Abstract
: The mobility of the rst metatarsophalangeal joint (I MPTJ) has been related to the proper windlass mechanism and the triceps surae during the heel-o phase of running gait; the orthopedic treatment of the I MPTJ restriction has been made with typical Morton extension orthoses (TMEO). Nowadays it is unclear what e ects TMEO or the novel inverted rocker orthoses (NIRO) have on the EMG activity of triceps surae during running. Objective: To compare the TMEO e ects versus NIRO on EMG triceps surae on medialis and lateralis gastrocnemius activity during running. Study design: A cross-sectional pilot study. Methods: 21 healthy, recreational runners were enrolled in the present research (mean age 31.41 4.33) to run on a treadmill at 9 km/h using aleatory NIRO of 6 mm, NIRO of 8 mm, TMEO of 6 mm, TMEO of 8 mm, and sports shoes only (SO), while the muscular EMG of medial and lateral gastrocnemius activity during 30 s was recorded. Statistical intraclass correlation coe cient (ICC) to test reliability was calculated and the Wilcoxon test of all ve di erent situations were tested. Results: The reliability of values was almost perfect. Data showed that the gastrocnemius lateralis increased its EMG activity between SO vs. NIRO-8 mm (22.27 2.51 vs. 25.96 4.68 mV,p<0.05) and SO vs.
during 30 s was recorded. Statistical intraclass correlation coe cient (ICC) to test reliability was calculated and the Wilcoxon test of all ve di erent situations were tested. Results: The reliability of values was almost perfect. Data showed that the gastrocnemius lateralis increased its EMG activity between SO vs. NIRO-8 mm (22.27 2.51 vs. 25.96 4.68 mV,p<0.05) and SO vs. TMEO-6mm (22.27 2.51 vs. 24.72 5.08 mV,p<0.05). Regarding gastrocnemius medialis, values showed an EMG notable increase in activity between SO vs. NIRO-6mm (22.93 2.1 vs. 26.44 3.63,p<0.001), vs. NIRO-8mm (28.89 3.6,p<0.001), and vs. TMEO-6mm (25.12 3.51,p<0.05). Conclusions: Both TMEO and NIRO have shown an increased EMG of the lateralis and medialis gastrocnemius muscles activity during a full running cycle gait. Clinicians should take into account the present evidence when they want to treat I MTPJ restriction with orthoses, and consider the inherent triceps surae muscular cost relative to running economy. Keywords:triceps surae; rst metatarsophalangeal joint; surface electromyography 1. Introduction Coterill [1] was the rst author who described painful osteoarthritis (OA) of the rst metatarsophalangeal joint (IMTPJ), which is known as hallux rigidus (HR). HR is the last stage Sensors2020,20, 3205; doi:10.3390 /s20113205 /journal/sensors
Sensors2020,20, 3205 2 of 12 of the IMTPJ degeneration, with functional hallux limitus [2] (FHL) at the beginning of the pathological progress [3]. Joint disease is thought to be caused by repetitive impacts on the dorsal aspect of the base of the proximal phalanx of the hallux by the rst metatarsal head during the propulsion phase of gait and running in feet with multifactorial biomechanical and/or structural de cits [4]. The limitation of IMTPJ has been linked to gait problems [5] and its consequences on ankle, knee, hip, or low back during running [6]. The treatment of this injury has been addressed in several conservative non-surgical and surgical ways. Non-surgical management is valid to treat HR in the earliest stages [7,8] and includes ultrasound therapy, in ltrative drugs, shoe modi cations, hallux bandages, manual mobilization, exor strengthening, and orthoses to improve the joint problems. There are a few references on treatment of OA using plantar insoles in HR and FHL. Traditional Morton's extensions are orthoses with a at light modi cation under the rst ray that has been used to treat HR [911] to avoid the impact between the proximal phalanx and rst metatarsal bones. This opens the IMTPJ dorsally but