Vertical Research Articles

Validation of an ear-worn sensor for gait monitoring using a force-plate instrumented treadmill

A force-plate instrumented treadmill (Hp Cosmos Gaitway) was used to validate the use of a miniaturised lightweight ear-worn sensor (7.4g) for gait monitoring. Thirty-four healthy subjects were asked to progress up to their maximum walking speed on the treadmill (starting at 5km/h, with 0.5km increments). The sensor houses a 3D accelerometer which measures medio-lateral (ML), vertical (VT) and anterior–posterior (AP) acceleration. Maximum signal ranges and zero crossings were derived from accelerometer signals per axis, having corrected for head motion and signal noise. The maximal force, measured by the instrumented treadmill correlated best with a combination of VT and AP acceleration (R-squared=0.36, p=0), and combined VT, ML, and AP acceleration (R-squared=0.36, p=0). Weight-acceptance peak force and impulse values also correlated well with VT and AP acceleration (Weight acceptance: R-squared=0.35, p=0, Impulse: 0.26, p=0), and combined VT, ML, and AP acceleration (Weight acceptance: R-squared=0.35, p=0, Impulse: 0.26, p=0). Zero crossing features on the ML axis provided an accurate prediction of the gait-cycle, with a mean difference of 0.03s (−0.01, 0.05 confidence intervals).

Age- and speed-related differences in harmonic ratios during walking

Harmonic ratios (HRs), derived from trunk accelerations, measure smoothness of trunk motion during gait; higher ratios indicate greater smoothness. Previous research indicates that young adults optimize HRs at preferred pace, exhibiting reduced HRs at speeds faster and slower than preferred. Recent studies examining HRs and other trunk acceleration measures challenge this finding. The purpose of this study was to examine age-related differences in HRs across a range of self-selected overground walking speeds. Anteroposterior (AP), vertical (VT), and mediolateral (ML) HRs were examined in 13 young adults (ages 20–23), 13 healthy older adults (ages 60–69), and 13 healthy old-old adults (ages 80–86) while walking overground at very slow, slow, preferred, fast, and very fast speeds. Young and older adults exhibited similar HRs in all directions of motion across speeds, while old-old adults exhibited lower AP- and VT-HRs. All groups exhibited reduced HRs at speeds slower than preferred. However, there were no differences in HRs between preferred and faster speeds, with the exception of reduced VT-HRs in the very fast condition for the older groups. The ML-HR was not different between groups, and varied less across speeds. Stride time variability exhibited inverse relations with, and independently contributed to, HRs across speeds; lower stride time variability was associated with greater smoothness of trunk motion. Older groups were not disproportionately affected by walking more slowly and smoothness of trunk motion did not show a clear pattern of optimization at preferred pace for any group.

Validation and comparison of ActiGraph activity monitors

Objective: To compare activity counts from the ActiGraph GT3X to those from the ActiGraph GT1M during treadmill walking/running. A secondary aim was to develop tri-axial vector magnitude (VM3) cut-points to classify physical activity (PA) intensity. Methods: Fifty participants wore the GT3X and the GT1M on the non-dominant hip and exercised at 4 treadmill speeds (4.8, 6.4, 9.7, and 12 km h −1). Vertical (VT) and antero-posterior (AP) activity counts (counts min −1) as well as the vector magnitudes of the two axes (VM2) from both monitors were tested for significant differences using two-way ANOVA's. Bland–Altman plots were used to assess agreement between activity counts from the GT3X and GT1M. Linear regression analysis between VM3 counts min −1 and oxygen consumption data was conducted to develop VM3 cut-points for moderate, hard and very hard PA. Results: There were no significant inter-monitor differences in VT activity counts at any speed. AP and VM2 activity counts from the GT1M were significantly higher ( p < 0.01) than those from the GT3X at 4.8, 9.7 and 12 km h −1. High inter-monitor agreement was found for VT activity counts but not for AP and VM2 activity counts. VM3 cut-points for moderate, hard, and very hard PA intensities were 2690–6166, 6167–9642, >9642 counts min −1. Conclusion: Due to the lack of congruence between the AP and VM2 activity counts from the GT1M and the GT3X, comparisons of data obtained with these two monitors should be avoided when using more than just the VT axis. VM3 cut-points may be used to classify PA in future studies.

