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Original Article

Gait among Patients with Myotonic Dystrophy Type 1: A Three‑Dimensional Motion Analysis Study

Vincent Tiffreau1, Christine Detrembleur2, Peter Van Den Bergh3, Anne Renders3, Virginie Kinet3, André Thevenon1, Etienne Allart4,5, Thierry Lejeune2 1PMR Unit, University Hospital of Lille, Research Unit 4488 Health, Physical Activityand Muscle, University of Lille, F-59000 Lille Cedex, 2Rehabilitation and Physical Medicine Unit, Avenue Mounier, 53 – UCL 5375, 1200 Brussels, Belgium, 3Neuromuscular Disease Center, Saint-Luc Hospital, 1200 Brussels, Belgium, 4Neurorehabilitation Unit, Lille University Hospital, F-59000 Lille, France, 5Inserm U 1171, Degenerative and Vascular Cognitive Disorders, University of Lille, F-59045 Lille, France

Abstract

Objective: The objective was to characterize the gait abnormalities in myotonic dystrophy type 1 patients. Material and Methods: Outcomes variables were kinematic and kinetic parameters, timing of muscles, mechanical work and energy cost, and the motor function measure. Results: Despite a high cadence and a low ankle range of motion ratio, ankle extension power, and first extension moment of the knee during the stance, the mechanical work and energy cost were normal. The duration of electromyography activation of the gastrocnemius lateralis (GL) muscle was abnormally long. Conclusion: The hypothesis of a myotonic activity of the GL during the swing phase should be investigated.

Keywords: Electromyography, gait analysis, kinematics, kinetics, myotonic dystrophy type 1, treadmill

Introduction Although the myotonia is typically noted in the hand muscles of DM1 sufferers, it is not usually described in leg muscles. Myotonic dystrophy type 1 (DM1, also known as Steinert’s Nevertheless, Logigian et al. showed that waxing–waning disease) is the most prevalent hereditary neuromuscular myotonia occurred in distal leg muscles of patients with DM1.[6] disease (NMD) in Western countries.[1,2] The condition’s muscle‑related symptoms include distal and axial muscle Patients with DM1 suffer from gait impairments and have an [7] weakness and myotonia (residual resistance after muscle increased risk of falls. The gait impairment in DM1 has been [8] contraction that is attributed to a decrease in membrane attributed to distal muscle weakness and impaired balance. chloride permeability). Mechanisms such as peripheral neuropathy and central nervous system dysfunction have also been suspected.[9,10] The genetic defect underlying DM1 is an unstable, expanded CTG triplet repeat in the untranslated region of In 1996, Wright et al. provided the first report on gait in DM1 (in five participants).[11] The researchers showed that gait the dystrophia myotonica protein kinase (DMPK) gene on abnormalities in DM1 were related to distal weakness and the chromosome 19.[3] Recent molecular genetic studies have excessive use of hip muscles. described the impact of the CUG repeats in the DMPK transcripts on the biogenesis of several mRNAs, which cause Galli et al. analyzed the gait parameters of ten DM1 patients. the polymorphic symptoms in DM1. It has been shown that In addition to the expected distal muscle weakness, the RNA inclusions in the nuclei of patients with DM1 interfere researchers also observed abnormal muscle activation in the with splicing of the chloride channel 1 gene (CLCN1) mRNA. This leads to the abnormal inclusion of CLCN1’s alternative Address for correspondence: Dr. Vincent Tiffreau, PMR Unit, University Hospital of Lille, Rue du Pr Verhaegue, [4] exons 6B and/or 7A and retention of intron 2. The end result F‑59037 Lille Cedex, France. is abnormally high membrane resistance for CLC‑1, which has E‑mail: vincent.tiffreau@chru‑lille.fr been correlated with the electrical hyperexcitability of muscle [5] fibers and therefore myotonia. This is an open access journal, and articles are distributed under the terms of the Creative Commons Attribution‑NonCommercial‑ShareAlike 4.0 License, which allows others to Access this article online remix, tweak, and build upon the work non‑commercially, as long as appropriate credit Quick Response Code: is given and the new creations are licensed under the identical terms. Website: For reprints contact: [email protected] www.jisprm.org

