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Bilateral Biomechanical Asymmetry During 30 Seconds Isokinetic Sprint-Cycling Exercise

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The purpose of present study was to examine the bilateral differences of pedalling kinetics and thigh muscle activity patterns according to leg dominance during the 30 seconds maximal cycling exercise and to analyse the relationships between asymmetries of pedalling kinetics and muscle activity. Methods: The pedalling power (POW), power production smoothness (PS) and EMG of VL, RF and BF of 17 competitive cyclists (19.2±1.6y.; 1.82±0.07m; 74.1±8.2kg) were measured bilaterally during maximal 30s isokinetic (cadence limit 100 rpm) seated cycling exercise. The dynamics of POW, PS and normalized EMG-RMS amplitude and median frequency (MF) of dominant (DO) and non-dominant (ND) side were measured. The directional asymmetry indexes (AI%) between DO and ND side were computed and compared with student t-test for paired samples. Correlation analyse between AI(%) of pedalling kinetics and EMG patterns was made. Results: The DO side POW and PS values were significantly (p<0.05) higher than ND during the all exercise time (except POW between 5-10 sec). No significant bilateral differences were found between normalized EMG amplitude values. The AI(%) of POW and PS were significantly lowered during the exercise. Significant correlations were found between AI (%)-s of PS and VL EMG MFr (r=-0.64) and between AI(%)-s of POW and VL normalized EMG amplitude (r=0.63).Conclusions: Results of the present study indicate that during 30 seconds maximal intensity cycling does exist leg dominance dependent asymmetries in pedalling power patterns, which decreased during the exercise and was related with bilaterally asymmetry of vastus lateralis muscle firing patterns. Key words: Surface EMG, Pedalling Power, Leg Dominance
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LASE JOURNAL OF SPORT SCIENCE 2015/6/2 | 3
p-ISSN: 1691-7669/e-ISSN: 1691-9912/ISO 3297
Copyright © by the Latvian Academy of Sport Education in Riga, Latvia
DOI: 10.1515/ljss-2016-0001
ORIGINAL RESEARCH PAPER
BILATERAL BIOMECHANICAL ASYMMETRY DURING 30
SECONDS ISOKINETIC SPRINT-CYCLING EXERCISE
Indrek Rannama, Kristjan Port
Institute of Health Sciences and Sport, Tallinn University, Estonia
Corresponding author: Indrek Rannama
Adress: Räägu 49, 11311 Tallinn, Estonia
Phone: +372 5141077
E-mail: rannama@tlu.ee
Abstract
The purpose of present study was to examine the bilateral
differences of pedalling kinetics and thigh muscle activity patterns
according to leg dominance during the 30 seconds maximal cycling exercise
and to analyse the relationships between asymmetries of pedalling kinetics
and muscle activity. Methods: The pedalling power (POW), power
production smoothness (PS) and EMG of VL, RF and BF of 17 competitive
cyclists (19.2±1.6y.; 1.82±0.07m; 74.1±8.2kg) were measured bilaterally
during maximal 30s isokinetic (cadence limit 100 rpm) seated cycling
exercise. The dynamics of POW, PS and normalized EMG-RMS amplitude
and median frequency (MF) of dominant (DO) and non-dominant (ND) side
were measured. The directional asymmetry indexes (AI%) between DO and
ND side were computed and compared with student t-test for paired
samples. Correlation analyse between AI(%) of pedalling kinetics and EMG
patterns was made. Results: The DO side POW and PS values were
significantly (p<0.05) higher than ND during the all exercise time (except
POW between 5-10 sec). No significant bilateral differences were found
between normalized EMG amplitude values. The AI(%) of POW and PS
were significantly lowered during the exercise. Significant correlations were
found between AI (%)-s of PS and VL EMG MFr (r=-0.64) and between
AI(%)-s of POW and VL normalized EMG amplitude (r=0.63).Conclusions:
Results of the present study indicate that during 30 seconds maximal
intensity cycling does exist leg dominance dependent asymmetries in
pedalling power patterns, which decreased during the exercise and was
related with bilaterally asymmetry of vastus lateralis muscle firing patterns.
