Reaching While Learning to Sit: Capturing the Kinematics of Co-Developing Skills at Home.

This study examined the co-development of infant reaching and postural control across the transition to arms-free sitting at home. We observed infants with typical likelihood (TL; n = 24) and elevated likelihood (EL; n = 20) for autism at four biweekly sessions spanning the transition to arms-free sitting (infant age = 4.5-8 months at first session). At each session, infants sat on a pressure-sensitive mat with external support or independently, wore magneto-inertial sensors on both wrists, and reached for toys presented at midline. Analyses focused on characterizing and comparing control of sitting during reaching actions and standard kinematic metrics of reaching during Supported versus Independent Sitting. Although EL infants achieved arms-free sitting later than TL peers, there were no group differences on any measures. Across sessions, infants' control of the sitting posture during concurrent reaching movements improved in both contexts, though they were less stable as they reached when sitting independently compared to when sitting with support. A similar effect was apparent in the kinematics of reaches, with overall improvement over time, but evidence of poorer control in Independent relative to Supported Sitting. Taken together, these findings underscore the mutually influential and dynamic relations between emerging skills and well-established behaviors.

Enhancing physical activity and augmenting upper limb function in sedentary stroke survivors: the transformative impact of chair transitions.

In post-stroke individuals with walking difficulties, prolonged sitting can lead to increased mortality. Interventions targeting increased physical activity for these individuals are limited. Consequently, many such stroke survivors become reliant on wheelchairs, leading to prolonged inactivity. This report highlights a case where a chronic stroke patient, with walking challenges, was transitioned from a wheelchair to regular chair sitting by nursing staff in a facility lacking specialised rehabilitation professionals. This simple act of transitioning from a wheelchair to a chair during daily routines led to improvements in the patient's physical activity and upper limb functionality and reduced the need for help during meals.

Impact of Standing and Sitting Postures on Spinal Curvature and Muscle Mechanical Properties in Young Women: A Photogrammetric and MyotonPro Analysis.

BACKGROUND This study aimed to evaluate the effect of standing and sitting positions on spinal curvatures evaluated using projection moire and muscle tone and stiffness using the MyotonPRO hand-held device in young women. MATERIAL AND METHODS Thirty-three healthy women, aged 21 to 23 years, volunteered in the study. We used the projection moire method to examine spinal curvatures in both positions and the MyotonPRO device to measure the tone and stiffness of muscles in 3 regions. We evaluated the effects of positions (standing vs sitting), regions (cervical, thoracic, and lumbar), and side factor (right vs left) using multivariate analysis. RESULTS The sitting position significantly decreased the lumbosacral and thoracolumbar angles (P<0.001), but had no effect on the superior thoracic angle. Muscle tension and stiffness were the highest (P<0.001) in the cervical region and did not differ between positions (P>0.05) in this region. We found significantly higher muscle tone and stiffness in the thoracic and lumbar regions during sitting than during standing (P<0.001). There was symmetry in the muscle tone and the stiffness between the right and left sides of the spine. CONCLUSIONS The sitting posture decreased lumbosacral and thoracolumbar angles but increased muscle tension and stiffness in the lumbar and thoracic regions only. The symmetry of muscle tone and transverse stiffness in both positions was the normative value. This study provides insight into the adaptive physiological changes in spinal curvature and muscle mechanical properties in young women and serves as an important reference point for clinical studies of women.

Exploring the Real-Time Variability and Complexity of Sitting Patterns in Office Workers with Non-Specific Chronic Spinal Pain and Pain-Free Individuals.

