EFFECTS OF OBESITY ON GAIT PATTERN IN YOUNG INDIVIDUALS WITH DOWN SYNDROME
Manuela Galli1,2, Veronica Cimolin1, Chiara Rigoldi1, Claudia Condoluci2, Giorgio Albertini2 1 Department of Electronics, Information and Bioengineering. Politecnico di Milano, Milano, Italy 2 IRCCS “San Raffaele Pisana”, San Raffaele SpA, Roma, Italy
Corresponding author: Veronica Cimolin, PhD
Department of Electronics, Information and Bioengineering Politecnico di Milano
p.zza Leonardo Da Vinci 32 20133 Milano Italy veronica.cimolin@polimi.it 1 2 3 5 6 7 8 9 10 11 12 13 14 15 16 17
EFFECTS OF OBESITY ON GAIT PATTERN IN YOUNG INDIVIDUALS WITH DOWN SYNDROME
ABSTRACT
In individuals with Down syndrome (DS) the prevalence of obesity is widespread; despite this, there are no experimental studies on the effect of obesity on gait strategy in DS individuals. The aim of this study is to assess the clinical gait analysis of a group of obese individuals with DS and a group of non-obese individuals with DS to see if obesity produces a different gait pattern in these participants. In addition, although females and males share a similar mass, they are characterized by different fat distribution and/or accumulation; so the presence of differences between females and males inside the two DS groups was investigated. Gait Analysis data of a group of 78 young individuals with DS and 20 normal weight participants in the 5-18 year age range were considered. Among DS individuals, 40 were classified as obese (Obese DS group), while 38 were classified as normal weight (non-obese groups). A 3D Gait Analysis was conducted using an optoelectronic system, force platforms and video recording. Spatio-temporal, kinematic and kinetic parameters were identified and calculated for each participant. Our results show that most of parameters were similar in the two groups of DS participants; the only differences were in terms of stance duration, longer in obese DS group, and dorsiflexion ability during swing phase, which was limited in obese DS group. The two DS groups were significantly different in terms of ankle stiffness (Ka index): both groups were characterised by reduced values as compared to the control group (CG), but the Obese group presented lower values with respect to non-obese participants. The data showed that females were characterised by significant modifications of gait pattern compared to males in both groups, in particular at proximal levels, such as hip and pelvis. Our findings reveal that the presence of obesity has effects on gait pattern in DS individuals and in particular on ankle joint stiffness. These results may have special clinical relevance; the biomechanical comparison of gait in young obese and non-obese DS individuals may provide a basis for developing either specific or common rehabilitative strategies. 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45
INTRODUCTION
Down Syndrome (DS) is a chromosomal disorder characterised by obesity, muscular hypotonia, ligament laxity and intellectual disability; it is associated with a number of signs and symptoms including intellectual disabilities, heart defects, craniofacial dysmorphia and childhood leukaemia (Wiseman et al., 2009). Obesity is more prevalent in DS than in any other disorder characterized by intellectual disability as well as in the non-affected population (Melville et al., 2005; Rimmer et al., 2010; Rubin et al., 1998). The percentage of individuals with DS who are overweight is estimated at above 30% in children and adolescents, but is likely to reach values up to 70-80% in adults (Melville et al., 2005; Rubin et al., 1998; Fujiura et al., 1997). Obesity raises concerns as regards its role as a risk factor for metabolic and cardiovascular diseases as well as a source and consequence of mobility limitations (Prasher et al., 1995; Luke et al., 1996; Bandini et al., 2005; Melville et al., 2005; Rimmer et al., 2010).
Obesity can be considered directly responsible for a wide range of musculoskeletal disorders (MSD) involving back, hip, knee, ankle and foot (Wearing et al., 2006a) and plays a major role in the functional limitation of daily activities (e.g. standing, walking, rising from a chair or a bed) due to impaired postural control, altered gait mechanics and reduced muscular strength (Wearing et al., 2006b).
Motor problems are most prominent in infancy, but continue to be of clinical importance in adulthood due to hypotonia, ligament laxity, decreased muscle mass and the excessive amount of fat, which influences the biomechanics of activities in everyday life, causing and increasing functional limitations over time (Rigoldi et al., 2011; Cimolin et al., 2010). Within the wide spectrum of physical and intellectual disabilities associated with DS, musculoskeletal diseases represent a serious issue, as they affect a significant proportion of individuals with DS; thus, treatment, increased physical activity and surveillance are fundamental in ensuring a good quality of life, especially considering the near normal life expectancy of DS adults. Musculoskeletal diseases tend to worsen progressively as the clinical picture advances, thus severely limiting individuals’ quality of life.
