Antagonism of 5-HT2 receptors attenuates self-sustained firing of human motor units.

5-HT2 receptors on motoneurones play a critical role in facilitating persistent inward currents (PICs). Although facilitation of PICs can enhance self-sustained firing after periods of excitation, the relationship between 5-HT2 receptor activity and self-sustained firing in human motor units (MUs) has not been resolved. MU activity was assessed from the tibialis anterior of 10 healthy adults (24.9 ± 2.8 years) during two contraction protocols. Both protocols featured steady-state isometric contractions with constant descending drive to the motoneurone pool. However, one protocol also included an additional phase of superimposed descending drive. Adding and then removing descending drive in the middle of steady-state contractions altered MU firing behaviour across the motor pool, where newly recruited units in the superimposed phase were unable to switch off (P = 0.0002), and units recruited prior to additional descending drive reduced their discharge rates (P < 0.0001, difference in estimated marginal means (∆) = 2.24 pulses/s). The 5-HT2 receptor antagonist, cyproheptadine, was then administered to determine whether changes in MU firing were mediated by serotonergic mechanisms. 5-HT2 receptor antagonism caused reductions in MU discharge rate (P < 0.001, ∆ = 1.65 pulses/s), recruitment threshold (P = 0.00112, ∆ = 1.09% maximal voluntary contraction) and self-sustained firing duration (P < 0.0001, ∆ = 1.77s) after the additional descending drive was removed in the middle of the steady-state contraction. These findings indicate that serotonergic neuromodulation plays a key role in facilitating discharge and self-sustained firing of human motoneurones, where adaptive changes in MU recruitment must occur to meet the demands of the contraction. KEY POINTS: Animal and cellular preparations indicate that somato-dendritic 5-HT2 receptors regulate the intrinsic excitability of motoneurones. 5-HT2 receptor antagonism reduces estimates of persistent inward currents in motoneurones, which contribute to self-sustained firing when synaptic inputs are reduced or removed. This human study employed a contraction task that slowly increased (and then removed) the additional descending drive in the middle of a steady-state contraction where marked self-sustained firing occurred when the descending drive was removed. 5-HT2 receptor antagonism caused widespread reductions in motor unit (MU) discharge rates during contractions, which was accompanied by reduced recruitment threshold and attenuation of self-sustained firing duration after the removal of the additional descending drive to motoneurones. These findings support the role that serotonergic neuromodulation is a key facilitator of MU discharge and self-sustained firing of human motoneurones, where adaptative changes in MU recruitment must occur to meet the demands of the contraction.

Blockade of 5-HT2 receptors suppresses motor unit firing and estimates of persistent inward currents during voluntary muscle contraction in humans.

