very long time without fatigue' as initially proposed by Monod and Scherrer (1965) with
physiological steady state not attained.
CP is a good indicator of endurance performance and is a useful parameter for training
prescription, since it demarcates the heavy and severe exercise intensity domains (Poole et al.
1988; de Lucas et al. 2013). Consequently, this aerobic index provides information regarding the
boundary intensity between a high-intensity continuous and the onset intensity to perform an
interval exercise (Vanhatalo et al. 2011; de Lucas et al. 2012).
In long track speed skating competitions, the relative contribution from different energy
pathways depends on the distance of the race; however, both aerobic and anaerobic energy
sources are decisive for an optimal performance (Foster et al. 2003). The 1500-m distance, which
is considered to be the single most representative event in speed skating, takes around 2 to 2.5
minutes to be completed and has nearly equal contribution from aerobic and anaerobic energy
systems (Foster et al. 1993). Considering the physiological requirements of this main
representative distance, the critical skating intensity could be a decisive parameter to consider for
training prescription and performance assessment of speed skaters.

Despite the fact that critical intensity tests are relatively simple to perform, the CP or
critical speed (CS) during skating has not yet been reported in the literature. The lack of
investigations related to specific protocols to evaluate speed skating performance is partially
related to difficulties in reproducing the skating movement in a laboratory environment and
partially related to controlling test conditions on an ice track (Foster et al. 1993). To overcome
these limitations, the use of a slide board to mimic the skating movement with intensity
represented by changes in skating cadence has been investigated. Slide board skating has been
shown to be a reliable and a more specific method to evaluate speed skating performance, as
physiological and neuromuscular responses are similar to real world skating (Piucco et al. 2017a,
Piucco et al. 2017b; Piucco et al. 2018). Recently, Piucco and de Lucas (2019) have applied the
critical intensity model during skating simulated on a slide board, i.e critical cadence. However,
the physiological meaning of this intensity remains to be determined.
Therefore, the purposes of this study were twofold: 1) to examine the physiological and
neuromuscular responses at critical cadence (CC) while skating on a slide board ergometer until
exhaustion; 2) to investigate whether CC is a meaningful parameter for speed skating
performance in different distances when compared to the respiratory compensation point (RCP)
and maximal O2 uptake.

Materials and Methods

Participants

13 well-trained long track speed skating athletes (9 males and 4 females, 19.8 ± 4.2 years,
69.6 ± 9.06 kg), participated in this study. The study was conducted after the competition season.
Participants were familiar with slide board skating and participated in a systematic training
program with a volume of 2 hours/day, 5 days per week. All participants regularly participated in
long track speed skating competitions. Mean performance time for 500m = 39.5± 2.2s, 1000m =
78.6 ± 6.4s 1500m = 123.2 ± 8.4s, 5000m = 453.4 ± 37.1s). Time-trial performances were
performed by the coach at the same time and under the same conditions for all participants at the
time of the testing. The study was conducted in accordance with ethical standards of the
local Human Research Ethics Board (HREB 100940). All participants gave their written
informed consent to the experimental procedures after having the possible risks and benefits of
participation explained to them. All participants were free of cardiac, metabolic, or respiratory
diseases, according to the self-reporting.

Experimental design

The subjects were tested on 5 to 6 separate occasions over the period of three weeks to
complete the entire protocol. Each subject performed: (1) An incremental skating test (IT) to
measure peak physiological parameters and maximal skating cadence (CADmax); (2) 3 to 4
constant-cadence tests performed to exhaustion in order to model intensity-duration
relationships; (3) A test to exhaustion at CC (TTE-CC) on slide board to analyse physiological
and neuromuscular responses. The subjects were all familiar with simulating skating on a slide
board. They were instructed to avoid heavy training prior to testing and to refrain from caffeine
and alcohol consumption 6 and 24 hours before each test, respectively.