How to cite this article: Tiffreau V, Detrembleur C, Van Den Bergh P, DOI: Renders A, Kinet V, Thevenon A, et al. Gait among patients with myotonic 10.4103/ijprm.ijprm_8_18 dystrophy type 1: A three-dimensional motion analysis study. J Int Soc Phys Rehabil Med 2018;1:65-71.

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Tiffreau, et al.: Gait among patients with DM1

distal leg muscles during gait.[10] Bachasson et al. observed Three‑dimensional instrumented gait analysis that the center of pressure (CoP) velocity was greater in Anthropometric parameters were measured and recorded. The DM1 patients than in healthy controls and correlated with neck participants were instructed to walk barefoot on a motorized flexion and ankle plantar flexion weakness.[12] Radovanović treadmill mounted on four 3D strain‑gauge force transducers.[17] et al. showed that temporal and stride characteristics were For each patient, the highest comfortable walking speed on the altered in DM1 and DM2 compared to healthy controls.[13] treadmill was recorded. Since previous studies have probably not elucidated all the gait abnormalities in DM1, we decided to assess gait in a group of Gait was assessed by 3D analysis. DM1 patients. Our study included a functional assessment and Segmental kinematics were measured with the Elite System (BTS, a three‑dimensional (3D) motion analysis (including kinematic, Italy) at 200 Hz. Eight CCD‑infrared cameras measured the 3D kinetic, and mechanical parameters, electromyography [EMG], coordinates of 19 reflective markers positioned on specific and energy cost). Hence, the objectives of the present study anatomical landmarks. Euler angles and Newtonian mechanics were to (i) characterize gait abnormalities in a population of were used to compute the angular displacements of the pelvis, hip, patients with DM1 and (ii) analyze the relationship between knee, and ankle.[18] For each participant, 10 successive walking gait variables and functional impairment. The results should cycles were recorded and averaged. Data were normalized allow an improvement of the rehabilitation interventions. against time expressed as a percentage of the gait cycle, with Preliminary results of this study were presented at the 0% corresponding to the initial foot contact on the analyzed Biomechanical Society Congress in Toulouse (France) in side. Spatiotemporal parameters were assessed as 3D kinematics [19] October 2012 and published in a short report.[14] according to the method described by Mickelborough et al. Kinetics Materials and Methods Kinetic data (Mz: muscle moment and Mk: power) were Participants computed by synchronization of the kinematics and 3D ground The study participants were all affected by DM1 and had a reaction forces (GRFs). The algorithm described by Davis and [20] confirmed molecular diagnosis (>50 CTG repeats) aged from Cavanagh enables determination of the CoP and vertical GRF 14 to 53 years. They were recruited from the NMD outpatient under each foot. Using an inverse dynamic approach, exploitation center at Saint‑Luc University Hospital (Brussels, Belgium). of the GRF, kinematic, and anthropometric data enabled us to The participants had to be able to walk at least 100 m without compute the net joint moments of the hip, knee, and ankle in the [18] assistance and were not included in the study if they presented sagittal plane. The power at each joint was calculated as the any of the following criteria: inability to walk on the treadmill, product of the angular speed and the net joint moment. damage to the central nervous system or musculoskeletal Mechanical parameters system that could affect the person’s ability to walk, and The total positive mechanic work (Wtot) performed by the finally, pregnancy. muscles during walking was divided into two components: (i)

