How to cite this article: Olaya-Mira N, Soto-Cardona I, Ciro-Vargas K, Rodríguez-Buitrago P. Biomecánica de la región dorsolumbar durante
el levantamiento manual de pacientes. Ciencia e Innovación en Salud. 2020. e82: 197-207. DOI 10.17081/innosa.82
Biomechanics of the dorsolumbar region during manual patient lifting
Biomecánica de la región dorsolumbar durante el levantamiento manual
de pacientes
Natali Olaya-Mira
1
*, Isabel C. Soto-Cardona
2
, Karla C. Ciro-Vargas
3
y Paola A. Rodríguez-
Buitrago
4
1
Research and Biomedical Innovation Group GI2B, Instituto Tecnológico Metropolitano, Medellín – Colombia
2
Biomechanics and Rehabilitation Engineering Laboratory.Instituto Tecnológico Metropolitano, Medellín – Colombia
3
Faculty of Exact and Applied Sciences.Instituto Tecnológico Metropolitano, Medellín – Colombia
4
Faculty of Exact and Applied Sciences.Instituto Tecnológico Metropolitano, Medellín - Colombia
* Dirigir correspondencia a: nataliolaya@itm.edu.co
ABSTRACT
Background: Many work-related accidents and diseases that affect nursing assistants’ health and the
economy of companies are attributed to manual load handling. Among the available methods to analyses these
tasks, NIOSH is one of the most commonly adopted. Furthermore, the implementation of biomechanical
techniques enables to create and assess records that quantify the complexity of injuries. The objective is to
evaluate the biomechanics of manual patient handling by the NIOSH method complemented with
electromyography of the lumbar region and videogrammetry of the gesture. Methods: In a simulated work
environment a patient was lifted to a gurney while the stability of the dorsolumbar region was calculated using
electromyography. At the same time, the kinematics of the main joints involved in the gesture were recorded
using videogrammetry. These data were compared with those of the NIOSH method to establish the main
factors that may have an influence on the performance of manual load lifting. Results: The maximum
recommended weight was found to be above the lifted weight. Besides, the lifting index suggested that the task
could cause musculoskeletal issues. The coactivation of the pairs of medial muscles presented values under
50%. The kinematics of all the joints exhibited points of inflection during lifting and a wide variation of the
amplitude of movement throughout the gesture. Conclusions: The variables that affect lifting depend on the
design of the work environment. Moreover, they are closely related to articular kinematics and the height of the
participants, who demonstrated good stability in the dorsolumbar region.
Keywords: Patient lifting; NIOSH; EMG; Kinematics; Occupational Health.
Article History
Received: 06 11 19
Accepted: 04 06 20
Published:13 08 20
DOI
10.17081/innosa.82
©Copyright 2020
Olaya-Mira
1
et al.
I. INTRODUCTION
In the health care sector, practitioners often need to move patients who lack
functional autonomy whether for rehabilitation, treatment, or hygiene (1).
This task is known as “manual load lifting” because it requires a physical
effort (2).
These activities have to be carried out manually due to the absence of
technical equipment adapted to the conditions of a typical space where
non-autonomous individuals are transported (1). However, they entail work-
related accidents and diseases that have consequences on practitioners’
health and the economy of companies (3) As a result, the profitability of the
latter is reduced along with the employability and work capacity of the
affected individuals, while the social cost of public health rise (2).
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There is an important relationship between manual load lifting and the onset of dorsolumbar
conditions and pains. Morbidity and disability rates related to these pathologies are still high,
which reveals a lack of understanding of a condition that is therefore underrated and undertreated
(4). As a result, their effects are one of the most important action points for prevention in
occupational health (more specifically, ergonomics).
Several epidemiological and biomechanical studies have identified the main risk factors
associated with pain caused by manual load lifting, such as frequent leaning, spine rotations, and
movement repetitions (5) However, indirect or direct methods can be employed to analyse this
task. The former is based on observing the activity, e.g. the NIOSH (National Institute for
Occupational Safety and Health) equation. The latter require different types of electronic devices
and equipment to capture data (3) e.g. biomechanical analyses such as videogrammetry and
electromyography. Said methods support in-depth studies of the dorsolumbar region and suggest
the correct way individuals should perform manual load liftings.
Nevertheless, indirect and direct techniques have not been part of the same study. As a result,
connecting the information and identifying the main factors behind pains in the dorsolumbar
region of practitioners that complete said task every day constitutes a novel approach (6). This
project analyses biomechanical and functional aspects that provide a more comprehensive
description of this professional gesture in health care.
