Reliability and External Validity of Tensiomyography Measurements

Following Strength Exercise

Rauno Álvaro de Paula Simola

, Christian Raeder

, Michael Kellmann

2,3

, Tim Meyer

Mark Pfeiffer

and Alexander Ferrauti

Department of Training and Exercise Science, Faculty of Sports Science, Ruhr-University Bochum, Bochum, Germany

Department of Sport Psychology, Faculty of Sports Science, Ruhr-University Bochum, Bochum, Germany

School of Human Movement Studies and School of Psychology, The University of Queensland, Brisbane, Australia

Institute of Sports and Preventive Medicine, Saarland University, Saarbruecken, Germany

Institute of Sports Science, Johannes-Gutenberg University, Mainz, Germany

Keywords: Tensiomyography, Reliability, Validity, Strength Exercise.

Abstract: Tensiomyography (TMG) reliability and external validity using maximal voluntary isometric contraction

(MVIC) following different strength training protocols (STP) were analysed. Twenty healthy male were

tested two times over one week and TMG reliability was analysed in the muscles Rectus Femoris (RF),

Biceps Femoris (BF), and Gastrocnemius Lateralis (GL), after an individual maximal and submaximal

electrical stimulation. Moreover, TMG external validity was assessed through Pearson correlation between

changes in TMG muscle mechanical properties in RF and changes in MVIC in squat exercise after five

different lower-limb STPs. Maximal electrical stimulation showed the highest ICC scores for TMG muscle

properties reliability in all muscles investigated. Significant Pearson correlation coefficients were found

between changes in TMG mechanical properties and changes in MVIC after STPs characterized by high

intensity, time under tension and eccentric overload. TMG is a valid and reliable method to assess muscle

mechanical properties especially under maximal condition.

1 INTRODUCTION

Different methods and techniques have been used to

assess neuromuscular function, such as torque

recordings during voluntary or evoked contractions,

mechanical power, surface electromyography,

magnetic resonance imaging and ultrasound (Tous-

Fajardo et al., 2010). In this context, a novel

technique, tensiomyography (TMG), may have an

additional advantage. TMG measures can be carried

out quickly, are not producing additional fatigue and

do not depend on voluntary motivation. It allows a

non-invasive muscular function analysis, through the

assessment of different specific muscle mechanical

properties (Dahmane et al., 2001; García-Manso et

al., 2012). Although the reliability of TMG was

already reported (Rey et al., 2012), it is still unclear

its reliability from submaximal electrical stimuli.

Despite many existing techniques to evaluate

neuromuscular function, muscle force has been

considered the best indicator of the ability of the

muscle to perform (Jackman et al., 2010). Effective

strength training programs can be performed with

different ranges of load intensity, repetition number

and rest period between sets, type of muscle action

and time under tension (Kraemer and Ratamess,

2004). As far as we know, no study has correlated

the acute strength performance changes with

changes in TMG muscle properties after the

execution of different strength training protocols

used in the applied field.

Therefore, the purpose of the present study was to

analyse the TMG reliability and external validity

using maximal voluntary isometric contraction

(MVIC). The reliability values were investigated

within maximal and submaximal electrical stimuli.

Changes in MVIC were assessed after five different

lower-body strength training protocols. We

hypothesized that TMG is a reliable method to

assess muscular function within submaximal and

maximal electrical stimuli and that changes in TMG

muscle mechanical properties correlate with changes

in MVIC values after different strength training

protocols.

174

Simola, R., Raeder, C., Kellmann, M., Meyer, T., Pfeiffer, M. and Ferrauti, A..

Reliability and External Validity of Tensiomyography Measurements Following Strength Exercise.

In Proceedings of the 3rd International Congress on Sport Sciences Research and Technology Support (icSPORTS 2015), pages 174-178

ISBN: 978-989-758-159-5

2 METHODS

2.1 Experimental Design

The current study was organized in two different

parts. In the first part of the study, it was analysed

the reliability of the TMG mechanical properties.

Twenty healthy male (age: 26.5 ± 6.7 years; body

mass: 78.5 ± 6.8 kg; height: 181.0 ± 5.5 cm) were

tested two times over one week period. Muscles

analysed were rectus femoris (RF), biceps femoris

(BF) and gastrocnemius lateralis (GL) left and right

sides, after an individual maximal and a submaximal

electrical stimulation (40 mA). Absolute reliability

was assessed by the standard error of measurement

(SEM) whereas the relative reliability by the

intraclass correlation coefficient (ICC).