Chronic spinal pain (CSP) is a prevalent condition, and prolonged sitting at work can contribute to it. Ergonomic factors like this can cause changes in motor variability. Variability analysis is a useful method to measure changes in motor performance over time. When performing the same task multiple times, different performance patterns can be observed. This variability is intrinsic to all biological systems and is noticeable in human movement. This study aims to examine whether changes in movement variability and complexity during real-time office work are influenced by CSP. The hypothesis is that individuals with and without pain will have different responses to office work tasks. Six office workers without pain and ten with CSP participated in this study. Participant's trunk movements were recorded during work for an entire week. Linear and nonlinear measures of trunk kinematic displacement were used to assess movement variability and complexity. A mixed ANOVA was utilized to compare changes in movement variability and complexity between the two groups. The effects indicate that pain-free participants showed more complex and less predictable trunk movements with a lower degree of structure and variability when compared to the participants suffering from CSP. The differences were particularly noticeable in fine movements.

Muscle synergy and kinematic synergy analyses during sit-to-stand motions in hallux valgus patients before and after treatment with Kinesio taping.

OBJECTIVES: To explore the impact of hallux valgus (HV) on lower limb neuromuscular control strategies during the sit-to-stand (STS) movement, and to evaluate the effects of Kinesio taping (KT) intervention on these control strategies in HV patients. METHODS: We included 14 young healthy controls (HY), 13 patients in the HV group (HV), and 11 patients in the HV group (HVI) who underwent a Kinesio taping (KT) intervention during sit-to-stand (STS) motions. We extracted muscle and kinematic synergies from EMG and motion capture data using non-negative matrix factorization (NNMF). In addition, we calculated the center of pressure (COP) and ground reaction forces (GRF) to assess balance performance. RESULTS: There were no significant differences in the numbers of muscle and kinematic synergies between groups. In the HV group, knee flexors and ankle plantar flexors were abnormally activated, and muscle synergy D was differentiated. Muscle synergy D was not differentiated in the HVI group. CONCLUSION: Abnormal activation of knee flexors and plantar flexors led to the differentiation of module D in HV patients, which can be used as an indicator of the progress of HV rehabilitation. KT intervention improved motor control mechanisms in HV patients.

Characterizing the Effects of Adding Virtual and Augmented Reality in Robot-Assisted Training.

Extended reality (XR) technology combines physical reality with computer synthetic virtuality to deliver immersive experience to users. Virtual reality (VR) and augmented reality (AR) are two subdomains within XR with different immersion levels. Both of these have the potential to be combined with robot-assisted training protocols to maximize postural control improvement. In this study, we conducted a randomized control experiment with sixty-three healthy subjects to compare the effectiveness of robot-assisted posture training combined with VR or AR against robotic training alone. A robotic Trunk Support Trainer (TruST) was employed to deliver assistive force at the trunk as subjects moved beyond the stability limits during training. Our results showed that both VR and AR significantly enhanced the training outcomes of the TruST intervention. However, the VR group experienced higher simulator sickness compared to the AR group, suggesting that AR is better suited for sitting posture training in conjunction with TruST intervention. Our findings highlight the added value of XR to robot-assisted training and provide novel insights into the differences between AR and VR when integrated into a robotic training protocol. In addition, we developed a custom XR application that suited well for TruST intervention requirements. Our approach can be extended to other studies to develop novel XR-enhanced robotic training platforms.

A planar neuromuscular controller to simulate compensation strategies in the sit-to-walk movement.

Standing up from a chair is a key daily life activity that is sensitive to functional limitations as we age and associated with falls, frailty, and institutional living. Predictive neuromusculoskeletal models can potentially shed light on the interconnectivity and interdependency of age-related changes in neuromuscular capacity, reinforcement schemes, sensory integration, and adaptation strategies during stand-up. Most stand-up movements transfer directly into walking (sit-to-walk). The aim of this study was to develop and validate a neuromusculoskeletal model with reflex-based muscle control that enables simulation of the sit-to-walk movement under various conditions (seat height, foot placement). We developed a planar sit-to-walk musculoskeletal model (11 degrees-of-freedom, 20 muscles) and neuromuscular controller, consisting of a two-phase stand-up controller and a reflex-based gait controller. The stand-up controller contains generic neural pathways of delayed proprioceptive feedback from muscle length, force, velocity, and upper-body orientation (vestibular feedback) and includes both monosynaptic an antagonistic feedback pathways. The control parameters where optimized using a shooting-based optimization method, based on a high-level optimization criterium. Simulations were compared to recorded kinematics, ground reaction forces, and muscle activation. The simulated kinematics resemble the measured kinematics and muscle activations. The adaptation strategies that resulted from alterations in seat height, are comparable to those observed in adults. The simulation framework and model are publicly available and allow to study age-related compensation strategies, including reduced muscular capacity, reduced neural capacity, external perturbations, and altered movement objectives.

