Assessing the reliability of biomechanical variables during a horizontal deceleration task in healthy adults.

Horizontal deceleration technique is an underpinning factor to musculoskeletal injury risk and performance in multidirectional sport. This study primarily assessed within- and between-session reliability of biomechanical and performance-based aspects of a horizontal deceleration technique and secondarily investigated the effects of limb dominance on reliability. Fifteen participants completed four horizontal decelerations on each leg during test and retest sessions. A three-dimensional motion analysis system was used to collect kinetic and kinematic data. Completion time, ground contact time, rate of horizontal deceleration, minimum centre of mass height, peak eccentric force, impulse ratio, touchdown distance, sagittal plane foot and knee angles at initial contact, maximum sagittal plane thorax angle, and maximum knee flexion moment were assessed. Coefficients of variation (COV) and intraclass correlation coefficients (ICC) were used to assess within- and between-session reliability, respectively. Seven variables showed "great" within-session reliability bilaterally (COV ≤9.13%). ICC scores were 'excellent' (≥0.91; n = 4), or 'good' (0.76-0.89; n = 7), bilaterally. Limb dominance affected five variables; three were more reliable for the dominant leg. This horizontal deceleration task was reliable for most variables, with little effect of limb dominance on reliability. This deceleration task may be reliably used to assess and track changes in deceleration technique in healthy adults.

A comparison of clinical assessment with common diagnostic tools for monitoring concussion recovery in adolescent rugby union players.

OBJECTIVES: To characterise the incidence, severity and recovery of sport-related concussion (SRC) in schoolboy rugby players and explore whether the Sports Concussion Assessment Tool (SCAT), Cogstate Brief Battery (CBB) and the King-Devick test (K-D test) can be used to monitor concussion status through to full recovery. DESIGN: Prospective cohort study. SETTING: Rugby union has a high rate of SRC; however, there is little research investigating how concussion affects adolescent rugby players. PARTICIPANTS: Schoolboy rugby players. MAIN OUTCOME MEASURES: Participants completed baseline tests in the preseason. Participants diagnosed with SRC during the season attended for post-concussion testing on a weekly basis until recovered. RESULTS: 135 schoolboy rugby players (16.7 ± 0.82y) participated in the study. There were 18 SRCs in 16 participants. Concussion incidence was 9/1000 player hours. CBB and K-D tests were poorly associated with clinical assessment and produced high false negative rates (0.58 and 0.52 respectively). CONCLUSIONS: This study reports a relatively high match SRC incidence for an adolescent population. Analysis of clinical recovery with CBB and K-D test revealed a relatively poor ability to accurately monitor concussion status compared to clinical assessment suggesting that these tools should not be used in isolation for monitoring SRC recovery in adolescents.

Skin-to-deltoid-muscle distance at three recommended sites for intramuscular vaccination in a population with obesity: an observational study.

AIM: Worldwide, immunisation guidelines variably locate the deltoid injection site based on anatomical landmarks. This may influence the skin-to-deltoid-muscle distance and therefore the needle length required to achieve intramuscular injection. Obesity is associated with increased skin-to-deltoid-muscle distance, but it is unknown whether the injection site location chosen in individuals with obesity impacts the needle length required for intramuscular injection. The aim of the study was to estimate the differences in skin-to-deltoid-muscle distance between three different vaccine injection sites recommended by the national guidelines of the United States of America (USA), Australia and New Zealand, in obese adults. The study also explored i) the associations between skin-to-deltoid-muscle distance across the three recommended sites with sex, body mass index (BMI), and arm circumference, and ii) the proportion of participants with a skin-to-deltoid-muscle distance >20 millimetres (mm), in whom the standard 25mm needle length would not ensure deposition of vaccine within the deltoid muscle. METHOD: Non-interventional cross-sectional study in a single site, non-clinical setting in Wellington, New Zealand. Forty participants (29 females), aged ≥18 years, with obesity (BMI>30 kilograms [km]/m[[2]]). Measurements included distance from acromion to injection sites, BMI, arm circumference, and skin-to-deltoid-muscle distance measured by ultrasound at each recommended injection site. RESULTS: Mean (SD) skin-to-deltoid-muscle distances for USA, Australia and New Zealand sites were 13.96mm (4.54), 17.94mm (6.08) and 20.26mm (5.91) respectively, with a mean (95% confidence interval) for the distance between Australia minus New Zealand -2.7mm (-3.5 to -1.9), P<0.001; and USA minus New Zealand -7.6 mm (-8.5 to -6.7); P<0.001. Skin-to-deltoid-muscle distance was greater in females and was positively associated with BMI and arm circumference. The proportions with a skin-to-deltoid-muscle distance >20 mm were 45%, 40% and 15% for the New Zealand, Australia and USA sites respectively. However, the sample size was relatively small, limiting interpretation in specific sub-groups. CONCLUSION: There were marked differences in the skin-to-deltoid-muscle distance between the three recommended injection sites studied. When choosing the required needle length to achieve intramuscular vaccination in obese vaccine recipients, consideration needs to be given to the injection site location, sex, BMI and/or arm circumference, as these factors all influence the skin-to-deltoid-muscle distance. A standard needle length of 25mm may be insufficient to ensure deposition of vaccine into the deltoid muscle in a substantive proportion of adults with obesity. Research is urgently required to determine anthropometric measurement cut-points that can be used to enable appropriate needle length selection to ensure intramuscular vaccination.