II. METHODS
2.1. Population. The sample was composed of 26 men with the following characteristics on
average: age 38.04 (Standard Deviation: 11.379); height, 1.73 m (SD: 0.060); weight, 78.00 kg
(SD: 9.526); and no background of musculoskeletal conditions that may affect the study.
2.2. Study Design. A gurney and a chair were installed to recreate the load lifting environment
in health care and the conditions of the interaction between assistants and patients. The
participants were instructed to freely repeat three times the gesture: lifting and moving an active
patient with a weight of 73.2 kg from a 0.43m-tall chair to a 0.8m-tall gurney located 0.8 m away
from said chair in the horizontal plane. Additionally, to analyze the kinematics of the
movements, the gesture was divided into 5 phases: Preparation (phase 0) starts with the
assistant in anatomical position and continues until after the knee is bent. Lifting (phase 1)
occurs when the load (active patient) is held by the assistant. Initial carrying (phase 2) is the
vertical movement of the patient. Final carrying (phase 3) refers to the horizontal displacement
of the load. Finally, during unloading (phase 4) the assistant places the patient onto the gurney.
2.3. Data Processing. This gesture was characterized by incorporating anthropometric
variables and those related to the work environment found in the NIOSH equation, as usually
applied in this type of studies to define the Recommended Weight Limit (RWL) (7, 8) given by
equation 1.
(1)
where LC, is the load constant; HM, horizontal location; VM, vertical location; DM, vertical
distance of the movement; AM, asymmetry; FM, frequency; and CM, grip.
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The Lifting Index (LI) was calculated as the quotient between the weight of the lifted load and
the RWL established for the task, as given in equation 2.
(2)
This index defines the risk the task represents in three intervals: LI ≤ 1, no problem is caused;
, problems may be caused; , some workers will suffer problems (7, 8)
The signals of the surface electromyography (EMGs) were captured with 3M® surface
electrodes placed 2 cm apart on muscles in the abdominal and dorsolumbar regions(9,10):
straight abdominal (SA), external (EO) and internal (IO) abdominal oblique muscles,
longissimus (LO), iliocostalis (IL), and lumbar multifidus (LM) (Figure 1).
Figure 1. Placement of the surface electrodes
The signal was acquired with an ML138 differential bioamplifier integrated to a PowerLab
16/35 polygraph manufactured by AD Instruments Inc. A sampling frequency of 2 kHz was
selected, and the signal was preprocessed with LabChart Pro software that implemented a
60-Hz notch filter and a bandpass filter with a cut-off frequency between 10 and 500Hz.
Matlab software was employed to calculate the coactivation percentage, which is a measure
of the stability of the dorsolumbar region. The signals obtained from the muscles were filtered
once again using a fifth-order digital Butterworth bandpass filter with cutoff frequencies
between 10 Hz and 300Hz. The Root Mean Square (RMS) value of each resulting signal
was calculated with a window of 250 samples and an overlapping of 50 samples. As a result,
four muscle groups were created: SA/LO, SA/IL, SA/LM and EO/IO. Subsequently, each one
of them was normalized using equation 3.
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(3)
where
represents the normalized signal; , the original signal; and
and
, the
minimum and maximum values of the original signal, respectively. Next, the coactivation
percentage between muscle pairs was calculated with equation 4.
(4)
where is the coactivation percentage between agonist and antagonist muscles;
, the area of muscle A under the curve of the processed EMG signal; ,
the area of muscle B under the curve of the processed EMG signal;
and, the common area of activity between muscles A and B (9) (Figure
2).
Figure 2. Area of the percentage of muscle coactivation
Two high-speed video cameras (Basler acA 640-120gc) connected to Contemplas software
were used to capture the kinematics. In addition, reflective markers were placed on the most
prominent bony landmarks, according to a modified Davis protocol (11). Subsequently, the
articular movements of the ankle, knee, hip, and the lumbar spine were recorded in the
sagittal plane. The lumbar spine was also studied in the posterior frontal plane.
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Figure 3. Placement of the reflective markers
2.4. Statistical analysis. The statistical package SPSS 24.0 was used to treat the data, and
the Shapiro-Wilk determined the normality of the data. The level of statistical significance
considered in this study was 0.05.
2.5. Ethical aspects. Nursing assistants at a public mental health-care institution —namely
ESE Hospital Mental de Antioquia—voluntarily participated in this study. They signed an
informed consent approved by the ethics committee of Instituto Tecnológico Metropolitano that
observes the regulations introduced by the Declaration of Helsinki, as recommended by the
World Medical Association (12)
III. RESULTS
All the variables related to the NIOSH equation exhibited normality. The mean weight limit
recommended for the population under study is 38.7 kg (SD: 2.0), and the lifting index is 1.9
(SD: 0.1).