Differences in Running Mechanics and Economy between Collegiate Runners and Triathletes Identified Using High-Resolution Accelerometers

We have previously reported differences in economy between trained and untrained runners using high-resolution accelerometers (HRA) and indirect calorimetry. In these runners though, differences may have been due to discrepancies in metabolic fitness level. PURPOSE: To determine if HRA could identify differences in economy and mechanics of running between collegiate runners (XC) and triathletes (TRI), of comparable metabolic fitness, during treadmill locomotion. METHODS: Procedures were approved by the Eastern Michigan University CHHS Human Subject Review Committee and subjects gave informed consent. 23 runners, 16 XC (22.1±1.5yr, 66.5±5.7 kg, 71.1±5.2 ml/kg/min) and 8 TRI (25.6±3.8yr, 70.8±3.7 kg, 66.2±4.2 ml/kg/min) performed incremental VO2max trials while wearing HRA (Microstrain, VT; 617 Hz). Aggregate acceleration for vertical (VT), anterior/posterior (AP), medial/lateral (ML), axes were recorded and Euclidian resultants were computed (RES). Trials consisted of 3 min stages starting at 8kph and increasing 2kph until exhaustion. Group comparisons were made from 10-18kph, as all subjects completed these stages. Axial root mean square (RMS), RMS relative to speed (EC), and ratio of RMS/RES (RA) were compared between XC and TRI to identify differences in running mechanics between groups. Expired gases were collected using an Oxycon Mobile (Viasys, CA). VO2 and RER were used to determine O2 cost (O2C) and energy expenditure (EE). MANOVAs were performed using PASW 17.0 (SPSS; IL) α=.05. RESULTS: Total weekly training time (14.8±2.1 hr) was not different between groups but XC ran significantly more than TRI(13.5±1.9 vs. 5.6±1.5 hr). All HRA parameters (RMS, EC, RA) were significantly greater for XC vs. TRI in VT, and lower (p<.05) for XC vs. TRI in ML and AP, except MLRA. Significant speed by group interactions (p<.05) were also present for all HRA parameters except MLEC and MLRA. RER was not different between groups (.91±0)indicating similar fitness for XC and TRI, but VO2 and EE were significantly higher for TRI vs. XC (47.4±.5 vs. 40.8±.3 ml/kg/min and.23±.0 vs.20±.0 kcal/kg/min). CONCLUSION: These data show that XC accelerate more in the VT but less in the AP than TRI. Therefore improved running economy with training may come more from reduced accelerations in AP than VT or ML.

Fatiguing Exercise Increases Complexity of Postural Control: Control Entropy of High-Resolution Accelerometry

We have previously used Control Entropy (CE) analysis of high-resolution accelerometer (HRA) signal to show complexity of gait decreases during exhaustive treadmill running. PURPOSE: To determine if complexity of postural control decreases following fatiguing Wingate exercise using CE of HRA. METHODS: Ten participants (5 M/5 F; 25±3 yr; 169.4±11.7 cm; 79.0±16.9 kg) consented to participation approved by Western Oregon University IRB and completed two trials separated by 2-7 days. Trials consisted of two single-legged balance tests separated by a Wingate anaerobic test (WAnT; PreWant/PostWant), or rest period (PreRest/PostRest). Balance tests consisted of a series of five single-legged stances, separated by 30 s rest, performed while standing on the dominant leg for 15-s with the participant crossing the arms over the chest and flexing the non-dominant knee to 90 degrees. HRA (MicroStrain, VT) were fixed superficial to L3/L4 at the approximate center of mass (COM). Triaxial signals from the HRA were streamed in real time to a base station at a frequency of 625 Hz and then exported to Matlab (Natick, MA) for analysis. COM accelerations were recorded in g's for vertical (VT), medial/lateral (ML), and anterior/posterior (AP). A newly developed statistic (R-test) was applied to group response shapes generated by Karhunen Loeve (KL) analysis modes resulting from Control Entropy (CE) analysis. RESULTS: R-tests showed a significant mean vector difference (p<.05) within conditions, between axes in all cases, except PostWant, indicating the shape of the complexity response was different in these cases. R-test between conditions, within axis, differences were only present in PostWant for AP (p<.05; 2.95 × 10-3) vs. PreWant (2.86× 10-3). T-tests showed a significantly higher overall CE PostWant in VT and ML compared to PreWant and PostRest (p<.0001). PostWant CE was also higher than PostRest in AP (p<.0001). CONCLUSIONS: These data indicate that fatiguing exercise eliminates the differential complexity response of postural control between axes, but increases complexity in all axes compared to the non-fatigued condition. This has implications with regard to the effects of fatigue on strategies of the control system to maintain postural control.

