Effect of Phase Change Material Cooling Vests on Body Thermoregulation and Thermal Comfort of Patients With Paraplegia: A Human Subject Experimental Study

Abstract

Study design

Randomized experimental study.

Objective

Compared to able-bodied people, patients with paraplegia due to thoracic spinal cord injury (SCI) are at an increased risk of heat illnesses during exercise due to impaired thermoregulatory responses. To overcome this limitation, we investigated the performance of three phase change material (PCM) cooling vests of different melting temperatures (Eijsvogels, #49) and coverage area of the trunk.

Methods

Sixteen participants were divided into three groups according to their injury level. All were tested for V20 full vest (20°C Tm, 75% coverage). Mid-thoracic and high-thoracic groups were tested for V14 vest (14°C T_m, 75% coverage). The mid-thoracic group was tested for V20 half vest (20°C T_m, 50% coverage). The participants performed a 30-min arm-crank exercise followed by a recovery period inside a controlled hot climatic chamber. The heart rate, segmental skin (T_skin), and core temperature (T_core) values were recorded, and subjective questionnaires were taken.

Results

Compared to no vest (NV) test, all the vests showed an effective decrease in T_skin values of the trunk. However, the decrease in T_skin was not enough to induce a significant decrease in T_core in all three groups. Mid-thoracic and low-thoracic groups showed a reduction in the increasing T_core by the end of the exercise and recovery period. Finally, the level of thermal comfort was enhanced for the three groups.

Conclusion

The effectiveness of cooling vests for persons with paraplegia is dependent on injury level and thus the ratio of sensate to insensate skin. Future studies necessitate the investigation of the cooling effects of PCM vests at a lower Tm with a larger sample size.

Keywords

spinal cord injury thoracic spinal cord paraplegia thermoregulation cooling vests

Introduction

Spinal cord injury (SCI) is an insult to the spinal cord that alters its function and can even lead to death, depending on the site of injury. According to the National Spinal Cord Injury Statistical Center (NSCISC), there are 17 810 new cases of SCI yearly, with a total approaching 300 000 cases in the United States (National Spinal Cord Injury Statistical Center, 2020). The causes of SCI are many, but motor vehicle accidents have been in the lead for the past 40 years, followed by falls, crimes and violence, sports injuries, and medical and surgical complications, among others¹ (National Spinal Cord Injury Statistical Center, 2020).

Regardless of the spinal cord injury level, SCI can be classified as either complete or incomplete. According to the American Spinal Injury Association (ASIA), a complete injury refers to the total loss of the sensory and motor functions below the injury level, whereas an incomplete injury refers to the maintenance of certain sensory and/or motor functions below the injury level. SCI may lead to physiological disturbances, the most important of which are the disorders caused by the autonomic nervous system. The loss of the sympathetic nervous system and the compensatory attempt by the parasympathetic one can potentially results in bradycardia, hypotension, thermoregulatory dysfunction, and disruption in the skin blood flow.²

One of the fundamental homeostatic mechanisms in the body is the regulation of the core body (T_core) temperature. Under normal conditions, T_core is 37^oC ± 0.5^oC, despite any fluctuations in the ambient temperature. A slight deviation from this range may alter the function of the vital organs and disrupt homeostasis.³ Patients with thoracic SCI, commonly referred to as paraplegia (PA), experience thermoregulatory dysfunction that induces thermal strain due to unsafe elevation in their core body temperature (T_core). The impaired spinal cord affects the synchronization of the human sympathetic activity resulting in the disruption of the vasomotor (blood vessel vasodilatation/vasoconstriction) and sudomotor (shivering/sweating) responses. Hence, patients with PA are unable to maintain a balanced body temperature below the threshold of thermal strain (37.5°C) due to the loss of the sweating and vasodilatation responses and the vasoconstriction and shivering responses which normally occur when the body temperature is above or below its thermoneutral state, respectively.⁴ By this, for the health and well-being of patients with PA, it is of important interest to investigate the performance of phase change material (PCM) cooling vests of different melting temperatures and coverage area of the trunk during exercise in hot conditions to alleviate thermal strain for this population.

Since this group of people cannot maintain their body temperature under thermal stress, physical activity and exercises are considered challenging. The trunk contains the largest share of thermoreceptors for coldness sensitivity and sweat glands, in comparison to other body segments.^5,6 Therefore, paraplegic patients cannot balance the heat gain due to the high metabolic rate with the peripheral heat loss since a significant portion of the trunk skin area is insensate.