In literature, some studies have focused on the quantification of motor performance in individuals with DS; these studies evidence abnormal gait pattern and postural ability and a delay in performance maturation with respect to healthy individuals. In general, these studies are based on the characterization of motor performance of DS participants compared to normal weight individuals or other genetically obese individuals (Galli et al., 2008; Cimolin et al., 2010; Cimolin et al., 2013; Cimolin et al., 2011; Galli et al., 2013). Surprisingly, despite the wide prevalence of obesity in young individuals with DS, to the author’s knowledge there are no experimental studies
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on the effect of obesity on gait strategy in DS individuals. Only one study characterized the effect of obesity on foot-ground contact in young individuals affected by DS during quiet upright stance (Pau et al., 2013). The authors found that the anomalies introduced in the foot-ground contact by obesity are likely to aggravate existing negative podiatric issues associated with DS; in addition, significant differences were found in terms of gender. According to clinical experience, we expected that the association of obesity and DS would exacerbate gait alterations in these individuals.
It would be interesting to analyse clinically if, and to what extent, obesity modifies the gait pattern in a sample of young individuals with DS so as to define specific rehabilitative and/or weight reduction programs.
This retrospective observational study evaluates the clinical gait analysis of a group of obese individuals with DS and a group of non-obese individuals with DS with the aim of determining if obesity produces a different gait pattern in these participants. In addition, since females and males of similar mass are characterized by different body fat distribution and/or accumulation, we assessed gender differences within the two DS groups.
The results may be useful in defining a specific approach to rehabilitative management of young obese individuals with DS to foresee and prevent possible negative consequences during adulthood, especially as regards limitations on mobility in everyday life.
MATERIALS AND METHODS
Participants
The Gait Analysis (GA) data of a group of 78 young individuals with DS in the 5 to 18-year-old age range were extracted from the database of the Gait Analysis Lab of IRCCS San Raffaele Pisana in Rome. The distribution of chromosomal anomalies is pure trysomy 21 in all the DS individuals. Of these, 40 were classified as obese (Obese DS group) while 38 were classified as normal weight (Normal weight DS group). Participants were defined obese when their body mass index (BMI) resulted higher than the 95th percentile value of the growth charts calculated by Myrelid et al. (Myerelid et al., 2002) for a population of 354 Swedish individuals with DS aged 0-18. Such a BMI cut-off has also been proven reliable in identifying elevated fatness in young individuals with DS (Bandini et al., 2012). The participants with DS were all admitted to the Rehabilitation Unit of the IRCCS San Raffaele Pisana, Tosinvest Sanità, Roma, Italy, for multidisciplinary rehabilitation. Inclusion criteria for DS individuals were low to medium intelligence quotient (IQ), no clinical signs of dementia, no previous surgery or other significant orthopaedic treatments. All participants were able to understand and complete the test and to walk independently without the assistance or use of crutches, walkers or braces.
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Twenty age-matched individuals were included as controls (control group: CG). Exclusion criteria for the control group included overweight/obese and prior history of cardiovascular, neurological or musculoskeletal disorders. They showed normal flexibility and muscle strength and no obvious gait abnormalities.
The main anthropometric features of the three groups are reported in Table 1.
[Insert Table 1 About Here]
Written informed consent was obtained from the parents or, when applicable, from the participants.
Experimental set-up
Participants were assessed with a gait analysis test at the Movement Analysis Lab of the IRCCS San Raffaele Pisana, Tosinvest Sanità, Roma, Italy, using a 12-camera optoelectronic system (ELITE2002, BTS, Milan, Italy) with a sampling rate of 100 Hz, two force platforms (Kistler, CH) and 2 TV cameras Video System (BTS, Italy) synchronized with the system and the platforms for video recording.
