A novel motorized office chair causes low-amplitude spinal movements and activates trunk muscles: A cross-over trial.

INTRODUCTION: Inactivity and long periods of sitting are common in our society, even though they pose a health risk. Dynamic sitting is recommended to reduce this risk. The purpose of this study was to investigate the effect of continuous passive motion (CPM) conducted by a novel motorized office chair on lumbar lordosis and trunk muscle activation, oxygen uptake and attentional control. STUDY DESIGN: Randomized, single-session, crossover with two periods/conditions. METHODS: Twenty office workers (50% women) sat for one hour on the motorized chair, one half with CPM, the other not. The starting condition (CPM/no CPM) was switched in half of the sample. The participants were equipped with a spirometric cart, surface EMG, the Epionics SPINE system and performed a computer-based test for attentional control (AX-CPT). Outcomes were lumbar sagittal movements and posture, number of trunk muscle activations, attentional control and energy expenditure. RESULTS: The CPM of the chair causes frequent low-amplitude changes in lumbar lordosis angle (moved: 498 ± 133 vs. static: 45 ± 38) and a higher number of muscle activations. A periodic movement pattern of the lumbar spine according to the movement of the chair was observed in every participant, although, sitting behavior varied highly between individuals. Attentional control was not altered in the moved condition (p = .495; d = .16). Further, oxygen uptake did not increase higher than 1.5 MET. CONCLUSION: The effects of the motorized chair can be particularly useful for people with static sitting behavior. Further studies should investigate, whether CPM provides the assumed beneficial effects of dynamic sitting on the spine.

Abundance of Hard-Hexagon Crystals in the Quantum Pyrochlore Antiferromagnet.

We propose a simple family of valence-bond crystals as potential ground states of the S=1/2 and S=1 Heisenberg antiferromagnet on the pyrochlore lattice. Exponentially numerous in the linear size of the system, these can be visualized as hard-hexagon coverings, with each hexagon representing a resonating valence-bond ring. This ensemble spontaneously breaks rotation, inversion, and translation symmetries. A simple, yet accurate, variational wave function allows a precise determination of the energy, confirmed by the density matrix renormalization group and numerical linked cluster expansion, and extended by an analysis of excited states. The identification of the origin of the stability indicates applicability to a broad class of frustrated lattices, which we demonstrate for the checkerboard and ruby lattices. Our work suggests a perspective on such quantum magnets, in which unfrustrated motifs are effectively uncoupled by the frustration of their interactions.

Metabolic power in the men's European handball championship 2020.

PURPOSE: To ascertain the typical metabolic power characteristics of elite handball players of different positions, and whether changes occur within matches. METHODS: 414 elite male handball players were included. During all 65 matches of the EURO 2020, local positioning system data were collected, yielding 1853 datasets. Field players were categorised into six positional groups: centre backs (CB), left/right wings (LW/RW), left/right backs (LB/RB) and pivots (P). Metabolic power, total energy expenditure, high-power energy, and the equivalent distance index were calculated. We used linear mixed models with players as random and positions as fixed effects models. Intensity models adjusted for time-dependency by incorporating the duration of play. RESULTS: LW/RW spent most time on the court, expanded most total energy, and most relative energy per kg body weight in the high-intensity categories. CB played at the highest mean metabolic power (7.85 W/kg; CI95% [7.67, 8.03]). Playing intensity decreased by 2.5% (0.2 kJ/kg/s; CI95% [0.17, 0.23]) per 10 min played. CONCLUSION: Positional differences in metabolic power parameters exist. In general, wing players had the highest volume and CB the highest intensity of match-play. Analysis of metabolic intensity in handball should take position and players' time on the court into account.

The mechanical loading of the spine in physical activities.

PURPOSE: To summarize the mechanical loading of the spine in different activities of daily living and sports. METHODS: Since the direct measurement is not feasible in sports activities, a mathematical model was applied to quantify spinal loading of more than 600 physical tasks in more than 200 athletes from several sports disciplines. The outcome is compression and torque (normalized to body weight/mass) at L4/L5. RESULTS: The data demonstrate high compressive forces on the lumbar spine in sport-related activities, which are much higher than forces reported in normal daily activities and work tasks. Especially ballistic jumping and landing skills yield high estimated compression at L4/L5 of more than ten times body weight. Jumping, landing, heavy lifting and weight training in sports demonstrate compression forces significantly higher than guideline recommendations for working tasks. CONCLUSION: These results may help to identify acute and long-term risks of low back pain and, thus, may guide the development of preventive interventions for low back pain or injury in athletes.

Dose-response relationship and effect modifier of stabilisation exercises in nonspecific low back pain: a project-wide individual patient data re-analysis on 1483 intervention participants.