Validation of assessments to accurately analyze the body composition of highly trained sitting volleyball players: A pilot study.

Body composition is a fundamental component of physical fitness related to the performance of Sitting volleyball (SV) players. Also, establishing the best method for evaluating the body composition of these para-athletes would be highly necessary for this field. The purpose of this study was (1) to describe the body composition of male and female highly trained SV players, (2) to compare the values obtained from this population by two different methods and (3) to establish validity on one of these methods. Thirteen Brazilian SV national team players (five males and eight females) participated in this study. The air-displacement plethysmography (ADP) method as the criterion assessment and the skinfolds (SF) method were conducted for each player. Results showed that there were no significant differences between the values of all players, which ADP and SF measured for body fat percentage (BF%) and body density (BD) (p > 0.05). We found significantly different values between male and female players for BF% by SF (p = 0.04) and BD by SF (p = 0.04). A high degree of reliability was found between ADP and SF measures for BF% and BD. There were statistically significant positive correlations between BF% and BD in all values for both methods (p < 0.01). This pilot study suggests that considering the magnitude of space, expense, and other limitations related to the ADP method against the SF method, we recommend using the SF method, which is a valid, viable and reliable method for measuring body composition in elite SV players.

A single trial of the five-repetition sit-to-stand test provides adequate measures in community-dwelling older adults: A cross-sectional study.

PURPOSE: To investigate whether the number of trials would affect the results of the Five-Repetition Sit-to-Stand Test (5STSt) and its measurement properties in community-dwelling older adults. METHODS: Three trials of the 5STSt, after familiarization, were performed by 50 older adults (69.9 ± 5.5 years). The one-way ANOVA was used to compare the number of trials of the 5STSt (the first trial, the best trial, the mean of two trials, and the mean of three trials). Intraclass Correlation Coefficient (ICC) was calculated to investigate inter-rater and test-retest reliabilities, and SEM and MDC95% were also calculated. The magnitude of the correlations was classified as very low≤0.25; low = 0.26-0.49; moderate = 0.50-0.69; high = 0.70-0.89; and very high = 0.90-1.00. (α = 0.05). RESULTS: The values provided by different numbers of trials were similar in session-1 (F = 1.315; p = 0.271), as well as in session-2 (F = 0.668; p = 0.574). Inter-rater and test-retest reliabilities were significant and classified as moderate to high for all number of trials (0.63

Effects of routine physical therapy with and without kinesio taping in improving gross motor function in sitting and standing in spastic diplegic cerebral palsy children.

OBJECTIVE: To determine the effectiveness of Kinesio taping along with routine physical therapy on improving gross motor function in sitting and standing among spastic diplegic Cerebral Palsy children. DESIGN: Randomized controlled trial. SETTINGS: University Teaching Hospital University of Lahore, Lahore. PARTICIPANTS: 53 participants with diagnosed spastic diplegic cerebral palsy were randomly allocated in control and experimental groups. INTERVENTION: 26 Participants were treated by kinesio taping which was applied in a criss-cross manner along with routine physical therapy program while the control group (n = 27) received NDT exercise program that comprises of stretching, functional reaching, weight-bearing exercises and walking. OUTCOME MEASURE: Gross motor function was assessed using 2 components of Gross Motor Function Classification System (GMFCS-88), i.e., sitting as well as standing at the base line and after every 3rd week for 12 weeks follow up. RESULTS: In study and control group the mean score of gross motor function for sitting at baseline was 33.96 ± 3.11 and 31.50 ± 3.32 respectively. After intervention, it changed to 47.70 ± 5.46 and 43.46 ± 1.81 respectively. Mean score for Gross Motor Function calculated at base line in study and control group for standing was 27.37 ± 1.14 and 26 ± 3.01 respectively. At the end of intervention, the score improved to 36.55 ± 4.27 and 33.69 ± 2.46 respectively. CONCLUSION: In comparison to control group, significant increase in gross motor function of intervention group was seen after the 12 weeks of intervention. In this way, over back muscles the application of kinesio tape in a Criss-Cross manner may be helpful. Also it can be used as an additional approach along with routine physical therapy to improve standing and sitting in spastic diplegic children.