A total of 15 patients participated to this study (10 males the external work (Wext) performed to move the center of body and 5 females; mean ± standard deviation [SD] age: mass (COMb) relative to the surroundings and (ii) the internal 38.1 ± 11.4 years; mean time since disease onset: work (Wint) performed to move body segments relative to 16.3 ± 7.9 years). All the participants had been provided with the COMb. The internal and external works were computed written information on the study’s objective and protocol and following the method described by Willems et al.[21,22] had given their written, informed consent before involvement Electromyography in any study‑specific procedures. The muscle electrical activity of the vastus lateralis (VL), This study was approved by the Independent Ethics Committee semitendinosus (ST), tibilalis anterior(TA), and gastrocnemius at Saint‑Luc University Hospital. lateralis (GL) muscles was recorded by a wireless EMG system (BTS, Italy) through surface electrodes (Medi‑Trace, Data collection Graphic Controls Corporation, NY, USA). The onset and cessation The participants underwent a clinical examination and of muscle activity were both visually and mathematically functional assessments: determined by computing the EMG threshold voltage, as described 1. A manual muscle test according to the 11‑point medical [23] [15] by van Boxtel et al. The mean onset and cessation time for each research council scale activation sequence was calculated over 10 gait cycles, and the 2. The motor function measure (MFM), a 32‑item functional duration of the muscle activity was computed accordingly. scale that was developed to assess the severity of NMD. The MFM was validated in a large population of Energetics participants affected by various NMDs[16] The metabolic cost of walking was determined from the [24] 3. A timed 10‑m walking test: The participants were asked to patient’s breath-by-breath oxygen consumption (Vo2) and walk 10 m at a comfortable speed. The average completion carbon dioxide production measured throughout the treadmill time for three trials was recorded. test with an ergospirometer (Quark b2, Cosmed, Italy).