To prevent the uncontrolled and risky elevations in T_core, previous studies tested various cooling methods on this vulnerable population. Limited studies investigated the use of phase change materials (PCMs) cooling vests on paraplegic patients. Cooling the sensate skin of the trunk and lowering T_skin values help in increasing the conduction heat transfer from the core to the periphery, thus lowering T_core values. In the mentioned studies, there were no suitable control groups and the participants performed different types of exercise which may change their effort and thermal response. Most importantly, these studies have not taken into consideration the variations among the participants in terms of injury level while designing the vests. And the injury level is determinant of the altered physiology state and the thermoregulatory dysfunction level.

In the current study, the authors investigated the effect of three PCM vests on patients with paraplegia with SCI during exercise according to their different injury level.

Experimental Methods

Human Subjects

The ethical approval to perform the experiments on human subjects was obtained from the Institutional Review Board (IRB) at the American University of Beirut (AUB) (IRB ID: BIO2018-0401). All participants signed a consent form to participate in the project and publish their data. The spinal cord injury level was obtained from the patient’s medical record, and the severity of the injury whether complete/incomplete was determined by a physical exam performed by a neurosurgeon according to the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) exam.

In the current project, the participants, with SCI, were divided into three groups according to their thoracic injury level (Figure 1). Group I: participants with T1-T3 SCI (n = 3), group II: participants with T4-T8 SCI (n = 8), and group III: participants with T9-T12 SCI (n = 5). Figure 1 shows the percentage of insensate skin and the impaired region in each group.

Figure 1.

Schematic representation of the impaired regions of the torso according to the spinal cord injury level.

Grouping participants into these three groups was aimed to address the dependency of cooling vests effectiveness on the injury level and the degree of thermoregulatory impairments. The categorization was done based on the percentage of sensate skin of the trunk of a person with PA. Based on literature, people with T1-T3 (high-thoracic) injury had at least 75% of the trunk as insensate; whereas people with T4-T8 (mid-thoracic) injury had at least 50% of the trunk as insensate; finally, people with T8-T12 (low-thoracic) injury had at least 25% of the trunk as insensate. Therefore, grouping these subjects as high-, mid-, and low-thoracic SCI favored the objective of the study while taking into consideration the sensate portion of the skin of the trunk. Table 1 summarizes the injury level and its severity for each participant.

Table 1.

Spinal cord injury level and AIS for the participants.

		Level of injury	ASIA impairment scale (AIS)
Group I	Subject 1	T3	B
	Subject 2	T3	B
	Subject 3	T3	B
Group II	Subject 4	T8	B
	Subject 5	T8	C
	Subject 6	T8	B
	Subject 7	T8	C
	Subject 8	T6	C
	Subject 9	T8	C
	Subject 10	T7	B
	Subject 11	T6	C
Group III	Subject 12	T11	C
	Subject 13	T12	B
	Subject 14	T11	C
	Subject 15	T12	B
	Subject 16	T12	B

The inclusion criteria were (i) thoracic SCI (T1-T12) (Tanabe, #199); (ii) the age in the range of 25–45 years; (iii) the average weight in the range of 75 ± 10 kg and the average height in the range of 170 ± 10 cm; (iv) the duration of injury of minimum one year for medical stability; (v) the participant of a wheelchair user; and (vi) no implanted electro-medical device or gastrointestinal disease. Table 2 summarizes the physical properties of the participants.

Table 2.

Physical properties of the participants represented as mean ± SD.

	Age (years)	Weight (kg)	Height (cm)	Duration of injury (years)
Group I	29 ± 5	72 ± 8	173 ± 7	4 ± 3
Group II	32 ± 7	64 ± 10	170 ± 7	12 ± 11
Group III	31 ± 4	67 ± 15	171 ± 9	8 ± 5

The recruited participants were middle-aged (31 ± 6 years) males and females with thoracic SCI with an average weight and height of 67 ± 11 kg and 171 ± 7 cm, respectively (Tables 1 and 2).

Finally, all participants signed the consent form, committed to a physiotherapy program provided by the recreation center and exercised at least two times per week.

