Organic Chemical Contaminants in Water System Infrastructure Following Wildfire.

Wildfires have destroyed multiple residential communities in California in recent years. After fires in 2017 and 2018, high concentrations of benzene and other volatile organic compounds (VOCs) were found in public drinking water systems in fire-affected areas. The sources of the contamination and appropriate remediation have been urgent matters for investigation. This study characterizes target and non-target VOCs and semi volatile organic compounds (SVOCs) in water from a highly contaminated service line after the 2018 Camp Fire (Paradise, CA). Ninety-five organic compounds were identified or tentatively identified in the service line. Laboratory combustion experiments with drinking water pipes made of polyvinyl chloride (PVC), cross-linked polyethylene (PEX) and high-density polyethylene (HDPE) and a review of the literature were used to evaluate potential sources of the detected chemicals. Among the service line contaminants were thirty-two compounds associated with PVC pyrolysis and twenty-eight organic compounds also associated with the pyrolysis of polyethylene. The service line sample also contained fifty-five compounds associated with uncontrolled burning of biomass and waste materials. The findings support hypotheses that wildfires can contaminate drinking water systems both by thermal damage to plastic pipes and intrusion of smoke. Residual chlorine disinfectant in the water system modifies the contaminant distribution observed.

[The Importance of the "Big Five" Personality Traits for Subjective Health and Life Satisfaction in Adolescence: Results of the National Educational Panel Study (NEPS)]. / Die Bedeutung der "Big Five"-Persönlichkeitsmerkmale für die subjektive Gesundheit und Lebenszufriedenheit im Jugendalter: Ergebnisse des Nationalen Bildungspanels (NEPS).

BACKGROUND: The role of personality traits in self-rated health and well-being of adolescents has barely been studied in Germany so far. The aim of this study was to analyze the association between the Big Five personality traits and self-reported health as well as life satisfaction of adolescents in Germany. METHODS: The study data are based on the National Educational Panel Study (NEPS), starting cohort 3 (wave 3, 2012). This sample includes (n=5,440) 7th grade adolescents in regular schools. Personality traits were measured by the Big Five-Inventory (BFI-10): Extraversion, Agreeableness, Conscientiousness, Neuroticism, Openness. Statistical analyses were carried out using bivariate methods and binary-logistic multilevel models, taking into account individuals nested in school classes and schools. RESULTS: Adolescents with pronounced neuroticism had a higher risk of both poor self-rated health (OR: 1.33) and low life satisfaction (OR: 1.46). In contrast, adolescents with high levels of conscientiousness had a reduced risk of poor health (OR: 0.72) and low life satisfaction (OR: 0.59). High levels of extraversion (OR: 0.78) and agreeableness (OR: 0.72) also correlated with higher life satisfaction, but not with better self-reported health. The characteristic of openness was not associated with either self-reported health or the life satisfaction of adolescents. CONCLUSION: The results suggest that certain personality traits, namely the Big Five can be important indicators of health and life satisfaction of adolescents in early adolescence. However, further studies are needed to assess the link between the Big Five and its generalizability to other age groups.

Measurement and Analysis of Biomechanical Outcomes of Chiropractic Adjustment Performance in Chiropractic Education and Practice.

