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A longitudinal study to evaluate the development of independent walking in infants using inertial sensors: Preliminary results
No full textIntroduction: Many studies have been observing infants at the onset of walking in order to evaluate the development of different strategies and coordination [1–3]. These studies regard most of the times small groups (<10) and only few studies observed longitudinally the evolution of independent walking (on 2 or 5 subjects) [4,5]. To the author knowledge, these observations were always made using optoelectronic or video-based data. The use of wireless inertial sensors is more practical when aiming at the measurements of large populations. Moreover, inertial sensors can be worn under the clothes facilitating the experiments with infants who are not distracted by markers and can freely walk in any environment. The aim of the present study is to observe longitudinally a large group of infants using inertial sensors over a 6-month period after onset of independent walking (period in which the most dramatic changes of maturation of many gait parameters occurs [6]). This database will allow evaluating the changes in gait temporal parameters, postural stability and coordination at the beginning of independent walking.
Methods: Twenty healthy infants (77 ± 2 cm, 9.3 ± 0.8 kg, 13 ± 2 months) were included in the study. All of the infants had no known developmental delays. The tests were scheduled once a month after the onset of independent walking for three months, and one after six months. When possible, a test was performed during the very first week of independent walking. Three tri-axial wireless inertial sensors (OPALS, Apdm, USA) were mounted on the lower back and on the right and left legs, respectively. The participants were asked to walk straight in the room. Heel-strike and toe-off instants were estimated from the angular velocity of the lower limbs [7]. Median stride (strT), swing (swT), stance (stanceT) and double support (dsT) times were calculated. Step-, stride-regularity (stepR and strR) and step symmetry (stepS) were evaluated using trunk vertical acceleration [8]. Up to now only five infants completed all the scheduled tests, thus the presented results are preliminary.
Results: Up to now no significant trends were shown in the evaluated parameters even if, generally, the swT showed and increase with months of experience. In Table 1, median (and 25th-, 75th percentile) strT, swT, stanceT, dsT, stepR, strR, stepS, calculated on the five infants are shown for each tested period of gait maturation.
Table 1. Median, 25th and 75th percentiles of evaluated gait parameters for each tested period of gait maturation.
1st week 1st month 2nd month 3rd month 6th month
Median 25th perc 75th perc Median 25th perc 75th perc Median 25th perc 75th perc Median 25th perc 75th perc Median 25th perc 75th perc
strT 0.81 0.75 1.06 0.71 0.65 0.72 0.68 0.66 0.71 0.71 0.71 0.75 0.75 0.67 0.79
swT 0.31 0.30 0.34 0.33 0.31 0.33 0.35 0.34 0.35 0.36 0.34 0.37 0.36 0.34 0.37
stanceT 0.42 0.41 0.70 0.38 0.33 0.39 0.34 0.32 0.37 0.38 0.34 0.38 0.39 0.32 0.42
dsT 0.35 0.35 0.35 0.33 0.33 0.34 0.34 0.33 0.35 0.35 0.34 0.37 0.38 0.37 0.38
stepR 0.48 0.31 0.50 0.34 0.33 0.38 0.26 0.21 0.33 0.39 0.28 0.41 0.36 0.33 0.39
strP 0.29 0.20 0.29 0.33 0.25 0.38 0.37 0.32 0.40 0.31 0.24 0.35 0.29 0.26 0.32
stepS 1.66 1.44 1.72 1.43 0.90 1.48 0.95 0.55 1.57 0.96 0.93 1.52 1.19 1.09 1.40
Discussion: The increased swT with months of experience evidenced the fear of falling of the infants during the beginning of independent walking. Gait regularity was low in all the infants, as expected. StepS is higher than 1, showing high symmetry but it is calculated as stepR/strideR, which values are close to 0, therefore it is not a reliable value
Development of gait motor control: What happens after a sudden increase in height during adolescence?