Equipment

All tests were performed on a slide board (2.0×0.6 ×0.2 m) which was connected to a
custom-made software to control the parameters of the test (Piucco et al. 2017a). Participants
wore a pair of wool socks over their shoes while simulating skating (i.e a proper skating posture
and technique was visually controlled by the researcher during each test). The slide board was
polished before each test. Pulmonary gas exchange was continuously measured during test (1)
and (3) by using a TrueMax 2400 computerized metabolic system (Parvo Medics, Utah, USA).
Before each test, the O2 and CO2 analysis systems were calibrated using ambient air and a gas of
known O2 and CO2 concentration according to the manufacturer’s instructions, while the gas
analyzer turbine flow-meter was calibrated using a 3-L syringe. Heart rate was monitored
throughout each test (Polar, Kempele, Finland). Muscle activity of the vastus lateralis (VL) and
gluteus maximum (GM) was continuously measured at 2000 Hz during test (3) using a Miotool
system (MioTec Biomedical, Porto Alegre, Brazil) with 16-bit resolution and pairs of Ag/AgCl
electrodes (bipolar configuration) with a diameter of 22 mm (Kendall Meditrace, Mansfield,
USA) as recommended by SENIAM. A reference electrode was placed over the tibial tuberosity.

Incremental test

After a 10-minute warm up on a cycle ergometer and a subsequent 5-minute rest period,
the incremental skating protocol started at a cadence of 30 push-offs per minute (ppm) and
increased by

3

ppm

every

minute

until volitional

exhaustion,

despite strong verbal

encouragement (Piucco et al 2017a). Pulmonary ventilation (V̇E), respiratory exchange ratio
(RER), and oxygen consumption (V̇O2) were reduced to 15-s averages. The peak 15-s averaged
value recorded during the incremental test was considered as peak V̇O2 (V̇O2peak). The respiratory
compensation point (RCP) was visually identified by two examiners as the point where end-tidal
PCO2 began to fall after a period of isocapnic buffering (Whipp et al. 1989). This point was
confirmed by examining V̇E/V̇CO2 plotted against V̇O2 and by identifying the second breakpoint
in the V̇E-to-V̇O2 relationship. The rate of perceived exertion (RPE) during the tests was
assessed using a Borg scale (6-20 points) at the end of each stage (Borg 1982).

Critical cadence trials

Subjects warmed up on the slide board for 5-minutes at a low cadence (around 30 ppm).
The subjects performed three to four maximal constant work rate tests until exhaustion from 90
to 107% of maximal cadence achieved during the IT (CADmax). CC was determined from 3 trials
in three participants due to competition schedule. The SEE was less than 2% for these athletes,
so we decided to include them in the analysis. The trials lead the subjects to exhaustion between
3 and 15 min, which is the recommended range of predictive trial to minimize the influence of
aerobic inertia in CP or CV values (Hill and Ferguson 1999; Bishop et al. 1998). The trials were
ended when the subjects could no longer maintain the required cadence, despite verbal
encouragement, and the time to exhaustion (tlim) was recorded to the nearest second. HR values
were 191 ± 9.2, 195 ± 7.5, 198 ± 13.1 and 199 ± 6.2 bpm for trial 1, 2, 3 and 4, respectively.
Individual CC was estimated using two models: the hyperbolic (CAD–tlim) model, where the

workload is plotted against time (Eq. 1); the linear model (CAD-1/tlim) where the workload is
plotted against inverse of time (Eq. 2).
(Eq. 1) tlim = W′/(CAD − CC)
(Eq. 2) CAD = (W′/tlim) + CC
The work-time relationship model was not considered in this study due to difficulties to
proper estimate power output on the slide board, as recently reported by our group (Piucco and
de Lucas, 2019).
The standard error of the estimate (SEE) associated with the CC was expressed as
coefficients of variation (CV %). The CC was individually selected from the best fit model, i.e.
lower SSE followed by higher coefficient of determination (R2) when SEE values were the same
(Vanhatalo et al. 2011).