Serotonergic neuromodulation contributes to enhanced voluntary muscle activation. However, it is not known how the likely motoneurone receptor candidate (5-HT2 ) influences the firing rate and activation threshold of motor units (MUs) in humans. The purpose of this study was to determine whether 5-HT2 receptor activity contributes to human MU behaviour during voluntary ramped contractions of differing intensity. High-density surface EMG (HDsEMG) of the tibialis anterior was assessed during ramped isometric dorsiflexions at 10, 30, 50 and 70% of maximal voluntary contraction (MVC). MU characteristics were successfully extracted from HDsEMG of 11 young adults (four female) pre- and post-ingestion of 8 mg cyproheptadine or a placebo. Antagonism of 5-HT2 receptors caused a reduction in MU discharge rate during steady-state muscle activation that was independent of the level of contraction intensity [P < 0.001; estimated mean difference (∆) = 1.06 pulses/s], in addition to an increase in MU derecruitment threshold (P < 0.013, ∆ = 1.23% MVC), without a change in force during MVC (P = 0.652). A reduction in estimates of persistent inward current amplitude was observed at 10% MVC (P < 0.001, ∆ = 0.99 Hz) and 30% MVC (P = 0.003, ∆ = 0.75 Hz) that aligned with 5-HT changes in MU firing behaviour attributable to 5-HT2 antagonism. Overall, these findings indicate that 5-HT2 receptor activity has a role in regulating the discharge rate in populations of spinal motoneurones when performing voluntary contractions. This study provides evidence of a direct link between MU discharge properties, persistent inward current activity and 5-HT2 receptor activity in humans. KEY POINTS: Activation of 5-HT receptors on the soma and dendrites of motoneurones regulates their excitability. Previous work using chlorpromazine and cyproheptadine has demonstrated that the 5-HT2 receptor regulates motoneurone activity in humans with chronic spinal cord injury and non-injured control subjects. It is not known how the 5-HT2 receptor directly influences motor unit (MU) discharge and MU recruitment in larger populations of human motoneurones during voluntary contractions of differing intensity. Despite the absence of change in force during maximal voluntary dorsiflexions, 5-HT2 receptor antagonism caused a reduction in MU discharge rate during submaximal steady-state muscle contraction, in addition to an increase in MU derecruitment threshold, irrespective of the submaximal contraction intensity. Reductions in estimates of persistent inward currents after 5-HT2 receptor antagonism support the viewpoint that the 5-HT2 receptor plays a crucial role in regulating motor activity, whereby a persistent inward current-based mechanism is involved in regulating the excitability of human motoneurones.

Blockade of 5-HT2 receptors suppresses rate of torque development and motor unit discharge rate during rapid contractions.

Serotonin (5-HT) is a neuromodulator that is critical for regulating the excitability of spinal motoneurons and the generation of muscle torque. However, the role of 5-HT in modulating human motor unit activity during rapid contractions has yet to be assessed. Nine healthy participants (23.7 ± 2.2 yr) ingested 8 mg of the competitive 5-HT2 antagonist cyproheptadine in a double-blinded, placebo-controlled, repeated-measures experiment. Rapid dorsiflexion contractions were performed at 30%, 50%, and 70% of maximal voluntary contraction (MVC), where motor unit activity was assessed by high-density surface electromyographic decomposition. A second protocol was performed where a sustained, fatigue-inducing dorsiflexion contraction was completed before undertaking the same 30%, 50%, and 70% MVC rapid contractions and motor unit analysis. Motor unit discharge rate (P < 0.001) and rate of torque development (RTD; P = 0.019) for the unfatigued muscle were both significantly lower for the cyproheptadine condition. Following the fatigue inducing contraction, cyproheptadine reduced motor unit discharge rate (P < 0.001) and RTD (P = 0.024), whereas the effects of cyproheptadine on motor unit discharge rate and RTD increased with increasing contraction intensity. Overall, these results support the viewpoint that serotonergic effects in the central nervous system occur fast enough to regulate motor unit discharge rate during rapid powerful contractions.NEW & NOTEWORTHY We have shown that serotonin activity in the central nervous system plays a role in regulating human motor unit discharge rate during rapid contractions. Our findings support the viewpoint that serotonergic effects in the central nervous system are fast and are most prominent during contractions that are characterized by high motor unit discharge rates and large amounts of torque development.

Time to Be Negative About Acceleration: A Spotlight on Female Football Players.

ABSTRACT: Griffin, J, Horan, S, Keogh, J, Andreatta, M, and Minahan, C. Time to be negative about acceleration: A spotlight on female football players. J Strength Cond Res 36(11): 3264-3271, 2022-Women's football requires players to perform frequent changes in velocity (i.e., speed and direction) for successful performance. Although increases in velocity ("acceleration") are important, decreases in velocity ("deceleration") should also be considered equally important to performance and load monitoring. Currently, there is a disproportionate focus on acceleration and creating faster players. The aim of this review is to provide an understanding of deceleration for female football players. Given the limited research in this area, data from studies involving male football players and from other team-sport athletes were used to supplement the review where necessary. Most research focused on eccentric strength and its relationship with deceleration ability, highlighting the importance of slow eccentric strength of the quadriceps and hamstrings to deceleration. Technical and kinematic characteristics of deceleration were also investigated. Importantly, with deceleration being a unilateral motor skill, development requires similar amounts of training for both legs. Imbalances between legs in skill and strength characteristics may compromise performance or increase the risk of injury. Given the dependent nature of deceleration, several contextual factors were identified as important when considering deceleration as a part of training programs and performance. Deceleration is affected by the following factors: an athlete's momentum, the approach speed, change of direction angle, time or distance, anticipated or unanticipated task, fatigue, and the positional requirements of female football players. Further research is needed into deceleration and the physical characteristics associated with deceleration performance, particularly for female football players.