Cooling Vest Characteristics

The polyester cooling vests were commercially designed to hold up to 22 equally sized PCM packets, which were made of a salt mixture of sodium sulfate and water known as Glauber’s salt⁷ with a melting point of either 20°C or 14°C.

Two types of PCM vests were used. The first vest of a 20°C melting temperature consisted of two subtypes: V20 full, composed of PCM packets covering the full trunk (chest, upper back, middle back, and abdomen), and V20 half covering half of the trunk (chest and upper back) to target the sensate skin area only (Figure 2), which resulted in lower vest weight. The weight of V20 half and its PCM coverage area of the trunk were both 36% less than in V20 full $[(V 2 - V 1 / V 1) * 100]$ .

Figure 2.

Schematic representation of the total phase change material coverage at the front and back of the torso for V20 full and V20 half vests.

The second vest of a 14°C melting temperature covering the full trunk (V14) included the use of 4 packets of non-toxic carbon-based liquid (Alkane Blend).

Group I: tested with V20 full and V14 full.

Group II: tested with V20 full, V20 half, and V14 full.

Group III: tested with V20 full.

The comparison between V20 full and V20 half is indicative whether cooling the sensate skin only can be as effective as cooling the full trunk. V20 half was tested in the mid-thoracic group only since it is the only group that has variations in the sensate/insensate areas.

Physiological and Physical Measurements

Dry bulb temperature and relative humidity sensor (OM-EL_WIN_USB, OMEGA, UK, .5°C and .5% resolution) measured every 1 min the ambient conditions of the climatic chamber. The accuracy of this sensor is reported to be ±.5°C at typical temperature range (35–80°C) and 3% at typical relative humidity range (20–80%). Temperature iButton sensors (iButton DS19221, Maxim Integrated, CA, USA, .0625°C resolution) were taped on seven body segments at 10 positions (chest, upper back, lower back, pelvis, forehead, forearm, palm, thigh, calf, and foot) and recorded a measurement every 1 min throughout 60-min period of preconditioning, exercise, and post-exercise. The average accuracy of the iButton temperature sensors is .1°C when used at the environmental conditions of (30°C and 50%) with a maximum deviation of .4°C. To ensure proper contact with the skin, a surgical tape was used to place the sensors on the different segments.

Heart rate was recorded every 5 mins using a pulse oximeter (Model 2500A PalmSAT, NONIN, USA, ± 3 bpm accuracy). The values of T_core were measured in two ways: using an activated ingestible pill and an infrared tympanic thermometer, IRTT. The ingestible pill was configured using e-Celsius Performance Manager software and its monitor (eViewer Perf CE monitor, BodyCap, France) to read every 30 s the gastrointestinal temperature, as an indicator of T_core. The accuracy of the pill is ±.2⁰C. In addition, recording of the tympanic temperature was done every 5 min using IRRT (Braun ThermoScan 7 IRT6520, Braun, Kronberg, Germany, accuracy ±.2⁰C).

Subjective questionnaires were explained to the participants and taken every 5 mins during the 30-min exercise period. The whole body and torso thermal sensation, the thermal comfort, the wetness sensation on skin and clothing, and the rating of perceived exertion were evaluated.^8-13 The reference scales of the subjective ratings by the participants are summarized in the supplemental table.

The three experimental vests differ in either their melting temperature or their coverage proportion of the trunk. Subjective questionnaires and objective data, including the heart rate and segmental T_skin and T_core values were taken every 5 mins of the experiment.

The heart rate increased safely during the exercise period (from 15 mins to 45 mins) and then decreased in the recovery period (from 45 mins to 60 mins) and remained relatively stable in each period; besides, none of the patients experienced extreme discomfort.

Experimental Design

All experiments were conducted at the same time in the afternoon inside a climatic chamber. The latter was equipped by a centralized air-conditioning ducted system and contained the arm-crank ergometer (Angio rehab with automatic stand, Lode, the Netherlands). All participants performed arm-crank exercise at constant load of 30 W to limit the variability in metabolic rate generation between subjects of the same group. However, performing the same load of exercise, patients with PA are expected to generate different metabolic rates based on the injury level because the latter affects maximal oxygen uptake as lung capacity is lower in high-thoracic levels.^14-16

The climatic chamber conditions were set at hot humid conditions of 30°C room temperature and 50% relative humidity. These conditions were monitored and measured using a temperature and a relative humidity sensor. The reported measurements for all experiments showed a small deviation from set conditions (30.6 ± .1°C and 50 ± 5% humidity). Figure 3 summarizes the detailed steps of the protocol on the day of the experiment. During the 60-min experiment, core and skin temperatures were recorded every 5 mins using the ingestible pill and skin sensors, respectively. Precautions were implemented for stopping the experiment if any of the two conditions occurred to avoid any risk for the participants: (i) the core temperature reaches 38.5°C and/or (Tanabe, #199) if the participant wishes to stop any time during the experiment.

