Entropy Measures Detect Changes in Movement Variability: Sliding

across a Novel Slide Vibration Board in Ice Hockey Players

J. F. Gisbert-Orozco

, B. Fernández-Valdés

, V. Illera-Domínguez

S. Rodríguez-Jiménez

and G. Moras

National Institute of Physical Education of Catalonia, University of Barcelona, Av. de l’Estadi 12-22, Barcelona, Spain

Estel Grup, S. L., Abrera, Spain

1 OBJECTIVES

Slideboard (SB) exercise is a multifaceted, closed

kinetic chain that imparts low-impact forces to the

lower extremities and is used to enhance strength,

endurance, proprioception, agility, balance, body

composition, and cardiorespiratory fitness (Diener,

1994; Weber and Ware, 1998). Additionally, based

on previous research we can use the SB exercise as a

specific and practical off-ice test to evaluate

performance in speed skating, prescribe exercise

training and monitor adaptations due to training

programs (Piucco et al., 2016, 2017).

Apart from this, there is an emerging profile of

application of vibration as an exercise modality that

is mostly practiced as whole body vibration (WBV),

i.e. while standing on oscillating or synchronously

platforms and it is now seen as potentially beneficial

in certain areas of sports, exercise, rehabilitation and

preventive medicine (Rittweger, 2010).

In both issues, either in off-ice hockey training in

ice hockey players (Boland et al., 2017; Boucher et

al., 2017; Peterson et al., 2016) as in WBV in elite

athletes (Hortobágyi et al., 2015), specific tasks are

recommended. In this way, although several studies

have analysed both SB and WBV separately, no

studies have been found with a Slide Vibration

Board (SVB). Moreover, the studies analysed in

metabolic, electromyographic and performance

parameters, but no studies have used non-linear

analyses.

In the same way, from constraint-led approaches,

an additional category of experiments conducted to

date has manipulated the environment. Increasing

environment complexity or motor behaviour can be

seen as environmental constraints since the

performer has to adapt in order to perform

successfully (Rienhoff et al., 2016). In this sense,

WBV while sliding upon a SB could led us to

improve specificity and develop challenging training

environments, which increases movement variability

and adaptability (Button et al., 2006) using WBV as

a environment constraint.

To evaluate the effect of constraint in non-linear

terms is important, because when assessing

measures from complex systems such as human

movement, there are components that can provide

insight into the underlying nature of the system

(McGregor and Bollt, 2012).

What is yet unknown, is how these constraints

affect the dynamics of kinematic variables and,

ultimately, the performance outcomes. The

conventional approaches that describe variability

using linear measures, provide very limited

information about how the motor control system

responds to changes, either within or between

individuals (Stergiou, 2016).

In movement variability assessment, entropy is

among the most popular and promising complexity

measures for biological signal analyses (Gao et al.,

2012). When considering time series data variables,

describing agent interactions in social

neurobiological systems, measures of regularity can

provide a global understanding of such systems

behaviours. Sample Entropy (SampEn) analysis has

become relatively popular as a measure of system

complexity. It has been used to describe locomotive

movements and manipulations in resistance training,

using the acceleration signal as a non-invasive tool

to assess training status (Murray et al., 2017; Moras

et al., 2018).

Thus, from a non-linear perspective, when using

tools like entropy, the functional variability of

athletes during the performance of a movement must

be perceived as a key element to identify the amount

of perturbation in task constraints (Couceiro et al.,

2013).

Therefore, the aim of this study was to compare

the effect of WBV as an environment constraint

(VEC) and without vibration (NV) when performing

an slide exercise across SVB using SampEn

analyses.

Gisbert-Orozco, J., Fernández-Valdés, B., Illera-Domínguez, V., Rodríguez-Jiménez, S. and Moras, G.

Entropy Measures Detect Changes in Movement Variability: Sliding across a Novel Slide Vibration Board in Ice Hockey Players.

In Extended Abstracts (icSPORTS 2018), pages 29-32

2 METHODS

Ten elite ice hockey players from a professional

team at the Spanish national league volunteered to

participate in this study (mean ± SD: age 20.4 ± 2.07

years, height 1.79 ± 0.05 m, weight 75.97 ± 5.44

kg). The procedures of this study complied with the

Declaration of Helsinki (2013) and were approved

by the local ethics committee “Comitè d’Ètica

d’Investigacions Clíniques de l’Administració

Esportiva de Catalunya” (06/2018/CEICGC).

The study was conducted on a 2m synchronously

slide vibration board (SVB) (Patent, P201630075).

