Muscle Activation of the Lower Limb in Healthy Subjects in Response to a Medio-lateral Imbalance in Monopodal Stance: a Preliminary Study
Phase: NA
Conditions: Healthy
Sponsor: Manusapiens

 
 
Muscle activation of the lower limb 
in response to a mid-lateral imbalance 
in monopodal stance: 
a preliminary experimental study 
 
 
 
7-7-2020 
 
Approved by Comitato Etico di Area Vasta Nord RER 
protocol n° 2020/0110000 of 09-24-2020 
(translated version) 
 
 
 
 

A. Title of the study (translated) 
Muscle activation of the lower limb in response to a mid-lateral imbalance in monopodal stance: a 
preliminary experimental study 
Identification code: SM01 
Unique Protocol ID: 957/2020/SPER/AUSLRE 
Version: 03 of 7-7-2020 
Approved by Comitato Etico di Area Vasta Nord RER, protocol n° 2020/0110000 of 09-24-2020. 
 
B. Promoter and participants 
1) Promoter: Manusapiens, a non-profit technical-scientific association with the aim of promoting research 
and dissemination of manual and functional therapy. 
2) Principal Investigator (PI): Corrado Borghi, Biomedical engineer (PhD) and physiotherapist (Unimore 
adjunct professor) 
3) Responsible Investigator: Corrado Borghi, Biomedical engineer (PhD) and physiotherapist (Unimore 
adjunct professor) 
 
C. Index 
A. Title of the study  
B. Promoter and participants  
C. Index  
D. Background  
E. The Study 
F. Study design 
G. Population  
H. Outcome measures  
I. Measurement methods  
J. Duration of the study  
K. Statistical aspects 
L. Data management (privacy) 
M. Authorization aspects 
N. Responsibility and publication policy 
O. Insurance aspects 
P. Bibliography 

D. Background 
From a neurophysiological point of view, maintaining balance is a complex function, especially in the high 
instability of one-foot support (monopodalic support). It requires the integration of many systems for the 
collection of information (vestibular apparatus, proprioception, baroception, sight), for the processing of the 
information itself (carried out by the central nervous system - CNS, with particular contribution from the 
cerebellum), and for the activation and management of the responses to be given (through the muscles) 
(Horak, 1986; Winter, 1995; Adkin, 2000; Wang, 2014). 
The "static" monopodalic posture (i.e. in a position that is as still as possible), with the drastic reduction of 
the support base that it entails, undermines the balance maintenance system and generally requires 
significant muscle activation with consequent energy expenditure. 
For this reason, it is widely used to evaluate and train the balance itself. In the literature, it has been 
extensively analyzed for therapeutic exercise, functional assessment and sports training (Katayama, 2004; 
Chang, 2005; Granacher, 2011; Greenwood, 2011; Pfusterschmied, 2013; Brachman, 2017; Alfuth, 2017; 
Rahman, 2017). The goals are to test and/or increase balance, proprioception, strength and muscle 
endurance. A major issue concerns the prevention of falls in the elderly (Donath, 2016; Kurz, 2018; 
Granacher, 2011; Muehlbauer, 2015). 
Another aspect of interest linked to the analysis of monopodalic support is the study of the strategies for 
maintaining balance and stabilization of the joints (Kristensen, 2016; Wolburg, 2016; Mirzaie, 2019; Kurz, 
2018). 
Numerous studies in the literature have examined static monopodalic equilibrium, taking into account 
different experimental conditions and outcome measures. Usually, with regard to muscle activity, the 
average intensity of activation and response latency were measured (Greenwood, 2011; Dingenen, 2015; 
Donath, 2016; Wolburg, 2016; Alfuth, 2017; Rahman, 2017; Mirzaie , 2019; Kurz, 2018). A distinction has 
never been made, however, between activities related to medial and lateral imbalances respectively, if not 
at the level of the ankle (Morey-Klapsing, 2005). There is therefore no global approach, which involves at 
least the entire lower limb, and evaluates in detail the motor strategies used by the body to obtain balance. 
 