Full text linkBackground: Basic understanding of motor control and its processes is a topic of well-known high relevance. During adolescence walking is theoretically a well-achieved fundamental skill, having reached a mature manifestation; on the other hand, adolescence is marked by a period of accelerated increases in both height and weight, referred as growth spurt. Thus, this period was chosen as a controlled and natural environment for partially isolating one of the factors influencing motor development (segment growth). The aim of the study was to compare gait performance of growing and not growing male adolescents during walking in single task (ST) and dual task (DT), in order to study which are the modifications that motor control handles when encountering a sudden change in segment length. Methods: 19 adolescents were selected as growing adolescents (they showed a height increase greater than 3 cm in 3 months). A group of BMI-matched peers were selected as not growing adolescents (they showed a height increase lower than 1 cm in 3 months). Measures of acceleration of the trunk (L5 level) were collected using one tri-axial wireless inertial sensor. The participants were asked to walk at self-selected speed back and forth four times in a 10 m long corridor in ST and DT conditions. The following characteristics of gait performance were evaluated using different indices: variability, smoothness, regularity, complexity and local dynamic stability. An unpaired t-test was performed on the two groups for each method. Results: Different indices followed the hypothesized trend in the two groups, even if differences were not always statistically significant: not growing adolescents showed a lower variability and complexity of gait and a higher smoothness/rhythm. Stability results showed a similarly stable gait pattern (or even higher in DT) in the growing adolescents when compared to their not growing peers. Conclusions: The findings of the present work suggest that growth spurt affects gait variability, smoothness and regularity but not gait stability. It could be argued that sudden peripheral changes of the body affect the manifestation and the performance of gait, but, on the other hand, gait control is able to handle these modifications, maintaining the stability of the system
Objective assessment of movement competence in children using wearable sensors: An instrumented version of the TGMD-2 locomotor subtest
No full textMovement competence (MC) is defined as the development of sufficient skill to assure successful performance in different physical activities. Monitoring children MC during maturation is fundamental to detect early minor delays and define effective intervention. To this purpose, several MC assessment batteries are available. When evaluating movement strategies, with the aim of identifying specific skill components that may need improving, widespread MC assessment is limited by high time consumption for scoring and the need for trained operators to ensure reliability. This work aims to facilitate and support the assessment by designing, implementing and validating an instrumented version of the TGMD-2 locomotor subtest based on Inertial Measurement Units (IMUs) to quantify MC in children rapidly and objectively. 45 typically developing children, aged 6–10, performed the TGMD-2 locomotor subtest (six skills). During the tests, children wore five IMUs mounted on lower back, on ankles and on wrists. Sensor and video recordings of the tests were collected. Three expert evaluators performed the standard assessment of TGMD-2. Using theoretical and modelling approaches, algorithms were implemented to automatically score children tests based on IMUs’ data. The automatic assessment, compared to the standard one, showed an agreement higher than 87% on average on the entire group for each skill and a reduction of time for scoring from 15 to 2 min per participant. Results support the use of IMUs for MC assessment: this approach will allow improving the usability of MC assessment, supporting objectively evaluator decisions and reducing time requirement for the evaluation of large groups
Evaluation of toddlers different strategies during the first 6 months of independent walking: A longitudinal study
No full textIntroduction and aim: Many studies have been observing infants at the onset of walking in order to evaluate the development of different strategies and coordination [1,2]. These studies regard most of the times small groups (20) using inertial sensors over a 6-months period after onset of independent walking. These data will allow evaluating the changes in gait temporal parameters and coordination at the beginning of independent walking. Moreover they will permit to evaluate quantitatively differences in strategies at the very beginning of walking [5] and to eventually correlate these differences with children characteristics.
Patients/materials and methods: Twenty healthy infants (77 ± 3 cm, 10 ± 2 kg, 13 ± 2 months) were included in the study. All of the infants were full-term at birth and had no known developmental delays. Tests on the infants were scheduled once a month after the onset of independent walking for 3 months and one after 6 months. When possible, a test during the very first week of independent walking was performed. Three tri-axial wireless inertial sensors (OPALS, Apdm, USA) were mounted respectively on the lower back and on the two legs. The participants were asked to freely walk in a corridor. Ten consecutive strides were analyzed. Right heel strike (HS) and toe off (TO) instants were estimated from the angular velocity of the lower limb [6]. Stride (strT), swing (swT), stance (stanceT) times, cadence (Cad) and normalized cadence (nCad) were calculated. Trunk accelerations were used to estimate step and stride regularity (stepR and strR) [7], peak to peak range and variability of trunk accelerations. Median, 25° and 75° percentiles of estimated parameters were calculated at each developmental stage.