Secular trends and sociodemographic, biological, and behavioural factors associated with handgrip strength in adolescents in southern Brazil: An allometric approach.

The purpose of this study was to analyse secular trend in handgrip strength (HGS) in adolescents using an allometric approach and identify the factors associated. The sample comprised 657 and 1004 adolescents (14 to 19 years) in 2007 and 2017/2018, respectively, of public schools in Florianópolis, Brazil. The dependent variable was HGS normalised to body mass and height. Covariance analysis was used to examine secular trends in HGS, and multiple linear regression was used to identify associated factors. The independent variables were sociodemographic, biological, and behavioural factors. Comparison of HGS between surveys indicated a negative secular trend in both sexes (p < 0.001). In boys, there was a positive association of HGS with age and FFM in both surveys. In 2017/18, there was a positive association with sexual maturation and a negative association with sitting time and fat percentage. In girls, FFM was positively associated with HGS in both surveys. In 2007, there were positive associations of HGS with age and vigorous physical activity, whereas, in 2017/18, negative associations were observed with economic level and sitting time. The findings of the present study show a decline in adolescent HGS. And behavioural changes appear to be contributing to declines in HGS.

Sit-to-stand performance in children with cerebral palsy: a population-based cross-sectional study.

BACKGROUND: Sit-to-stand (STS) is one of the most commonly performed functional movements in a child's daily life that enables the child to perform functional activities such as independent transfer and to initiate walking and self-care. Children with cerebral palsy (CP) often have reduced STS ability. The aim of this study was to describe STS performance in a national based total population of children with CP and its association with age, sex, Gross Motor Function Classification System (GMFCS) level, and CP subtype. METHODS: This cross-sectional study included 4,250 children (2,503 boys, 1,747 girls) aged 1-18 years from the Swedish Cerebral Palsy Follow-Up Program (CPUP). STS performance was classified depending on the independence or need for support into "without support," "with support," or "unable." "With support" included external support from, e.g., walls and furniture. Physical assistance from another person was classified as "unable" (dependent). Ordinal and binary logistic regression analyses were used to identify associations between STS and age, GMFCS level, and CP subtype. RESULTS: 60% of the children performed STS without support, 14% performed STS with support, and 26% were unable or needed assistance from another person. STS performance was strongly associated with GMFCS level and differed with age and subtype (p < 0.001). For all GMFCS levels, STS performance was lowest at age 1-3 years. Most children with GMFCS level I (99%) or II (88%) performed STS without support at the age of 4-6 years. In children with GMFCS level III or IV, the prevalence of independent STS performance improved throughout childhood. CP subtype was not associated with STS performance across all GMFCS levels when adjusted for age. CONCLUSIONS: Independent STS performance in children with CP is associated with GMFCS level and age. Children with CP acquire STS ability later than their peers normally do. The proportion of children with independent STS performance increased throughout childhood, also for children with GMFCS level III or IV. These findings suggest the importance of maintaining a focus on STS performance within physiotherapy strategies and interventions for children with CP, including those with higher GMFCS level.

Sex Differences in Physical Activity Levels and Sitting Time in Patients With Atrial Fibrillation.