In the second part of the study, external validity

of the most appropriate TMG mechanical properties

verified in the first part of the current study from left

and right muscle rectus femoris (RF) were assessed

after the execution of five different lower-body

strength training protocols in a randomized cross-over

design with multiple repeated measures. Fourteen

healthy male (age: 23.0 ± 1.9 years; body mass: 76.6

± 7.8 kg; height: 179.4 ± 6.8 cm), experienced in

strength training participated in this part of the study.

All participants attended a familiarization session to

introduce the testing and training procedures to

minimize any learning effect. Average baseline

values were collected on two occasions interspaced

by one week including measures of body

composition, TMG mechanical properties, one

repetition maximum (1RM), and maximal voluntary

isometric contraction (MVIC) for the parallel squat.

The five different squat training protocols were

randomly assigned for each participant and

performed once per week, separated by six days in

between, within 1.5 - 2 hours at the same time of the

day throughout the study. It was told to the subjects

not to exercise at the day before training, and to

consume their last meal (caffeine-free) at least 2

hours before training and testing. TMG followed by

MVIC measurements were conducted up to 0.5 hours

after the end of each training protocol (post-train).

Subjects were informed about all details of the

experimental procedures and the associated risks

and discomforts. All participants gave their written

consent to participate in the study and were free to

withdraw from the study at any time. The

experimental protocol followed the world medical

association’s declaration of Helsinki on research with

humans and was approved by the local Ethics

Committee of the Ruhr-University Bochum.

2.2 Training Protocols

Multiple Sets (MS): A smith rack machine with a

guided barbell was used for training (TechnoGym

Multipower, Italy). The protocol consisted of 4 sets

of 6RM (i.e., 85% 1RM) parallel squats (knees are

flexed until the inguinal fold is in a straight

horizontal line with the top of the knee

musculature), intended explosive during the concen-

tric phase and 2 seconds in eccentric phase,

approximately 72 seconds of time under tension

(TUT), and 3 minutes rest between sets (Drinkwater

et al., 2005). A laser imager and an acoustic stimulus

were used to standardize the range of motion (ROM)

of approximately 110-120°.

Drop Sets (DS): Subjects performed DS with the

same barbell machine and ROM as described for

MS. 1 set of 6RM (i.e., 85% 1RM), 4 seconds in

eccentric and 2 seconds in concentric phase

respectively, and approximately 130-150 seconds

TUT was conducted (Skurvydas et al., 2010).

Immediately after the first set, the load was reduced

for the next three sets (70%, 55% and 40% 1RM,

respectively), so that the subjects continued to train

until concentric failure for each load, which was

defined as the point when the muscles involved can

no longer produce force enough to sustain the given

load (Yarrow et al., 2007).

Eccentric Overload (EO): This protocol

combined concentric with enhanced eccentric

muscle actions (Yarrow et al., 2007) with the same

barbell machine and ROM as the two protocols

described before. 4 sets of 6 repetitions at a load of

70% concentric and 100% eccentric of their

individual 1RM, 3 minutes rest between sets, were

performed during approximately 4 seconds each

repetition (i.e., 2 seconds eccentric, 1 second

isometric, and intended explosive in concentric

phase), and approximately 96 seconds TUT. Two

helpers organized the weight changes during the

upright and lower position.

Flywheel (FW): A YoYo squat flywheel machine

was used for training (YoYo Technology, Stockholm,

Sweden). Subjects performed 4 sets of 6 maximal

rep- etitions, approximately 96 seconds TUT, 3

minutes rest between sets. Besides 6 intended

maximal repetitions, 2 previous repetitions were

selected for initial movement acceleration. The squat

movement was executed with a ROM of about 95-

105°, starting the concentric action at approximately

60-70° until about 165° of internal knee angle,

carefully controlled by an experienced supervisor

(Norrbrand, 2010). Subjects were asked to perform

each repetition with a maximum effort, accelerating

Reliability and External Validity of Tensiomyography Measurements Following Strength Exercise

175

the wheel in the concentric action and upon

completion, decelerating the wheel by means of an

eccentric action.

Plyometrics (PL): Subjects performed 4 sets of

15 drop jumps from a 60 cm-jump box, with 5

seconds rest between repetitions, and 3 minutes rest

between sets (de Villarreal et al., 2009). The study

participants were asked to land until the knees are

flexed of about 90° followed by a simultaneous

explosive knee extension and arms swing for

maximum vertical jump height.