Relationship of High-resolution Triaxial Accelerometry With VO2 In Highly-trained Runners During Treadmill Locomotion

PURPOSE: The use of accelerometers as tools to quantify human movement has become increasingly prevalent in recent years. For estimation of VO2, "Activity Monitors" are typically low resolution, and higher resolution instruments may be of value. The purpose of this study was to determine the test-retest reliability of wireless high frequency, high-resolution accelerometers (HRA), and examine the relationship of HRA signals with VO2 during treadmill locomotion in highly trained runners. METHODS: Procedures were approved by the local HSRC. Seven NCAA D-I distance runners (21.4±1.7yr, 65.5±5.7 kg, 70.1±6.2 ml/kg/min) performed repeated incremental treadmill trials at 1% grade, starting at 2 kph and increasing 2 kph/2 min to volitional exhaustion. This protocol elicited a range of gaits from slow walking to maximal running in these highly trained subjects. Metabolic gasses were collected using an Oxycon Mobile (Viasys, CA). Wireless triaxial HRA (Microstrain, VT) were affixed to subject's lower back and data was streamed at 625 Hz. Raw signal from three axes was integrated to obtain resultant acceleration scalars (RES; Matlab; Mathworks, MA). Root-Mean-Square (RMS), for the last minute of each stage, for Vertical (VT), Medio-Lateral (ML), Fore-Aft (FA) and (RES) were compared to the corresponding minute average of relative VO2 (REL). Pearson's product correlation (r) and coefficient of variation (CV) were determined for VT, LT, FA and RES. Test-retest reliability was examined using Interclass correlations (ICC) and Chronbach's Alpha (SPSS, IL; α = 05). RESULTS: RMS of VT, LT, FA and RES was strongly correlated with REL (r =.87,.88,.95 and.95 respectively; p<.001). CV's were 5.7, 24.4, 24.5 and 5.2% for VT, ML, FA and RES, respectively. Both ICC's and Chronbach's alpha were.98,.97,.97 and.99 for VT, ML, FA and RES. CONCLUSIONS: Test-retest reliability of high frequency HRA displays strong validity and reliability across a wide range of walking/running speeds during treadmill locomotion in highly trained runners. Further, RMS of RES is strongly correlated with VO2, which indicates that RMS of unfiltered HRA is a valid means to determine VO2 during treadmill locomotion. These insights may allow for both clinicians and coaches to effectively monitor subjects for either rehabilitation and/or training purposes.

Correlations between photogrammetric measurements of tooth mobility and the Periotest method

Objective. The purpose of the present study was to investigate whether or not the quantitative Periotest values of anterior teeth correlate with quantitative metric values of tooth mobility under vertical (VL) and horizontal load (HL) in periodontally healthy subjects. Materials and methods. Thirty-one subjects with good periodontal conditions were included and subjected to two different tooth mobility measurement techniques. Periotest values were measured at reproducible measurement points in the vertical (vPT) and horizontal (hPT) dimensions of upper central and lateral incisors and canine teeth. Using the optical measurement technique (photogrammetry), tooth mobility was measured under load in the horizontal (HL) and vertical loading directions (VL) at different load forces. Pearson's correlation coefficients were used to determine exploratory associations. Results. The comparison between hPT and HL showed no correlations between the two measurements except for ‘weak’ and ‘moderate’ correlations for teeth 21 and 23. The analysis of correlations between vPT and VL data showed statistically significant correlations for both the left and right canine teeth that ranged from ‘weak’ to ‘high’. Comparisons between hPT values and VL and between vPT and HL showed significant correlations at a few loading forces only. Conclusion. Quantitative Periotest values cannot be used to draw conclusions about the metric assessment of tooth mobility. For this purpose, the photogrammetric technique could be an additional tool for scientific questions.

Lower extremity fatigue increases complexity of postural control during a single-legged stance