restricts its dorsi exion movement, while rocker-sole footwear modi cations have shown a reduction in the peak pressure under the IMTPJ. This decreases the average gait cycle that is spent in the stance phase [12] and increases muscle activity of the lower limb [13]. However, there is no reference to either the inverted rocker-sole orthoses e ects or the e ect of footwear modi cations on muscle activity during running. On the other hand, running economy (RE) has been described as the oxygen cost of running at a given speed in every case [14] and factors such as biomechanics and muscular fatigue can in uence the RE [15]. Additionally, barefoot running has shown di erences in biomechanical behaviour [16] and muscular responses [17,18] when it is compared with classical running shoes. Compared to fatigue, strength training added to a normal training program for distance running can improve RE between
speed in every case [14] and factors such as biomechanics and muscular fatigue can in uence the RE [15]. Additionally, barefoot running has shown di erences in biomechanical behaviour [16] and muscular responses [17,18] when it is compared with classical running shoes. Compared to fatigue, strength training added to a normal training program for distance running can improve RE between 2% and 8%. An increase in muscle mass training programs around the proximal region of the lower limb, such as quadriceps or hamstring [19], or around the distal regions, such as the triceps surae [20] with plantar exion and dorsi exion ankle exercises, has shown some bene ts on RE. Accordingly, triceps surae and its relationship with the windlass mechanism [21] in the propulsion phase of gait and running has been reported to provide between 8% and 17% of the elastic energy that is needed for the heel-o phase [22,23] toward a suitable IMTPJ dorsi exion [24,25]. However, the electromyography (EMG) e ects in the triceps surae with limited dorsi exion of the IMTPJ that is induced by any orthotic dorsi exion restriction has never been studied. Understanding the EMG activity of this muscle will allow us to understand if the subjects could be increasing their energy cost during running, which is very important for an e cient RE [19]. However, no previous research has studied the e ect of a novel inverted rocker orthoses (NIRO) on the EMG activity of the triceps surae compared to traditional Morton's extension orthoses (TMEO) during running in the healthy population. Because of the restricting IMTPJ e ect of TMEO and its in uence on the windlass mechanism that is linked with the triceps surae [24,25], we hypothesized that TMEO (6 mm and 8 mm) may increase the EMG activity of the gastrocnemius medialis and lateralis muscles compared to the shoe only (SO) condition during running activity; in addition, regarding previous muscular activity changes that are reported with classical rocker soles [13], we hypothesized that NIRO (6 mm and 8 mm) may reduce the EMG of gastrocnemius medialis and lateralis compared to TMEO (6
mm) may increase the EMG activity of the gastrocnemius medialis and lateralis muscles compared to the shoe only (SO) condition during running activity; in addition, regarding previous muscular activity changes that are reported with classical rocker soles [13], we hypothesized that NIRO (6 mm and 8 mm) may reduce the EMG of gastrocnemius medialis and lateralis compared to TMEO (6 mm and 8 mm), and this may increase EMG compared to SO in healthy people during running activity. 2. Materials and Methods The public institutional review board at Virgen Macarena-Virgen del Roc½o hospitals, reviewed and approved the present study (certi cate number f7f4a6567676d7ba7163bce0d15e7f98c9f33354). Ethical and human criteria were followed according to the Declaration of Helsinki, and signed informed consent was obtained from all subjects.
