Effects of Different Postural Conditions on Handwriting Variability

During their career, forensic document examiners will inevitably be confronted with handwriting carried out under unusual conditions (UnC). A questioned document signed on top of a car or on a vertical surface like a wall are two examples. These atypical circumstances may give rise to more variability of the signatures or written words, in particular if the body was in non-traditional writing position without the traditional support. Few studies were devoted to handwriting variability under unusual writing conditions. The current study investigates whether individual variability changes with special writing conditions. In a previous study (Sciacca & al, 2009), we found that eight repetitions were sufficient to obtain a correct estimation of the variance. In the present study, twelve subjects were asked to write two word sets eight times in upper and eight times in lower case, under different conditions : sitting and writing on a horizontal (usual condition UC) or vertical support; and standing, kneeling or laying while writing on a horizontal or vertical support (unusual conditions UnC). Words were written on a pen tablet, normalized in space and time and then averaged. The variance of the eight words was measured under all conditions. Results showed only an increase in variability under the laying and kneeling / vertical UnC. Within the five other postural conditions tested, handwriting was shown to be very stable.

Kinematics and dynamic complexity of postural transitions in frail elderly subjects.

The aim of this study was to propose a methodology allowing a detailed characterization of body sit-to-stand/stand-to-sit postural transition. Parameters characterizing the kinematics of the trunk movement during sit-to-stand (Si-St) postural transition were calculated using one initial sensor system fixed on the trunk and a data logger. Dynamic complexity of these postural transitions was estimated by fractal dimension of acceleration-angular velocity plot. We concluded that this method provides a simple and accurate tool for monitoring frail elderly and to objectively evaluate the efficacy of a rehabilitation program.

Automatic recognition of postural allocations.

A significant part of daily energy expenditure may be attributed to non-exercise activity thermogenesis and exercise activity thermogenesis. Automatic recognition of postural allocations such as standing or sitting can be used in behavioral modification programs aimed at minimizing static postures. In this paper we propose a shoe-based device and related pattern recognition methodology for recognition of postural allocations. Inexpensive technology allows implementation of this methodology as a part of footwear. The experimental results suggest high efficiency and reliability of the proposed approach.

Hypobaric versus normobaric hypoxia: same effects on postural stability?

AIMS: To test the hypothesis that postural stability would be more affected during acute exposure in hypobaric (HH) than in normobaric (NH) hypoxia.¦METHODS: In separate trials, 12 subjects stood on a posturographic platform for two successive 25.6 sec tests in three conditions: eyes open (EO), eyes closed (EC), and verbal dual task (DT). Ambient pressure in O(2) was matched between HH and NH at 1700 and 3000 m, respectively.¦RESULTS: Compared to NH, the length of Centre of Pression trajectory in Y-axis was increased (p<0.05) in HH for EO at 1700 m, EC at 1700 and 3000 m, and for DT at 1700 m, whereas the variance of speed of CoP was decreased (p<0.05) in EO, EC, and DT at 1700 m. Compared to normobaric normoxia (NN; 400 m), the surface of CoP trajectory was increased (p<0.05) in HH in EO and EC at 3000 m.¦CONCLUSIONS: HH deteriorated postural stability in the antero-posterior plane, for the variance of speed and the surface of CoP in 3 conditions, whereas no difference was observed between NH and NN. These results suggest that hypobaria instead of hypoxia per se plays an important role to the altered balance classically reported in altitude.

Alterations in Postural Control during the World's Most Challenging Mountain Ultra-Marathon

We investigated postural control (PC) effects of a mountain ultra-marathon (MUM): a 330-km trail run with 24000 m of positive and negative change in elevation. PC was assessed prior to (PRE), during (MID) and after (POST) the MUM in experienced ultra-marathon runners (n = 18; finish time = 126+/-16 h) and in a control group (n = 8) with a similar level of sleep deprivation. Subjects were instructed to stand upright on a posturographic platform over a period of 51.2 seconds using a double-leg stance under two test conditions: eyes open (EO) and eyes closed (EC). Traditional measures of postural stability (center of pressure trajectory analysis) and stabilogram-diffusion analysis (SDA) parameters were analysed. For the SDA, a significantly greater short-term effective diffusion was found at POST compared with PRE in the medio-lateral (ML; Dxs) and antero-posterior (AP) directions (Dys) in runners (p<0.05) The critical time interval (Ctx) in the ML direction was significantly higher at MID (p<0.001) and POST (p<0.05) than at PRE in runners. At MID (p<0.001) and POST (p<0.05), there was a significant difference between the two groups. The critical displacement (Cdx) in the ML was significantly higher at MID and at POST (p<0.001) compared with PRE for runners. A significant difference in Cdx was observed between groups in EO at MID (p<0.05) and POST (p<0.005) in the ML direction and in EC at POST in the ML and AP directions (p<0.05). Our findings revealed significant effects of fatigue on PC in runners, including, a significant increase in Ctx (critical time in ML plan) in EO and EC conditions. Thus, runners take longer to stabilise their body at POST than at MID. It is likely that the mountainous characteristics of MUM (unstable ground, primarily uphill/downhill running, and altitude) increase this fatigue, leading to difficulty in maintaining balance.