3.1. Muscle Coactivation. The coactivation of the muscles involved in flexion and extension
presented normality; conversely, the coactivation of oblique muscles exhibited non-normality
during torso rotation. Furthermore, the coactivation percentage of the straight abdominal
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muscle compared to the longissimus was 35% (SD: 22.1); to the iliocostalis, 37% (SD: 19.27);
and to the lumbar multifidus, 33% (SD: 22.33). Likewise, the coactivation potential of the oblique
muscles reached 36.13% (SD: 18.89) during rotation (Figure 4).
Figure 4. Muscle coactivation percentage
3.2. Articular Kinematics. The data of all the angles of the joints involved in the gesture
showed normality in all the phases, except for the ankle during preparation, the spine in the
frontal plane in lifting, the knee during the two phases of carrying, and the spine in the sagittal
plane in final carrying. Additionally, all the joints revealed points of inflection during lifting and
variations in the amplitude of movement throughout the execution of the gesture (Figure 5).
From the sagittal plane, the gesture starts with a plantar flexion of the ankle during phase 0
that changes to dorsiflexion in phase 1. Between those two movements, the average angle of
this joint was calculated at 15.67° (SD: 14.68), which varies in approximately 10.81° (SD:
18.72) (Figure 5a).
The knee joint exhibits a full flexion from the start, and it reaches a maximum angle in phase
1, approximately 55.86° (SD:17.9). This movement continues during carrying and unloading,
and the extension varies 0.81° on average (SD: 21.52) (Figure 5b).
In this gesture, the hip starts in a flexion position that reaches its highest point, 35.93° (SD:
20.35), during phase 1, followed by an extension that continues to phase 2. This position is
maintained until the movement is stabilised and completed in a joint range between 5.85° (SD:
10.72) and 12.34° (SD: 12.11) (Figure 5c).
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Figure 5. Kinematics of joint angles - Sagittal Plane a) Ankle; b) Knee; c) Hip; d) Lumbar
Spine
The movement of the lumbar spine observed from the sagittal plane is composed of a
maximum flexion (48.98° on average, SD:26.21) followed by a slight extension (6.44° on
average, SD: 10.28) to be able to lift, move, and unload the patient until reaching the
anatomical position while trying to achieve balance (Figure 5d).
Finally, the joint kinematics of the vertebral column in the frontal plane in phase 0 revealed a
rightward inclination and, at the exact moment of the lifting in phase 1, it smoothly changed
leftward, balancing between both sides to try to achieve balance so that mobility can be
compensated during the execution of the gesture (Figure 6).
Figure 6. Lumbar Spine - Frontal Plane
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IV. DISCUSSION
The spatial distribution of furniture and equipment in the workplace, as well as the execution of the task,
should be changed. In this case, the lifted weights exceeded the recommendations and low muscle
coactivation was detected, which means adequate stability of the dorsolumbar region. Points of
inflection were observed in all the joints during lifting, along with a wide variation of the amplitude of
movement throughout the gesture.
The RWL calculated for the population under study depends on the lifting and carrying distances (8); in
this study, it is greater than the lifted weight, which is reflected in an LI between 1 and 3 (8);. In
accordance with the work by Pérez Domínguez and Caicedo (3, 13) these results suggest that nursing
assistants are exposed to risks that may result in problems in the dorsolumbar region when they
manually lift and carry patients.
In general, the coactivation percentages of all the muscle pairs were under 50%. When this percentage
approaches 100%, stability decreases; when it tends to 0%, it increases (13).
Additionally, during flexion and extension movements, the straight abdominal and multifidus muscles
presented the lowest coactivation. This may be due to the role of the multifidus in the stabilization of the
vertebral column, since this muscle is activated before the load is supported or an extreme movement
is executed and it contributes to the control of the neutral position of the spine (14). Likewise, the
abdominal straight coordinates the main flexing actions of the trunk because it controls the external
forces the vertebral column experiences (15). Furthermore, the straight abdominal and iliocostalis
muscle pair presented the highest coactivation percentage, which suggests low lumbar stability for
flexion and extension movements. This is because the iliocostalis is a deep muscle of the trunk located
close to the centre of rotation of the vertebral segment, which makes it better prepared to control the
mobility at the segmental and not at the global level (16)l
The coactivation data suggest adequate lumbar stability during rotation, because lumbar
muscles are involved in physical activities and provide rigidity that helps to balance external
loads, thus controlling the mobility of the lumbar spine (17) Moreover, the non-normality of the
coactivation data of trunk rotation may have been due to the fact that, during the task, some
participants moved the patients while rotating the trunk and others configured the posture with
some steps to prepare to unload.