To evaluate the kinematics of each body segment, passive markers were positioned on participants’ bodies as described by Davis (Davis et al., 1991). After collection of anthropometric measures (height, weight, tibial length, distance between femoral condyles or knee diameter, distance between the malleoli or ankle diameter, distance between the anterior iliac spines and pelvis thickness), passive markers were placed at specific points of reference directly on the individual’s skin, and in particular at C7, sacrum and bilaterally at the ASIS, greater trochanter, femoral epicondyle, femoral wand, tibial head, tibial wand, lateral malleolus, lateral aspect of the foot at the fifth metatarsal head and at the heel (only for static offset measurements). All acquisitions were acquired by the same operator to assure reproducibility of the acquisition technique and to avoid the introduction of errors due to different operators. After placement of the markers, participants completed two or more practice trials across the plate walkway to ensure that they were comfortable with the experimental procedure. After familiarization, a trial was considered valid when the following criteria were met: (1) a natural walk with self-preferred walk speed and (2) a whole foot was measured on the plate. Average values of three valid trials from each side foot were analysed. For each trial, the participant was measured with a right or a left foot strike on the plate. Six repeated trials (3 for each foot) were conducted to guarantee reproducibility of the results (kinematics, kinetics and plantar pressures). All trials were undertaken while barefoot. Participants were asked to walk from a start line to a finish line at their normal or comfortable speed. The start
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line was approximately 3 meters in front of the force platforms and the stop line was 3 meters behind the plates. Participants were allowed to rest between trials if they felt tired.
Data analysis
All graphs obtained from GA were normalized as a percentage of gait cycle and kinetic data were normalized for individual body weight. For each participants (DS and control) three representative trials demonstrating a consistent gait pattern (spatio-temporal, kinematic and kinetic) were extracted for the analysis. From these data we identified and calculated the parameters described in Table 2.
[Insert Table 2 About Here]
To evaluate the effect of ligament laxity and hypotonia on joint kinetics and kinematics, as already proposed in previous studies (Davis & DeLuca 1996; Frigo et al., 1996), hip and ankle stiffness (hip stiffness: Kh index; ankle stiffness: Ka index) were expressed by plotting the values of the flexion–extension moment versus the flexion–extension angle over the gait cycle interval between 10% and 30%. The 10% to 30% interval (corresponding to the second rocker) of the gait cycle was selected and the linear regression was fitted. The angular coefficient of the linear regression corresponded to the joint stiffness index, as described previously (Fig. 1).
Statistical analysis
All the previously-defined parameters were computed for each participant and then the mean values and standard deviations of all indexes were calculated for each group.
The Kolmogorov-Smirnov test indicated that the gait parameters were not normally distributed, so Mann-Whitney U tests were used to compare data of the right and left sides. After that, data of the two DS groups and the controls were compared with the Kruskal-Wallis test followed by post-hoc comparison. A comparison between male and female participants was also conducted in the groups considered (obese DS group, non-obese DS group, control group). Null hypotheses were rejected when probabilities were below 0.05.
RESULTS
According to the classification of obese and non-obese participants (Table 1), the clinical characteristics of the two sub-groups are reported; no statistical differences were found for age and height, with the exception of BMI.
In Table 3 the mean values and standard deviations of the spatiotemporal, kinematic and kinetic indices considered in this study for the two groups of DS individuals and CG are reported.
[Insert Table 3 about here]
148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181
Both the obese and non-obese group presented typical features in terms of gait pattern already found in literature (Galli et al., 2008; Cimolin et al., 2010). DS individuals were in general characterised by reduced values of step length, cadence and velocity of progression. As for the kinematics, the hip joint exhibited excessive flexion during the whole gait cycle (HIC and HmSt indices) with a low range of motion (HFE-ROM index). The knee flex-extension plot revealed a low maximum value of knee flexion during the swing phase (KMSw index) The analysis of the ankle kinematics showed a plantar flexed position with reduced range of motion (ADP-ROM index) during the whole stance phase (AIC, AMSt indices). As for kinetic parameters (ankle moment and power), both DS groups showed a lower maximum of ankle moment and ankle power generation during terminal stance than did controls. In terms of joint stiffness, DS generally showed a significantly stiffer hip and a reduced value as compared to healthy participants.
A comparison between the obese and non-obese group showed that both DS groups were characterised by common features, which were lower velocity, cadence and step length in comparison with CG; the only difference was found in terms of stance duration, which was longer in the obese group, in comparison with the non-obese group and controls.