Figure 3.

Schematic illustration of the experimental design.

Statistical Analysis

Comparison of the effectiveness of the cooling vest was considered within each group separately due to the variability of metabolic rate among thoracic SCI levels at the same load of arm-crank exercise (30W). Data are presented as ± standard error of the mean (SEM). Statistical analysis was performed by ANOVA and paired-sample t test with significance was set at P-value .05.

Results

The vests described in this article have not been previously tested in patients with paraplegia. To determine the effectiveness of these vests, the participants performed a 30-min arm-crank exercise followed by a 15-min recovery period. Every 5 mins, the skin temperature (T_skin) for the trunk segments (chest, pelvis, upper, and lower back) and the core temperature (T_core) were measured.

Group I

Figure 4 shows that group I, patients with high-thoracic (T1-T3) SCI, wearing V20 full trunk had a decrease, but did not reach significance, in the segmental T_skin and T_core. The T_skin at the chest area increased non-significantly in patients wearing V20 full in comparison to the control (NV); however, the T_skin at the pelvis, upper, and lower back for V20 full is lower than that of the control. Nevertheless, even if the segmental T_skin decreased T_core, it did not reach significance.

Figure 4.

Graphs showing the variation of the heart rates, segmental T_skin (chest, pelvis, upper, and lower back), and T_core values as a function of time (mins) for the high-thoracic group (T1-T3) wearing V20 and V14 full trunk. Data are means ± SEM, asterisk indicates P < .05 with respect to the control no vest (NV), *P < .05, **P < .01, ***P < .001.

Another PCM cooling vest was developed with lower melting temperature (14°C instead of 20°C). Figure 4 shows that vest V14 full trunk caused a decrease in T_core and T_skin in all segments except the upper back, in comparison to the control (NV) and V20 full trunk; however, this decrease did not reach significance.

These objective findings were in concordance with the subjective ones (Supplementary Figure 1). The participants reported improvement in the thermal comfort level from “uncomfortable” with no vest to “slightly uncomfortable” with V20 full and “comfortable” with V14. Similarly, for the whole body and torso thermal sensations, where the impressions changed from “hot” with no vest to “slightly warm” and “neutral” with V20 full and V14, respectively. The vests had a non-significant effect on the perceived exertion and skin wetness.

Group II

Spinal cord injuries at the level of the high- or low-thoracic spine have similar ratios of sensate and insensate skin in the same group, unlike those at the mid-thoracic (T4-T8) level. Therefore, patients in group II were also tested for V20 half trunk, covering the sensate skin only, in comparison to the control NV and V20 full trunk. Surprisingly, V20 half increased T_skin non-significantly in the upper and lower back and pelvic regions, while decreased the temperature non-significantly in the chest region, in comparison to the NV group. At the same time, V20 half group registered the lowest T_core values in comparison to the NV and V20 full groups. V20 full caused a non-significant decrease in the T_skin at the chest, upper back, and pelvic regions and significant decrease in the insensate skin of the lower back from time 20 mins to 60 mins. This decrease in the temperature in the sensate skin area was not enough to induce a significant decrease in the T_core (Figure 5), yet T_core was below the threshold of thermal strain (37.5°C).

Figure 5.

Graphs showing the variation of the heart rates, segmental T_skin (chest, pelvis, upper, and lower back), and T_core values as a function of time (mins) for the mid-thoracic group (T4-T8) wearing V20 full trunk and V20 half trunk. Data are means ± SEM, asterisk indicates P < .05 with respect to the control no vest (NV), bar and asterisk indicates P < .05 of V20 half with respect to V20 full, *P < .05, **P < .01, ***P < .001.

Similar findings were shown with V14 vest. Non-significant decrease in the segmental T_skin and T_core was registered, yet the change in the T_core was below the threshold of thermal strain (37.5°C). In addition, V14 caused a more pronounced decrease in the T_core, in comparison to V20 full trunk in the recovery period (Figure 6).