Maintenance of Functional Gains Following a Goal-Directed and FES-Assisted Cycling Program for Children With Cerebral Palsy.

PURPOSE: This study investigated whether the functional improvements associated with functional electrical stimulation-assisted cycling, goal-directed training, and adapted cycling in children with cerebral palsy were maintained 8 weeks after the intervention ceased. METHODS: The intervention (2 × 1-hour supervised sessions and 1-hour home program/week) ran for 8 weeks. Primary outcomes were the Gross Motor Function Measure (GMFM-88) and the Canadian Occupational Performance Measure (COPM). Secondary outcomes included the GMFM-66 and goal scores, 5 times sit-to-stand test (FTSTS), Participation and Environment Measure-Children and Youth (PEM-CY), Pediatric Evaluation of Disability Inventory Computer Adaptive Test (PEDI-CAT), and cycling power output (PO). Outcomes were assessed at baseline, 8 and 16 weeks. RESULTS: Twenty children participated (mean age = 10 years 3 months; SD = 2 years 11 months; Gross Motor Function Classification System II = 5, III = 6, and IV = 9). Improvements were retained above baseline at 16 weeks on the GMFM and COPM. Improvements in cycling PO, PEDI-CAT scores, PEM-CY environmental barriers and FTSTS were also retained. CONCLUSION: Functional improvements in children with cerebral palsy were retained 8 weeks post-intervention.

Plantar load transfer in children: a descriptive study with two pathological case studies.

BACKGROUND: Typical gait is often considered to be highly symmetrical, with gait asymmetries typically associated with pathological gait. Whilst gait symmetry is often expressed in symmetry ratios, measures of symmetry do not provide insight into how these asymmetries affect gait variables. To fully understand changes caused by gait asymmetry, we must first develop a normative database for comparison. Therefore, the aim of this study was to describe normative reference values of regional plantar load and present comparisons with two pathological case studies. METHODS: A descriptive study of the load transfer of plantar pressures in typically developed children was conducted to develop a baseline for comparison of the effects of gait asymmetry in paediatric clinical populations. Plantar load and 3D kinematic data was collected for 17 typically developed participants with a mean age of 9.4 ± 4.0 years. Two case studies were also included; a 10-year-old male with clubfoot and an 8-year-old female with a flatfoot deformity. Data was analysed using a kinematics-pressure integration technique for anatomical masking into 5 regions of interest; medial and lateral forefoot, midfoot, and medial and lateral hindfoot. RESULTS: Clear differences between the two case studies and the typical dataset were seen for the load transfer phase of gait. For case study one, lateral bias was seen in the forefoot of the trailing foot across all variables, as well as increases in contact area, force and mean pressure in the lateral hindfoot of the leading foot. For case study two, the forefoot of the trailing foot produced results very similar to the typical dataset across all variables. In the hindfoot of the leading foot, medial bias presents most notably in the force and mean pressure graphs. CONCLUSIONS: This study highlights the clinical significance of the load transfer phase of gait, providing meaningful information for intervention planning.

Lower limb kinematics of single-leg squat performance in patients with anterior cruciate ligament deficiency.