BackgroundNon-linear approaches to assessment of postural control can provide insight that compliment linear approaches. Control entropy (CE) is a recently developed statistical tool from non-linear dynamical systems used to assess the complexity of non-stationary signals. We have previously used CE of high resolution accelerometry in running to show decreased complexity with exhaustive exercise. The purpose of this study was to determine if complexity of postural control decreases following fatiguing exercise using CE.MethodsTen subjects (5 M/5 F; 25 ± 3 yr; 169.4 ± 11.7 cm; 79.0 ± 16.9 kg) consented to participation approved by Western Oregon University IRB and completed two trials separated by 2-7 days. Trials consisted of two single-legged balance tests separated by two Wingate anaerobic tests (WAnT; PreFat/PostFat), or rest period (PreRest/PostRest). Balance tests consisted of a series of five single-legged stances, separated by 30 s rest, performed while standing on the dominant leg for 15-s with the participant crossing the arms over the chest and flexing the non-dominant knee to 90 degrees. High resolution accelerometers (HRA) were fixed superficial to L3/L4 at the approximate center of mass (COM). Triaxial signals from the HRA were streamed in real time at 625 Hz. COM accelerations were recorded in g's for vertical (VT), medial/lateral (ML), and anterior/posterior (AP) axes. A newly developed statistic (R-test) was applied to group response shapes generated by Karhunen Loeve (KL) transform modes resulting from Control Entropy (CE) analysis.ResultsR-tests showed a significant mean vector difference (p < .05) within conditions, between axes in all cases, except PostFat, indicating the shape of the complexity response was different in these cases. R-test between conditions, within axis, differences were only present in PostFat for AP vs. PreFat (p < .05). T-tests showed a significantly higher overall CE PostFat in VT and ML compared to PreFat and PostRest (p < .0001). PostFat CE was also higher than PostRest in AP (p < .0001).ConclusionsThese data indicate that fatiguing exercise eliminates the differential complexity response between axes, but increases complexity in all axes compared to the non-fatigued condition. This has implications with regard to the effects of fatigue on strategies of the control system to maintain postural control.

Control Entropy Of Accelerometry During Discontinuous Treadmill Tests In Intercollegiate Runners Across a Competitive Season

PURPOSE: Complexity of gait parameters during running are of interest for both clinical and practical purposes. A recently developed regularity statistic, Control Entropy (CE), not dependent upon conditions of stationarity, has previously been applied to high resolution accelerometry (HRA) and demonstrated distinct constraints on individual axes of movement during running. The purposes of this study were to apply CE to individual axes of HRA signal to determine i) if distinctive constraints exist in different axes during a discontinuous incremental running test in highly trained runners and ii) if CE responses to the same test change after a competitive inter-collegiate cross country season. METHODS: Procedures were approved by the Eastern Michigan University CHHS HSRC. Seven NCAA D-1 runners (21.7 ±1.4 yr, 68.1±6.7 kg, 69.3±4.2 ml/kg/min) performed two discontinuous incremental treadmill trials (T1 and T2), separated by 12 weeks. Trials consisted of 3 min stages starting at a speed equivalent to 20km pace minus 50m/min and increasing speed 15 m/min until exhaustion. 20 km paces were established using a 3 km and 10 km standard field test and extrapolation using the Mercier nomogram. HRA was collected in g's from portable triaxial wireless nodes (Microstrain, VT) streaming at 617 Hz, which were affixed to the lower back superficial to the L3 vertebrae. CE (CEKS[x(t)] =hKS[sign(dx/dt(t))] was calculated for signal from each axis [vertical (VT), medial/lateral (M/L) and anterior/posterior (AP)] using 8 bit partitions and multi-scale window lengths and compared using Karhunen-Loeve (K-L) analysis in a new and novel way to the patterns of CE response. RESULTS: CE declined significantly in the VT and M/L axes (p<.05), but not in the A/P. Dominant CE modes in K-L analysis showed that during running CE declined first in the VT, then M/L (p<.05). These patterns did not change between T1 and T2. CONCLUSIONS: These results indicate that, as with continuous running tests, during discontinuous incremental running, constraints are apparent earliest in the VT axis. There is no clearly dominant CE mode in the A/P as previously observed for continuous incremental trials. It does not appear as though constraints of running under laboratory conditions change across a collegiate cross country season in these highly trained athletes.

High-resolution Triaxial Accelerometry Is Strongly Correlated With VO2 In Inter-collegiate Runners During Level Treadmill Locomotion