Results: StrT decreased from month 0 to month 2 and then increased with months of experience. The opposite trend was shown by Cad and nCad. StT followed the same trend of StrT, while SwT increased constantly with months of experience. StepR and strR did not show a general trend for all the children. Medio-lateral trunk accelerations showed a constant decrease in peak to peak range and variability in all the children.
Discussion and conclusions: The trend of Cad and nCad found is in contrast to what found by Looper (2012) [2] in longitudinal study on 8 children but is in agreement with Sutherland [8] who analysed a large number of subjects of different ages (children to adults). An analysis of different children characteristics (e.g. age at the first test) could be interesting for explaining these different results. The low swT at the very beginning of walking could be an evidence of children fear of falling. StepR and strR did not show a general trend among the whole group: future works will focus on evaluating if there are two or more typical trends in the whole group or if regularity is not a significant descriptive index for toddlers. Variability and peak to peak range of trunk medio-lateral accelerations decreased with experience indicating a more and more regular and less and less oscillating gait.
Future works will evaluate the possibility of identifying the strategies descripted by McCollum [5] by sensor data and to describe quantitatively how these strategies develop towards the pendulum mechanism with experience.
Acknowledgments: This research was funded by the project “Fall risk estimation and prevention in the elderly using a quantitative multifactorial approach” (project ID number 2010R277FT) awarded by MIUR
Characterization of gait maturation using frequency domain analysis of CoM acceleration
No full textIntroduction: The use of inertial sensors, placed at approximately CoM level (L5 level), is today a common practice in gait analysis [1]: CoM acceleration data allow indeed evaluating spatio-temporal gait parameters [2] and characterizing different populations [3]. Frequency domain analysis of the CoM acceleration signal has been already proposed in literature, in order to assess the range of frequency spectrum and its dependency on the motor task [4–6] or in order to evaluate characteristics of the signal in relation to task event (e.g. impact-related shock, Parkinson's freezing) [7,8]. The aim of this study was to investigate the use of the frequency domain analysis of CoM acceleration in characterizing gait maturation from childhood to adulthood, evidencing deterioration of gait performance during ageing.
Methods: The study was conducted on: 7 toddlers at two weeks of walking experience (T2wks, 13 ± 2 mo, 10 ± 2 kg, 78 ± 4 cm), 7 toddlers at 6 months of walking experience (T6mo, 18 ± 2 mo, 11 ± 2 kg, 82 ± 2 cm), 7 4-year old children (4YC, 4 y, 16 ± 2 kg, 101 ± 3 cm), 7 6-year old children (6YC, 6 y, 23 ± 1 kg, 121 ± 2 cm), 7 adolescents (15YA, 15 y, 60 ± 13 kg, 162 ± 6 cm), 7 young adults (25YA, 25 ± 1 y, 171 ± 9 cm, 67 ± 14 kg) and 7 elderlies (E, 75 ± 7 y, 77 ± 11 kg, 167 ± 6 cm). The participants performed an instrumented over ground gait task wearing a tri-axial wireless inertial sensors (OPALS, Apdm, USA) (fs 128 Hz) located on L5. Ten consecutive strides, for all the participants, were analyzed [9]. The FFT of the acceleration signals was used to determine the frequency corresponding to the maximum of the monolateral signal spectrum (fMAX). The signal power (PW) was calculated integrating the potential spectrum density (psd), obtained with the Matlab built-in function pwelch. Then PW was normalized with the maximum value of it, obtaining the normalized signal power (PW%). The frequencies corresponding to the 50% (f50%) and 98% (f98%) of the PW%. were calculated. fMAX, f50% and f98% were calculated along the three axes (AP, ML V). The estimated parameters were tested with gaussianity test in such way was possible performed the right statistical analysis: Kruskal–Wallis test with a p-value of 5%. When age effect was found, a multiple comparison test was performed.