Key words: Surface EMG, Pedalling Power, Leg Dominance
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Introduction
Bicycling is a bilateral cyclical movement and for that reason in
most of studies, analysing cycling biomechanics, assuming that cyclists are
pedalling symmetrically and have mainly focused on measurements of only
one body side (Carpes, Mota & Faria, 2010). In same time the numbers of
studies have found a notable asymmetry in the bilateral biomechanical
patterns of the pedalling and muscle strength values of competitive cyclists
(Rannama et al., 2013; Yanci & Arcos, 2014). Earlier studies focused on
recreational population and noted between-legs differences in pedalling
kinetic variables like a work (Cavanagh et al., 1974) and crank peak torque
(Daly & Cavanagh, 1976). Most of latest researches in this field have been
focused on pedalling kinetics and have declared bilateral asymmetry in
competitive cyclist’s population in crank torque (Carpes et al., 2007; Bini &
Hume, 2014) or different pedal force components profile (Sanderson, 1990;
Smak, Neptune & Hull, 1999) and pedal power output (Smak, Neptune &
Hull, 1999). Also in some studies have found asymmetry in lower limbs
joint kinematics and kinetics patterns (Smak, Neptune & Hull, 1999;
Rodano, Squadrone & Castagna, 1996; Edeline et al., 2004), but there have
been made only a few studies about between-legs differences in muscle
activation patterns (Carpes et al., 2010; Carpes et al., 2011).
There are noted differences in pedalling kinetics variables according
to leg dominance, identified by kicking preference. Daly & Cavanagh
(1976) stated the direction of asymmetry was unrelated of limb dominance
and varied day to day. Smak, Neptune & Hull (1999) found that, at the work
rate of 250 W and in cadences between 60 to 120 rpm, cyclist’s dominant
leg contributed significantly greater average crank power than non-dominant
leg, despite the relatively small difference (0.5-2%). Same study (Smak,
Neptune & Hull, 1999) also found higher average positive and negative
crank powers in non-dominant side, which refers to different bilateral
pedalling technique. There are also described higher crank peak torque
values of dominant leg in low to submaximal powers of incremental test
(Carpes et al., 2008) and in 40km long simulated time trial (Carpes et al.,
2007). It seems that higher power output (Carpes et al., 2008; Sanderson et
al., 1991) or accumulated fatigue (Carpes et al., 2007), as indicators of
increased effort (Carpes, Mota & Faria, 2010), improve the symmetry of
pedalling kinetics, but there are also opposing findings (Bini & Hume,
2014). The asymmetry of pedalling kinetics is also influenced by pedalling
rate, but those relations are at the moment not fully understood (Carpes,
Mota & Faria, 2010). In the cadence range between 60 and 90 rpm cyclists
have individual variations in change of bilateral leg contribution (Smak,
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Neptune & Hull, 1999), but there is a trend of increasing absolute
asymmetry in higher (over 120rpm) and very low cadences (less than 60),
especially in non-cyclists population (Liu & Jensen, 2012; Smak, Neptune
& Hull, 1999).