PURPOSE: The use of accelerometers as tools to quantify human movement has become increasingly prevalent in recent years. For estimation of VO2, "Activity Monitors" are typically low resolution, and higher resolution instruments may be of value. The purpose of this study was to determine the test-retest reliability of wireless high frequency, high-resolution accelerometers (HRA), and examine the relationship of HRA signals with VO2 during treadmill locomotion in highly trained runners. METHODS: Procedures were approved by the local HSRC. Seven NCAA D-I distance runners (21.4±1.7yr, 65.5±5.7 kg, 70.1±6.2 ml/kg/min) performed repeated incremental treadmill trials at 1% grade, starting at 2 kph and increasing 2 kph/2 min to volitional exhaustion. This protocol elicited a range of gaits from slow walking to maximal running in these highly trained subjects. Metabolic gasses were collected using an Oxycon Mobile (Viasys, CA). Wireless triaxial HRA (Microstrain, VT) were affixed to subject's lower back and data was streamed at 625 Hz. Raw signal from three axes was integrated to obtain resultant acceleration scalars (RES; Matlab; Mathworks, MA). Root-Mean-Square (RMS), for the last minute of each stage, for Vertical (VT), Medio-Lateral (ML), Fore-Aft (FA) and (RES) were compared to the corresponding minute average of relative VO2 (REL). Pearson's product correlation (r) and coefficient of variation (CV) were determined for VT, LT, FA and RES. Test-retest reliability was examined using Interclass correlations (ICC) and Chronbach's Alpha (SPSS, IL; a=.05). RESULTS: RMS of VT, LT, FA and RES was strongly correlated with REL (r =.87,.88,.95 and.95 respectively; p<.001). CV's were 5.7, 24.4, 24.5 and 5.2% for VT, ML, FA and RES, respectively. Both ICC's and Chronbach's alpha were.98,.97,.97 and.99 for VT, ML, FA and RES. CONCLUSIONS: Test-retest reliability of high frequency HRA displays strong validity and reliability across a wide range of walking/running speeds during treadmill locomotion in highly trained runners. Further, RMS of RES is strongly correlated with VO2, which indicates that RMS of unfiltered HRA is a valid means to determine VO2 during treadmill locomotion. These insights may allow for both clinicians and coaches to effectively monitor subjects for either rehabilitation and/or training purposes.

High Resolution Accelerometry Can Identify Changes in Running Dynamics Across an Inter-collegiate Cross Country Season

PURPOSE:: We have previously demonstrated differences in high-resolution accelerometry (HRA) between trained and untrained runners. The purpose of this study was to determine if differences in HRA parameters or oxygen cost of running could be detected in collegiate distance runners before and after a competitive season. METHODS: Procedures were approved by the Eastern Michigan Human Subjects Review Committee. Seven intercollegiate distance runners (21.7 ±1.4 yr, 68.1±6.7 kg, 69.3±4.2 ml/kg/min) performed two discontinuous incremental treadmill trials (T1 and T2), separated by 12 weeks. Trials consisted of 3 min stages starting at a speed equivalent to 20km pace minus 50m/min and increasing speed 15 m/min until exhaustion. 20 km paces were established using a 3 km and 10 km standard field test and extrapolation using the Mercier nomogram. Expired gasses were collected with an Oxycon Mobile (Viasys, CA). HRA was collected in g's from portable wireless nodes (Microstrain, VT) streaming at 617 Hz, which were affixed to the lower back superficial to the L3 vertebrae. Root mean square (RMS) of accelerations in the vertical (VT), medial/lateral (M/L) and anterior/posterior (A/P) axes, and resultant scalars (RES) were determined using Signal Express 3.0 (Labview, TX). The ratio of axial RMS/RES (RA) and axial RMS relative to speed (EC) were examined for all axes. From VO2 and RER, O2 cost (O2C; ml/kg/km) and energy expenditure (EE; kcal/kg/min) were also determined. Variables were compared using MANOVA (SPSS, IL), a = 0.05. RESULTS: Significant trial effects were observed where VT-RMS, VT-RA, VT-Ec and ML-Ec were reduced at T2 vs. T1, while AP-RA and AP-Ec increased (P <.01). Differences in metabolism indicated a shift toward reduced fat utilization with an increased RER (P<.05) and a trend for increased O2C (P=.09) at T2 vs. T1. No effect was observed for EE (P=.55) CONCLUSIONS: Differences in running dynamics among intercollegiate distance runners before and after a competitive season can be identified with the use of HRA. These differences are in contrast to those reported elsewhere between trained and untrained runners. Additionally they are not reflective of changes in EE or trends in O2C. Therefore more work is necessary to determine the effects, if any, that these changes may have on performance.