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Treadmill test protocol cases and in adulthood in others. According to their medical Energy consumption was measured throughout the treadmill history, none of our participants had lower extremity surgery. test. Data acquisition started with the rest period. Thereafter, The mean spontaneous comfortable gait speed in the 10‑m the participants walked at a self‑chosen, comfortable speed. walking test was 3.9 ± 0.9 km/h. Depending on the patient, the Kinematic, kinetic, mechanical, and EMG data were analyzed gait speed during the treadmill test ranged from 1.3 to 4 km/h. together during the same 40‑s acquisition. Energy consumption The mean motor function measure (MFM) was 91.9% ± 5.8%. measurement required a steady state of at least 2 min. Two Gait parameters acquisitions were recorded. Cadence was higher in all DM1 patients than in healthy Selected gait variables controls (101.3 ± 13.9 and 81.15 ± 21.5, respectively, Several variables were extracted from the computed mean P < 0.0001), whereas step length was lower in all patients kinetic and kinematic curves: other than patient 5 (0.48 ± 0.14 and 0.58 ± 0.14, respectively, 1. The sagittal hip range of movement (ROM) was calculated P = 0.023). as the difference between the maximum hip extension and maximum hip flexion positions Kinematics 2. The highest knee extension angle during stance phase The hip ROM was lower in patients relative to healthy 3. The ankle sagittal ROM ratio (AROMr) was calculated controls (35.1 ± 7.8 and 39.8 ± 7, respectively, P = 0.0024). as the ankle dorsiflexion ROM during the swing phase Five patients showed hyperextension of the knee during the divided by the ROM over the entire gait cycle stance phase. 4. The maximum extension and flexion moments and power of the hip The AROMr during the swing phase was dramatically lower 5. The first (MzKnee) and second extension moments of the in the patient population than in healthy controls (24 ± 23 and knee during the stance phase 63.8 ± 15.1, respectively, P < 0.0001) [Figure 1a‑c]. 6. The maximum extension moment (MzA) and power (PwA) Kinetics of the ankle before toe‑off. The positive extension moment of the hip during the The duration of the EMG activity of the GL was recorded, as initial stance phase (MzH1) was higher in patients than in described above. healthy controls (0.38 ± 0.21 and 0.29 ± 0.17, respectively, P < 0.0001), whereas the negative flexion moment (MzH2) Type of values during swing phase was lower in patients than in healthy The values are presented in diagrams that also show reference controls (−0.48 ± 0.7 and −0.4 ± 0.22, respectively, P = 0.03). values from a population of eight healthy volunteers (mean The hip extension power (PwH1) was lower in patients than in age: 29 ± 16 years; weight: 65 ± 10 kg; height: 1.74 ± 0.05 m; controls (0.24 ± 0.1 and 0.27 ± 0.24, respectively, P < 0.0001), no history of orthopedic or neurologic pathologies affecting [25] and the hip flexion power (PwH2) was lower in patients than in the legs) evaluated at walking speeds from 1 to 6 km/h. The controls (0.3 ± 0.14 and 0.32 ± 0.27, respectively, P = 0.0021). previous study of Lobet et al. described the gait on the treadmill of a normal population of eight participants: as walking speed The negative extension power of the knee (Pknee) was was shown to influence gait variables,[25] the values of the studied higher in patients than in healthy controls (−0.82 ± 0.17 parameters were presented for the normal population with the and −1.22 ± 0.71, respectively, P = 0.0043). normal mean values (±1 SD) as a regression line. The values The plantar flexion moment of the ankle during the of the patients were plotted as a function of gait speed, with the propulsion phase (MzA) was lower in patients than in healthy normal as described above. For the EMG, the activation time of controls (0.7 ± 0.35 and 0.81 ± 0.24, respectively, P = 0.0022). the GL was plotted with the normative data that were published by Stoquart et al. for a population of 12 healthy volunteers.[26] Mechanical work The external work (W ) in DM1 patients did not differ from Statistical analysis ext healthy controls, whereas the internal work (W ) was higher in A covariance analysis including participants as a variant int patients (0.32 ± 0.06 and 0.19 ± 0.06, respectively, P < 0.0001). was performed. Statistical analyses were performed using Moreover, the metabolic cost of DM1 patients did not differ SigmaStat software (version 2.0; Systat Software Inc., from healthy controls. Chicago, IL, USA) and SPSS software (version 15.0; SPSS Inc., Chicago, IL, USA), with the significance level set to Results of gait parameters, kinematic and kinetic data, and P = 0.05. mechanical work in patients and controls are reported in Table 2. Results Electromyography Description of the participants Activation of the GL was abnormally long in DM1 patients Descriptive data on the study population are summarized in and persisted during the swing phase. Figure 2 shows the Table 1. The onset of DM1 had occurred in childhood in three GL activation for each participant, compared with a normal

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Table 1: Description of the population Subject Gender Age Weight Height BMI Time since Spontaneous MFM T MFM D1 MFM D2 MFM D3 (male/ (years) (kg) (cm) (kg/m2) onset speed (%) (%) (%) (%) female) (years) (km/h1) 1 Female 53 50 160 19.5 3 2.9 89.58 79.49 97.22 100 2 Male 48 100 185 29.2 28 3.4 84.38 64.1 97.2 95.24 3 Male 49 85 191 23.3 24 2.8 71.88 48.72 94.44 76.19 4 Female 38 70 167 25.1 11 2.58 93.75 87.18 97.22 100 5 Male 38 71.5 178 22.6 23 3.2 89.58 79.49 94.44 100 6 Male 40 72 175 23.5 10 4.1 91.67 87.18 97.22 90.48 7 Male 46 98 177 31.3 10 3.55 95.83 92.31 100 95.24 8 Male 47 88 178 27.8 27 4.6 100 100 100 95.24 9 Male 42 86 177 27.5 24 3.27 82.29 66.67 91.67 95.24 10 Male 19 80 175 26.1 14 4.4 87.5 79.49 94.44 90.48 11 Female 38 53 165 19.5 21 4.4 96.88 94.44 97.22 100 12 Female 35 66 170 22.8 15 4.5 95.93 89.74 100 100 13 Male 22 69 190 19.1 18 5.1 100 100 100 100 14 Male 14 54 179 16.8 12 5.1 98.95 100 100 95.23 15 Female 42 51 161 19.7 5 4.7 98.96 100 100 90.48 Mean±SD 38.1±11.4 72.9±16.5 175.2±9.4 23.6±4.2 16.3±7.9 3.9±0.9 91.81±7.89 84.59±15.24 97.40±2.67 94.92±6.35 Minimum 14 50 160 16.8 3 2.58 71.88 48.72 91.67 76.19 Maximum 53 100 191 31.3 28 5.1 100 100 100 100 SD: Standard deviation, BMI: Body mass index, MFM: Motor function measure