[Purpose] This study investigated the parameters that characterize the knee, hip, and pelvic kinematics during a single-leg squat in preoperative anterior cruciate ligament rupture injury. [Participants and Methods] Overall, 15 patients with unilateral anterior cruciate ligament deficiency were enrolled in this study. For each single-leg squat, data from two-dimensional video cameras and three-dimensional motion analysis were collected. Measurement indices included the articular angles of the knee, hip, and trunk. The anterior cruciate ligament-injured leg was compared with the uninjured leg. [Results] The maximum knee valgus and flexion angles during a single-leg squat were smaller in the injured leg than in the uninjured leg. During the single-leg squat, the effect of "compensatory mechanisms" appeared as knee valgus and flexion movements. In particular, the knee valgus angle decreased in the anterior cruciate ligament-injured leg compared to that in the uninjured leg. [Conclusion] This phenomenon suggests that it is possible to utilize recurrence prevention training for anterior cruciate ligament injury.

Machine learning to quantify habitual physical activity in children with cerebral palsy.

AIM: To investigate whether activity-monitors and machine learning models could provide accurate information about physical activity performed by children and adolescents with cerebral palsy (CP) who use mobility aids for ambulation. METHOD: Eleven participants (mean age 11y [SD 3y]; six females, five males) classified in Gross Motor Function Classification System (GMFCS) levels III and IV, completed six physical activity trials wearing a tri-axial accelerometer on the wrist, hip, and thigh. Trials included supine rest, upper-limb task, walking, wheelchair propulsion, and cycling. Three supervised learning algorithms (decision tree, support vector machine [SVM], random forest) were trained on features in the raw-acceleration signal. Model-performance was evaluated using leave-one-subject-out cross-validation accuracy. RESULTS: Cross-validation accuracy for the single-placement models ranged from 59% to 79%, with the best performance achieved by the random forest wrist model (79%). Combining features from two or more accelerometer placements significantly improved classification accuracy. The random forest wrist and hip model achieved an overall accuracy of 92%, while the SVM wrist, hip, and thigh model achieved an overall accuracy of 90%. INTERPRETATION: Models trained on features in the raw-acceleration signal may provide accurate recognition of clinically relevant physical activity behaviours in children and adolescents with CP who use mobility aids for ambulation in a controlled setting. WHAT THIS PAPER ADDS: Machine learning may assist clinicians in evaluating the efficacy of surgical and therapy-based interventions. Machine learning may help researchers better understand the short- and long-term benefits of physical activity for children with more severe motor impairments.

Functional electrical stimulation cycling, goal-directed training, and adapted cycling for children with cerebral palsy: a randomized controlled trial.

AIM: To test the efficacy of functional electrical stimulation (FES) cycling, goal-directed training, and adapted cycling, compared with usual care, to improve function in children with cerebral palsy (CP). METHOD: The intervention was delivered between 2017 and 2019 and included three sessions per week for 8 weeks (2×1h sessions at a children's hospital, and 1h home programme/week). Hospital sessions included 30 minutes of FES cycling and 30 minutes of goal-directed training. Home programmes included goal-directed training and adapted cycling. The comparison group continued usual care. Primary outcomes were gross motor function assessed by the Gross Motor Function Measure (GMFM) and goal performance/satisfaction assessed using the Canadian Occupational Performance Measure (COPM). Secondary outcomes were sit-to-stand and activity capacity, participation in home, school, and community activities, and power output. Linear regression was used to determine the between-group mean difference immediately post-training completion after adjusting for baseline scores. RESULTS: This randomized controlled trial included 21 participants (mean age=10y 3mo, standard deviation [SD]=3y; Gross Motor Function Classification System level: II=7, III=6, IV=8) who were randomized to the intervention (n=11) or usual care group (n=10). Between-group differences at T2 favoured the intervention group for GMFM-88 (mean difference=7.4; 95% confidence interval [CI]: 2.3-12.6; p=0.007), GMFM-66 (mean difference=5.9; 95% CI: 3.1-8.8; p<0.001), COPM performance (mean difference=4.4; 95% CI: 3.9-5.3; p<0.001) and satisfaction (mean difference=5.2; 95% CI: 4.0-6.4; p<0.001). INTERPRETATION: Children with CP achieved meaningful functional improvements after FES cycling, goal-directed training, and adapted cycling training. Cycling programmes for children with CP should be individualized and goal directed.