The relations between asymmetries of different biomechanical
variables, such as pedalling kinetics, movement kinematics and muscles
activity, are not frequently discussed. Edeline et al., (2004) demonstrated
that even with a symmetrical pedal force production there was existing
bilateral difference in the pedalling kinematics and this leads to the
asymmetry in joint torques and muscle loads. In same line are findings of
Smak, Neptune & Hull (1999) about leg dominance driven differences in
knee and hip joint torque profiles. The bilateral leg dominance driven
asymmetries have found in normalized EMG amplitude values of squat
jump (Ball & Scurr, 2014) which is similar movement to cycling. In contrast
Carpes, et al., (2010b) compared dominant and non-dominant legs
normalized EMG-s of 3 muscle groups during single leg cycling at
submaximal constant load intensity and found no dominance related
differences. During the incremental cycling test Carpes et al., (2011) noted
lower EMG variability in Biceps femoris, Gastrochnemius and Vastus
lateralis muscles of dominant leg in some conditions, but no significant
bilateral differences were found in normalized EMG amplitude values. To
best of our knowledge no studies about relationships between bilateral
asymmetry of pedalling kinetics and muscle activity of leg muscles are
presented.
Competitive road cycling requires for success not only good
endurance, but also ability to produce high level maximum power during a
short period of time (Ebert et al., 2006; Jeukendrup, Craig & Hawley, 2000).
Above discussed researches looked asymmetry in submaximal and mainly
in aerobic exercise conditions, but there is lack of known about between-
legs differences in pedalling biomechanics and muscle activity patterns
during short term maximum anaerobic performance. It is known that during
submaximal cycling dominating muscles are knee extensors (Broker &
Gregor, 1994; Ericson, 1988) but in maximal cycling condition larger
portion of power is generated by hip extensors that produced nearly twice
the power compared to knee extension (Martin & Brown, 2009). Also
relatively less knee extension and more knee flexion power will be produced
(Elmer et al., 2011). The relative larger increase (5 9 times) of hip flexors
and extensors and knee flexors muscle activity have been found with power
increase from 150W to maximum, whereas ankle plantar flexors and knee
6 | Rannama et al: BILATERAL BIOMEHANICAL ASYMMERRY ...
extensors activity increased only 2-3 times (Dorel, Guilhem, Couturier &
Hug, 2012).
During 30 seconds maximal cycling trial the fatigue occurred at
different rates the hip extensors sustain their power longer and at higher
rate, while ankle joint power tends to decrease most rapidly compared to
other lower limb joints and in knee joint the flexors power decline is lower
than in extensors (Martin & Brown, 2009). On sEMG values reported
significant decline in median frequency of the power spectrum of ankle
plantar flexors and knee extensors (averagely 14-19%), but sEMG
amplitude values are significantly reduced only in plantar flexors and not in
knee extensors (Greer et al., 2006; Hunter et al., 2003). There is a lack of
evidence about role of laterality and existence of bilateral differences in
muscle fatiguing during anaerobic single-sprint exercise.
The purpose of present study was to examine the bilateral
differences of pedalling kinetics and thigh muscle activity patterns
according to leg dominance during the 30 seconds maximal cycling exercise
and analyse the relationships between asymmetries of pedalling kinetics and
muscle activity.
Material and methods
Participants. The study participants were 17 competitive U23 class
male road cyclists of age ranging from 18 to 22 (21.1±3.5years,
181.5±5.0cm, 74.8±7.0kg). All athletes had at least 6 years focused
endurance cycling training and competition experience. 16 cyclists were
right leg dominant and one was left leg dominant, identified by kicking
preference (Smak et al., 1999).
All participants were informed about the research procedures,
requirements, benefits and risks before the testing. All participants were
asked not to do a heavy or intensive training at least two days before the
testing. The study was performed in November after the end of competitive
season and before the start of new preparation period for cyclists.
Procedures
Experimental cycling exercise were performed using the participants
personal racing bike, which was mounted on a research grade cycling
ergometer platform Cyclus 2 (Avantronic, Cyclus 2, Leipzig, Germany) that
allows lateral incline of the bike that matches real life cycling. Exercise
protocol consisted 4 stages: 10 minutes warm-up of steady ride in power
level up to 150W, 6 seconds of isokinetic maximal sprint with cadence set
in 100rpm for EMG amplitude normalization, 25 30 minutes warm up
with mixed power up to VO2 max level to and 30 seconds maximal
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isokinetic sprint performance with limited cadence set in 100rpm. All
experimental cycling tests were conducted in sitting position hands on the
drops. For measurement of pedalling kinetics bicycle of each participant
equipped with same pair of Garmin Vector power meter pedals (Garmin
Vector™). Vector pedals were installed and calibrated before each testing
session according to description of manufacturer guidelines.