E. The Study 
Hypothesis and rationale. Colonna (2012) assumes, basing on the interpretative approach of myofascial 
chains, that the management of balance occurs through the anterior and posterior spiral chains. According 
to the myofascial chain approach, muscles are no longer considered independent, but connected in series 
via the connective tissue (muscle fascia, tendons, ligaments, ...). The concept of myofascial chains suggests 
that mechanical force can be transferred not only within a limb between synergistic or antagonistic muscles, 
but also between muscles arranged in series (Wilke, 2018). 
Colonna’s hypothesis, which has never been experimentally verified, is based on the intuitive search for the 
most effective system to respond to the perturbations that destabilize the equilibrium. The "cruciate" system 
that the spiral chains form in the lower limb appears to be the most appropriate response, as it is more 
stabilizing. 
This preliminary study is not intended to provide direct treatment indications. It is therefore not a study 
aimed at clinical practice. 
The aim is to carry out a preliminary study to test the reasonableness of the hypothesis that the spiral 
myofascial chains intervene in the monopodalic equilibrium, verifying the feasibility of the proposed method 
to analyze the response to a medial and lateral imbalance. 

The results of this study will be used to determine the opportunity for future investigations (with statistically 
significant number of subjects, assessment of muscle activation variations as a function of different 
pathologies, etc.) and the eventual definition of an optimal experimental setting and methodology. 
 
F. Study design. 
Setting: preliminary experimental 
Type: non-pharmacological 
Organization: monocentric 
Enrollment: consecutive 
Conduction: open 
 
G. Population 
The study aims to carry out a preliminary assessment of the feasibility and reasonableness of hypotheses. 
The sample to be examined must therefore be composed of healthy subjects, in order to limit the variables 
determined by possible pathologies that alter physiological behavior. The age of the subjects must allow a 
full maturity of the neuro-musculoskeletal system and precede its degeneration. As this is a preliminary 
study, a sample size to provide statistical significance is not sought. The sample must be functional to test 
the method and to verify whether the hypothesized motor strategy can be detected in the subjects 
considered. The recruitment can be achieved through the search for volunteers among the acquaintances of 
the experimenters. 
Number of subjects: 5 
Inclusion criteria: healthy adult subjects, aged between 18 and 65 years. 
Exclusion criteria: skeletal or neuromotor pathologies, past or current, which may compromise the 
maintenance of balance and / or modify the strategies in implementing it (in the opinion of the investigators). 
 
H. Outcome measures 
The core of the study consists in carrying out a measurement of activation of the muscles of the lower limb. 
In particular, it will be necessary to measure this activation as a response to an imbalance / perturbation in 
monopodal stance. 
Muscle activity will be evaluated for 1500ms, 500ms before and 1000ms after the disturbance. The early 
response to the stimulus will be identified in the interval of 100-500ms after the stimulus. 
The muscles considered will be, for the anterior spiral chain, the adductor longus and the peroneus longus, 
for the posterior spiral chain, the glutei (medium and large) and the tibialis anterior. Therefore, both muscles 
of the thigh (glutei and adductor longus) and of the leg (peroneus longus and tibialis anterior) will be 
examined. 
The goal is to understand which of these muscles are activated together, in particular if the muscles belonging 
to the same myofascial chain are activated together. The simultaneous activation will be measured with the 
calculation of the correlation coefficient. The hypothesis of spiral chains use for the balance will be 

considered reasonable if it is possible to observe greater correlation between the peroneus longus-adductor 
longus and between the glutei-tibialis anterior than the correlation between the glutei-peroneus longus and 
between the tibialis anterior- adductor longus. 
The outcome measures will therefore be: 
• Maximum intensities of early activation, normalized with respect to the electrical intensity measured in the 
maximal contraction, respectively in response to a stimulus that causes a medial and lateral imbalance; 
• Correlation coefficients between the electrical activities of: 
• 
adductor longus-peroneus longus 
• 
glutei-tibialis anterior 
• 
glutei-peroneus longus 
• 
adductor longus-anterior tibialis 
in response to a stimulus that causes medial imbalance; 
• Correlation coefficients between the electrical activities of: 
• 
adductor longus-peroneus longus 
• 
glutei-tibialis anterior 
• 
glutei-peroneus longus 
• 
adductor longus-anterior tibialis 
in response to a stimulus that causes lateral imbalance. 
 