Table 2: Results of gait parameters, kinematic and kinetic data, and mechanical work in patients and controls Patients Controls P n Mean±SD Minimum Maximum n Mean±SD Minimum Maximum Cadence (step/min) 15 101.3±13.9 74.2 123 32 81.15±21.5 43.7 114.2 <0.0001 Step length (m) 14 0.48±0.14 0.27 0.67 32 0.58±0.14 0.3 0.81 0.023

Wext (J/kg/m) 14 0.28±0.08 0.15 0.45 31 0.29±0.06 0.2 0.42 0.7

Wint (J/kg/m) 15 0.32±0.06 0.22 0.43 31 0.19±0.06 0.09 0.32 <0.0001

Wtot (J/kg/m) 14 0.6±0.12 0.43 0.86 31 0.49±0.07 0.36 0.61 0.0004 Cost (J/kg/m) 14 2.56±1.34 0.83 6.44 31 2.5±1 1.29 5.24 0.734 Hip ROM (°) 15 35.1±7.8 19.7 46 32 39.8±7 24.6 52.5 0.0024 Knee ROM (°) 15 51.9±7.1 41 65 32 55±9.7 37.5 74.9 0.314 AROMr (°) 15 24±23 0.02 68.4 32 63.8±15.1 41.1 86.7 <0.0001 MzH1(N.m/kg) 15 0.38±0.21 0.09 0.79 32 0.29±0.17 0.08 0.77 <0.0001 MzH2 (N.m/kg) 15 −0.48±0.7 −3 −0.06 32 −0.398±0.22 −0.85 −0.12 0.0298 MzKnee (N.m/kg) 15 0.21±0.18 −0.01 0.67 32 0.55±0.22 0.26 1.06 0.3157 MzA (N.m/kg) 15 0.7±0.35 0.08 1.26 32 0.81±0.24 0.37 1.29 0.0022 PwH1(W/kg) 15 0.24±0.1 0.09 0.4 32 0.27±0.24 0.02 0.95 <0.0001 PwH2 (W/kg) 15 0.3±0.14 0.05 0.62 32 0.32±0.27 0.08 1.08 0.0021 Pknee (W/kg) 15 −0.82±0.17 −1.14 −0.55 32 −1.22±0.71 −2.88 −0.39 0.0043 PwA (W/kg) 15 0.74±0.71 0.05 2.15 32 1.52±1 0.18 3.84 0.4399

Wext: External work, Wint: Internal work, Wtot: Total work, Cost: Metabolic cost of walking, ROM: Range of motion, AROMr: Ankle range of motion ratio, MzH1 and 2: First and second muscle moment of the hip, MzKnee: Muscle moment of the knee, MzA: Muscle moment of the ankle, PwH1 and 2: First and second muscle power of the hip, Pknee: Muscle power of the knee, PwA: Muscle power of the ankle, SD: Standard deviation

activation phase and as a function of speed. The normative Discussion data were published by Stoquart et al. for a population of 12 The present study’s primary objective was to describe gait healthy volunteers.[26] abnormalities in a population of people with DM1. Although The Spearman coefficient showed that the duration of the DM1 prevalence is not different according to the gender, muscle activation was negatively correlated with the we have to notice that men were twice more included (10 men AROMr (right leg: r = −0.58, P = 0.028; left leg: r = −0.63, vs. 5 women) in our study.[27] Moreover, since the inclusion P = 0.015). criteria included the ability to walk 100 m, the clinical severity