2.3 Measurements

Tensiomyography (TMG): TMG measurements were

conducted using a specific electrical stimulator

(TMG-S2), the TMG-OK 3.0 software, as well as a

displacement sensor tip with a prefixed tension of

0.17 N m-1, which was positioned perpendicular to

the selected muscle belly (TMG-BMC, Ljubljana,

Slovenia). Mechanical properties under submaximal

(40 mA) and individual maximal conditions were

obtained after a single 1 ms electrical stimuli.

Maximal electrical stimulation and maximal muscle

belly displacement were found by progressively

increasing the electric current by 20 mA for each

stimuli. An average from two consecutive stimuli

from both legs was taken and a rest period of 10 s

was interspersed between the measurements. The

measuring point for each muscle was carefully

determined as a point of maximal muscle belly

displacement during voluntary contraction. The

measurements were performed in the lower limbs in

a supine position and a knee joint angle of 120°

was kept by using supporting pads. The electrodes

(5 x 5 cm) were placed five cm distally and five

cm proximally to the sensor. The positions of

electrodes and sensor were marked and kept

constant during the complete experimental period.

All the measurement procedures were accomplished

according Rey et al. (2012). Maximal radial muscle

displacement (Dm), time contraction (Tc),

determined from 10% to 90% Dm, delay time (Td),

determined from onset of electrical stimulus to 10%

Dm, sustain time (Ts), determined as time between

50% Dm during muscle contraction and relaxation,

relaxation time (Tr), determined from time of fall

from 90% to 50% Dm, mean contraction velocity

until 10% Dm (V

) and mean contraction velocity

until 90% Dm (V

) were analysed.

One Repetition Maximum (1RM): The

hypothetical one repetition maximum (1RM) for

each participant in a smith rack machine

(TechnoGym Multipower, Italy) was assessed by the

formula proposed by Brzycki (1993). Subjects were

instructed to position into a shoulder bride stand and

the barbell was placed on the trapezius muscle and

posterior deltoid muscle. In the parallel squat, the

knees are flexed until the inguinal fold is in a straight

horizontal line with the top of the knee musculature.

A laser imager and an acoustic stimulus served to

standardize the ROM of approximately 105-110°.

Subjects started with two warm-up sets consisting of

five repetitions with an intensity of 50% of the

individual body weight with two minutes pause.

After that, a work set including five repetitions with

an intensity of 80 to 85% of the individual body

weight was performed. Finally, after five minutes,

the test supervisor asked to increase the weight for

estimating the 1RM. The test was stopped when

subjects were unable to raise the barbell with a

proper technique or without the help of the

supervisor. If subjects exceeded the limit of ten

repetitions, the supervisor stopped the test and the

intensity was increased. The test ended when

subjects achieved five to ten maximum repetitions

and the 1RM was estimated in kg.

Maximal Voluntary Isometric Contraction

(MVIC): MVIC was measured in a half squat

isometric exercise using a Multitrainer 7812-000

(Kettler Profiline, Germany) and analogous user

software (DigiMax Version 7.X). The subjects were

directed to position under the shoulder upholstery

into a shoulder bride stand. Subsequently the subject

was set up into a testing position up to a knee-joint

angle of 90° using a custom made goniometer.

Without moving explosively, but low rate of force

development they were asked to produce a maximal

voluntary isometric contraction over a 3 second time

interval, as recommended by Blazevich et al. (2002).

All subjects performed two MVICs with 2 min rest in

between and the mean of both attempts was

recorded.

2.4 Statistical Analyses

Data are presented as the mean ± standard deviation

(SD). These data were analysed using the Statistical

Package for the Social Sciences 18.0 Software

(SPSS Inc., USA). The Kolmogorov-Smirnov test

was used to check the normality of the data

distribution. In the first part of the study, absolute

reliability was assessed by the standard error of

measurement (SEM) whereas the relative reliability

by the intraclass correlation coefficient (ICC). After

the calculation of the changes in TMG parameters

and MVIC from each protocol from baseline to post-

train, Pearson correlation coefficient between those

icSPORTS 2015 - International Congress on Sport Sciences Research and Technology Support

176

Table 1: Intraclass correlation coefficient (ICC) and standard error of measure (SEM) for TMG parameters under

maximal stimulation for the muscles RF, BF and GL (* p

0.01).