High Resolution MEMS Accelerometers to Compare Running Mechanics between Trained and Untrained Runners

We have previously reported the validity and reliability of microelectromechanical system (MEMS) high resolution accelerometers (HRA) relative to VO2 in highly trained and untrained individuals during walking and running. PURPOSE: To determine if MEMS HRA could identify differences in mechanics of running between trained (T) and (UT) runners during treadmill locomotion. METHODS: Procedures were approved by the Eastern Michigan University CHHS Human Subjects Review Committee and subjects gave informed consent. 18 runners, [9 T (21.4±1.7yr, 65.5±5.7 kg, 70.1±6.2 ml/kg/min) and 9 UT (31.6±1.5yr, 69.8±3.7 kg, 49.2±4.2 ml/kg/min)] performed 2 incremental VO2max trials while wearing HRA (Microstrain, VT). Aggregate acceleration for vertical (VT), anterior/posterior (AP), medial/lateral (ML), axes were recorded and Euclidean resultants were computed (RES). Trials consisted of 2 min stages starting at 2kph and increasing 2kph until exhaustion. Group comparisons were made from 8-16 kph, as all subjects completed these stages. Axial root mean square (RMS), RMS relative to speed (EC), and ratio of RMS/RES (RA) were compared between T and UT to determine if differences in running mechanics could be identified between the two groups. Expired gasses were collected using an Oxycon Mobile (Viasys, CA). VO2 and RER, were used to determine O2 cost (O2C) and energy expenditure (EE). RESULTS: Regression of RES was strongly related to VO2, but the regression trend for T was significantly different than UT (p<.001) across running speeds. T exhibited lower RMS and EC than UT in all axes (p <.003). Although MLRA was also lower for T vs UT, VTRA was higher (p <.001). All of these differences while running were despite higher VO2, O2 cost, and lower RER in T vs. UT, indicating greater fat utilization in T. There was no significant difference in energy expenditure between groups. CONCLUSIONS: These results demonstrate that T runners accelerate less in all axes and relative to all speeds than UT, yet allocate a greater proportion of their RES acceleration in the VT axis. These differences in acceleration parameters are not necessarily reflected in lower O2C or EE of running in T vs UT. Therefore, it is unclear if these differences confer a performance advantage in T runners over UT, and the importance of these differences is yet to be determined.

Reliability of mechanomyography and triaxial accelerometry in the assessment of balance

Reliability of high-resolution accelerometery (HRA) and mechanomyography (MMG) was evaluated for the assessment of single-leg balance. Subjects (5M/5F, 25 ± 3 yr; 169.4 ± 11.7 cm; 79.0 ± 16.9 kg) participated in fifteen (three randomized bouts of five repetitions) 15-s dominant leg stances. A single HRA was fixed superficial to L3/L4 segment to capture motions relative to the center-of-mass, and three-uniaxial accelerometers were fixed on the surface of the dominant leg correspondent to the vastus medialis (VM), vastus lateralis (VL), and soleus (SOL) muscles to record MMG. Triaxial signals from the HRA (s.r. = 625 Hz) were streamed to a base station, simultaneously with MMG (s.r. = 1000 Hz). Signals were sampled, recorded and later analyzed. HRAs were recorded in g’s for vertical (VT), medial/lateral (ML), anterior/posterior (AP) directions, and resultant (RES) scalar. Intraclass correlation coefficients (ICC) were computed for each and Pearson’s r was calculated for the relationships between MMG and HRA (α ⩽ 0.05). Except for RES (ICC = 0.36), all measures demonstrated moderately strong reliability (ICC = 0.75, 0.73, 0.63, 0.87, 0.89, and 0.86 for VM, VL, SOL, VT, ML, and AP, respectively). HRA and MMG provide reliable information pertaining to balance, and may have application in evaluating postural control and stability.

Lower trunk motion and speed-dependence during walking

BackgroundThere is a limited understanding about how gait speed influences the control of upper body motion during walking. Therefore, the primary purpose of this study was to examine how gait speed influences healthy individual's lower trunk motion during overground walking. The secondary purpose was to assess if Principal Component Analysis (PCA) can be used to gain further insight into postural responses that occur at different walking speeds.MethodsThirteen healthy subjects (23 ± 3 years) performed 5 straight-line walking trials at self selected slow, preferred, and fast walking speeds. Accelerations of the lower trunk were measured in the anterior-posterior (AP), vertical (VT), and mediolateral (ML) directions using a triaxial accelerometer. Stride-to-stride acceleration amplitude, regularity and repeatability were examined with RMS acceleration, Approximate Entropy and Coefficient of Multiple determination respectively. Coupling between acceleration directions were calculated using Cross Approximate Entropy. PCA was used to reveal the dimensionality of trunk accelerations during walking at slow and preferred speeds, and preferred and fast speeds.ResultsRMS acceleration amplitude increased with gait speed in all directions. ML and VT trunk accelerations had less signal regularity and repeatability during the slow compared to preferred speed. However, stride-to-stride acceleration regularity and repeatability did not differ between the preferred and fast walking speed conditions, partly due to an increase in coupling between frontal plane accelerations. The percentage of variance accounted for by each trunk acceleration Principal Component (PC) did not differ between grouped slow and preferred, and preferred and fast walking speed acceleration data.ConclusionThe main finding of this study was that walking at speeds slower than preferred primarily alters lower trunk accelerations in the frontal plane. Despite greater amplitudes of trunk acceleration at fast speeds, the lack of regularity and repeatability differences between preferred and fast speeds suggest that features of trunk motion are preserved between the same conditions. While PCA indicated that features of trunk motion are preserved between slow and preferred, and preferred and fast speeds, the discriminatory ability of PCA to detect speed-dependent differences in walking patterns is limited compared to measures of signal regularity, repeatability, and coupling.