Walking-induced muscle fatigue impairs postural control in adolescents with unilateral spastic cerebral palsy.

BACKGROUND: Fatigue is likely to be an important limiting factor in adolescents with spastic cerebral palsy (CP). AIMS: To determine the effects of walking-induced fatigue on postural control adjustments in adolescents with unilateral CP and their typically developing (TD) peers. METHODS: Ten adolescents with CP (14.2±1.7yr) and 10 age-, weight- and height-matched TD adolescents (14.1±1.9yr) walked for 15min on a treadmill at their preferred walking speed. Before and after this task, voluntary strength capacity of knee extensors (MVC) and postural control were evaluated in 3 conditions: eyes open (EO), eyes closed (EC) and with dual cognitive task (EODT). RESULTS: After walking, MVC decreased significantly in CP (-11%, P<0.05) but not in TD. The CoP area was only significantly increased in CP (90%, 34% and 60% for EO, EC and EODT conditions, respectively). The CoP length was significantly increased in the EO condition in CP and TD (20% and 21%) and was significantly increased in the EODT condition by 18% in CP only. CONCLUSIONS: Unlike TD adolescents, treadmill walking for 15min at their preferred speed lead to significant knee extensor strength losses and impairments in postural control in adolescents with unilateral spastic CP.

Reduction of the hand representation in the ipsilateral primary motor cortex following unilateral section of the corticospinal tract at cervical level in monkeys.

BACKGROUND: After sub-total hemi-section of cervical cord at level C7/C8 in monkeys, the ipsilesional hand exhibited a paralysis for a couple of weeks, followed by incomplete recovery of manual dexterity, reaching a plateau after 40-50 days. Recently, we demonstrated that the level of the plateau was related to the size of the lesion and that progressive plastic changes of the motor map in the contralesional motor cortex, particularly the hand representation, took place following a comparable time course. The goal of the present study was to assess, in three macaque monkeys, whether the hand representation in the ipsilesional primary motor cortex (M1) was also affected by the cervical hemi-section.¦RESULTS: Unexpectedly, based on the minor contribution of the ipsilesional hemisphere to the transected corticospinal (CS) tract, a considerable reduction of the hand representation was also observed in the ipsilesional M1. Mapping control experiments ruled out the possibility that changes of motor maps are due to variability of the intracortical microstimulation mapping technique. The extent of the size reduction of the hand area was nearly as large as in the contralesional hemisphere in two of the three monkeys. In the third monkey, it represented a reduction by a factor of half the change observed in the contralesional hemisphere. Although the hand representation was modified in the ipsilesional hemisphere, such changes were not correlated with a contribution of this hemisphere to the incomplete recovery of the manual dexterity for the hand affected by the lesion, as demonstrated by reversible inactivation experiments (in contrast to the contralesional hemisphere). Moreover, despite the size reduction of M1 hand area in the ipsilesional hemisphere, no deficit of manual dexterity for the hand opposite to the cervical hemi-section was detected.¦CONCLUSION: After cervical hemi-section, the ipsilesional motor cortex exhibited substantial reduction of the hand representation, whose extent did not match the small number of axotomized CS neurons. We hypothesized that the paradoxical reduction of hand representation in the ipsilesional hemisphere is secondary to the changes taking place in the contralesional hemisphere, possibly corresponding to postural adjustments and/or re-establishing a balance between the two hemispheres.

Botulinum toxin A in non-dystonic tremors.