I. Measurement methods 
Setting 
The subjects involved in the research will be analyzed at the LAMBDA laboratory (UDGEE), AUSL-IRCCS of 
Reggio Emilia. 
Tools 
The elective methodology for this type of investigation is the electromyographic analysis, which allows to 
highlight the timing of muscle activation and therefore the motor coordination that underlies the balance. 
Surface electromyography will be used, which is neither painful nor invasive. 
The detection system is able to acquire up to 16 channels with a sampling frequency of 1000Hz. Each channel 
corresponds to a device capable of pre-filtering and amplifying the signal, before transmitting it via wireless 
to the PC dedicated to the acquisition of the signal itself. Each of these devices is placed on a muscle. The 
connection with the skin takes place via two adhesive electrodes in Ag-AgCl, equipped with conductive gel 
(they are the same used for the electrocardiogram). The electrodes measure a potential difference, recording 
the surface current generated by muscle contraction (as does the ECG for the heart). 
During the measurement, other parameters are monitored by: 
• force platforms: two AMTI® platforms capable of detecting the center of pressure (COP), the direction and 
the intensity of the resultant of the forces applied on them with a frequency of 1000Hz; 
• optoelectronic system: Vicon® system (Oxford Metrics Group, UK) with 7 infrared cameras capable of 
detecting the position in space of reflective markers with an accuracy of 1mm (for the identification of the 
3D position of a marker it is necessary that it is visible for at least two cameras at the same time; each camera 

is equipped with a crown of infrared LEDs to increase the visibility of the markers without disturbing the 
acquired subjects; the sampling frequency is 100Hz, sufficient to accurately detect the body kinematics; 
• video cameras: two video cameras with perpendicular axes that acquire at 100Hz and allow you to 
immediately provide an overview. 
Thanks to these systems it is possible to monitor the movement of the COP with respect to the foot in support 
(it allows to visualize the medial and lateral imbalance), and to evaluate the loads and movements of the 
various body segments (the motor strategies for maintaining balance are displayed). 
Measurement protocol 
The analysis will be carried out on the right lower limb of each subject. 
The electromyographic devices will be applied to the tibialis anterior, peroneus longus, gluteus medius, 
gluteus maximus and adductor longus. 
The reflective markers will then be applied (using double-sided tape) according to the Total3DGait protocol, 
which identifies the body segments of the forearms, arms, trunk, pelvis, thighs, legs, and feet. 
The subject must position himself with his right foot on a force platform. 
The toe of the left foot will be allowed to rest on the ground (on the other power platform placed at the 
rear), with the verbal indication to load as little weight as possible on it: this indication is aimed at reducing 
muscle activation in the absence of external perturbations, in order to highlight only the activity caused by 
the perturbations themselves. Only acquisitions in which the load on the left foot will be less than 30% of the 
weight will be considered valid. 
The hands will be placed on the hips to limit the variables to be controlled and to standardize the posture, in 
order to focus the contribution to the balance of the lower limb. The left thigh has to be kept vertical. Finally, 
it will be required to find, within the constraints described above, the posture that is as comfortable as 
possible, with minimal muscle contraction. The distance between the feet is therefore freely chosen by each 
subject. 
The operator positions himself behind the subject to be examined, and without being seen performs lateral 
thrusts with the medial margin of the hand at the proximal third of the thigh. At least ten pushes per side will 
be performed, with random timing. The thrusts will be quick but without causing pain. 
The operator will then request maximal contractions from the subject, in order to normalize the electrical 
activity of each muscle with respect to its maximum. It will be required to perform the dorsiflexion and 
pronation of the foot against resistance, then the adduction, abduction and extension of the hip. 
The whole procedure takes about an hour. 
Data processing 
Electromyographic signals are processed in the following way: 
• high pass filter: to eliminate any disturbances (movement artifacts) and keep only the high frequency signal 
typical of muscle activity; 
• rectification: the signal, which is an oscillation around zero, is taken only as an absolute value; 
• envelope: application of the Root Mean Square on a span of 200ms (before and after) and moving average, 
to quantify the extent of muscle activation; 

• normalization: muscle activation is normalized with respect to the maximum contraction value; it is 
therefore expressed as a percentage of this value; 
• median: for each muscle of each subject the median of the different response activations is calculated; the 
median, once a series of values has been placed in ascending order, is constituted by the central value; 
compared to the average, it allows to reduce the influence on the final value of the most anomalous cases 
compared to the majority; 
• correlation coefficient: calculation of the correlation coefficient to verify any synergies present between 
the different muscle groups. 
 