Test to exhaustion at CC (TTE-CC)

On a separate day, following a 10-min warm-up on a cycle ergometer and subsequent 5min of rest period, subjects were encouraged to skate for as long as possible at the CC
determined individually. VE, RER, V̇O2, and HR were continuously measured and RPE was
registered every 5 min. Peak values were defined as the highest average 15-s value recorded
during the test. Physiological values during TTE-CC were also averaged starting from 25 to
100% of TTE-CC duration (TTE-CCavg) to avoid the adjustment phase of cardiovascular
responses. To analyse the physiological responses, we used the 45-sec averaged values at 25%,
50%, 75% and 100% of TTE-CC test. We opted to not start from time zero to avoid the
adjustment phase (i.e. on-kinetics) of physiological parameters. In addition, the absolute increase

in V̇O2 from the third minute of exercise to the end of TTE-CC was calculated (ΔV̇O2) (Bull et
al. 2008).
EMG of VL and GM muscles was recorded continuously during the test. Raw signals
were filtered using a combination of 5th order band-pass Butterworth filters between 20 and 500
Hz. The rectified EMG was integrated with respect to time (EMGi), with an EMGi value
computed 45-sec at 25%, 50%, 75% and 100% of total TTE-CC test time. This data was
individually normalized by the value at 25% of total time. Due to technical problems, data of
only 6 participants were considered for the EMG analysis. The test was completed when the
subject could no longer maintain the pre-determined cadence or at voluntary exhaustion. The
time to failure was described to the nearest second.

Statistical analysis

Student’s paired t-test was used to compare peak values during IT (ITpeak) and TTE-CC
(TTE-CCpeak) as well as submaximal values at IT test (ITRCP) and TTE-CCavg. One-way repeatedmeasures ANOVA was performed and Scheffe post-hoc comparisons were used to determine
changes in physiological and neuromuscular parameters along the TTE-CC test. Correlation
between cadence and V̇O2 values at different intensities was determined using the Pearson
product moment correlation test. All the analyses were carried out using the GraphPad Prism
software package for Windows (version 5.0; GraphPad Prism Software Inc., San Diego, CA,
USA). The level of significance was set at p < 0.05.

Results

Averaged values for CC was 55.3 ± 5.0 ppm (the linear model was selected for 11
participants and the hyperbolic model for 2 participants). The R2 values for the fitting model
used to calculate CC was 0.94 ± 0.05 and the SEE was 1.99 ± 1.74%.
Table 1 depicts the mean values of the maximal and submaximal physiological responses
and cadence values during IT and TTE-CC.
TABLE 1
V̇O2 (p = 0.02), HR (p = 0.03), VE, RER, CAD, and RPE (p < 0.001) values at TTECCpeak were significantly smaller than the values during the ITpeak. V̇O2, HR, VE (p < 0.001),
CAD (p = 0.02), and RPE (p = 0.01) were significant higher during TTE- CCpeak compared to
ITRCP values. CC was correlated to CADmax (r = 0.88) and to CAD at RCP (r = 0.89).
Figure 1 shows the V̇O2 during IT and during TTE-CC test of one representative subject.
FIGURE 1
The mean duration of TTE-CC test was 23.0 ± 4.8 min, ranging from 12.2 to 30.1
minutes. V̇O2, HR, VE, RER, and RPE significantly increased 4.9% (p = 0.002), 13.0% (p =
0.04), 24.3% (p < 0.001), 4.8% (p = 0.002), and 41.5% (p < 0.001) from 25 to 100% of TTE-CC,
respectively. Figure 2 shows the HR and V̇O2 responses during TTE-CC test.
FIGURE 2

V̇O2 at 25% of TTE-CC test represented 83% of V̇O2peak., while V̇O2 at 100% of TTE-CC
represented 88% of V̇O2peak. The averaged ΔV̇O2 value was 686.5±396 mL∙min-1.

Figure 3 represents the mean EMG amplitude values for the VL and GM muscles during
the TTE-CC test.
FIGURE 3

Correlations between RCP, CC and V̇O2 (L∙min-1) at different intensities and performance
time on different skating distances are presented in table 2.
TABLE 2
Figure 4 shows the linear regression and correlation between CC and performance on
1500 meters skating distance (panel A) and between V̇O2 at CC and performance on 1500 meters
skating distance (panel B) are presented in figure 4.
FIGURE 4

Discussion

The main findings to this study were: a) the CC was significantly higher than the cadence
at the RCP and significantly lower than CADmax, although the variables were strongly
correlated; b) physiological parameters and the EMGi increased significantly over time during
the TTE-CC test. c) V̇O2 at CC presented better correlations with skating performances on ice
than V̇O2peak and V̇O2 at RPC.