OBJECTIVE: The purpose of this study was to compare biomechanical measures of chiropractic adjustment performance of the McTimoney toggle-torque-recoil (MTTR) technique among students and chiropractors. METHODS: Fifty-three participants (15 year-3 [Y3] and 16 year-5 chiropractic students and 22 McTimoney chiropractors [DCs]) participated in this study. Each applied 10 MTTR thrusts to a dynamic load cell, 5 each with their left and right hands. Biomechanical variables including preload force, peak force, time to peak force, thrust duration, and total thrust time were computed from each of the force-time histories and compared within groups using a series of 2-way analysis of variance to evaluate the effects of sex and handedness, and between groups to determine the effect of experience using a series of 3-way analysis of variance. The Games-Howell post hoc test was used to further assess pairwise comparisons. RESULTS: Mean time to peak force was more than 3 × shorter for DCs (69.96 ms) compared with Y3 students (230.36 ms) (P = .030). Likewise, mean thrust duration was also found to be nearly 2.5-fold significantly shorter for DCs (117.77 ms) compared with Y3 students (283.84 ms) (P = .030). The DCs took significantly less total thrust time (mean = 1.27 seconds) in administering MTTR thrusts than Y3 students (1.89 seconds) (P = .006). No significant differences were found among any of the 3 clinician groups for peak force or in time to peak force or thrust duration for comparisons of all 10 MTTR thrusts among year-5 students and DCs. Higher peak forces were observed for thrusts delivered with clinicians' dominant hands (P = .001), and the fastest thrusts were found for the dominant hands of DCs (P = .001). Sex had no significant effect on biomechanical variables. The Y3 students had significant greater variability in thrust times for each hand and for analyses of both hands combined (P = .001). CONCLUSION: Training and experience were found to result in shorter MTTR thrust times and other biomechanical variables that have been identified as important factors in the mechanisms of chiropractic adjustments. Identification of such biomechanical markers as performance outcomes may be of assistance in providing feedback for training in chiropractic education and technique application.

[An Explorative Study about Educational Pathways after a Moderate and Severe Traumatic Brain Injury]. / Eine explorative Studie zu den schulischen Verlaufswegen nach einem mittelschweren bis schweren Schädel-Hirn-Trauma.

PURPOSE: Empirical data on educational pathways after a traumatic brain injury (TBI) are rare and obsolete. Less is known about the success of executed initial recommendations and the following school career. This study examines the course of school career after a moderate to severe TBI. In particular, based on the school recommendations at the end of inpatient rehabilitation, the linearity or nonlinearity of the processes and the long-term success in the educational system should be understood. METHODS: The sample included 49 students. We analysed descriptive clinical data, school-related recommendations and standardised questionnaires for evaluating scholastic reintegration. 2-9 years later a standardized questionnaire was used to evaluate the outcome and success of the course in the school system. The analysis is based on descriptive statistics due to Stata 15.1. RESULTS: 59,2% of the respondents returned in their former school class immediately after hospital discharge. 24,5% initially changed the educational institution. All in all, there were changes and ruptures in more than a half of the cases as aftereffect of the TBI. CONCLUSION: The results of the study are discussed regarding the discontinuities in school careers. The study confirms a high level of breaks and nonlinearity in the scholastic pathway after a moderate to severe TBI. Recommendations of the rehabilitation clinic appear helpful, but they are no guarantee for an obstacle-free re-education. Professional guidance in the process of school re-habilitation is recommended. The results of the study verify the requirement of a professional, systemic and individualized follow-up care in each particular school context. More empirical research about courses of TBI in the school system is needed to identify the aspects, which increase the risks of disruptions or prevents the fitting in the school career and to identify the aspects which support the success of fitting for the individual student.

Mechanical misconceptions: Have we lost the "mechanics" in "sports biomechanics"?

Biomechanics principally stems from two disciplines, mechanics and biology. However, both the application and language of the mechanical constructs are not always adhered to when applied to biological systems, which can lead to errors and misunderstandings within the scientific literature. Here we address three topics that seem to be common points of confusion and misconception, with a specific focus on sports biomechanics applications: (1) joint reaction forces as they pertain to loads actually experienced by biological joints; (2) the partitioning of scalar quantities into directional components; and (3) weight and gravity alteration. For each topic, we discuss how mechanical concepts have been commonly misapplied in peer-reviewed publications, the consequences of those misapplications, and how biomechanics, exercise science, and other related disciplines can collectively benefit by more carefully adhering to and applying concepts of classical mechanics.

A general model for estimating lower extremity inertial properties of individuals with transtibial amputation.