Kinematic parameters revealed that neither group presented differences in terms of proximal level: they both walked with a flexed hip position during the whole gait cycle and showed a reduced range of motion during gait with a limited knee flexion in the swing phase (KMSw index), thus leading to a low knee range of motion. As concerns the ankle joint, both groups showed plantarflexion at initial contact (AIC index), with reduced ankle dorsiflexion ability and low range of motion during the stance phase. The only difference was displayed in terms of ankle dorsiflexion during the swing phase (AMSw index).
The kinetic parameters showed that a lower peak of ankle moment and ankle power during terminal stance was found in comparison to healthy participants, with no differences between the two DS groups.
Joint stiffness data showed that no statistical differences were found for hip stiffness (Kh index) (Obese: 0.05+0.01 N*m/kg*deg; Non-obese: 0.06+0.01 N*m/kg*deg; p> 0.05; CG: 0.03+0.01 N*m/kg*deg). On the contrary, the two DS groups were significantly different in terms of ankle stiffness (Ka index): both groups were characterised by reduced values as compared to CG, but the obese group presented lower values (Obese: 0.04+0.01 N*m/kg*deg; Non-obese: 0.07+0.02 N*m/kg*deg; p< 0.05; CG: 0.10+0.02 N*m/kg*deg).
As concerns the differences between males and females, only the statistically significant results are reported (Table 4).
[Insert Table 4 about here]
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The obese group presented differences in terms of hip joint in the sagittal and frontal planes. Obese females walked with a more flexed hip during the stance phase (HIC and HmSt indices) with respect to obese males and female controls.
The obese group showed differences at the proximal level (pelvis and hip joint); non-obese females were characterised by a higher range of pelvis motion in the frontal (PO-ROM index) and transversal (PR-ROM index) planes and of hip motion in the frontal plane (HAA-ROM index) compared to non-obese males and normal weight females.
DISCUSSION
Our results show that most parameters were similar in the two groups of participants with DS. Obese participants presented a longer stance duration compared to non-obese and CG and a limited dorsiflexion ability during the swing phase. Interestingly, the two DS groups were significantly different in terms of ankle stiffness (Ka index): both groups featured reduced values as compared to CG, but the obese group presented lower values with respect to non-obese participants. This result may be connected with a different degree of hypotonia and ligament laxity, which are probably exacerbated in presence of obesity.
The results obtained in DS participants about the effects of obesity on gait strategy were in contrast with literature on normal weight individuals. A recent study revealed significant differences in sagittal and frontal kinematics and kinetics of the lower extremities between obese and healthy weight adolescents (McMillan et al., 2010). Individuals who were obese appeared to use movement strategies that minimized joint moments, especially at the hip and knee during walking. This was especially true at the knee, a joint which is prone to damage and injury. The authors hypothesized that muscle weakness may be one potential cause of these movement differences. On the contrary, from our results on DS individuals, the gait alterations found in such participants appear to be associated with the specific syndrome and not directly connected to the presence/absence of obesity,
In addition, our results showed that the gait alterations induced by obesity are gender-moderated. Data showed that females were characterised by significant modifications of the gait pattern compared to males in both groups, in particular at proximal levels, such as hip and pelvis. It is reasonable to hypothesize that females and males, while sharing a similar mass (both a normal and excessive mass), are characterized by different fat distribution and/or accumulation. The fat mass is usually concentrated in the thorax-abdominal region in males (android shape), while it is usually around the hips and the upper portion of the legs in females (gynoid shape); therefore, the excess of fat mass in females may be the cause of the differences in terms of proximal levels (hip
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and pelvis) we found during gait in DS females. No significant differences were found in general between normal weight males and females; this result is in agreement with literature on adolescents, even though the authors analysed only spatio-temporal parameters (Dufek et al., 2012). Previous studies conducted on young adults (20-40 years old) showed that females had significantly greater hip flexion and less knee extension before initial contact, greater knee flexion moment in pre-swing, and greater peak mechanical joint power absorption at the knee in pre-swing (Kerrigan et al., 1998). In our study, we did not find the same differences in terms of hip kinematics and the reason may be owing to the different age of our participants (young participants).