Sensors2020,20, 3205 3 of 12 2.1. Design and Sample Size The statistics unit at the Spanish public university used software to assess the suitable sample size to perform this cross-sectional observational study and to study the di erence in the EMG changes in the gastrocnemius medialis and lateralis muscles between SO, NIRO 6 mm, NIRO 8 mm, TMEO 6 mm, and TMEO 8 mm groups during running. Previous data on the triceps surae showed7.0 0.6 millivolts (mV)wearing 9-mm heel lifts compared to 4.9 0.6 mV wearing typical shoes [26]. Taking into account a statistical power of 80%, =20%, a 95% con dence interval (CI), and =0.05, 30 subjects were needed to complete the study. Considering the typical loss of 20% subjects, 24 participants were recruited. However, three individuals were excluded from the study because they felt pain and discomfort during the EMG assessment. Reporting of Observational Studies in Epidemiology (STROBE) [27] criteria and a randomly consecutive sampling technique were followed to develop the present research. 2.2. Subjects The following inclusion criteria were used to select the participants: (1) healthy participants, between 18 and 30 years old; (2) recreational runners with 34 h of training per week with more than 1 year of experience; (3) neutral foot posture index (FPI) with values between 0 and+5 points according to a validity tool [28]; and (4) no injuries or pain at the time of the test. The exclusion criteria were as follows: (1) any lower limb injury during the last 6 months; (2) less movement in either foot joint than what is required to perform the optimal biomechanics according to normal values [29,30]; or (3) under the in uence of any drugs e ects at the time of the measurements. Body mass index (BMI) was taken into account to select a homogeneous sample, using Quetelet's equation as follows: BMI=weight (kg)/height (m 2 ) [31]. 2.3. Instrumentation and Assessments Neurotrac ® Simplex Plus (Verity Medical Ltd., Braish eld, UK) EMG electronic device with a USB-Bluetooth [32] was used to study the triceps surae activity during the running test. The recording range on the device
(BMI) was taken into account to select a homogeneous sample, using Quetelet's equation as follows: BMI=weight (kg)/height (m 2 ) [31]. 2.3. Instrumentation and Assessments Neurotrac ® Simplex Plus (Verity Medical Ltd., Braish eld, UK) EMG electronic device with a USB-Bluetooth [32] was used to study the triceps surae activity during the running test. The recording range on the device was 0.2 mV to 2000 mV, with a sensitivity of 0.1 mV RMS, 10 m of free wireless (Bluetooth) connection range and an accuracy of 4% of the reading from mV+/ 0.3 mV to 200 Hz, with a bandpass lter of 18 Hz+/ 4 Hz to 370 Hz+/ 10% for readings below 235 mV. The signal was assessed using self-adhesive circular surface electrodes that were 30 mm in diameter and made of high-quality hydrogel and conductive carbon lm to detect the electrical action of the muscle bers. The signal from each electrode was captured by the receiver module and ltered automatically by the Neurotrac ® software (Verity Medical Ltd., Braish eld, UK). It was sent by a unidirectional radioelectric secure connection to the computer and it was digitally transformed by the software to generate activity patterns data for each electrode. 2.4. Materials NIRO was made using a at sheet of ethylene-vinyl acetate (EVA) with a semi-rigid density that was 3 mm thick, without any orthotic element that could interface with normal biomechanical behaviour of the foot. NIRO had an inverted rocker composed of EVA medium that was 5 cm long, 2 cm wide, and 6 mm thick. Its proximal and distal edges were smoothly polished, and it was placed on the IMTPJ. The whole orthotic was covered with an EVA soft layer that was 1 mm thick (Figure). The TMEO was made with the same at sheet of semi-rigid EVA that was 3 mm thick without any orthotic element and with a rectangular at piece of EVA medium (6 mm thick) that was placed under the IMTPJ area and it was covered with an EVA soft layer that was 1 mm thick (Figure). The neutral SOs were New Feel PW
was made with the same at sheet of semi-rigid EVA that was 3 mm thick without any orthotic element and with a rectangular at piece of EVA medium (6 mm thick) that was placed under the IMTPJ area and it was covered with an EVA soft layer that was 1 mm thick (Figure). The neutral SOs were New Feel PW 100M medium grey (ref. number: 2018022). NIRO and TMEO were made in an external orthopedic laboratory that was blinded to the study protocol.