Lower extremity joint moment magnitudes during swing are dependent on the inertial properties of the prosthesis and residual limb of individuals with transtibial amputation (TTA). Often, intact limb inertial properties (INTACT) are used for prosthetic limb values in an inverse dynamics model even though these values overestimate the amputated limb's inertial properties. The purpose of this study was to use subject-specific (SPECIFIC) measures of prosthesis inertial properties to generate a general model (GENERAL) for estimating TTA prosthesis inertial properties. Subject-specific mass, center of mass, and moment of inertia were determined for the shank and foot segments of the prosthesis (n=11) using an oscillation technique and reaction board. The GENERAL model was derived from the means of the SPECIFIC model. Mass and segment lengths are required GENERAL model inputs. Comparisons of segment inertial properties and joint moments during walking were made using three inertial models (unique sample; n=9): (1) SPECIFIC, (2) GENERAL, and (3) INTACT. Prosthetic shank inertial properties were significantly smaller with the SPECIFIC and GENERAL model than the INTACT model, but the SPECIFIC and GENERAL model did not statistically differ. Peak knee and hip joint moments during swing were significantly smaller for the SPECIFIC and GENERAL model compared with the INTACT model and were not significantly different between SPECIFIC and GENERAL models. When subject-specific measures are unavailable, using the GENERAL model produces a better estimate of prosthetic side inertial properties resulting in more accurate joint moment measurements for individuals with TTA than the INTACT model.

Oscillation and reaction board techniques for estimating inertial properties of a below-knee prosthesis.

The purpose of this study was two-fold: (1) demonstrate a technique that can be used to directly estimate the inertial properties of a below-knee prosthesis, and (2) contrast the effects of the proposed technique and that of using intact limb inertial properties on joint kinetic estimates during walking in unilateral, transtibial amputees. An oscillation and reaction board system was validated and shown to be reliable when measuring inertial properties of known geometrical solids. When direct measurements of inertial properties of the prosthesis were used in inverse dynamics modeling of the lower extremity compared with inertial estimates based on an intact shank and foot, joint kinetics at the hip and knee were significantly lower during the swing phase of walking. Differences in joint kinetics during stance, however, were smaller than those observed during swing. Therefore, researchers focusing on the swing phase of walking should consider the impact of prosthesis inertia property estimates on study outcomes. For stance, either one of the two inertial models investigated in our study would likely lead to similar outcomes with an inverse dynamics assessment.

Mechanical factors associated with the development of high ball velocity during an instep soccer kick.

The purpose of this study was to determine whether joint velocities and segmental angular velocities are significantly correlated with ball velocity during an instep soccer kick. We developed a deterministic model that related ball velocity to kicking leg and pelvis motion from the initiation of downswing until impact. Three-dimensional videography was used to collect data from 16 experienced male soccer players (age = 24.8 +/- 5.5 years; height = 1.80 +/- 0.07m; mass = 76.73 +/- 8.31 kg) while kicking a stationary soccer ball into a goal 12 m away with their right foot with maximal effort. We found that impact velocities of the foot center of mass (CM), the impact velocity of the foot CM relative to the knee, peak velocity of the knee relative to the hip, and the peak angular thigh velocity were significantly correlated with ball velocity. These data suggest that linear and angular velocities at and prior to impact are critical to developing high ball velocity. Since events prior to impact are critical for kick success, coordination and summation of speeds throughout the kicking motion are important factors. Segmental coordination that occurs during a maximal effort kick is critical for completing a successful kick.

A mechanics comparison between landing from a countermovement jump and landing from stepping off a box.

It is common practice to study jump landing mechanics by having subjects step off a box set at a certain height instead of landing from a jump. This practice assumes that the landing mechanics are similar between stepping off a box and a countermovement jump as long as the heights can be matched. The mechanics of the two methods had never been compared when landing from identical heights. Thus, the purpose of this study was to compare the mechanics of landing from a countermovement jump to landing from a step-off. Participants performed three maximal countermovement jumps. The mechanics of one countermovement jump was compared with a center of mass fall height matched step-off landing. The step-off landing showed a more rapid time to peak ground reaction force (GRF) in both genders and greater GRF peak and loading rate in males only. No difference was observed between joint angles at initial contact; however, the countermovement jump showed significantly greater joint flexion angles at peak GRF for both genders. EMG showed greater muscle activity during the countermovement jump condition in all subjects. It was concluded that countermovement jump landings are different from step-off landings; thus, results from analyses involving step-off landings should be taken with caution if the aim is to relate them to landing from a jump.