Numerous studies have shown that CP or CS is significantly higher than the mean power
output/speed associated with the second lactate threshold and/or maximal lactate steady state
during swimming, running, and cycling (Hill 1993; Dekerle et al. 2005; Dekerle et al., 2010; de
Lucas et al. 2002; Denadai et al. 2005; de Lucas et al. 2012; Mattioni et al. 2016), but no study
has investigated the critical intensity parameter during skating. The results of this study
corroborate with the aforementioned studies, where skating exercise performed at CC was nonsustainable and physiologically non-steady (Figure 2B). The V̇O2, HR, VE, RER, and RPE
significantly increased overtime during skating at CC. The exhaustion time around 23 minutes
and the oxygen uptake increased from a mean of 83% to 88% V̇O2peak between the beginning
(25%) and at the end (100%) of TTE-CC. These values are similar to that reported by de Lucas
et al. (2013), whom reported mean TTE of 22.9 min, and Brickley et al. (2002) and Pringle and
Jones (2002) whom reported a significant V̇O2 increase from around 80% to 90% of maximum
values, and time durations slightly below 30 minutes when cycling at the CP. The ΔV̇O2 value of
686.5±396 mL∙min-1 found in this study was higher than the V̇O2 slow component found during
cycling at CP of 247 ml·min-1 (de Lucas et al. 2013) and during running at CV of 442 ml·min-1
(Bull et al. 2008), when critical intensity was determined using the linear model.
Muscle activity (i.e. EMGi) of GM and VL also increased during the TTE-CC test for all
athletes (Figure 3). The increase in EMGi represents the recruitment of previously inactive motor
units and/or increased firing rate of the activated motor units required to maintain force
production in the face of muscle fatigue (Hunter et al. 2001). The simultaneous slow rise in
pulmonary V̇O2 and increases in EMGi from the exercising muscles during heavy and severe
exercise has been taken as evidence that the serial recruitment of the less-efficient type II motor
units is related to the V̇O2 slow component (Barstow et al. 1996; Jones et al. 2011).

However, Pringle and Jones (2002) and Scheuermann et al. (2001) were unable to detect
significant increase in EMGi during cycling at a heavy intensity that elicited a V̇O2 slow
component. A noteworthy characteristic that should be considered is the relative long duty cycle
during skating (contraction-relaxation cycle) when compared to cycling and running exercises.
The increased intramuscular pressure accompanied by the low posture is known to trigger blood
flow occlusion altering O2 delivery and increasing metabolites accumulation during skating
(Foster et al. 1999; Rundell 1996). These characteristics could be related to the significant
increase in muscle activity found in the present study, since an increase in EMGi have been
shown in response to moderate blood flow restriction and local accumulation of metabolites
(Loenneke et al. 2010; Yasuda et al. 2009). In addition, the metabolites accumulation has also
been considered to be a putative mediator of the V̇O2 slow component (Jones et al. 2011).
Interestingly, the GM presented a more pronounced increase in EMGi than VL (Figure
3). Despite both GM and VL significantly contributing to power output during skating, only the
GM showed significant changes in frequency components during skating to exhaustion,
suggesting that this muscle is more sensitive to fatigue (Piucco et al. 2017a).
Recent studies have shown that CP is decreased with reduced O2 delivery induced by
hypoxia or blood flow occlusion (Dekerle et al. 2012; Broxterman et al. 2015) and lower for 50%
duty cycle than the 20% duty cycle as a result of reduced blood flow (Broxterman et al. 2014).
However, if CC intensity is affected or not during skating due to these characteristics remains to
be investigated.
As expected, in the present study, exercising at CC did not result in an increase in oxygen
consumption to the maximal level as attained during the incremental protocol (Figure 1). One
could speculate that the attainment of the V̇O2max does not occur when exercising at critical