Muscle activity data were recorded bilaterally by surface
electromyography (sEMG) from three tight muscles: the long head of biceps
femoris (BF), the rectus femoris (RF) and the vastus lateralis (VL) muscles.
These muscles were chosen because they are dominant muscles from tree
different muscle synergy group involved in cycling (Hug, Turpin, Guevel &
Dorel, 2010). Due to technical problems with one sEMG probe during the
experimental time only 9 persons sEMG of BF were included to future
analysis.
The skin of participants was shaved and cleaned with alcohol to
improve the skin impedance. A pair of Ag/AgCl electrodes with inter-
electrodes distance of 30 mm was applied on each muscle symmetrically for
dominant (DO) and non-dominant (ND) limb, following the SENIAM
recommendations (Hermens et al., 2000). Always the same person attached
all the electrodes. A wireless electromyography BTS FreeEMG 300
measurement system (BTS, Inc., Milan, Italy) was used to collect sEMG
data from six bipolar wireless probes (8.5g). The system features an A/D
converter within an EMG sensor for eliminating external noises. Six sEMG
channels and one pedal position and start triggering switch channel sampled
at 1000 Hz frequency.
The sEMG signal was synchronized with pedalling cycle kinematics
by magnetic switch positioned in bottom dead centre of left crank and with
cycle ergometer and power pedals by start switch.
Measures. The kinetics of pedalling are described by pedalling
power (POW) and pedalling smoothness (PS=pedalling cycle Average
power/Maximum power*100(%)) collected from Garmin Vector pedals with
1 seconds interval separately from DO and ND side from start to end of
experimental exercise. The muscle activity patterns were normalized RMS
EMG (%) and EMG median frequency (MFr). For all patterns average
values of 30 seconds and six (from 0 to 5; 5 to 10; 10 to 15; 15 to 20; 20 to
25 and 25 to 30 seconds) consecutives 5 seconds long time periods were
taken to future analyse. Measurements and initial analysis of values were
expressed as a mean of dominant and nondominant leg.
8 | Rannama et al: BILATERAL BIOMEHANICAL ASYMMERRY ...
The directional asymmetry index (AI(%)=100*(DO-
ND)/0.5*(DO+ND)) was calculated (Robinson, Herzog & Nigg, 1987) for
pedalling kinetic and sEMG variables.
Analysis
The stored sEMG data were analysed with BTS SEMGAnalyzer
(BTS, Inc., Milan, Italy) with custom made analyse protocols. Raw EMG
signals of 6 seconds normalization and 30 seconds experimental trail were
high-pass filtered (10Hz, Butterworth filter) to eliminate possible external
noises. To compare the bilateral muscle firing rate patterns and fatigue
accumulation during the exercise the median frequency (MFr) values of
sEMG power spectrums of whole test and six consecutive 5 seconds time
periods were computed. Filtered sEMG signals of normalization and
experimental trial were root mean squared (RMS) with 0.025 seconds
moving time window to make linear envelope of sEMG amplitude. The
sEMG amplitude normalization was made by peak amplitude method
according to the directions of Ball and Scurr (2013). Highest 0.025 second
RMS value of 6 seconds normalization sprint for each muscle for DO and
ND side were taken for normalization of RMS values of experimental trail.
Average normalized sEMG RMS amplitude values of whole exercise and
every 5 seconds time period were computed and incorporated to the future
analyse.