PURPOSE: While research demonstrates low levels of physical activity (PA) among adults living with atrial fibrillation (AF), there is limited evidence investigating sex differences in moderate to vigorous intensity physical activity (MVPA) and sedentary time in this population. The primary aim was to examine sex differences in MVPA levels and sitting time between women and men with AF. Secondary aims explored sex differences in sociodemographic factors, outcome expectations, and task self-efficacy toward PA levels. METHODS: This was a subanalysis of the CHAMPLAIN-AF cohort study. Women and men with AF completed a survey, including the Short-Form International Physical Activity Questionnaire. RESULTS: A total of 210 women (median = 66.0 yr: 95% CI, 63.5-68.0) and 409 men (median = 66.0 yr: 95% CI, 64.0-67.0) were included. No sex differences were observed in median weekly MVPA (60 min/wk: 95% CI, 0-120 in women vs 120 min/wk: 95% CI, 85-150 in men) and daily sitting time (5.5 hr/d: 95% CI, 5.0-6.0 in women vs 6.0 hr/d: 95% CI, 5.0-6.0 in men). Women engaged in significantly less vigorous-intensity PA than men ( P = .03) and demonstrated significantly lower task self-efficacy ( P < .01). Significant positive correlations in PA levels with outcome expectations (mostly weak) and task self-efficacy (mostly strong) were observed in both sexes. CONCLUSION: Most women and men with AF did not meet the global MVPA guidelines but met the sitting time recommendation. Women presented with lower vigorous-intensity physical activity levels and confidence than men. Strategies to increase physical activity behavior, considering sociodemographic factors and task self-efficacy, are needed and may differ between sexes.

Sitting Pressure Measurements in Wheelchair Users-Can the Effects of Daily Relief Activities Be Depicted?

Seat pressure measurements in wheelchair users have been available for some time; however, repeated measurements from a commercially available pressure mat over 90 min did not differ in the pressure-loaded measurement area or the coordinates of the center of pressure, even in participants who were able to reposition themselves in the wheelchair. The question therefore arises: to what extent are there other parameters that reflect the activity of wheelchair users with the pressure mat? To investigate this, a commercial pressure mat (BodiTrak®) was used to perform the measurements of pressure of 33 adult wheelchair-dependent people with spinal cord injury after 30 and 90 min sitting on the cushion. In addition to the standard output of the pressure mat, graph-based surface analyses (calculation of the area of maximum pressure, calculation of the pressure-loaded measurement area, and pressure-area ratio) was performed retrospectively using Python 3.7. The analysis of the measurements after 30 and 90 min was performed by distinguishing the participants between those who could actively change their position (N = 24) and those who could not (N = 9). The parameters of the pressure mat and the graph-based analyses remained unchanged for active participants. In participants who were unable to actively change their position, the area of maximum pressure and the pressure-area ratio (ratio of maximum pressure area and total pressure-loaded area) increased. Significant differences between minutes 30 and 90 are only found for the pressure-area ratio. Thus, when measuring the seat pressure of wheelchair users, the pressure-area ratio should be taken into account as it reflects the daily relief activities of wheelchair users.

Meta-heuristic optimization algorithms based feature selection for joint moment prediction of sit-to-stand movement using machine learning algorithms.

The sit-to-stand (STS) movement is fundamental in daily activities, involving coordinated motion of the lower extremities and trunk, which leads to the generation of joint moments based on joint angles and limb properties. Traditional methods for determining joint moments often involve sensors or complex mathematical approaches, posing limitations in terms of movement restrictions or expertise requirements. Machine learning (ML) algorithms have emerged as promising tools for joint moment estimation, but the challenge lies in efficiently selecting relevant features from diverse datasets, especially in clinical research settings. This study aims to address this challenge by leveraging metaheuristic optimization algorithms to predict joint moments during STS using minimal input data. Motion analysis data from 20 participants with varied mass and inertia properties are utilized, and joint angles are computed alongside simulations of joint moments. Feature selection is performed using the Manta Ray Foraging Optimization (MRFO), Marine Predators Algorithm (MPA), and Equilibrium Optimizer (EO) algorithms. Subsequently, Decision Tree Regression (DTR), Random Forest Regression (RFR), Extra Tree Regression (ETR), and eXtreme Gradient Boosting Regression (XGBoost Regression) ML algorithms are deployed for joint moment prediction. The results reveal EO-ETR as the most effective algorithm for ankle, knee, and neck joint moment prediction, while MPA-ETR exhibits superior performance for hip joint prediction. This approach demonstrates potential for enhancing accuracy in joint moment estimation with minimal feature input, offering implications for biomechanical research and clinical applications.