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Tiffreau, et al.: Gait among patients with DM1

40 AROM ratio (%) 100 A2 ) A4 80 20 A1 60

0 40

Ankle displacement (° 20 -20 0 A3

-40 23456 Stance Phase Swing Phase -1 Gait stride(%) speed (km.h ) a b

df

40 )

20

0

Ankle displacement (° -20

100% -40 Stance phase Swing phase Gait stride (%) c Figure 1: (a) Change in ankle displacement (in degree) as a function of the gait stride (in percentage). We calculated the ankle sagittal range of motion ratio: A2–A3 represents the entire ankle sagittal range of motion and A4–A3 represents the dorsiflexion range of movement during the swing phase. The ankle sagittal range of motion ratio is defined as (A4–A3)/(A2–A3).(b) The ankle sagittal range of motion ratio for each patient (black circles) as a function of treadmill speed. The black line and the gray area represent the mean (±1 standard deviation) values for healthy controls. (c) The ankle displacement of patient #5. The green and red lines represent the right and left ankle displacements, respectively. The black line and the gray area represent the mean (±1 standard deviation) values for healthy controls. Note the almost complete absence of dorsiflexion (df) during the swing phase

of our population, with a mean MFM score of 91.9%, was not 7 Lateral Gastrocnemius representative of the DM1 population. 6 Although gait in DM1 has already been characterized in the

5 literature, this is the first study that calculated the mechanical work and energy cost of gait in patients with DM1. Despite )

-1 4 a higher internal work in our results, we did not observe an increase in metabolic cost. This might have been due to 3 effective proximal and axial muscle compensations.

Speed (km. h 2 Furthermore, no studies have reported gait analysis in DM1 on a treadmill except the short preliminary results published 1 in 2012.[14] There are several advantages in using a treadmill 0 for gait analysis. First, the speed is controlled, which enables 020406080100 comparison with a control population under the same gait Swing phase Stance phase conditions. Second, the duration of gait is much longer, so Gait stride (%) it is possible to record a large number of successive gait cycles. Third, since our laboratory includes a treadmill Figure 2: The activation phase of the gastrocnemius lateralis in equipped with strain‑gauge sensors, it enables the energy patients (dark thin lines), compared with normal activation (gray area). The dashed line corresponds to the transition from stance (to cost calculation. Gait on a treadmill can be considered as the left of the dashed line) to the swing phase (to the right of the “abnormal,” since the patient has to control his/her gait in dashed line). Normal data are extracted from the study of Stoquart order to follow the treadmill. Balance can also be perturbed. et al.[26] This explains why the gait speed on the treadmill was lower