intensity since the rate of increase in V̇O2 is slow (0.4 L∙min-1 over ~23 minutes duration of
TTE-CC) and exercise is terminated due to other factors before the aerobic system is fully
recruited (Brickley et al. 2002; de Lucas et al. 2013). Indeed, de Lucas et al. (2013) showed that
only at intensity 5% above CP could lead V̇O2 to the maximal values at the termination of
exercise.
Although the characteristics of technique and body posture of speed skating could
suppose a limitation in the sustainability of endurance time such as at TTE-CC on slide board, no
important difference was observed when compared to running (Penteado et al. 2014; Bull et al.
2008) and cycling exercises (Brickley et al. 2002; Pringle and Jones 2002).
CC and V̇O2 at CC were better associated to skating performance on ice in selected
distances (i.e. 500m, 1000, 1500m, and 5000m) than RCP, V̇O2 max and V̇O2 at anaerobic
threshold intensity (Table 2 and Figure 4). Critical intensity has been suggested as a good
indicator of endurance performance (Florence and Weir 1997), and especially for continuous
activities performed at a severe-intensity exercise domain (Vanhatalo et al. 2011). Therefore,
good correlation values between CC and performance on long track speed skating distances were
expected since these competitions take around less than 1-10 minutes of maximal intensity effort.
Therefore, for a more individual training prescription that represents the highest limit of
heavy exercise intensity it is worth to submit the athletes to short predictive trials to exhaustion
and calculate the CC to get a more precise value than RCP. Because slide board skating
promotes similar physiological stress to actual skating, the HR at CC on slide board could be
used as an indicator of workload intensity for training prescription on ice.

Acknowledgements

This work was supported by the Internal Research Grant Fund of Mount Royal University.
The authors have no conflicts of interest to report

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Table 1. Maximal and submaximal values during the incremental (IT) and constant cadence tests
(TTE-CC).
ITpeak

ITRCP

TTE-CCpeak

TTE-CCavg

V̇O2 (mL∙min-1∙kg-1)

48.0 ± 6.1

41.0 ± 5.2

46.3 ± 6.8*

41.6 ± 6.0

HR (bpm)

202.2 ± 8.6

185.9 ± 7.3

198.7 ± 9.2*

188.3 ± 12.6

VE (L∙min-1)

130.6 ± 26.3

86.8 ± 17.0

118.9 ± 27.5*

100.2 ±20.2#

RER

1.16 ± 0.03

1.01 ± 0.05

1.02 ± 0.05*

0.97 ± 0.03#

RPE

19.6 ± 0.6

15.6 ± 1.3

17.7 ± 1.16*

15.0 ± 1.4

CAD (ppm)

61.6 ± 4.3

53.5 ± 4.0

55.3 ± 5.0*

55.3 ± 5.0#

ITpeak peak values during incremental test; ITRCP respiratory compensation values; TTE-CCpeak peak values during
time to exhaustion at critical cadence test. *significantly different than ITpeak value p<0.05. # significantly different
than ITRCP p<0.05.

Table 2. Correlations between V̇O2peak, RCP, V̇O2 at RCP, CC and V̇O2 at CC and performance
on 500, 1000, 1500 and 5000m long track skating distances on ice.
500 m

1000 m

1500 m

5000 m

V̇O2peak

-0.70**

-0.58*

-0.70**

-0.79**

RCP (ppm)

-0.56*

-0.62*

-0.63*

-0.55

V̇O2 at RCP

-0.69*

-0.59*

-0.70**

-0.77**

CC (ppm)

-0.60*

-0.66*

-0.75**

-0.84**

V̇O2 at CC

-0.77**

-0.68*

-0.79**

-0.84**

* significant correlation at p < 0.05. ** significant correlation at p < 0.01.

Figure 1. V̇O2 during IT (panel A) and during TTE-CC test (panel B). Dashed horizontal lines
indicate the peak value at IT.

Figure 2. Heart rate (panel A) and relative oxygen uptake (panel B) responses during TTE-CC
test. * significant difference from 25%; § significant difference from 50%; # significant
difference from 100%. p < 0.05.

Figure 3. Integrated EMG values of VL (open circles) and GM (solid circles) during TTE-CC
test. § significantly different from 100% for VL. * significantly different from 100% for GM. p <
0.05.

Figure 4. Linear regression (95% CI and identity line) between CC (panel A) and V̇O2 at CC
(panel B) and skating performance on 1500m.