Sensors2020,20, 3205 4 of 12Sensors 2020, 20, x FOR PEER REVIEW 4 of 12 Figure 1. Novel inverted rocker orthotic (NIRO). A flat sheet of ethylene-vinyl acetate (EVA) with an inverted rocker piece of EVA medium 6 mm thick under IMTPJ (bulked raised shape) covered with a yellow EVA soft layer that was 1 mm thick. Figure 2. Typical Morton’s extension orthotic (TMEO). A flat sheet of ethylene-vinyl acetate (EVA) with a rectangular flat piece of EVA medium 6 mm thick under IMTPJ covered with a black EVA soft layer that was 1 mm thick. 2.5. Procedure The podiatric clinician researcher (RSG) performed a physical assessment of the subjects and applied the eligibility criteria. To visualize the muscle belly, each subject was asked to perform plantarflexion of the ankle joint for a few seconds. The surface electrodes were then placed longitudinally onto the most prominent bulge of the gastrocnemius medialis and lateralis, based on the “European recommendations for surface EMG” [33]. The subjects were then asked to stand on one leg in the tip-toe position using their dominant foot for 5 s to set the maximal voluntary contractions that were needed in the strongest limb to calibrate the software and to normalize EMG data amplitudes for each test [34]. This was followed by acclimatization of subjects to a motorized treadmill at 5.17 km/h for 3 min [17]. The participants were divided randomly in gastrocnemius lateralis or medialis group by choosing a sealed envelope that assigned them to one group or another to begin the test; after that, they selected one of the five sealed envelopes with each of the five different conditions of the study (SO, NIRO 6 mm, NIRO 8 mm, TMEO 6 mm, TMEO 8 mm) to set randomly the order of the test. The 11 subjects who began with medialis gastrocnemius assessments, did the lateralis test following the same randomized protocol for each of the five different conditions and vice versa for the 12 participants who began with the lateralis test (Figure 3). Three running trials at 9 km/h [35] under five different conditions (SO, NIRO 6
randomly the order of the test. The 11 subjects who began with medialis gastrocnemius assessments, did the lateralis test following the same randomized protocol for each of the five different conditions and vice versa for the 12 participants who began with the lateralis test (Figure 3). Three running trials at 9 km/h [35] under five different conditions (SO, NIRO 6 mm, NIRO 8 mm, TMEO 6 mm, and TMEO 8 mm) on the same day were randomly performed. The duration of each trial was 1 min. For each subject, the mean EMG muscle activity pattern [36] of the gastrocnemius medialis of the dominant leg was recorded during the last 30 s of each 1-min trial, which was performed three times, leaving 5 min of rest between each test [37]. To avoid a potential imbalance, the same condition was added to contralateral foot. The same protocol was performed to Figure 1.Novel inverted rocker orthotic (NIRO).Sensors 2020, 20, x FOR PEER REVIEW 4 of 12 Figure 1. Novel inverted rocker orthotic (NIRO). A flat sheet of ethylene-vinyl acetate (EVA) with an inverted rocker piece of EVA medium 6 mm thick under IMTPJ (bulked raised shape) covered with a yellow EVA soft layer that was 1 mm thick. Figure 2. Typical Morton’s extension orthotic (TMEO). A flat sheet of ethylene-vinyl acetate (EVA) with a rectangular flat piece of EVA medium 6 mm thick under IMTPJ covered with a black EVA soft layer that was 1 mm thick. 2.5. Procedure The podiatric clinician researcher (RSG) performed a physical assessment of the subjects and applied the eligibility criteria. To visualize the muscle belly, each subject was asked to perform plantarflexion of the ankle joint for a few seconds. The surface electrodes were then placed longitudinally onto the most prominent bulge of the gastrocnemius medialis and lateralis, based on the “European recommendations for surface EMG” [33]. The subjects were then asked to stand on one leg in the tip-toe position using their dominant foot for 5 s to set the maximal voluntary contractions that were needed in the strongest limb to calibrate the software and to