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than the spontaneous comfortable speed in the 10‑m walking the present study, we decided to quantify muscle activation by test. Nevertheless, this method has shown good reliability identifying the onset and cessation of each muscle activation when measured at 1‑day and 1‑month intervals in adult sequence and computing the average duration of activation patients after stroke.[28] for each patient and for each leg. As shown in Figure 2, activation was abnormally long or even permanent (i.e., When compared with a control (healthy) population, all but during the swing phase) in some cases. Moreover, we one of the patients had an abnormally low step length and used observed that the duration of muscle activity was negatively an abnormally high cadence to maintain their speed on the correlated with the AROMr. This is an unexpected result. treadmill. We suggest that the ankle plantar flexor weakness and the abnormal agonist/antagonist co‑activations in the Since DM1 affects both ankle dorsal flexion and plantar leg muscles restrict the ability to lengthen the step in DM1. flexion muscle, abnormal prolonged activity of GL has not already been described. Nevertheless, DM1 is associated We studied the AROMr, which is related to foot drop. The ROM with delayed relaxation following contraction. Whereas ratio (ROMr) was described by Ferrarin et al. in a population of myotonic muscle activity is present in most of the limb, it is children with Charcot–Marie–Tooth disease.[29] Since the overall classically observed in the hand and affects hand function. ROM for ankle dorsiflexion can be low when the Achilles tendon Nevertheless, is has although been described in lower limb shortens, the ROMr is a better guide to active dorsiflexion ability muscles according to Mankodi and Grunseich.[31] Since GL during the swing phase [Figure 1]. Our present kinematic and was abnormally active during the swing phase in our study, kinetic analyses showed an impairment of the AROMr and ankle we suggest that impairment of the AROMr is a consequence propulsion moment in DM1, as previously described by Wright of abnormal calf muscle activation combined with muscle et al. and Galli et al.[10,12] Although this could be due to weakness impairment of dorsal flexion muscles. of the dorsal flexors, our observation of abnormally long (and sometimes permanent) EMG activity in the GL suggests that Our study did not reveal any mechanical work and metabolic dorsal flexion is reduced by the abnormal activation of the cost abnormalities in DM1 patients. Despite high internal work, antagonists during the swing phase. Nevertheless, we notice the metabolic cost was normal. As shown by Stoquart et al., that passive ankle dorsiflexion of the ankle was not recorded, the energy cost increase in hemiplegic patients is due to the whereas this could although affect AROMr. mechanical work performed by the healthy limb in moving the [32] COMb . This is not the case in DM1, which affects the body We did not observe the abnormal hip motion in the stance symmetrically. We suggest that biomechanical adaptations [12] phase described by Wright et al. involving the less impaired muscles are effective. A larger Although the knee flexion moment was not higher in our study with more patients comparing more affected with less population than in the patients studied by Wright et al., we affected patients could probably be more informative. This observed a decrease in the knee extension power during the hypothesis must be assessed in mechanical analyses of other stance phase. This knee extension power is due to eccentric muscular dystrophies. contraction of the quadriceps during the initial stance phase and There are several limitations in this study. Although DM1 is impaired in the DM1 population by low knee flexion (and, is one of the most frequent hereditary NMDs, it is still a in some cases, hyperextension) during stance. rare disease; this explains why the population is small and A major kinetic abnormality observed in our study was the heterogeneous. A study including adults at the onset of the impairment of the ankle extension moment before toe‑off. This disease could be more informative. observation is directly related to plantar flexor weakness. As The patients’ data were compared to a data set of eight healthy shown in Figure 2a, ankle extension power was abnormally participants who walked at different velocities. The normal low in 13 of the 15 patients – even in less affected patients who population had been described previously and is not matched scored the highest possible MFM. Although distal weakness to the patient population. Nevertheless, the normal population is a very typical feature in DM1, mild clinical impairment did not differ from the patients on in term of age and gender. of the GL is not easy to assess because it is one of the most powerful muscles in the body. Thus, kinetic analysis enables We conclude that kinematics and kinetics are affected in the the assessment of ankle extension moment loss in less affected population of patients affected by DM1, even in a patient patients. This clinically almost undetectable calf weakness with light functional impairment. Furthermore, we noted that can also explain the gait difficulties observed in patients who the duration of GL activation was abnormal in all patients. appear to have normal muscle function. The use of dynamic Although it is not possible to affirm that this hyperactivation orthotics may be indicated in the latter patients; Aiello et al. is a manifestation of myotonia, it seems to play a major role described the benefits of using an ankle‑foot orthosis with in gait abnormality in DM1. anterior support, which improved power absorption and created a push‑off effect in patients with DM1.[30] Conclusion Another major feature was abnormal muscle activation, as The major gait abnormalities in patients with DM1 are assessed by EMG and as recently observed by Galli et al.[10] In weakness and abnormal activation of the calf muscles.

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The Journal of the International Society of Physical and Rehabilitation Medicine ¦ Volume 1 ¦ Issue 2 ¦ July-September 2018 71