Our findings underscore that the gait alterations found in DS are associated both with the specific syndrome and with the excess of mass, in particular in relation to ankle joint stiffness. These results may have special clinical relevance; the biomechanical comparison of gait in obese and non-obese DS young individuals may provide a basis for developing either specific or common rehabilitative strategies. Our results show that both groups of participants should be encouraged to walk owing to the positive impact of this activity on muscle mass, strength and energy balance; on the other hand, our data emphasize the need to overcome hypotonia and improve muscle strength at the distal joints, such as the ankle, especially in obese DS individuals. In addition, planning and selecting a rehabilitative approach based on specificities related to a participant’s gender is necessary. Our data show in fact that in DS an improvement in pelvis and hip range of motion would represent a specific major goal in optimizing gait pattern and preventing the onset of compensatory strategies, and this is especially true in female DS participants.
Acknowledgments
The authors would like to acknowledge Eng. Giulia Monaco and Selene Ponzini for their valuable contribution in data analysis.
Competing Interest
All authors have not any conflicts of interest and any financial interest. All authors attest and affirm that the material within has not been and will not be submitted for publication elsewhere.
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TABLES
Table 1: Clinical characteristics of the study groups. *= p< 0.05, Obese DS group vs. Non-obese
group; += p< 0.05, if compared to CG.
DS group Control Group
Obese Non-obese
Participants (M/F) 21/19 18/20 10/10
Age (years) 12.4 (2.8) 13.0 (3.1) 13.7 (3.5)
Weight (kg) 55.8 (12.4)*, + 36.8 (18.0) 35.8 (16.4)
BMI (kg/m2) 28.5 (3.9)*, + 18.4 (2.3) 19.3 (3.7)
*All values are mean + sd 346 347 348 349 350 351
Table 2: Gait parameters and descriptors.
Gait Parameter Description
Spatio-temporal parame ters
% stance (%gait cycle) % of gait cycle that begins with initial contact and ends at toe-off of the same limb; Step length longitudinal distance from one foot strike to the next one, normalized to individual’s
height
Cadence (step/min) Number of step for
Velocity (m/s) mean velocity of progression
Kinematics (degrees)
PT-ROM the range of motion at pelvis in the sagittal plane (Pelvic Tilt graph) during the gait cycle, calculated as the difference between the maximum and minimum values of the plot
PO-ROM the range of motion at pelvis in the frontal plane (Pelvic Obliquity graph) during the gait cycle, calculated as the difference between the maximum and minimum values of the plot
PR-ROM the range of motion at pelvis in the transversal plane (Pelvic Rotation graph) during the gait cycle, calculated as the difference between the maximum and minimum values of the plot
HIC value of Hip Flexion-Extension angle (hip position in the sagittal plane) at initial contact, representing the position of hip joint at the beginning of gait cycle
HmSt minimum of hip flexion (hip position in sagittal plane) in stance phase, representing the extension ability of hip during this phase of gait cycle
H-ROM the range of motion at hip joint in the sagittal plane (Hip Flex-Extension graph) during the gait cycle, calculated as the difference between the maximum and minimum values of the plot
HAA-ROM the range of motion at hip joint in the frontal plane (Hip Ab-Adduction graph) during the gait cycle, calculated as the difference between the maximum and minimum values of the plot
KIC value of Knee Flexion-Extension angle (knee position in sagittal plane) at initial contact, representing the position of knee joint at the beginning of gait cycle
KmSt minimum of knee flexion (knee position on sagittal plane) in mid-stance, representing the extension ability of knee during this phase of gait cycle
KMSw peak of knee flexion (knee position in sagittal plane) in swing phase, representing the flexion ability of knee joint during this phase of gait cycle
K-ROM the range of motion at knee joint in the sagittal plane (Knee Flex-Extension graph) during the gait cycle, calculated as the difference between the maximum (KMSw) and minimum (KmSt) values of the plot;
AIC value of the ankle joint angle (in sagittal plane) at the initial contact, representing the position of knee joint at the beginning of gait cycle
AMSt peak of ankle dorsiflexion (in sagittal plane) during stance phase, representing the dorsiflexion ability of ankle joint during this phase of gait cycle
AmSt minimum value of the ankle joint angle (in sagittal plane) in stance phase, representing the plantarflexion ability of ankle joint at toe-off
AMSw peak of ankle dorsiflexion (in sagittal plane) during swing phase, representing the dorsiflexion ability of ankle joint in this phase of gait cycle
A-ROM the range of motion at ankle joint in the sagittal plane (Ankle Dorsi-Plantarflexion graph) during the stance phase of the gait cycle, calculated as the difference between the maximum (AMSt) and minimum (AmSt) values of the plot;
Kinetics
AMMax (N*m/kg) the maximum value of ankle plantarflexion moment during terminal stance 352
APMax (W/kg) the maximum value of generated ankle power during terminal stance (maximum value of positive ankle power during terminal stance), representing the push-off ability of the foot during walking
353 354
Table 3: Spatio-temporal, kinematic and kinetic parameters of DS groups and CG. Data are
expressed as mean (standard deviation). *= p< 0.05, Obese DS group vs. Non-obese group; += p< 0.05, if compared to CG.