Women's Football: An Examination of Factors That Influence Movement Patterns.

Griffin, J, Larsen, B, Horan, S, Keogh, J, Dodd, K, Andretta, M, and Minahan, C. Title: Women's football: An examination of factors that influence movement patterns. J Strength Cond Res 34(8): 2384-2393, 2020-The popularity and professionalism of women's football has increased in conjunction with participation rates over the last 10 years, with projected female participation rates to double worldwide by 2026. Scientific interest has also increased, in part due to Fédération Internationale de Football Association now allowing global positioning system (GPS) units to be worn during all competitive matches, resulting in investigations into the match demands of women's football. Therefore, the purpose of the present review is to provide a summary of the literature specific to the movement patterns of women's football matches. Contemporary scientific investigation using GPS match data has led to a greater understanding of the movement patterns of football. Greater emphasis has been placed on high-speed running and sprinting during matches because of the strong link to scoring opportunities and being a distinguishing factor between international and national along with elite and subelite competition levels. Further research, however, is warranted in regard to accelerations and decelerations, given the high metabolic and mechanical loads and contribution to high-speed running and sprinting. With an influx of research into the movement patterns of match-play, investigators have begun to examine factors affecting match performance such as positional demands, age, level of competition, opponent, scoreline, and phase of the game. An understanding of the factors that influence match demands is vital to ultimately be able to understand the effects on performance and how manipulating these factors may improve football performance and reduce the risk of injury.

Efficacy of cycling interventions to improve function in children and adolescents with cerebral palsy: a systematic review and meta-analysis.

OBJECTIVES: The aim of this study was to determine the efficacy of cycling to improve function and reduce activity limitations in children with cerebral palsy; the optimal training parameters for improved function; and whether improvements in function can be retained. METHOD: Six databases were searched (until February 2019) and articles were screened in duplicate. Randomized or quasi-randomized controlled trials and pre-post studies were included. Methodological quality was assessed using the Downs and Black scale. Outcomes were reported under the International Classification of Functioning, Disability and Health domains of body functions and activity limitations. Quantitative analyses were completed using RevMan V5.3. RESULTS: A total of 533 articles were identified and 9 studies containing data on 282 participants met full inclusion criteria. Methodological quality ranged from low (14 of 32) to high (28 of 32). Significant improvements were reported for hamstring strength (effect size = 0.77-0.93), cardiorespiratory fitness (effect size = 1.13-1.77), balance (effect size = 1.03-1.29), 3-minute walk test distance (effect size = 1.14) and gross motor function (effect size = 0.91). Meta-analysis suggested that cycling can improve gross motor function (standardized mean difference = 0.35; 95% confidence interval = (-0.01, 0.70); P = 0.05); however, the effect was insignificant when a poor-quality study was omitted. CONCLUSION: Cycling can improve muscle strength, balance and gross motor function in children with cerebral palsy; however, optimal training doses are yet to be determined. There was insufficient data to determine whether functional improvements can be retained. Conclusions were limited by small sample sizes, inconsistent outcome measures and a lack of follow-up testing.

An examination of treadmill running familiarisation in barefoot and shod conditions in healthy men.