Data analyses were performed using the IBM SPSS Statistics version
21.0 for Windows. Descriptive data were computed for all variables and all
time period and expressed as mean ± standard deviation (SD). All the data
was tested for their normal distribution (Kolmogorov-Smirnov test). A
Student’s t-test for paired data was applied to compare values of DO and
ND leg and changes between time periods. The correlation analyze between
AI(%) of pedaling kinetic and sEMG values were made. Significance level
was set at p<0.05 for all analyses.
Results
The average absolute power of 30 seconds cycling sprint test was
846±115 W (ranged from 592 to 1124 W) and relative power was 11.4±1.0
W/kg (from 9.6 to 13.3 W/kg). The descriptive statistics of pedalling
kinetics, EMG amplitude and frequency results and between DO and ND
side asymmetry values are presented in Table 1. The dynamics of named
variables during the test within 5 seconds time stages are presented in
figures 1-4.
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Table 1
The descriptive statistics of pedalling kinetics, EMG amplitude and frequency
values of DO and ND leg, AI (%) and paired t-test results between bilateral values
of 30 seconds maximal cycling exercise
N
Mean
Std. Dev
AI (%)
Paired t-test Sig.
(2-tailed)
Mean
PS
DO
17
34.5
2.9
8.74
4.57
0.00*
ND
17
31.6
2.7
POW
DO
17
430.8
60.7
3.43
4.27
0.00*
ND
17
415.5
56.0
RF RMS
DO
17
18.3
4.9
-8.92
26.46
0.17
ND
17
20.0
5.1
VL RMS
DO
17
22.2
4.7
10.04
28.21
0.17
ND
17
20.1
4.1
BF RMS
DO
9
22.1
3.9
9.08
23.38
0.22
ND
9
20.1
3.1
RF MFr
DO
17
79.0
7.8
3.60
8.95
0.09
ND
17
76.0
6.3
VL MFr
DO
17
65.0
7.2
-1.99
14.98
0.55
ND
17
66.4
6.6
BF MFr
DO
9
68.5
10.5
-5.52
9.53
0.01*
ND
9
73.6
9.1
*- significant differece between DO and ND side (p<0.05)
The comparison of 30 seconds DO and ND leg average values
(Tab.1) refers to significantly (p<0.05) higher PS and POW of DO side and
higher MFr values of BF muscle. This trend is also shown in dynamics of
named variables during the exercise (figures 1 and 2), where PS and POW
bilateral differences are maintained from start to end part, but BF MFr
differences are disappearing during the last 10 seconds of the exercise.
Figure 1. Dynamics of average (+/-SD) DO and ND side pedalling power (POW)
(Figure 1A) and pedalling smoothness (PS)(Figure 1B) values observed within the
5 seconds time periods of exercise (n=17)
(#- significant differece between DO and ND side p<0.05)
10 | Rannama et al: BILATERAL BIOMEHANICAL ASYMMERRY ...
Figure 2. Dynamics of average (+/-SD) DO and ND leg sEMG firing rate values
observed as median frequencie of 5 seconds time periods for Rectus femoris (RF)
(Figure 2A), Vastus Lateralis (VL) (Figure 2B) and Biceps femoris long head (BF)
(Figure 2C) muscles (n=17; n=9 for BF)
(#- significant differece between DO and ND side p<0.05)
There does exist also some significant differences between DO and ND leg
for RF MFr in middle and for VL MFr in end part ot the exercise. No
significant bilateral differences were found between normalized EMG
amplitude values of any muscle at any stage of exercise.
Figure 3. Dynamics of average (+/-SD) DO and ND leg normalized sEMG
amplitude values observed within 5 seconds time periods for Rectus femoris (RF)
(Figure 3A), Vastus Lateralis (VL) (Figure 3B) and Biceps femoris long head (BF)
(Figure 3C) muscles (n=17; n=9 for BF)
(#- significant differece between DO and ND side p<0.05)
The AI(%) value of POW was higher (7.7 ±8.4%) at initial part of
exercise and after 5 seconds lowered significantly (to the level between
1.9±4.1 and 3.2± 6.3%), PS AI(%) had also significantly higher values in
first 10 than in last 10 seconds of effort (Figure 4A). The EMG AI(%)
LASE JOURNAL OF SPORT SCIENCE 2015/6/2 | 11
variables (Figure 4 B andC) have opposite directions in firing rate and
amplitude patterns and amount of AI(%) of RF and BF do have the trend to
decrease, but VL AI(%) has the trend to increase in the final stage of
exercise.