Figure 6.

Graphs showing the variation of the heart rates, segmental T_skin (chest, pelvis, upper, and lower back), and T_core values as a function of time (mins) for the mid-thoracic group (T4-T8) wearing V20 and V14 full trunk. Data are means ± SEM, asterisk indicates P < .05 with respect to the control no vest (NV), *P < .05, **P < .01, ***P < .001.

However, the subjective data showed that the participants experienced better thermal sensation and comfort levels upon wearing the vests, especially the V14 vest. Besides, the perceived exertion changed from “hard” with no vest to “fairly light” with V14 (Supplementary Figure 2).

Group III

Like the first two groups, patients with low-thoracic (T9-T12) SCI wearing V20 full trunk showed a non-significant decrease in the T_skin in the sensate areas (chest and upper back) and a significant decrease in the T_skin in the lower back area. These changes were not pronounced to induce a significant decrease in T_core; however, it is worth mentioning that Δ change in the T_core in this group is the highest among all groups (Figure 7).

Figure 7.

Graphs showing the variation of the heart rates, segmental T_skin (chest, pelvis, upper, and lower back), and T_core values as a function of time (mins) for the low-thoracic group (T9-T12) wearing V20 full trunk. Data are means ± SEM, asterisk indicates P < .05 with respect to the control no vest (NV), *P < .05, **P < .01, ***P < .001.

In addition, the torso thermal sensation improved from “uncomfortable” to “neutral” with the vest. The thermal comfort level, perceived exertion, and skin wetness significantly improved in the low-thoracic group upon wearing V20 full, in comparison to the control NV (Supplementary Figure 3)

Discussion

The literature body about the effectiveness of PCM cooling vests for patients with PA is still scarce. This is the first human study that documents the effect of these three PCM cooling vests on the segmental T_skin and T_core in patients with thoracic spinal cord injury at these melting temperatures (14°C and 20°C) and with such exercise protocol. The overall aim of the study was to investigate the effectiveness of the cooling vests in PA patients during exercise and whether their lowering temperature potential is dependent on the spinal cord injury level.

People with SCI lack the thermoregulatory response mechanism of the body where T_core changes according to the ambient temperature. This is due to an impaired sweating and vasomotor responses at the insensate skin.¹⁷ The impairment of the homeostatic process is dependent on the injury level and the ratio of insensate skin area to total skin area. The higher the level of the SCI, the more severe the symptoms are. Therefore, significant changes in the temperature in the insensate areas have no effect on the T_core due to the lack of vasodilation and vasoconstriction and thus the lack of the heat transfer mechanisms.¹⁸ This supports our findings where a significant decrease in the T_skin at the lower back area in the mid- and low-thoracic groups caused a decrease in the T_core to below the threshold of thermal strain (37.5°C). Moreover, the greatest change in T_core was shown in the low-thoracic group which has the lowest injury level and the highest ratio of sensate skin among the groups and thus the most preserved thermoregulatory mechanism.

In addition, the subjective and objective findings for V14 were better than that of V20 full trunk in the mid-thoracic group. V14 caused a more pronounced decrease in the segmental T_skin and T_core values in the resting period, in comparison to V20. Our findings are in accordance with previous studies. Goa et al. found that the cooling rate of the PCM vests depends on the temperature gradient between the subject and the PCM packets.¹⁹ A comparative study on the cooling effect of two PCM vests of different melting temperatures (24°C and 28°C) showed that the vest with the lower melting temperature had a more noticeable effect on the torso and mean T_skin.²⁰

Limitations

Several factors and limitations may affect the results. The eligible participants who were accepted for participation were all with incomplete injuries (ASIA B or C) as reported by the neurosurgeon who was in charge in examining them. No participant with complete injury participated in this study despite extensive recruitment efforts. This limitation was considered when evaluating the change in core temperature in NV test. The findings for each group showed gradual increase in core temperature as an indication of impaired autonomic system in persons with PA. Findings of change in T_cr values in NV test were like previous studies in literature which recruited participants with complete thoracic injury to perform exercise in hot environmental temperature (>30.0°C).^21-24

Besides, the cooling rate of the vests depends on the temperature gradient, melting temperature of the packets, and the covering area of the vest.¹⁹ Besides, the exercise protocols are highly variable in literature in terms of duration, experimental groups, exercise type, and the covered body region which limits the comparative nature among the studies. Future studies necessitate the investigation of the cooling effects of PCM vests at a lower melting temperature with a larger sample size.