Running on a treadmill is an activity that is novel to many people. Thus, a familiarisation period may be required before reliable and valid determinations of biomechanical parameters can be made. The current study investigated the time required for treadmill familiarisation under barefoot and shod running conditions. Twenty-six healthy men, who were inexperienced in treadmill running, were randomly allocated to run barefoot or shod for 20 minutes on a treadmill at a self-selected comfortable pace. Sagittal-plane kinematics for the ankle, knee and hip, and ground reaction force and spatio-temporal data were collected at two-minute intervals. For the barefoot condition, temporal differences were observed in peak hip flexion and peak knee flexion during swing. For the shod condition, temporal differences were observed for peak vertical ground reaction force. No temporal differences were observed after 8 minutes for either condition. Reliability analysis revealed high levels of consistency (ICC > 0.90) across all consecutive time-points for all dependent variables for both conditions after 8 minutes with the exception of maximal initial vertical ground reaction force loading rate. Participants in both barefoot and shod groups were therefore considered familiarised to treadmill running after 8 minutes.

Condom Communication: Reports of Sexually Active Young Adults' Recent Messages With New Partners.

The incidence of sexually transmitted infections is high, with recent estimates suggesting 110 million cases (CDC, 2013b). A key method to reducing the risk for sexually transmitted infections is the use of a condom. Consequently, this inquiry aimed to describe the content of and reactions to condom communication. Results revealed the following condom conversation strategies: condom possession, condom exploration, condom demand, and health concerns. Results both support and challenge previous condom studies, therefore extending and informing this line of research. Data further describe reactions to condom conversations and reasons for not having a condom conversation. Findings provide tangible evidence to be used in the training of sexually active young adults.

Muscle Size Not Density Predicts Variance in Muscle Strength and Neuromuscular Performance in Healthy Adult Men and Women.

The purpose of this study was to determine the relationships between peripheral quantitative computed tomography (pQCT)-derived measures of muscle area and density and markers of muscle strength and performance in men and women. Fifty-two apparently healthy adults (26 men, 26 women; age 33.8 ± 12.0 years) volunteered to participate. Dual-energy x-ray absorptiometry (XR-800; Norland Medical Systems, Inc., Trumbull, CT, USA) was used to determine whole body and regional lean and fat tissue mass, whereas pQCT (XCT-3000; Stratec, Pforzheim, Germany) was used to determine muscle cross-sectional area (MCSA) and muscle density of the leg, thigh, and forearm. Ankle plantar flexor and knee extensor strengths were examined using isokinetic dynamometry, and grip strength was examined with dynamometry. Impulse generated during a maximal vertical jump was used as an index of neuromuscular performance. Thigh, forearm, and leg MCSA strongly predicted variance in knee extensor (R = 0.77, p < 0.001) and grip strength (R = 0.77, p < 0.001) and weakly predicted variance in ankle plantar flexor strength (R = 0.20, p < 0.001), respectively, whereas muscle density was only a weak predictor of variance in knee extensor strength (R = 0.18, p < 0.001). Thigh and leg MCSA accounted for 79 and 69% of the variance in impulse generated from a maximal vertical jump (p < 0.001), whereas thigh muscle density predicted only 18% of the variance (p < 0.002). In conclusion, we found that pQCT-derived muscle area is more strongly related to strength and neuromuscular performance than muscle density in adult men and women.

Effect of sex and fatigue on single leg squat kinematics in healthy young adults.

BACKGROUND: The single-leg squat (SLS) test is widely used in screening for musculoskeletal injury risk. Little is known, however, of lower limb, pelvis, and trunk kinematics of SLS performance or the effect of sex and fatigue. Our aim was to determine sex differences and the influence of fatigue on SLS kinematics in healthy young adults. METHODS: We recruited 60 healthy men and women between the ages of 20 and 40 years. Three-dimensional kinematic data was collected for SLSs with a ten-camera VICON motion analysis system (Oxford Metrics, UK) before and after a lower limb fatiguing exercise regime. One-way ANCOVA was used to make sex comparisons of kinematic parameters and repeated measures ANOVA was used to determine the effect of fatigue and the interaction with sex. RESULTS: 30 men (25.6 ± 4.8 years) and 30 women (25.1 ± 3.8 years) volunteered to participate. Peak pelvic rotation (3.9 ± 4.1 vs. 7.7 ± 6.2 deg, P = 0.03), peak hip internal rotation (-1.8 ± 5.7 vs. 3.0 ± 7.3 deg, P = 0.02), hip adduction range (11.7 ± 4.8 vs. 18.3 ± 6.7 deg, P = 0.004), and hip rotation range (10.7 ± 3.9 vs. 13.0 ± 4.2 deg, P = 0.04) were smaller for men than for women. Likewise, distance of mediolateral knee motion (180 ± 51 vs. 227 ± 50 mm, P = 0.001) was shorter for men than for women. The kinematic response to fatigue was an increase in trunk flexion, lateral flexion and rotation, an increase in pelvic tilt, obliquity and rotation, and an increase in hip flexion and adduction range (P ≤0.05). CONCLUSIONS: Sex differences in SLS kinematics appear to apply only at the hip, knee, and pelvis and not at the trunk. Fatiguing exercise, however, produces changes at the trunk and pelvis with little effect on the knee.