These results reveal that the stability of the spine is activated when there is a combination of
muscles of the abdominal region and the lower back (18) working synergistically to balance the
external load so that the resulting force is transferred and handled by the local stabilization
system (16). As a result, if stability is good, part of the energy of the movements of the limbs
may displace the pelvis and the trunk, thus affecting the limbs involved in the gesture and
causing additional harmful stress on muscles. These circumstances produce several pains and
subsequent dorsolumbar pathologies (14).
These kinematic results show a high variability of the ankle, possibly due to the spatial
distribution of the workplace in relation to the height of the participants. More specifically, this
environment forced them to execute the bipedal standing supported on the metatarsal region
(standing on tiptoes) and a wide extension of the hip during initial and final carrying to reach
the necessary height to unload the patient onto the gurney.
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The maximum flexion experienced by the knee and the hip during lifting is necessary to gain
momentum in order to vertically move the load and thus avoid the incorrect flexion of the lumbar
spine in the sagittal plane. Similarly, lateral inclinations in the frontal plane should be avoided
when the gesture is executed.
Considering the fact that non-autonomous patients are lifted and carried every day and
throughout work shifts, this task should be performed by two assistants. Furthermore, nursing
assistants should be retrained in postural hygiene for the execution of this task in order to
reduce the risk of suffering from musculoskeletal injuries. Besides rearranging the furniture and
equipment at the workplace, implementing patient lifts should be considered as an alternative
to eliminate this occupational risk.
The techniques employed in this study, although more specific than traditional ones, may
present errors. For example, the signal of the surface electromyography may be affected by the
presence of adipose tissue in the abdominal region, and the videogrammetry may be disturbed
by the markers (19). Nevertheless, they provide a deeper understanding that enables the
biomechanical analysis of the dorsolumbar region during manual load lifting. Future works
should employ the method called Movement and Assistance of Hospital Patients (MAPO) (20)
or other relevant risk assessment strategies in this field.
Authors contribution: "Conceptualization: software; formal analysis, research, resources,
Antonio Diaz-Caballero.; data healing, writing: writing: review and editing, viewing, supervision,
all authors have read and accepted the published version of the manuscript. “Yes”
Acknowledgements. The authors would like to thank Hospital Mental de Antioquia (HOMO)
and the Biomechanics and Rehabilitation Laboratory at the Metropolitan Institute of Technology
in Medellín for providing the infrastructure and the assistant staff to conduct this study.
Conflicts of interest. The authors declare no conflict of interest.
REFERENCES
1. Álvares Casado E, Hernández Soto A, Rayo Gracía V. El riesgo asociado a la movilización de
pacientes. Gestión Práctica de Riesgos Laborales. 2010;67:26–9.
https://upcommons.upc.edu/handle/2117/12223
2. Ruiz LR. Manipulación manual de cargas. Guía Técnica del INSHT. INSHT, Inst Nac Segur e
Hig en el Trab [Internet]. 2011;30. Available from:
http://www.insht.es/MusculoEsqueleticos/Contenidos/Formaciondivulgacion/material
didactico/GuiatecnicaMMC.pdf
3. Caicedo G AM, Manzano G JA, Gómez Vélez DF, Gómez L. Factores de Riesgo, Evaluación,
Control y Prevención en el Levantamiento y Transporte Manual de Cargas. Rev Colomb Salud Ocup.
2015;5(2):5–9. DOI: 18041/2322-634X/rcso.2.2015.4890
4. Tulio M, Toro M. Dolor lumbar agudo: mecanismos, enfoque y tratamiento. Morfolia. 2009;1(3).
Avaible from: https://revistas.unal.edu.co/index.php/morfolia/article/view/10856
206
5. García Baonza S, Marco Sanz C. Análisis de factores de riesgo dinámicos en la manipulación
de cargas. Anal Dyn risk factors Handl loads [Internet]. 2013;10(18):16 p. Available from:
http://www.revistatog.com/num18/pdfs/original6.pdf
6. Sánchez Lite A, García García M, Manzanedo del Campo MÁ. Métodos de evaluación y
herramientas aplicadas al diseño y optimización ergonómica de puestos de trabajo. Qual Heal Saf Work
Environ [Internet]. 2007;239–50. Available from:
http://www.adingor.es/congresos/web/articulo/detalle/a/636
7. (NIOSH) NI for OS and H, TR W, Putz-Anderson V, Garg A. Applications Manual for the Revised
NIOSH Lifting Equation. DHHS Publication No. 94-110. 1994. p. 1–119.