Conclusion

The results of this experimental study indicated that all the vests showed better cooling effects in the low-thoracic and mid-thoracic groups, rather than in the high-thoracic one. This indicates that the cooling effect of these vests was dependent on the injury level, where the least effect was shown in group I (high-thoracic) since this group had the highest ratio of insensate skin. However, the decrease in the segmental T_skin values was not enough to induce significant decrease in T_core values in all the groups. Yet, the subjective findings showed an enhanced comfort level, in comparison to the control no vest group.

Supplemental Material

sj-pdf-1-gsj-10.1177_21925682211049167 – Supplemental Material for Effect of Phase Change Material Cooling Vests on Body Thermoregulation and Thermal Comfort of Patients With Paraplegia: A Human Subject Experimental Study

Supplemental Material, sj-pdf-1-gsj-10.1177_21925682211049167 for Effect of Phase Change Material Cooling Vests on Body Thermoregulation and Thermal Comfort of Patients With Paraplegia: A Human Subject Experimental Study by Charbel K. Moussalem, Farah Mneimneh, Rana Sarieddine, Shadi Bsat, Mohamad N. El Houshiemy, Georges B. Minassian, Nesreen Ghaddar, Kamel Ghali and Ibrahim Omeis in Global Spine Journal

Supplemental Material

sj-tif-1-gsj-10.1177_21925682211049167 – Supplemental Material for Effect of Phase Change Material Cooling Vests on Body Thermoregulation and Thermal Comfort of Patients With Paraplegia: A Human Subject Experimental Study

Supplemental Material, sj-tif-1-gsj-10.1177_21925682211049167 for Effect of Phase Change Material Cooling Vests on Body Thermoregulation and Thermal Comfort of Patients With Paraplegia: A Human Subject Experimental Study by Charbel K. Moussalem, Farah Mneimneh, Rana Sarieddine, Shadi Bsat, Mohamad N. El Houshiemy, Georges B. Minassian, Nesreen Ghaddar, Kamel Ghali and Ibrahim Omeis in Global Spine Journal

Supplemental Material

sj-tif-2-gsj-10.1177_21925682211049167 – Supplemental Material for Effect of Phase Change Material Cooling Vests on Body Thermoregulation and Thermal Comfort of Patients With Paraplegia: A Human Subject Experimental Study

Supplemental Material, sj-tif-2-gsj-10.1177_21925682211049167 for Effect of Phase Change Material Cooling Vests on Body Thermoregulation and Thermal Comfort of Patients With Paraplegia: A Human Subject Experimental Study by Charbel K. Moussalem, Farah Mneimneh, Rana Sarieddine, Shadi Bsat, Mohamad N. El Houshiemy, Georges B. Minassian, Nesreen Ghaddar, Kamel Ghali and Ibrahim Omeis in Global Spine Journal

Supplemental Material

sj-tif-3-gsj-10.1177_21925682211049167 – Supplemental Material for Effect of Phase Change Material Cooling Vests on Body Thermoregulation and Thermal Comfort of Patients With Paraplegia: A Human Subject Experimental Study

Supplemental Material, sj-tif-3-gsj-10.1177_21925682211049167 for Effect of Phase Change Material Cooling Vests on Body Thermoregulation and Thermal Comfort of Patients With Paraplegia: A Human Subject Experimental Study by Charbel K. Moussalem, Farah Mneimneh, Rana Sarieddine, Shadi Bsat, Mohamad N. El Houshiemy, Georges B. Minassian, Nesreen Ghaddar, Kamel Ghali and Ibrahim Omeis in Global Spine Journal

Footnotes

Acknowledgments

This publication was made possible by the Collaborative Research Stimulus grant award 24477-103557 of the American University of Beirut. The findings achieved herein are solely the responsibility of the authors. The authors thank the subjects for their motivation to participate, as well as their complete dedication to the experimental work. Theauthors also thank “Dr Mohammad Khaled Social Foundation”, physiotherapist Dr Iman Baydoun; research assistant Georges Manissian; andNurse Suzzane Seifeddin for their technical assistance during subjectrecruitment and experimental protocol.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Rana Sarieddine

Supplementary Material

Supplementary Material for this article is available online.

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