The comparison between initial 5 and last 5 seconds values shows
that pedalling kinetics (POW, PS) and EMG frequency decrease
significantly during the test. For EMG amplitude there was only significant
difference between DO BF start and end part values. But there does exist
significant differences between second stage (5-10 sec) and final stage DO
and ND BF normalized RMS EMG and between third stage (10-15 sec) and
final stage DO and ND VL normalized RMS EMG values.
Figure 4. Dynamics of average AI(%) of pedalling kinetic (Figure 4A), normalized
sEMG RMS amplitude (Figure 4B) and sEMG MFr (Figure 4C) values observed
within the 5 seconds time periods of exercise (n=17)
(1-significantely different from 1-st time period; 2 - from 2-nd period; 3 - from 3-nd period; 4 - from 4-th period; 5
- from 5-th period, p<0.05) Table 2
Correlations between computed 30 seconds average AI (%) values of pedalling
kinetics and muscle activity variables
AI (%) of
kinetics
PS
Pow
.533*
AI (%) of
EMG RMS
RF
0.07
0.02
VL
0.38
.626**
0.21
BF
0.24
0.27
0.41
0.22
AI (%) EMG
MFr
RF
-0.08
-0.24
-0.30
-0.47
-.749*
VL
-.639**
-0.16
-0.23
-0.30
0.07
-0.02
BF
0.09
0.44
.845**
0.47
0.47
-0.30
0.00
* Correlation is significant at the p<0.05 level (2-tailed).
** Correlation is significant at the p<0.01 level (2-tailed)
12 | Rannama et al: BILATERAL BIOMEHANICAL ASYMMERRY ...
Table 3
Correlations between computed 30 seconds average AI (%) values of pedalling
kinetics and muscle activity variables
AI (%) of Pedalling Smoothness
AI(%) of Power
0-5s
5-10s
10-15s
15-20s
20-25s
25-30s
0-5s
5-10s
10-15s
15-20s
20-25s
25-30s
AI (%) of
Power
.374
.203
.558*
.594*
.571*
.417
1
1
1
1
1
1
AI
(%) of
EMG
RMS
RF
-.194
-.209
.169
.075
.269
.519*
-.222
.266
.116
.284
-.008
.192
VL
.412
.165
.324
.532*
.420
.340
.197
.589*
.674**
.652**
.605*
.607**
BF
.305
.238
-.021
-.062
.266
.398
-.188
.273
.472
.350
.335
.353
AI
(%) of
EMG
MFr
RF
-.025
-.013
.234
-.072
-.112
-.352
-.046
-.287
-.125
-.099
-.180
-.080
VL
-.459
-.285
-.633**
-.746**
-.504*
-.375
.367
-.192
-.259
-.212
-.284
-.117
BF
.112
.136
.297
.233
-.183
-.112
.088
.627
.545
.542
.097
.295
* Correlation is significant at the p<0.05 level (2-tailed).
** Correlation is significant at the p<0.01 level (2-tailed)
The correlation analyse results are presented in Tables 2 and 3. Significant
correlations were found between AI (%)-s of PS and VL EMG MFr and
between AI (%)-s of POW and VL normalized EMG amplitude. If to look
correlations according to time periods, than stronger relations were found
during the middle part of exercise and no significant correlations were found
between initial stage values. Also the PS AI (%) and POW AI (%) values
are significantly correlated only in between 10 to 25 seconds of exercise.