J. Duration of the study 
Total expected duration: 6 months 
Enrollment: 1 month 
Measurements: 2 months 
Data processing: 3 months 
 
K. Statistical aspects 
As this is a preliminary study, a sample size such as to provide statistical significance is not sought. The sample 
must be functional to test the method and to verify if in the subjects considered it is possible to detect an 
(indicative) trend that is consistent with the hypothesized motor strategy. For this reason, the number of 5 
subjects was considered suitable and no parameters to be considered statistically significant will be 
calculated. 
 
L. Data management (privacy) 
Acquisition data are automatically stored on the laboratory's dedicated PC. 
The data of each subject are recorded with an identification number, without reference to personal data of 
the subject. 
Access to the PC is password protected, and the PC is not connected to the internet. 
Data processing is carried out directly on the PC itself, so no data transfers must take place. 
The CRF forms for data collection will be in paper format. 
 
M. Authorization aspects 
It is believed that the study does not present critical issues from an ethical point of view, as measurements 
are carried out with methods used in ordinary clinical activity and which are non-invasive, non-dangerous, 
short-term and on healthy subjects. 
The consent to the study will be signed before the measurements are taken, after a detailed explanation 
provided to each subject regarding the measurements themselves and the method of analysis. 

No financial agreements are envisaged. The study is carried out as a consensual agreement between all the 
parties involved. 
The AUSL-IRCCS di Reggio Emilia will process the personal data of the subjects participating in the trial as 
independent Data Controller, pursuant to and for the purposes of the European legislation referred to in 
GDPR 679/2016 and, as currently applicable, of Legislative Decree 196/2003 . 
The AUSL-IRCCS di Reggio Emilia is the owner of the data collected in clinical practice and for the use of 
personal and sensitive data of patients for research purposes, the express consent of the interested party 
will be requested, as required by the aforementioned legislation, on the basis of documents approved by the 
competent Ethics Committee . 
The data will be used solely for the purpose of carrying out this study. 
The Scientific Responsible of the study is identified as the Delegate for the processing of personal data, 
pursuant to the Deliberation of the General Manager n. 284/2018, and will appoint with a specific written 
deed the other collaborators as persons authorized to process personal data under the authority of the 
owner and the data processing delegate, pursuant to GDPR 679/2016. 
The study will be activated only after obtaining the favorable opinion of the Comitato Etico di Area Vasta 
Nord RER and will be carried out in accordance with this protocol, any amendments introduced and will be 
conducted in accordance with the ethical principles of the Declaration of Helsinki. 
The data will be managed ensuring the protection of privacy in accordance with the provisions of the law 
(GDPR 679/2016). 
The data necessary to respond to the objectives of the study will be recorded in coded form (in accordance 
with the GDPR 679/2016), therefore the processing of personal data will take place in such a way that the 
data can no longer be attributed to a specific data subject without the use of additional information, 
information that will be stored separately and will be subject to technical and organizational measures 
designed to ensure that it is not attributed to an identified or identifiable natural person. The data will be 
stored, whether in paper or electronic form, in places or media protected from access by unauthorized 
persons or intrusion by third parties. 
The PI will file and keep in paper format in a protected place, the patient's personal data combined with the 
assigned ID, together with the signed and dated informed consents and the clinical documentation collected 
according to the methods of its center (reports, copy of the relevant parts of the medical record). 
 
N. Responsibility and publication policy 
The data collected will be the property of the promoter. 
 
O. Insurance aspects 
Since it is believed that the measurement setting is safe and that the measurements to be carried out do not 
present risks, as they are non-invasive and non-dangerous, the stipulation of a specific insurance is not 
considered necessary. 
 
 

 
P. Bibliography 
 
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