Intranasal application of dopamine reduces activity and improves attention in Naples High Excitability rats that feature the mesocortical variant of ADHD

Based on findings of a profound action of intranasally applied dopamine (DA) on dopamine release in the striatum, we examined the possibility that intranasal application of DA would influence indices of attention and activity in juvenile male rats of the Naples High Excitability line. This rat model features the main aspects of Attention Deficit/Hyperactivity Disorder (ADHD). Juvenile NHE rats received an intranasal application of either DA (0.075 mg/kg, 0.15 mg/kg and 0.3 mg/kg) or vehicle into both nostrils daily for 15 days. On day 14, 1 h after treatment, they were tested in the Làt maze, and one day later, in the eight arm radial maze. Activity in the Làt maze: The highest dose of DA (0.3 mg/kg) decreased horizontal (HA) and vertical (VA) activity during the first 10 min of the test. No effect was found for rearing duration (RD), which indexes non-selective attention (NSA). Activity in the radial maze: No treatment effects were found for HA and VA components, and for RD. Attention indices: The intermediate dose of DA (0.15 mg/kg) significantly improved the number of arms visited before the first repetitive arm entry in the radial maze, an index of selective spatial attention (SSA). In conclusion, intranasal application of DA reduced hyperactivity at the highest dose used, whereas the intermediate dose improved attention in an animal model of ADHD. These results suggest the potential of employing intranasal DA for therapeutic purposes.

The role of the neck and trunk in facilitating head stability during walking

An apparent goal of the human postural system is to maintain head stability during walking. Although much is known about sensory-motor stabilising mechanisms associated with the head and neck, less is known about how the postural system attenuates motion between the trunk and neck segments in order to regulate head motion. Therefore the purpose of this study was to determine the role that the neck and the trunk play in stabilising the head at a range of walking speeds. Eight healthy male subjects (age: 23+/-4 years) performed self-selected slow, preferred, and fast walking speed trials along a 30 m walkway. Four custom-designed wireless triaxial accelerometers were attached to the head, upper trunk, lower trunk, and shank of each subject to measure vertical (VT), anterior-posterior (AP), and mediolateral (ML) accelerations. Acceleration data were examined in each direction using RMS, power spectral, harmonic, and regularity measures. Signal regularity was increased from the lower to upper trunk for all walking speeds and directions with the exception of the slow speed in the AP direction. Evidence from analysis of power spectral and amplitude characteristics of acceleration signals was suggestive that accelerations are also attenuated from the lower to upper trunk by dynamics of the intervening trunk segment. Differences in selected power spectral and amplitude characteristics between the accelerations of the upper trunk and head due to the intervening neck segment were only detected in the AP direction at preferred and fast walking speeds. Overall the findings of the present study suggest that the trunk segment plays a critical role in regulating gait-related oscillations in all directions. Only accelerations in the direction of travel at preferred and fast speeds required additional control from the neck segment in order to enhance head stability during walking.

Complex segregation analysis of two principal components derived from horizontal and vertical head size traits

Background: There is a wealth of publications establishing the involvement of genetic factors in the determination of inter-individual variability of head size traits. However, little is known about the mode of inheritance of craniofacial traits in the healthy population.Aim: The aims of this study were to investigate the mode of inheritance of horizontal (HOC) and vertical (VEC) components of head dimensions, and to test the hypothesis of a common major gene for these traits.Subjects and methods: The study was conducted on 1406 individuals belonging to 357 pedigrees. Univariate and bivariate complex segregation analyses were conducted on two principal components, HOC and VEC, extracted from 10 original head traits.Results: The hypothesis of Mendelian transmission was accepted in both studied traits. The inferred major genes explained 54.0% and 45.6% of HOC and VEC variance, adjusted for covariates. For both traits an additive mode of major gene alleles interaction was suggested. No positive evidence for a common major gene for both HOC and VEC was obtained.Conclusion: We conclude that head size in horizontal and vertical dimensions is determined by two different major genes together with modest and minor effect genes, the latter being partly shared by HOC and VEC.