Multicomponent control strategy underlying production of maximal hand velocity during horizontal arm swing.

Movement control responsible for generation of maximal hand velocity was studied on the example of horizontal arm swing that is a component of various sports activities. The movement was performed with the nondominant arm in similarity with the baseball bat swing. The task was to generate maximum hand velocity at a target. The movement included trunk long-axis rotation and horizontal shoulder and elbow extension. Kinematics and torque analyses were performed to study the organization of fastest movements and to compare trials representing the best and worst performance in each subject. Results revealed complex control strategy, with the trunk, shoulder, and elbow playing unique roles in generation of maximal hand velocity. The trunk provided a crucial contribution, directly, rotating the entire arm, and indirectly, exerting interaction torque that caused swift elbow extension. The major role of the shoulder was to transfer the mechanical effect of trunk motion to the elbow. However, the shoulder became the primary motion generator when the trunk reached its limits of rotation, revealing sequential organization of control. The role of the elbow was to maximally comply with passive influence of proximal joints. The findings are discussed in light of the leading joint hypothesis that offers a straightforward interpretation of control of horizontal arm swing as well as practically efficient recommendations for increases in movement speed. The revealed role of intersegmental dynamics in production of high movement speed suggests that movement slowness characteristic for some motor disorders may be partially a compensatory strategy that facilitates regulation of interaction torque.

Force-time profile characterization of the McTimoney toggle-torque-recoil technique.

OBJECTIVES: The purpose of this study was to characterize the force-time profile of the McTimoney toggle-torque-recoil (MTTR) technique. METHODS: Two licensed chiropractors trained in the McTimoney Method applied MTTR thrusts to a tabletop where a dynamic load cell had been mounted. Each clinician applied 10 thrusts (5 with each hand) to the load cell in a repeated measures design. Peak forces, time durations, and time to peak force were computed from each of the force-time histories. Descriptive statistics were performed to compare the forces, durations, and times to peak force of the MTTR thrusts. A Mann-Whitney U test compared variables between the 2 clinicians, whereas a Wilcoxon signed-rank test compared right- and left-handed thrusts within clinicians. RESULTS: Considering all MTTR thrusts, the average peak force was 87.22 N (SD = 24.18 N), the average overall thrust duration was 36.38 milliseconds (SD = 9.58 milliseconds), and the average time to peak force was 12.31 milliseconds (S.D. = 4.39 milliseconds). No significant differences in mean peak force, duration, or time to peak force were observed between clinicians. When comparing intraclinician right and left hand thrusts, differences in peak force and duration were observed individually (P < .05). CONCLUSION: For the 2 chiropractors tested, MTTR thrusts were relatively lower in peak force and appreciably faster than other commonly used chiropractic techniques. Future work aims to investigate the relationships between the force-time profiles of MTTR thrusts and resultant physiologic and clinical responses.

Front- or rear-weighted track start or grab start: which is the best for female swimmers?