Results: Kruskal–Wallis results showed effect of age on all the features in V direction and on f98% and f50% in AP direction. No significant results were found in ML direction.
In Fig. 1a and b are showed 25° 50° and 75° percentiles of fMAX_AP and fMAX_V respectively. Colours indicate differences found by the multiple comparison test for T2wks group (blue): red indicates statistical differences and grey no statistical differences.
Fig. 1
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Fig. 1.
Discussion: The results of the present work indicate that f50%, f98% and fMAX can be relevant and descriptive parameters of gait development. In particular, fMAX_AP, changes from high to low values with the increasing of the age and could describe improvement and deterioration of the motor development; moreover fMAX_V and f98%_V discern between immature and mature gait during gait development and could be used as an index of deterioration of gait performance during ageing
Newly Walking Toddlers: How Do Different Strategies Combine When Developing Pendulum Mechanism?
No full textChanges of human complexity during maturation: Quantitative assessment on trunk acceleration data
No full textGait performance in toddlers born preterm: A sensor based quantitative characterization
Full text linkBackground and Objectives: Preterm children have an increased risk of motor difficulties. Gait analysis and wearable technologies allow the assessment of motor performance in toddlers, identifying early deviations from typical development. Using a sensor-based approach, gait performance of full-term and preterm toddlers at different risk of motor delay was analysed. The aim was to measure quantitative differences among groups. Methods: Twenty-nine two-year old children born preterm ( <36 gestational weeks) and 17 full-term controls, matched for age and walking experience, participated in the study. Preterm children were further divided based on risk of motor delay: preterm at high risk ( n = 8, born at <28 gestational weeks or with <10 0 0 g of body weight), and at moderate risk ( n = 21). Children were asked to walk along a corridor while wearing 3 inertial sensors on the lower back and on the ankles. Gait temporal parameters, their variability, and nonlinear metrics of trunk kinematics (i.e. recurrence quantification analysis, multiscale entropy) were extracted from the collected data and compared among groups. Results: Children born preterm showed significantly longer stance and double support phases, higher variability of temporal parameters, and lower multiscale entropy values than peers born full-term. No difference was found for the other parameters when comparing preterm and full-term children. When comparing children grouped according to risk of delay, with increasing risk, children showed longer stride-, stance- and double-support-time, higher variability of temporal parameters, higher recurrence- and lower multiscale entropy values. Conclusions: Sensor-based gait analysis allowed differentiating the gait performance of preterm from fullterm toddlers, and of preterm toddlers at different risk of motor delay. When analysing the present results with respect to the expected trajectory of locomotor development, children born preterm, in particular those at higher risk of motor delay, exhibited a less mature motor control performance during gait: lower stability (i.e. longer support phases), and higher variability, although not structured towards the exploration of more complex movements (i.e. higher recurrence- and lower multiscale entropy values). These indexes can serve as biomarkers for monitoring locomotor development and early detecting risk to develop persistent motor impairments
Nonlinear Analysis of Human Movement Dynamics Offers New Insights in the Development of Motor Control during Childhood
No full textWhen aiming at assessing motor control development, natural walking (NW), and tandem walking (TW) are two locomotor tasks that allow analyzing different characteristics of motor control performance. NW is the reference locomotor task, expected to become more and more automatic with age. TW is a nonparadigmatic task used in clinics to highlight eventual impairments and to evaluate how a child deals with a new challenging motor experience. This work aims at investigating motor development in school-aged children, by assessing quantitatively their performance during TW and NW. Eighty children (6-10 years) participated in the study. Trunk acceleration data and nonlinear measures (recurrence quantification analysis (RQA), and multiscale entropy (MSE)) were used to characterize trunk postural control and motor complexity. The results were analyzed with respect to age and standard clinical assessment of TW (number of correct consecutive steps), by means of Spearman correlation coefficients. RQA and MSE allowed highlighting age-related changes in both postural control of the trunk and motor complexity, while classic standard assessment of TW resulted uniformly distributed in the different age groups. The present results suggest this quantitative approach as relevant when assessing the motor development in schoolchildren and complementary to standard clinical tests
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