(ms)

(mm)

(ms)

(mm.s

-1

)

(mm.s

-1

)

ICC

0.91*-0.94* 0.87*-0.92*

0.70*-0.93* 0.92*-0.95* 0.85*-0.88* 0.92*-0.94*

0.92*-0.95*

SEM

1.9-6.8

0.8-1.3

8.1-26.9

0.9-1.0

13.3-29.0

3.2-4.0

10.1-17.9

Table 2: Pearson correlation coefficients for changes from baseline to post-train, between Dm, V

, V

, and MVIC (*

p < 0.05; **p < 0.01).

EO FW PL

0.21 0.61* 0.72** 0.17 0.14

0.25 0.62* 0.76** 0.18 0.04

0.25 0.63* 0.66** 0.08 -0.04

changes was used to establish TMG external validity.

Moreover, it was established at baseline the

correlation between TMG parameters. Statistical

significance was set at p < 0.05.

3 RESULTS

Maximal electrical stimulation showed the highest

ICC significant values for TMG reliability in all the

muscles investigated (Table 1). Regarding

submaximal condition, not all TMG muscle

properties exhibited sufficient reliability. Tc, Td,

Dm, V

, and V

showed significant ICC scores

(0.66-0.92; 0.65-0.92; 0.81-0.96; 0.85-0.94; 0.85-0.93)

in the different muscles respec

tively.

It was found a high significant Pearson

correlation (r > 0.9; p < 0.001) between TMG

muscle properties Dm, V

, and V

. Pearson

correlation coefficients from each protocol between

MVIC changes and respective changes of Dm, V

and V

, are presented in Table 2.

4 DISCUSSION

Maximal electrical stimulation has demonstrated

higher reliability in comparison with submaximal

condition. In some muscles, under submaximal

stimuli, Tr and Ts have not been repeatable. As the

higher reliability scores were found after maximal

stimulation and not all TMG muscle properties were

repeatable, in the second part of the study, maximal

stimuli and muscle properties Dm, V

, and V

were used.

Dm has been considered as a measure of muscle

belly radial stiffness, and an increasing in such

variable indicates smaller muscle belly radial stiffness,

whereas its decreasing means greater muscle belly

radial stiffness (García-Manso et al., 2012; Hunter et

al., 2012; Rey et al., 2012). However, because of a

high positive Pearson correlation coefficients found

between the TMG muscle properties Dm, V

, and

(r > 0.90; p < 0.001), Dm might also indicate

the capacity to perform fast muscle contractions,

under the conditions of the present study.

It was observed a significant correlation between

changes in Dm, muscle contraction velocities, and

changes in MVIC after the execution of DS and EO (r

range between 0.61 and 0.76). These results are in

accordance with Hunter al. (2012), which

demonstrated a positive correlation between changes

in strength performance and changes in TMG

muscle properties after eccentric muscle actions. The

association between changes in TMG muscle

properties and changes in MVIC might be explained

by some specific characteristics of DS and EO,

possibly related to fatigue. The number of

repetitions at a high workload performed in DS led

to the highest TUT, compared to the other protocols.

Moreover, it has been shown greater fatigue levels

after drop-set strength protocols (Willardson, 2007),

as additional higher threshold motor units are

recruited and subsequently fatigued. Regarding EO,

because of a greater eccentric muscle acti

vation and

higher exercise-induced muscle damage (Norrbrand,

2010; Schoenfeld,

2012), this protocol may have a

special effect on fatigue. Eccentric muscle actions

have been shown to produce a greater amount of

force than isometric or concentric actions despite a

decreased motor units recruitment (Tesch et al.,

2004). The result is a higher tension produced per

cross-bridge and progressive sarcomere over-

stretching, predisposing to destruction of contractile

proteins and damage in cellular structures (Proske

Reliability and External Validity of Tensiomyography Measurements Following Strength Exercise

177

and Allen, 2005; Tesch et al., 2004).

TMG is a valid and reliable method to assess

muscle mechanical properties especially under

maximal conditions. Based on our results, we advise

researches that analyse the relationship between

TMG muscle properties and muscle fatigue after the

execution of strength training exercises.

ACKNOWLEDGEMENTS

The present study was initiated and funded by the

German Federal Institute of Sport Science. Rauno

Simola gratefully acknowledges CAPES for finan-

cial support. The authors disclose no conflicts of

interest.

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