Monday-Wednesday-Friday x2 weeks. Incremental exercise tessng. Session 2. (PRE Int). HDEMG and. Force measurements. Session 9. (POST Int). Incremental.
Monitoring changes in motor unit behavior following short-term high intensity interval training with highdensity surface electromyography motor unit tracking Eduardo Mar)nez-Valdes , Deborah Falla , Francesco Negro , Frank Mayer , Dario Farina 1
2
3
3
1. Department of Sports Medicine and Sports Orthopaedics, University of Potsdam, Potsdam, Germany. 2. School of Sport, Exercise and RehabilitaGon Sciences, University of Birmingham, Birmingham, United Kingdom. 3. InsGtute of NeurorehabilitaGon Systems, Bernstein Focus Neurotechnology GöOngen (BFNT), Bernstein Centre for ComputaGonal Neuroscience (BCCN), University Medical Center GöOngen, Georg-August University, GöOngen, Germany.
1
IntroducGon
Methods
Results
Discussion
• Physical InacGvity is a major cause of morbidity and mortality (Garber 2011)
• PrevenGon and treatment -> Endurance exercise (150 min/week) • “Lack of Gme” -> main reason for low compliance (Brownson 2011) • Studies decreased exercise volume and increased the intensity • High intensity interval training (HIIT) -> Brief, intermi^ent bursts of vigorous physical acGvity, interspersed by periods of rest or lowintensity exercise (Gibala 2012) • Similar or superior physiological changes a_er HIIT, compared to endurance training (Gibala 2012) • No studies inves,ga,ng changes in neuromuscular func,on
IntroducGon
Methods
Results
Discussion
• InvesGgaGon of the behavior and properGes of motor units provide a unique insight into the neural code underlying movements (Farina 2016) • Motor unit adaptaGons have shown to be highly specific according to the training regime (Vila-Cha 2010)
Vila-Cha et al. JAP 2010
• We aimed to invesGgate changes in motor output and motor unit central and peripheral properGes a_er a two-week HIIT intervenGon, using a novel motor unit tracking technique based on high-density surface EMG decomposiGon.
IntroducGon
Methods
Results
Discussion
• Six men (29±3yr, 178±7cm, 80±7kg) -> peak power = 352.3±55.4 W • Six sessions of HIIT (Li:le 2010) Ø Session 1-2 -> 8 bouts at 100% peak power Ø Session 3-4 -> 10 bouts 100% peak power Ø Session 5-6 -> 12 bouts 100% peak power
Thursday
Friday
HDEMG and Force measurements Session 1 (PRE Int)
Incremental exercise tesGng Session 2 (PRE Int)
24 hours
Monday-Wednesday-Friday x2 weeks
Monday
6 sessions of HIIT Sessions 3,4,5,6,7 and 8
HDEMG and Force measurements Session 9 (POST Int)
Next week
Next week
Tuesday Incremental exercise tesGng Session 10 (POST Int)
24 hours
IntroducGon
Methods
Results
PRE intervenGon
A)
Discussion
POST intervenGon MU 1 PRE + MU 1 POST
MU 1 PRE
70% MVC
3
3
2
2
1
1 4
6
8
10 12 14
16 18
2
20 22
4
6
8
Time [s]
B)
10
12
14
16
18
20
Cross CorrelaGon = 86%
Time [s]
PRE IntervenGon VM discharge rate
POST IntervenGon VM discharge rate 70% MVC
smoothed discharge rate (pps)
26
force
70% MVC
24 22 20
19.0 ± 1.7 pps
18
MU 3 MU 2
16 14 12
MU 1 2
4
6
time (s)
8
10
smoothed discharge rate (pps)
2
MU 1 POST
70% MVC
force
force
26
MU 3
24
MU 2 MU 1
22.0 ± 2.1 pps
22 20 18 16 14 12
1
2
3
4
5
time (s)
6
7
8
9
IntroducGon Increased Reliability
Methods
Results
Discussion
Tracked motor units provide…. Matched MUs
Vastus Medialis
Unmatched MUs Vastus Lateralis
Vastus Medialis
Vastus Lateralis
ICC
SEM
ICC
SEM
ICC
SEM
ICC
SEM
Recruitment Threshold (Nm)
.92
5.1
.92
4.5
.75
5.8
.63
7.0
Mean discharge rate (Hz)
.77
0.75
.87
0.63
.56
1.1
.61
1.0
Conduc,on Velocity (m/s)
.84
0.18
.88
0.12
.66
0.21
.56
0.22
Increased SensiGvity Conduction velocity 30% MVC VM unmatched
5.1 5.0 4.9 4.8 4.7 4.6 4.5 4.4 4.3 4.2 4.1 4.0 3.9
m/s
m/s
Conduction Velocity 30% MVC VM matched
Cohen's d: 1.864 p: 0.0026 PRE
POST
5.1 5.0 4.9 4.8 4.7 4.6 4.5 4.4 4.3 4.2 4.1 4.0 3.9
Cohen's d: 0.917 p: 0.0514 PRE
POST
Vastus medialis (VM) motor unit conducGon velocity results before (PRE) and a_er (POST) an endurance training IntervenGon with tracked motor units (le_) and unmatched motor unit populaGon samples (right) MarGnez-Valdes & Negro et al. 2016. In revision
IntroducGon
Methods
Results
Discussion
Cardiorespiratory Fitness Peak Power Output
VO2peak 60
*
55
400 W
ml/kg/min
50 45 40
350 300
35 30
*
450
P=0.0058
POST
PRE
P=0.0033
250
POST
PRE
Motor Output
Nm
300
*
2500
300
250 200
2000
250 200 150 100
150 100
50 P=0.0205
0
RFD
C)
350
Time (s)
350
Time to task failure (30% MVC)
B)
Peak torque
Nm·S-1
A)
1500 1000
P=0.0705
P=0.6387
500
POST PRE POST PRE POST PRE Individual values of changes in motor performance across the 2-wk training intervenGon. A: peak torque assessed during isometric maximal voluntary contracGons (MVC). B: Gme to task failure assessed during isometric contracGons at 30% MVC. C: rate of force development (RFD) during maximal explosive contracGons. Bars represent the mean of each group. *P