ABSTRACT: This planned MiSpEx-Network reanalysis was designed to derive a dose-response relationship under consideration of further effect modifiers in exercises on low back pain. One thousand four hundred eighty three intervention participants with low back pain (mean age, 40.9 years [SD 14 years]) performed stabilisation exercises (3 weeks supervised, 9 weeks self-administered). Patients reported pain intensity, disability, and disability days at baseline, 3 weeks, 12 weeks, and 6 months post randomisation. Exercise characteristics and effect modifiers were prospectively monitored. Beyond the comparison to the results of the control group, linear mixed models were calculated to determine a dose-response relationship. The interventions led to small but significantly larger symptom reductions than in the control group at each measurement. Longer durations of the intervention led to larger symptom reductions. Higher exercise frequencies were associated with a decrease in pain intensity: to train once more per week led to a mean decrease of 0.93 points in pain intensity [95% CI = -1.54 to -0.32]. Disability days were also impacted (estimate = -0.07 [-0.14 to 0.00]), but disability was not (-0.09 [-0.67 to 0.48]). Adding perturbation was superior to adding stretching or a behavioural module. The relationships were robust when additional effect modifiers were considered and against the control group' effects. The odds ratio for a clinically important effect with higher exercise frequencies decreased at 3 weeks (OR = 0.71 [0.618-0.813] for >2.5*week -1 ) and increased at 12 weeks (1.13 [1.006-1.270], >1.5*week -1 ). Using longer intervention durations, adding a perturbation component to the stabilisation trainings and using higher frequencies (up to a certain point) may lead to an even more beneficial response on exercise in patients with low back pain. Developing strategies to maintain a training frequency of at least 2 times per week may be relevant in stabilisation exercises to treat low back pain.

Perturbation-based trunk stabilization training in elite rowers: A pilot study.

INTRODUCTION: Low back pain is a major health issue in elite rowers. High training volume, frequent flexion movements of the lower spine and rotational movement in sweep rowing contribute to increased spinal strain and neuropathological patterns. Perturbation-based trunk stabilization training (PTT) may be effective to treat neuromuscular deficits and low back pain. METHODS: All boat classes (8+, 4+/-, 2-) of the male German national sweep rowing team participated in this non-randomized parallel group study. We included 26 athletes (PTT: n = 12, control group: n = 14) in our analysis. Physical and Sports therapists conducted 16 individualized PTT sessions á 30-40 minutes in 10 weeks, while the control group kept the usual routines. We collected data before and after intervention on back pain intensity and disability, maximum isometric trunk extension and flexion, jump height and postural sway of single-leg stance. RESULTS: We found less disability (5.3 points, 95% CI [0.4, 10.1], g = 0.42) for PTT compared to control. Pain intensity decreased similar in both groups (-14.4 and -15.4 points), yielding an inconclusive between-group effect (95% CI [-16.3, 14.3]). Postural sway, strength and jump height tend to have no between- and within-group effects. CONCLUSION: Perturbation-based trunk stabilization training is possibly effective to improve the physical function of the lower back in elite rowers.

Possible Inversion Symmetry Breaking in the S=1/2 Pyrochlore Heisenberg Magnet.

We address the ground-state properties of the long-standing and much-studied three-dimensional quantum spin liquid candidate, the S=1/2 pyrochlore Heisenberg antiferromagnet. By using SU(2) density-matrix renormalization group (DMRG), we are able to access cluster sizes of up to 128 spins. Our most striking finding is a robust spontaneous inversion symmetry breaking, reflected in an energy density difference between the two sublattices of tetrahedra, familiar as a starting point of earlier perturbative treatments. We also determine the ground-state energy, E_{0}/N_{sites}=-0.490(6)J, by combining extrapolations of DMRG with those of a numerical linked cluster expansion. These findings suggest a scenario in which a finite-temperature spin liquid regime gives way to a symmetry-broken state at low temperatures.

Comparative analysis of postural control and vertical jump performance between three different measurement devices.