onto the most prominent bulge of the gastrocnemius medialis and lateralis, based on the “European recommendations for surface EMG” [33]. The subjects were then asked to stand on one leg in the tip-toe position using their dominant foot for 5 s to set the maximal voluntary contractions that were needed in the strongest limb to calibrate the software and to normalize EMG data amplitudes for each test [34]. This was followed by acclimatization of subjects to a motorized treadmill at 5.17 km/h for 3 min [17]. The participants were divided randomly in gastrocnemius lateralis or medialis group by choosing a sealed envelope that assigned them to one group or another to begin the test; after that, they selected one of the five sealed envelopes with each of the five different conditions of the study (SO, NIRO 6 mm, NIRO 8 mm, TMEO 6 mm, TMEO 8 mm) to set randomly the order of the test. The 11 subjects who began with medialis gastrocnemius assessments, did the lateralis test following the same randomized protocol for each of the five different conditions and vice versa for the 12 participants who began with the lateralis test (Figure 3). Three running trials at 9 km/h [35] under five different conditions (SO, NIRO 6 mm, NIRO 8 mm, TMEO 6 mm, and TMEO 8 mm) on the same day were randomly performed. The duration of each trial was 1 min. For each subject, the mean EMG muscle activity pattern [36] of the gastrocnemius medialis of the dominant leg was recorded during the last 30 s of each 1-min trial, which was performed three times, leaving 5 min of rest between each test [37]. To avoid a potential imbalance, the same condition was added to contralateral foot. The same protocol was performed to Figure 2.Typical Morton's extension orthotic (TMEO). A at sheet of ethylene-vinyl acetate (EVA) with an inverted rocker piece of EVA medium 6 mm thick under IMTPJ (bulked raised shape) covered with a yellow EVA soft layer that was 1 mm thick. A at sheet of ethylene-vinyl acetate (EVA) with a rectangular at piece
foot. The same protocol was performed to Figure 2.Typical Morton's extension orthotic (TMEO). A at sheet of ethylene-vinyl acetate (EVA) with an inverted rocker piece of EVA medium 6 mm thick under IMTPJ (bulked raised shape) covered with a yellow EVA soft layer that was 1 mm thick. A at sheet of ethylene-vinyl acetate (EVA) with a rectangular at piece of EVA medium 6 mm thick under IMTPJ covered with a black EVA soft layer that was 1 mm thick. 2.5. Procedure The podiatric clinician researcher (RSG) performed a physical assessment of the subjects and applied the eligibility criteria. To visualize the muscle belly, each subject was asked to perform plantar exion of the ankle joint for a few seconds. The surface electrodes were then placed longitudinally onto the most prominent bulge of the gastrocnemius medialis and lateralis, based on the European recommendations for surface EMG [33]. The subjects were then asked to stand on one leg in the tip-toe position using their dominant foot for 5 s to set the maximal voluntary contractions that were needed in the strongest limb to calibrate the software and to normalize EMG data amplitudes for each test [34]. This was followed by acclimatization of subjects to a motorized treadmill at 5.17 km/h for 3 min [17]. The participants were divided randomly in gastrocnemius lateralis or medialis group by choosing a sealed envelope that assigned them to one group or another to begin the test; after that, they selected one of the ve sealed envelopes with each of the ve di erent conditions of the study (SO, NIRO 6 mm, NIRO 8 mm, TMEO 6 mm, TMEO 8 mm) to set randomly the order of the test. The 11 subjects who began with medialis gastrocnemius assessments, did the lateralis test following the same randomized protocol for each of the ve di erent conditions and vice versa for the 12 participants who began with the lateralis test (Figure). Three running trials at 9 km /h [35] under ve di erent conditions (SO, NIRO 6 mm, NIRO 8 mm, TMEO 6 mm, and TMEO 8 mm)
Description
The study investigates the impact of orthoses on muscle activity in runners.