evaluation of muscular emg activity variations wearing ski

evaluation of muscular emg activity variations wearing ski

EVALUATION OF MUSCULAR EMG ACTIVITY VARIATIONS
WEARING SKI-MOJO ON A SKIING TREADMILL
N. Petrone, G. De Bettio*
Department of Mechanical Engineering, University of Padova, Italy
*DolomitiCert Laboratories, Longarone BL, Italy
[email protected], http://www.fatigueteam.dim.unipd.it
[email protected], http://www.dolomiticert.it
INTRODUCTION
The aim of the investigation was the evaluation of the muscular activity patterns on a skier equipped with a ski~mojo device.
Tests were performed on a skiing treadmill by an experienced skier wearing the ski~mojo for the first time.
He skied performing narrow slaloms turns (SLALOM) and wide slaloms turns (GIGANTE) with ski~mojo OFF and ON.
MATERIALS AND METHODS: A SKIMAGIC treadmill was
used outdoor at Longarone-Italy for the tests.
The treadmill is made of a synthetic fur snow surface wetted
by water that is spinning at variable speeds. The tests were
performed at a speed of 22 km/h on a slope of 30°.
DATA ANALYSIS. EMG signals were analyzed and
averaged over ten turns. The average activity resulting over
the turn cycle on five dominant leg muscles are plotted.
Red curves are with ski~mojo ON,
Black curves are with ski~mojo OFF.
Retto Femorale Gigante
Retto Femorale Slalom
0.2
EMG [mv]
0.2
0
0
10
20
30
40
50
60
70
80
90
100
Cycle [%]
ON
OFF
0
10
20
30
40
50
60
70
80
90
100
Cycle [%]
ON
OFF
10
20
30
40
50
60
70
80
90
100
Cycle [%]
ON
OFF
EMG [mv]
Gastrocnemio Laterale Slalom
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
0
10
20
30
40
50
60
70
80
90
100
Cycle [%]
ON
OFF
Bicipite Femorale Slalom
EMG [mv]
0.1
0.08
0.06
0.04
0.02
0
0
10
20
30
40
50
60
70
80
90
100
Cycle [%]
ON
OFF
[Deg]
Flesso Estensione ginocchio Slalom
60
50
40
30
20
10
0
-10 0
-20
10
20
30
40
50
60
70
80
90
100
Cycle [%]
ON
Fig. 4. The skier performing special slalom with ski~mojo.
CONCLUSIONS:
The tests performed with the ski~mojo activated
consistently showed a relevant reduction of Muscle
Activation levels on five principal leg muscles, ranging from
-19% to -37%.
Although the tests were performed on a single skier, the
positive effects of ski~mojo in reducing fatigue are likely to
be statistically confirmed by further ongoing tests.
20
30
40
50
60
70
80
90
100
70
80
90
100
80
90
100
80
90
100
80
90
100
80
90
100
Cycle [%]
OFF
Vasto Mediale Gigante
0.6
0.5
0.4
0.3
0.2
0.1
0
0
10
20
30
40
50
60
Cycle [%]
ON
OFF
Tibiale Anteriore Gigante
OFF
RESULTS:
EMG signals were
consistently lower
when the ski~mojo
was activated (ON)
The average
reduction of the
EMG activation
signal is reported for
each muscle in the
two conditions of
Special Slalom (SS)
& Giant Slalom (GS)
EMG [mv]
0.2
0
Fig. 3. The skier performing giant slalom with ski~mojo.
10
ON
0.15
0.1
0.05
0
0
10
20
30
40
50
60
70
Cycle [%]
ON
OFF
Gastrocnemio Laterale Gigante
EMG [mv]
Fig. 2. EMG electrodes
being applied to the
skier’s legs.
0.1
0.05
0
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
0
10
20
30
40
50
60
70
Cycle [%]
ON
OFF
Bicipite Femorale Gigante
EMG [mv]
Fig. 1. The treadmill used for the tests
EMG [mv]
Tibiale Anteriore Slalom
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
0.15
0
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
0
10
20
30
40
50
60
70
Cycle [%]
ON
OFF
Flesso Estensione ginocchio Gigante
80
60
[Deg]
EMG [mv]
Vasto Mediale Slalom
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
ski~mojo ON Vs OFF
0.1
0.05
EMG [mv]
0.15
Knee Angle / Comparison of muscle activation:
EMG [mv]
0.25
40
20
0
-20
0
10
20
30
40
50
60
70
Cycle [%]
ON
OFF
Retto
Femorale :
-27 % SS
-37 % GS
Bicipite
femorale SX
- 26 % SS
-31 % GS
Vasto
mediale SX:
-37 % SS
-36 % GS
Gastrocnemio
mediale SX: - 20 % SS
-19 % GS
Tibiale
anteriore SX:
-30 % SS
-37 % GS
Results: With ski~mojo ON there is a general
Advantage (LOWER ACTIVATION) on all Muscles
Less
ACTIVATION
Less Muscle
FATIGUE
More
SKIING