OBJECTIVES: The aim of this study was to examine the concurrent validity of the HUMAC Balance System (HBS) and Balance Trainer BTG4 (BTG) in comparison to a laboratory-grade force platform (FP) for postural control (PC) and vertical jump performance (VJP) assessment. In addition, reliability of the three devices was measured for PC. METHODS: Overall 22 participants (age = 37.8 ± 13.3 years; gender = 9 male, 13 female; height = 174.1 ± 10.5 cm; body mass = 75.3 ± 17.6 kg) were recruited to participate. Double and single leg standing balance tests with eyes open or closed and counter movement jumps (CMJ) were performed on two separate occasions. Reliability and concurrent validity for COP parameters and VJP were examined using intraclass correlation coefficients (ICC), Bland-Altman plots (BAP), standard error of measurement (SEM) and minimum detectable change (MDC). RESULTS: COP path length test-retest reliability was predominantly good to excellent for all three devices (ICC = 0.80-0.95). SEM and MDC values were high for all plates (SEM% = 8.0-15.2; MDC% = 22.8-44.5), with the HBS MDC values higher than the KIS and BTG in three of the four trials. ICC scores for concurrent validity were good to excellent for the BTG (ICC = 0.76-0.93) and moderate to good for the HBS (0.49-0.83). Band-Altman plots revealed a systematic bias for the HBS towards higher COP path length values under all conditions and for the BTG in two out of four trials towards lower values. Validity of VJP was excellent for the BTG (ICC = 1.0) and poor for the HBS (0.34), with a systematic bias towards lower values. CONCLUSION: The comparative analysis of PC and VJP revealed reliable and valid results for the BTG in comparison to a laboratory-grade force plate. The HBS showed reliable results for PC assessment with restrictions regarding its validity. Results of VJP showed that the HBS revealed deficits in the assessment of activities that require rapid, high force movements such as jumping and running. Due to the variable results of all three devices, it is recommended not to use them interchangeably.

An Ecological Function Approach to Managing Harmful Cyanobacteria in Three Oregon Lakes: Beyond Water Quality Advisories and Total Maximum Daily Loads (TMDLs).

The Oregon Department of Environmental Quality (ODEQ) uses Total Maximum Daily Load (TMDL) calculations, and the associated regulatory process, to manage harmful cyanobacterial blooms (CyanoHABs) attributable to non-point source (NPS) pollution. TMDLs are based on response (lagging) indicators (e.g., measurable quantities of NPS (nutrients: nitrogen {N} and phosphorus {P}), and/or sediment), and highlight the negative outcomes (symptoms) of impaired water quality. These response indicators belatedly address water quality issues, if the cause is impaired riparian functions. Riparian functions assist in decreasing the impacts of droughts and floods (through sequestration of nutrients and excess sediment), allow water to remain on the land surface, improve aquatic habitats, improve water quality, and provide a focus for monitoring and adaptive management. To manage water quality, the focus must be on the drivers (leading indicators) of the causative mechanisms, such as loss of ecological functions. Success in NPS pollution control, and maintaining healthy aquatic habitats, often depends on land management/land use approaches, which facilitate the natural recovery of stream and wetland riparian functions. Focusing on the drivers of ecosystem functions (e.g., vegetation, hydrology, soil, and landform), instead of individual mandated response indicators, using the proper functioning condition (PFC) approach, as a best management practice (BMP), in conjunction with other tools and management strategies, can lead to pro-active policies and approaches, which support positive change in an ecosystem or watershed, and in water quality improvement.

Assessing Dungeness River Functionality and Effectiveness of Best Management Practices (BMPs) Using an Ecological Functional Approach.

Effective stream and wetland Best Management Practices (BMPs) restore the physical processes associated with ecological functions to their Proper Functioning Condition (PFC, i.e., the highest attainable ecological status of a riparian area without consideration of economic, administrative, or social constraints). Ecological functions connect stream monitoring and management to mitigate the causes of ecosystem degradation and enhance restoration. The ecological function approach supports sustainable management of many ecosystem services including water quality, water stability (aquifer recharge), and fish and wildlife habitats. The 1993 Forest Ecosystem Management Assessment Team (FEMAT) report listed the Dungeness River as a Tier 1 key watershed, noted that watersheds are the logical spatial unit for ecosystem management, and that watersheds are important in species management, and understanding the interdependence of physical processes. Watersheds are at the spatial scale where physical and biological disturbances can be observed, and where management constraints and planning options for restoration objectives and strategies can be readily assessed. The US Forest Service (USFS) developed a management strategy for the Middle Dungeness River, and in the 1990s, the Upper Dungeness River was listed as impaired due to sediment, which initiated a US Forest Service change to land management practices. The Lower Dungeness River and bay are listed as impaired due to fecal coliform contamination. Assessing and monitoring the drivers of ecosystem function (vegetation, hydrology, soil, and landform) as part of a watershed adaptive management plan, and implementing BMPs to increase ecological functions, will improve aquatic habitat and water quality. Most BMPs, such as Total Maximum Daily Loads (TMDLs), attempt to improve water quality by reducing the amount of external pollutants reaching the impacted waterbodies, but do not focus on improving the watershed functions. The Proper Functioning Condition (PFC) approach is used to examine the condition of wetlands and streams and provide guidance for quantitative approaches (e.g., TMDL, remote sensing) used in watershed restoration. Improving watershed functions is a BMP that facilitates increased flows of water, nutrients, sediment, and other materials, and improves habitat quality. Using improved watershed functions as a BMP, facilitated by the use of remote sensing, TMDLs, and the PFC methodology is a more effective means of reducing risks across a watershed than by using TMDLs alone.