Lunging Exercise Potentiates a Transient Improvement in Neuromuscular Performance in Young Adults.

High-load resistance-based exercise is a common approach to facilitating improved neuromuscular performance via postactivation potentiation. Popular field-based warm-up activities, however, have been largely overlooked despite their specificity and practicality for sports performance. Therefore, the aim of this study was to investigate the effect of repeated bouts of alternating lunges on neuromuscular performance determined by a maximal vertical jump (VJ). Forty-three healthy young adults (24 women and 19 men: age, 25.6 ± 4.4 years) participated in the study. Maximal VJ performance was quantified by jump height (in centimeters), relative impulse (in N·s·kg), flight time (in seconds), and normalized peak vertical ground reaction force (GRFz, bodyweight [BW]) at baseline and after each of 6 sets of 20 alternate split lunges. A rating of perceived exertion (1-10 scale) was recorded from participants before each VJ. Jump height was greater than baseline for the first 4 trials (3.1-3.8%, p ≤ 0.05), but no difference to baseline was observed on subsequent trials. Although there were no improvements for relative impulse over repeated trials, the sixth trial was significantly smaller than baseline (2.35 ± 0.38 vs. 2.26 ± 0.35 N·s·kg; p ≤ 0.001). Similarly, no improvements were observed for flight time, although the first, fourth, fifth, and sixth trials were reduced compared with baseline performance (p ≤ 0.01). No differences were observed for peak vertical GRFz (p > 0.05). In conclusion, a regimen of lunging exercise resulted in a transient improvement in maximal VJ performance. However, measures of flight time, impulse, and GRFz did not mirror the performance gain in jump height.

Swing kinematics of male and female skilled golfers following prolonged putting practice.

Given that males and females respond differently to endurance-based tasks, prolonged putting practice may provide an avenue to examine gender-related differences in golf swing kinematics. The aim of this project was to determine if 40 min of putting affects thorax and pelvis kinematics during the full swing of males and females. Three-dimensional trunk kinematics were collected during the swings of 19 male (age: 26 ± 7 years, handicap: 0.6 ± 1.1) and 17 female (age: 24 ± 7 years, handicap: 1.4 ± 1.7) golfers before and after 40 min of putting. Angular displacement at address, top of backswing and ball contact for the pelvis, thorax, and pelvis-thorax interaction were calculated, in addition to the magnitude of peak angular velocity and repeatability of continuous segment angular velocities. Female golfers had less pelvis and thorax anterior-posterior tilt at address, less thorax and thorax-pelvis axial rotation at top of backswing, and less pelvis and thorax axial rotation and pelvis lateral tilt at ball contact pre- to post-putting. Analysis of peak angular velocities revealed that females had significantly lower thorax-pelvis lateral tilt velocity pre- to post-putting. In conclusion, an endurance-based putting intervention affects females' thorax and pelvis orientation angles and velocities to a greater extent than males.

Deep phenotyping of post-infectious myalgic encephalomyelitis/chronic fatigue syndrome.