Discussion
The one purpose of present study was to examine the bilateral
differences of pedalling kinetics and thigh muscle activity patterns
according to leg dominance during the 30 seconds maximal cycling
exercise. With accordance of previous studies, done mainly in aerobic
exercise conditions (Smak, Neptune & Hull, 1999; Carpes et al., 2007;
Carpes et al., 2008), our results suggest that exist also leg dominance driven
asymmetry in pedalling kinetic patterns during the maximal short term
cycling. During the maximal cycling DO limb produces higher power with
more equally over the pedalling cycle, which is in line with findings of
Smak, Neptune & Hull (1999), that dominant leg generate higher average
pedalling power with lower average positive and negative power production
than ND limb.
Higher between legs bilateral differences were found during initial 5
seconds power and first 10 seconds pedalling smoothness values. After that
power asymmetry dropped significantly and stayed almost in same level till
the end of exercise. PS asymmetry and also pedal smoothness of DO and
LASE JOURNAL OF SPORT SCIENCE 2015/6/2 | 13
ND side lowered gradually and significantly and had lowest values in final 5
seconds. It seems that asymmetry of pedalling power production during
short duration maximal exercise is more sensitive to fatigue like long time
trial performance (Carpes et al., 2007), but not to the high power because
asymmetry of power production was larger in acceleration part at start of
exercise, when the power was higher.
Previous studies about comparison of DO and ND legs normalized
sEMG amplitude values did not found any dominance related differences in
incremental or single leg constant load intensity cycling (Carpes et al., 2010;
Carpes et al., 2011). The results of present experiment showed that there
were no significant dominance related differences between DO and ND side
normalized EMG RMS values of RF, VL, BF muscles at any time period of
exercise.
To the best of our knowledge no previous studies have done to
compare sEMG firing rate patterns between DO and ND thight muscles
during cycling exercise. Our data indicated that there exist some significant
bilateral leg dominance driven differences in BF MFr values during the
initial 20 seconds of exercise and those differences expiring in the end part
of exercise. Also were found bilateral differences in some time stages of VL
and RF MFr values. It is known that motor units firing frequency
modulation become predominant over motor units recruitment mechanism
when moderate or high force level is required (Moritani & Yoshitake 1998)
and that sEMG firing rate is more sensitive to fatigue than firing amplitude
during short term anaerobic exertion (Greer et al., 2006; Hunter et al.,
2003). From that view the future investigation of asymmetrical EMG
frequency patterns may have important role for understanding neurological
mechanisms of pedalling asymmetry.
The pedalling kinetics asymmetry was significantly correlated with
asymmetry of VL EMG patterns. Larger DO side PS were associated with
higher VL MFr values in ND side and higher DO side asymmetry in POW
values was related with same direction asymmetry in VL normalized RMS
amplitude. The relationship of VL muscle activity regarding to cycling
intensity is well known (Moritani & Yoshitake 1998; Berice et al., 2009)
and our findings suggest that between-legs differences in VL EMG
amplitude and firing rate may play significant role in directional asymmetry
of pedalling kinetics. For better understanding of mechanisms behind
cycling asymmetry in future research in the analysis should be incorporated
also pedalling kinematic and cyclist’s musculoskeletal state values.
14 | Rannama et al: BILATERAL BIOMEHANICAL ASYMMERRY ...
Conclusions
Results of the present study indicate that during 30 seconds maximal
intensity cycling do exist leg dominance dependent asymmetries in
pedalling power patterns, which decreased during the exercise and were
related to bilaterally asymmetry of vastus lateralis muscle firing patterns.
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... They show different systematic changes depending on the speed of pedaling [8]. On the other hand, the increase in torque applied to the crank and the increase in the exercise intensity cause a decrease in the asymmetry of pedaling [6,13]. Another study shows that asymmetry in peak torque increases at higher load power and this is due to the dominant leg [14]. ...
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