SVB provide three frequencies: 20, 25 or 32 Hz and

a 2mm amplitude with no choice. For the VEC

condition, the frequency selected was 32 Hz and the

amplitude was 2mm, which are in the range that

have been reported in the literature (frequency, from

20 to 50 Hz; and amplitude, from 2 to 10 mm) (Di

Giminiani et al., 2013). Participants were instructed

to refrain from heavy exercise in the 24 h before

each test, and to abstain from the ingestion of

stimulants (i.e, caffeine, nicotine) or alcohol. The

study was carried out on three days separated by six

to eight days. On the first day, players underwent a

familiarization session with the SVB. On the second

and third day, each player performed one sliding

test, under VEC or NV randomly. The experimental

protocol began with a standardized warm-up, after

which, 1 bout of 1 minute under VEC or NV was

performed. The cadence was 30 push-offs per

minute (ppm) and was controlled by metronome

(Korg KDM-3 Digital Metronome, Tokyo, Japan), in

order to avoid confusion variables.

Throughout each exercise trial, trunk acceleration

of the ice hockey players under both conditions (VEC

and NV) was measured using a wireless inertial

measurement unit (WIMU, Realtrack Systems,

Almeria, Spain), a 3D accelerometer 100G recording

at 1000 Hz. The accelerometer was attached to the

player using an elastic waist belt closed to the sacrum.

This position provide the best indication of whole

body movement, as the location is close to the

player’s center of mass (Montgomery et al., 2010).

SampEn were calculated in arbitrary units (a.u.) using

the module of the acceleration signal (Moras et al.,

2018).

Data analyses were performed using PASW

Statistics 21 (SPSS, Inc., Chicago, IL, USA).

Normality was assessed using the Shapiro-Wilk test.

The level of statistical significance was set at p < .05

and the confidence interval of the difference was set

at 95%. Data are expressed as mean SampEn (a.u.) ±

standard deviation. SampEn were analysed using a

paired-samples t-test to compare variables between

VEC and NV protocols.

3 RESULTS

The SampEn values for the ice hockey players were

0.07 ± 0.02 and 0.19 ± 0.08 for the NV and the VEC

conditions, respectively (Figure 1). There was

significantly higher entropy performing the VEC

protocol (0.13 ± 0.08 p = 0.001). The lower and

upper confidence intervals for the difference were

-0.18 and -0.07 respectively.

Figure 1: Significantly differences p = 0.001 were found

performing slide exercise adding VEC.

4 DISCUSSION

This study aimed to identify the differences in the

structure of variability of acceleration signal when

performing slide exercise (NV) adding VEC across

SVB to establish the amount of perturbation.

The main findings suggest that the vibration

constraint increase the structure of variability of

acceleration signal produced by the players.

Although this is the first work to assess the

acceleration while sliding across a SB with a

vibration constraint, slower performance in

constrained tasks by hockey sticks has previously

been reported in field hockey players (Wdowski and

Gittoes, 2013). More recently, increasing SampEn

were found in the structure of variability in body

acceleration when introduce specific ball constraints

(Moras et al., 2018).

Thus, the vibration constraint applied to the SVB

exercise affects the players during sliding

performance and may indicate detrimental

movement control or coordination when a vibration

icSPORTS 2018 - 6th International Congress on Sport Sciences Research and Technology Support

constraint is added. The perturbation showed under

VEC could be explained because on WBV platforms

the body loses contact with the ground and becomes

air-bound, due to the lack of a firm attachment

(Rittweger, 2010). These results suggest that SB

training could integrate vibration constraints in

training protocols in order to reach constraint-led

approach as we mentioned above.

The SampEn values increase in the VEC for all

players. These results indicate that the constraint

applied to the SB exercise induces a change in

system coordination patterns or establishes certain

combination of movement stability and adaptability

(van Emmerik and van Wegen, 2002). This is an

evidence of how specificity issues can foster the

adaptive aspects of movement variability. The

association of the degree of variability with skill

and health is changing (Hamill et al., 1999)

It has

been shown that some degree of motor variability is

beneficial as it allows a more adaptive system to

internal and external perturbations that constantly

act on the body.

To conclude, the use of VEC across SVB for ice

hockey players elicits different structure of

variability in body acceleration. Thus, ice hockey

players might benefit from performing constrained

environment tasks across SVB. Understanding

constraints and its motor adaptations may help

coaches and trainers to enhance the effectiveness of

training.

ACKNOWLEDGEMENTS

We thank the FC Barcelona ice hockey players who

took part in the study, especially Mr. Javier Poveda

who helped us contacting with the players.

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