Post-infectious myalgic encephalomyelitis/chronic fatigue syndrome (PI-ME/CFS) is a disabling disorder, yet the clinical phenotype is poorly defined, the pathophysiology is unknown, and no disease-modifying treatments are available. We used rigorous criteria to recruit PI-ME/CFS participants with matched controls to conduct deep phenotyping. Among the many physical and cognitive complaints, one defining feature of PI-ME/CFS was an alteration of effort preference, rather than physical or central fatigue, due to dysfunction of integrative brain regions potentially associated with central catechol pathway dysregulation, with consequences on autonomic functioning and physical conditioning. Immune profiling suggested chronic antigenic stimulation with increase in naïve and decrease in switched memory B-cells. Alterations in gene expression profiles of peripheral blood mononuclear cells and metabolic pathways were consistent with cellular phenotypic studies and demonstrated differences according to sex. Together these clinical abnormalities and biomarker differences provide unique insight into the underlying pathophysiology of PI-ME/CFS, which may guide future intervention.

Personal Workplace Relationships: Unifying an Understudied Area of Organizational and Personal Life.

Relationships that cross the work-life domain have long been of interest to scholars in multiple disciplines, including Communication, Management, and Psychology. Close relationships that span work-life borders are called personal workplace relationships. Personal workplace relationships are voluntary informal relationships between two members of the same organization. These relationships are mutual and consensual and have a relatively strong emotional component. They involve the partners knowing and communicating with each other as unique individuals. The goal of this Special Issue ("Personal Workplace Relationships: Implications for Work and Life in a Rapidly Changing Society") is to explore this specific form of work-life intersection. To that end, we present the scholarly work of researchers from diverse backgrounds who share the goal of better understanding workplace relationships. In this opening essay, we describe how we began to study this area, we preview the articles in this Special Issue, and we conclude with recommendations for future research on personal workplace relationships.

ACTIVE STRIDES-CP: protocol for a randomised trial of intensive rehabilitation (combined intensive gait and cycling training) for children with moderate-to-severe bilateral cerebral palsy.

INTRODUCTION: For children with cerebral palsy (CP), who are marginally ambulant, gross motor capacity peaks between 6 and 7 years of age with a subsequent clinical decline, impacting their ability to engage in physical activity. Active Strides-CP is a novel package of physiotherapy targeting body functions, activity and participation outcomes for children with bilateral CP. This study will compare Active Strides-CP to usual care in a multisite randomised waitlist-controlled trial. METHODS AND ANALYSIS: 150 children with bilateral CP (5-15 years), classified in Gross Motor Function Classification System (GMFCS) levels III and IV will be stratified (GMFCS III vs IV, age 5-10 years; 11-15 years and trial site) and randomised to receive either (1) 8 weeks of Active Strides-CP two times/week for 1.5 hours in clinic and one time/week for 1 hour alternating home visits and telehealth (total dose=32 hours) or (2) usual care. Active Strides-CP comprises functional electrical stimulation cycling, partial body weight support treadmill training, overground walking, adapted community cycling and goal-directed training. Outcomes will be measured at baseline, immediately post-intervention at 9 weeks primary endpoint and at 26 weeks post-baseline for retention. The primary outcome is the Gross Motor Function Measure-66. Secondary outcomes include habitual physical activity, cardiorespiratory fitness, walking speed and distance, frequency/involvement of community participation, mobility, goal attainment and quality of life. Analyses will follow standard principles for randomised controlled trials using two-group comparisons on all participants on an intention-to-treat basis. Comparisons between groups for primary and secondary outcomes will be conducted using regression models. A within-trial cost utility analysis will be performed. ETHICS AND DISSEMINATION: The Children's Health Queensland Hospital and Health Service, The University of Queensland, The University of Melbourne and Curtin University Human Research Ethics Committees have approved this study. Results will be disseminated as conference abstracts and presentations, peer-reviewed articles in scientific journals, and institution newsletters and media releases. TRIAL REGISTRATION NUMBER: ACTRN12621001133820.