The aim of this study was to compare three competitive swimming starts (grab, rear-weighted track, and front-weighted track). The starts were compared in terms of time and instantaneous horizontal velocity, both at take-off from the block and at 5 m from the wall. Twenty US college female swimmers performed three trials of each of the three randomly ordered starts. Swimmers left the block significantly sooner using the front-weighted track start (0.80 s) than the other two starts (both 0.87 s; P < 0.001). In the rear-weighted track start, however, the athletes left the blocks with significantly higher horizontal velocity than in the grab or front-weighted track start (3.99 vs. 3.87 and 3.90 m/s, respectively; each P < 0.001). By 5 m, the front-weighted track start maintained its time advantage over the grab start (2.19 vs. 2.24s; P = 0.008) but not the rear-weighted track start (2.19 vs. 2.21 s; P = 0.336). However, the rear-weighted track start had a significant advantage over the front-weighted track start in terms of instantaneous horizontal velocity at 5 m (2.25 vs. 2.18 m/s; P = 0.009). Therefore, the rear-weighted track start had a better combination of time and velocity than the front-weighted track start. There was also a trend for the rear-weighted track start to have higher velocity at 5 m than the grab start, although this did not reach statistical significance (2.25 vs. 2.20 m/s; P = 0.042). Overall, these results favour the rear-weighted track start for female swimmers even though most of the athletes had little or no prior experience with it. Additional research is needed to determine whether males would respond similarly to females in these three different swimming starts.

The biomechanical and clinical significance of the lumbar erector spinae flexion-relaxation phenomenon: a review of literature.

OBJECTIVES: The aim of this study was to review the biomedical literature to ascertain the biomechanical and clinical significance of the lumbar erector spinae flexion-relaxation phenomenon (FRP). DATA SOURCES: Index Medicus via PubMed, the Noble Science Library's e-journal archives, and the Manual Alternative and Natural Therapy Index System databases were searched using the same search terms. DISCUSSION: The presence of the FRP during trunk flexion represents myoelectric silence consistent with increased load sharing of the posterior discoligamentous passive structures. Passive contributions from erector spinae stretching during the flexion posture and active contributions from other muscles (quadratus lumborum and deep erector spinae among others) further assist in load sharing in the trunk flexion posture. A number of studies have shown differences in the FRP between patients with chronic low back pain and healthy individuals, and the reliability of the assessment. Persistent activation of the lumbar erector spinae musculature among patients with back pain may represent the body's attempt to stabilize injured or diseased spinal structures via reflexogenic ligamentomuscular activation thereby protecting them from further injury and avoiding pain. CONCLUSIONS: The myoelectric silencing of the erector spinae muscles in the trunk flexion posture is indicative of increased load sharing on passive structures, which tissues have been found to fail under excessive loading conditions and shown to be a source of low back pain. The studies that show differences in the presence of the FRP among patients and control subjects are encouraging for this type of clinical assessment and suggest that assessment of the FRP is a valuable objective clinical tool to aid in the diagnosis and treatment of patients with low back pain.

Manipulative treatment of carpal tunnel syndrome: biomechanical and osteopathic intervention to increase the length of the transverse carpal ligament: part 2. Effect of sex differences and manipulative "priming".

As a theoretical basis for treatment of carpal tunnel syndrome (CTS) and expanding upon part 1 of this study, the authors investigated the effects of static loading (weights) and dynamic loading (osteopathic manipulation [OM]) on 20 cadaver limbs (10 male, 10 female). This larger study group allowed for comparative analysis of results by sex and reversal of sequencing for testing protocols. In static loading, 10-newton loads were applied to metal pins inserted into carpal bones. In dynamic loading, the OM maneuvers used were those currently used in clinical settings to treat patients with CTS. Transverse carpal ligament (TCL) response was observed by measuring changes in the width of the transverse carpal arch (TCA) with three-dimensional video analysis and precision calipers. Results demonstrated maximal TCL elongation of 13% (3.7 mm) with a residual elongation after recovery of 9% (2.6 mm) from weight loads in the female cadaver limbs, compared to less than 1 mm as noted in part 1, which used lower weight loads and combined results from both sexes. Favorable responses to all interventions were more significant among female cadaver limbs. Higher weight loads also caused more linear translatory motion through the metal pins, resulting in TCA widening equal to 63% of the increases occurring at skin level, compared to only 38% with lower loads. When OM was performed first, it led to greater widening of the TCA and lengthening of the TCL during the weight loading that followed. Both methods hold promise to favorably impact the course of management of CTS, particularly in women.