DS group Control Group
Obese Non-obese
Spatio-temporal parameters
%stance (% gait cycle) 63.69 (3.50)*, + 59.00 (5.38) 59.57 (1.47)
Step length (m) 0.31 (0.08)+ 0.33 (0.08)+ 0.88 (0.21) Cadence (step/min) 95.50 (15.00)+ 97.07 (23.22)+ 114.80 (4.80) Velocity (m/s) 0.73 (0.23)+ 0.71 (0.32)+ 1.1 (0.21) Kinematics (degrees) PT-ROM 4.65 (1.91) 4.69 (3.07) 1.61 (3.67) PO-ROM 7.34 (6.25) 7.89 (5.05) 6.01 (2.57) PR-ROM 12.86 (10.66) 13.08 (10.54) 10.72 (5.32) HIC 36.58 (14.44)+ 36.30 (11.98)+ 27.22 (7.54) HmSt 2.29 (8.98)+ 0.38 (10.92)+ -13.92 (7.68) H-ROM 36.67 (9.55)+ 37.16 (8.58)+ 44.92 (5.36) HAA-ROM 13.67 (6.22) 12.94 (6.39) 11.92 (6.13) KIC 5.94 (12.21) 7.11 (11.68) 4.06 (6.63) KmSt 5.21 (9.06) 6.29 (11.49) 0.12 (3.82) KMSw 51.34 (7.01)+ 52.52 (8.31)+ 59.01 (6.18) K-ROM 44.63 (10.62)+ 49.08 (9.57)+ 60.28 (6.31) AIC -3.29 (6.60)+ -2.97 (5.81)+ 1.81 (4.87) AMSt 10.85 (7.16)+ 13.37 (9.05)+ 19.91 (5.97) AmSt -4.59 (8.55)+ -4.74 (7.47)+ -8.98 (6.19) A-ROM 15.99 (7.21)+ 17.56 (8.40)+ 27.72 (6.56) AMSw 4.65 (8.55)*, + 8.91 (8.08) 8.63 (9.93) Mean FP -22.17 (15.19)+ -20.69 (11.71)+ -14.88 (8.35) Kinetics AMMax (N*m/kg) 0.98 (0.35)+ 1.08 (0.38)+ 1.49 (0.25) APMax (W/kg) 1.48 (0.78)+ 1.59 (0.96)+ 3.73 (0.71) 355 356 357 358
Table 4: Parameters significant in the comparison between males and females in the two DS groups
and in CG. Data are expressed as mean (standard deviation). *= p< 0.05, male vs. females, += p< 0.05, if compared to CG of the same gender.
Males Females
Obese DS group Control Group
Obese DS group Control Group HIC 33.09 (9.18)*, + 26.75 (6.49) 38.74 (7.62)+ 28.72 (10.71) HmSt 0.35 (8.60)*,+ -12.97 (6.30) 6.69 (9.21)+ -14.15 (2.07)
Non-obese DS group Control Group
Non-obese DS group Control Group
PO-ROM 6.47 (2.60)* 6.93 (3.21) 9.83 (3.51)+ 6.99 (3.27) PR-ROM 12.25 (7.76)* 10.16 (3.37) 18.25 (6.15)+ 12.38 (2.91) HAA-ROM 11.49 (3.71)* 11.43 (4.85) 14.15 (3.71)+ 12.68 (3.41) 359 360 361 362 363
CAPTION TO FIGURE
Figure 1: An example of ankle angle–moment plot cycle during second rocker for an obese DS participant, for a non-obese DS participant and one healthy individual is reported. The slope of the joint moment plotted as a function of joint angle during second rocker represents ankle joint stiffness. 364 365 366 367 368