The present pilot study evaluated the effect of botulinum toxin A on primarily non-dystonic tremors using accelerometry in a single-blind, placebo-controlled design. Resting, postural, intention, or head tremor were assessed before and approximately 1 month after intramuscular saline and botulinum toxin A (25-50 U) respectively. Half of the patients showed > or = 30% placebo effect. Tremor in 10 of 17 patients (60%) studied improved further after botulinum toxin A (range 30-95%), exceeding the placebo effect by > or = 30%. Nine patients demonstrated clinically significant focal weakness in the extensor muscles after botulinum toxin A which interfered with fine movements. Patients were subdivided into PD-like and ET-like tremor(s). Both groups experienced large placebo effects for resting tremor, with little or no further improvement after botulinum toxin A. The improvement in postural tremor after botulinum toxin A, of 40% in the PD-like and 57% in the ET-like groups, however, was approximately twice that of placebo. In conclusion, botulinum toxin A exerts a modest tremorlytic effect, however the dose, and its distribution over the sites injected, need to be optimised to minimise focal weakness.

Effective exposure to solar UV in building workers: influence of local and individual factors.

Excessive exposure to solar UV light is the main cause of skin cancers in humans. UV exposure depends on environmental as well as individual factors related to activity. Although outdoor occupational activities contribute significantly to the individual dose received, data on effective exposure are scarce and limited to a few occupations. A study was undertaken in order to assess effective short-term exposure among building workers and characterize the influence of individual and local factors on exposure. The effective exposure of construction workers in a mountainous area in the southern part of Switzerland was investigated through short-term dosimetry (97 dosimeters). Three altitudes, of about 500, 1500 and 2500 m were considered. Individual measurements over 20 working periods were performed using Spore film dosimeters on five body locations. The postural activity of workers was concomitantly recorded and static UV measurements were also performed. Effective exposure among building workers was high and exceeded occupational recommendations, for all individuals for at least one body location. The mean daily UV dose in plain was 11.9 SED (0.0-31.3 SED), in middle mountain 21.4 SED (6.6-46.8 SED) and in high mountain 28.6 SED (0.0-91.1 SED). Measured doses between workers and anatomical locations exhibited a high variability, stressing the role of local exposure conditions and individual factors. Short-term effective exposure ranged between 0 and 200% of ambient irradiation, indicating the occurrence of intense, subacute exposures. A predictive irradiation model was developed to investigate the role of individual factors. Posture and orientation were found to account for at least 38% of the total variance of relative individual exposure, and were also found to account more than altitude on the total variance of effective daily exposures. Targeted sensitization actions through professional information channels and specific prevention messages are recommended. Altitude outdoor workers should also benefit from preventive medical examination.

Energy cost of walking and gait instability in healthy 65- and 80-yr-olds.

This study tested whether the lower economy of walking in healthy elderly subjects is due to greater gait instability. We compared the energy cost of walking and gait instability (assessed by stride to stride changes in the stride time) in octogenarians (G80, n = 10), 65-yr-olds (G65, n = 10), and young controls (G25, n = 10) walking on a treadmill at six different speeds. The energy cost of walking was higher for G80 than for G25 across the different walking speeds (P < 0.05). Stride time variability at preferred walking speed was significantly greater in G80 (2.31 +/- 0.68%) and G65 (1.93 +/- 0.39%) compared with G25 (1.40 +/- 0.30%; P < 0.05). There was no significant correlation between gait instability and energy cost of walking at preferred walking speed. These findings demonstrated greater energy expenditure in healthy elderly subjects while walking and increased gait instability. However, no relationship was noted between these two variables. The increase in energy cost is probably multifactorial, and our results suggest that gait instability is probably not the main contributing factor in this population. We thus concluded that other mechanisms, such as the energy expenditure associated with walking movements and related to mechanical work, or neuromuscular factors, are more likely involved in the higher cost of walking in elderly people.

BMI group-related differences in physical fitness and physical activity in preschool-age children: a cross-sectional analysis.

In the Ballabeina study, we investigated age- and BMI-group-related differences in aerobic fitness (20 m shuttle run), agility (obstacle course), dynamic (balance beam) and static balance (balance platform), and physical activity (PA, accelerometers) in 613 children (M age = 5.1 years, SD = 0.6). Normal weight (NW) children performed better than overweight (OW) children in aerobic fitness, agility, and dynamic balance (all p <.001), while OWchildren had a better static balance (p < .001). BMI-group-related differences in aerobic fitness and agility were larger in older children (p for interaction with age = .01) in favor of the NW children. PA did not differ between NW and OW (p > or = .1), but did differ between NW and obese children (p < .05). BMI-group-related differences in physical fitness can already be present in preschool-age children.