Coordination of head and trunk accelerations during walking

The purpose of this study was to investigate the relationship between oscillatory dynamics of the head and trunk in each plane of motion during walking. Head and trunk accelerations of ten healthy subjects (age: 23 +/- 4 years) were measured in the vertical (VT), anterior-posterior (AP) and mediolateral (ML) directions using a pair of tri-axial accelerometers. All subjects performed five walking trials along a level 20 m walkway at their preferred gait velocity (1.30 +/- 0.15 m s(-1)). Acceleration data were analysed using power spectral, harmonic and regularity measures. Results indicated that: (1) oscillations of the head were smoother, with a greater proportion of power at lower frequencies than oscillations of the trunk, (2) differences in power spectral properties between the head and trunk were most pronounced in the ML direction, (3) coupling between VT-AP, VT-ML, and AP-ML accelerations were greater for the head than trunk, and (4) for both segments, the weakest coupling was observed for AP-ML acceleration relations. Overall, the results of this study suggest that accelerations of the head are significantly attenuated, and more tightly controlled, compared to accelerations of the lower trunk. This attenuation process was particularly evident for the ML direction, whereby head accelerations showed the greatest differences compared to ML accelerations at the trunk.

Travel times and reflection points for reflected P-waves in transversely isotropic media

The travel time curve of reflection waves may not be hyperbolic, and the reflection point may not be located at the midpoint between the source and receiver for P-waves reflected from the bottom of a horizontal anisotropic layer. In this study, we used a physical model and numerical calculations to study travel times and reflection points for P-waves reflected from transversely isotropic media. We show that the reflection normal moveout (NMO) of the P-waves reflected from the bottom of a horizontal transversely isotropic (TI) layer is hyperbolic within the intermediate offset. The reflection points in the common midpoint (CMP) gather are located at the CMP of the P-waves reflected from TI strata with vertical (VTI) and horizontal (HTI) symmetry axes. However, the reflection points deviate from the CMP for media where the dip angles of the symmetry axes are not vertical and horizontal. The amount of deviation of the reflection points from the CMP depends not only on the offset but also on the dip angle, and the deviations are visualized by physical modeling. Thus, we must be extremely cautious about using the common depth point (CDP) shooting technique and NMO velocity to process seismic data reflected from anisotropic media.

Subthalamic Nucleus Deep Brain Stimulation for Parkinson’s Disease: Magnetic Resonance Imaging Targeting Using Visible Anatomical Landmarks

Background: The aim of the present study was to validate a magnetic resonance imaging (MRI) visual procedure to target the subthalamic nucleus (STN) based on surrounding anatomical landmarks. Methods: 31 consecutive bilaterally implanted parkinsonian patients were included in this study. After identification of the anterior commissure (AC), posterior commissure (PC) and midcommissural point on a three-dimensional T1-weighted sequence, inversion recovery (IR) T2-weighted coronal slices were performed orthogonal to the AC-PC line. On the slice showing the anterior pole of the red nucleus (RN), the target was placed in the inferolateral portion of the subthalamic zone, limited superiorly by the thalamus, laterally by the internal capsule, inferiorly by the substantia nigra and medially by the midline. The distribution of the targets was analyzed in the AC-PC referential. Results: The mean target coordinates were as follows: anteroposterior (AP) = –2.54 mm (±1.37 mm), lateral (LAT) = 12.03 mm (±0.91 mm) and vertical (VERT) = –6.10 mm (±1.52 mm) for the right side, and AP = –2.65 mm (±1.36 mm), LAT = –11.97 mm (±1.30 mm) and VERT = –5.89 mm (±1.52 mm) for the left side. They projected in the inferior portion of the STN on the Schaltenbrand and Wahren atlas [Stuttgart, Thieme, 1977]. Conclusion: Identification of the anterior pole of the RN and the subthalamic zone on coronal IR T2-weighted MRI performed orthogonal to the AC-PC line provides a precise visual procedure to target the STN.