Exploring lower limb muscle activity and performance variations during instrumented Sit-to-Stand-to-Sit in sedentary individuals: Influence of limb dominance and testing modalities.

PURPOSE: to explore lower limb muscle activity concerning limb dominance, as well as variations in force and power during the standing up and sitting down phases of the instrumented sit-to-stand-to-sit test in sedentary individuals, across isokinetic and isotonic modalities. METHODS: 33 sedentary individuals underwent testing using a functional electromechanical dynamometer in both isokinetic and isotonic modes, accompanied by surface electromyography. RESULTS: In the isokinetic mode, the non-dominant gastrocnemius medialis and vastus medialis exhibited significantly (p < 0.05) higher muscle activity values during the standing up and sitting down phase compared to dominant counterparts. In the isotonic mode standing up phase, significant differences in muscle activity were noted for non-dominant gastrocnemius medialis, vastus medialis, and biceps femoris compared to their dominant counterparts. The sitting down phase in isotonic mode showed higher muscle activity for non-dominant vastus medialis compared to dominant vastus medialis. Regard to performance outcomes, significantly lower (p < 0.0001) values were observed for standing up (12.7 ± 5.1 N/kg) compared to sitting down (15.9 ± 6.1 N/kg) peak force, as well as for standing up (18.7 ± 7.8 W/kg) compared to sitting down (25.9 ± 9.7 W/kg) peak power in isokinetic mode. In isotonic mode, lower values were found for sitting down (6.5 (6.3-7.1) N/kg) compared to standing up (7.8 (7.3-8.9) N/kg) peak force and for sitting down (18.5 (13.2-21.7) W/kg) compared to standing up (33.7 (22.8-41.6) W/kg) peak power. CONCLUSIONS: Limb dominance influences lower-limb muscle activity during the instrumented sit-to-stand-to-sit test, and the choice of testing mode (isokinetic or isotonic) affects muscle engagement and performance outcomes.

Feasibility and acceptability of general practitioners using sit-stand desks: a feasibility trial.

OBJECTIVES: The primary aim of this study was to investigate the feasibility and acceptability of general practitioners (GPs) using sit-stand desks to facilitate standing during consultations. A further aim was to examine the views of patients about GPs standing for their consultations. DESIGN: A pre-post single-group experimental trial design. SETTING: General practices in England, UK. PARTICIPANTS: 42 GPs (working a minimum of five clinical sessions per week) and 301 patients (aged ≥18 years). INTERVENTIONS: The intervention consisted of each GP having a sit-stand desk (Opløft Sit-Stand Platform) installed in their consultation room for 4 working weeks. Sit-stand desks allow users to switch, in a few seconds, between a sitting and standing position and vice versa, by adjusting the height of the desk. MAIN OUTCOME MEASURES: To test feasibility and acceptability, GPs reported their views about using sit-stand desks at work at baseline and follow-up. Sitting time and physical activity were also measured via accelerometer at baseline and follow-up. Patients who attended a consultation where their GP was standing were asked to complete an exit questionnaire about the perceived impact on the consultation. RESULTS: Most GPs reported using their sit-stand desk daily (n=28, 75.7%). 16 GPs (44.4%) used their sit-stand desk during face-to-face consultations every day. Most GPs and patients did not view that GPs standing during face-to-face consultations impacted the doctor-patient relationship (GPs; 73.5%, patients; 83.7%). GPs' sitting time during work was 121 min per day lower (95% CI: -165 to -77.58) at follow-up compared with baseline. CONCLUSIONS: Use of sit-stand desks is acceptable within general practice and may reduce sitting time in GPs. This may benefit GPs and help reduce sitting time in patients. TRIAL REGISTRATION NUMBER: ISRCTN76982860.