8. Diego Mas JA. Método NIOSH - Evaluación del levantamiento de carga [Internet]. Ergonautas,
Universidad Politécnica de Valencia. 2015. Available from:
https://www.ergonautas.upv.es/metodos/niosh/niosh-ayuda.php
9. Urquhart DM, Barker PJ, Hodges PW, Story IH, Briggs CA. Regional morphology of the
transversus abdominis and obliquus internus and externus abdominis muscles. Clin Biomech.
2005;20(3):233–41. DOI: 10.1016/j.clinbiomech.2004.11.007
10. Martín F, Colado JC, Tella V. Comparación de los niveles de activación de los músculos
estabilizadores del CORE y agonistas durante la realización del ejercicio. Universidad de Valencia;
2012. Available from:
https://books.google.es/books/about/Comparaci%C3%B3n_de_los_niveles_de_activaci.html?id=_DXL
jgEACAAJ&redir_esc=y
11. Hallal Camilla Zamfolini, Marques Nise Ribeiro, Vieira Edgar Ramos, Brunt Denis, Spinoso
Deborah Hebling, Castro Alex et al. Coactivación muscular del miembro inferior de jóvenes y ancianos
saludables durante la marcha con doble tarea funcional. Motríz: rev. educ. fis. Motriz Rev Educ Fis.
2013 Sep;19(3):620–6. DOI: 10.1590/S1980-65742013000300013
12. World Medical Association. World Medical Association Declaration of Helsinki Ethical Principles
for Medical Research Involving Human Subjects. Am Med Assoc [Internet]. 2013;310(20):2013–6.
Available from: https://jamanetwork.com/journals/jama/fullarticle/1760318
13. Perez S, Sánchez P. “Riesgos Ergonómicos En Las Tareas De Manipulación De Pacientes, En
Ayudantes De Enfermería Y Auxiliares Generales De Dos Unidades Del Hospital Clínico De La
Universidad De Chile”. [Internet]. Universidad de Chile; 2009. Available from:
http://www.tesis.uchile.cl/tesis/uchile/2009/me-perez_a/pdfAmont/me-perez_a.pdf
14. Le P, Best TM, Khan SN, Mendel E, Marras WS. A review of methods to assess coactivation in
the spine. Vol. 32, Journal of Electromyography and Kinesiology. 2017. p. 51–60.
15. Norris CM, Pasarello Clrice M. La estabilidad de la espalda : un enfoque diferente para prevenir
y tratar el dolor de espalda [Internet]. Hispano Europea; 2007. Available from:
https://books.google.es/books?hl=es&lr=&id=56TkGJuwDmQC&oi=fnd&pg=PA9&dq=estabilidad+del+
tronco&ots=0wm3OO-L2q&sig=MSFq-
FtpZGO4bCuykX4eYg_GYpc#v=onepage&q=estabilidad%20del%20tronco&f=true
16. Vidal Oltra A. Entrenamiento del CORE selección de ejercicios seguros y eficaces. Lect Educ
física y Deport. 2015;(210):7. Available from: https://www.efdeportes.com/efd210/entrenamiento-del-
core-seleccion-de-ejercicios.htm
207
17. Provenzano G. Estabilidad e inestabilidad postural. 2016. Available from:
http://redi.ufasta.edu.ar:8080/xmlui/handle/123456789/1068
18. Behm DG, Drinkwater EJ, Willardson JM, Cowley PM. Canadian society for exercise physiology
position stand: The use of instability to train the core in athletic and nonathletic conditioning. Appl Physiol
Nutr Metab. 2010 Feb;35(1):109–12. DOI: 10.1139/H09-128
19. H. Méndez D, Ponce Amorín M. Inestabilidad lumbar, parte I: fisiopatología. AKD. Available from:
http://www.akd.org.ar/img/revistas/articulos/art%203_28.pdf
20. Cuixart SN, Casado EÁ, Menoni O, Battevi N, Occhipinti E, Sandoval ST. Evaluación del riesgo
por manipulación manual de pacientes: método MAPO Risk assessment for manual handling of
patients: Method MAPO L’valuation des dangers pour la manutention manuelle de patients: Mthode
MAPO Redactores: C. 2011. https://www.insst.es/documents/94886/328579/907w.pdf/f36a3acb-9e8f-
4140-9e95-574e3eb6077c