Effect of two dynamic seat cushions on postural shift, trunk muscle activation and spinal discomfort in office workers.

We investigated the effect of two dynamic seat cushions on postural shift, trunk muscle activation and spinal discomfort. In this repeated-measures study, 30 healthy office workers were randomly assigned to a sequence of three conditions: sitting on a dynamic seat cushion-A, cushion-B and control (no seat cushion). The two dynamic seat cushions had different inflation levels. Participants typed a standard text for an hour and were monitored for postural shift by using a seat pressure mat, transversus abdominis/internal oblique and lumbar multifidus muscles activity by using surface EMG, spinal discomfort by using Borg's CR-10 scale. Two-way repeated ANOVAs showed no statistically significant interaction effects between condition and time on postural shift and muscle activation. Post hoc Bonferroni tests showed that postural shifts and lumbar multifidus activation during sitting on cushion-A were significantly higher (p < 0.01) than in the control and cushion-B conditions. Both cushions reduced spinal discomfort, compared to the control condition (p < 0.05).

Reliability of Three Landmine-Punch-Throw Variations and Their Load-Velocity Relationships Performed With the Dominant and Nondominant Hands.

PURPOSE: This study assessed the reliability and load-velocity profiles of 3 different landmine-punch-throw variations (seated without trunk rotation, seated with trunk rotation, and standing whole body) with different loads (20, 22.5, and 25.0 kg), all with the dominant hand and nondominant hand. METHODS: In a quasi-randomized order, 14 boxers (24.1 [4.3] y, 72.6 [10.1] kg) performed 3 repetitions of each variation with their dominant hand and their nondominant hand, with maximal effort and 3 minutes of interset rest. Peak velocity was measured via the GymAware Power Tool (Kinetic Performance Technologies). The interclass correlation coefficients and their 95% CIs were used to determine the intrasession reliability of each variation × load × hand combination. Additionally, a 2 (hand) × 3 (variation) repeated-measures analysis of variance assessed the load-velocity profile slope, and a 3 (variation) × 2 (hand) × 3 (load) repeated-measures analysis of variance assessed the peak velocity of each variation. RESULTS: Most variations were highly reliable (intraclass correlation coefficient > .91), with the nondominant hand being as reliable or more reliable than the dominant hand. Very strong linear relationships were observed for the group average for each variation (R2 ≥ .96). However, there was no variation × hand interaction for the slope, and there was no main effect for variation or hand. Additionally, there was no interaction for the peak velocity, but there were main effects for variation, hand, and load (P < .01). CONCLUSION: Each variation was reliable and can be used to create upper-body ballistic unilateral load-velocity profiles. However, as with other research on load-velocity profile, individual data allowed for more accurate profiling than group average data.

Traditional versus dynamic sitting: Lumbar spine kinematics and pain during computer work and activity guided tasks.

Dynamic sitting may mitigate low back pain during prolonged seated work. The current study compared pelvis and lumbar spine kinematics, pain, and work productivity, in traditional and dynamic sitting. Sixteen participants completed three 20-min blocks of computer work and activity guided tasks in a traditional office chair or backless and multiaxial rotating seat pan while kinematics were measured from accelerometers on the low back. Pain ratings were recorded on a visual analogue scale every 10 min. Similar pelvis and lumbar kinematics emerged when performing computer work in traditional and dynamic sitting. Pelvis and lumbar sagittal and frontal plane shifts and fidgets were largest for dynamic sitting in the activity guided tasks. Buttocks pain was higher in dynamic sitting, but low back pain and work productivity were unaffected. Dynamic sitting increased spine movement during activity guided tasks, without negatively impacting lumbar kinematics, low back pain, or productivity during seated computer work.