Body mass affects kinetic symmetry and inflammatory markers in adolescent knees during gait.

BACKGROUND: Early-onset osteoarthritis has been attributed to pro-inflammatory factors and biomechanical changes in obesity. However, research has yet to explore whether knee joint moments are asymmetrical in children with obesity and could precede the onset of knee osteoarthritis. The present study compares knee moment asymmetry between adolescents with and without obesity and examines the relationship between asymmetries and inflammatory biomarkers. METHODS: Twenty-eight adolescents (13-16 years) were classified as with (n = 12) or without (n = 16) obesity. Lower extremity kinetics were measured using three-dimensional motion analysis. Bilateral knee joint moments were analyzed in the sagittal, frontal, and transverse planes across stance phase. Kinetic asymmetry was calculated between the right and left sides and represented by the R2 value. Enzyme-linked immunosorbent assays analyzed serum 25-hydroxy vitamin D, interferon gamma, tumor nercrosis factor alpha, interleukin-6, and C-reactive protein levels. Parametric and non-parametric tests determined significant group differences in asymmetries and biomarkers, respectively. Spearman's correlations identified relationships between biomarkers and asymmetries with statistically significant group differences. FINDINGS: Adolescents with obesity had greater sagittal (loading, midstance) and frontal (midstance, pre-swing) plane kinetic knee asymmetry and higher concentrations of interleukin-6 and C-reactive protein. A moderately negative correlation existed between C-reactive protein and sagittal (loading, midstance) plane asymmetry, and also between interleukin-6 and frontal (pre-swing) plane asymmetry. INTERPRETATION: Inflammatory response increases with greater knee joint asymmetry, suggesting knee joint damage and altered joint loading co-exist in adolescents with obesity. Increased risk to joint health may exist in sub-phases where knee joints are improperly loaded.

COVID-19 vaccination and the skin to deltoid MUSCLE distance in adults with diabetes.

Objectives: To estimate the proportion of adult diabetics with a skin to deltoid muscle distance (SDMD) of > 25 mm, representing a distance greater than the standard needle length used for intramuscular COVID-19 vaccination, and to assess whether anthropometric measurements predict ultrasound SDMD measurements. Design: Non-interventional cross-sectional study. Setting: Single site, non-clinical setting, Wellington, New Zealand. Participants: One hundred participants (50 females) aged at least 18 years diagnosis with diabetes. All participants completed the study. Main outcome measures: The proportions of participants with a SDMD > 25 mm and a SDMD > 20 mm (indicating that the needle would not have penetrated at least 5 mm into the deltoid, which is considered necessary to ensure deposition of vaccine into muscle); the relationship between anthropometric measurements (body weight, body height, body mass index (BMI), skinfold thickness, arm circumference) and SDMD measured by ultrasound. Results: The proportion (95 %CI) of participants with a SDMD > 25 mm was 6/100; 6 % (2.2 to 12.6), and the proportion with a SDMD > 20 mm was 11 % (5.6 to 18.8), of which 9/11 had a BMI ≥ 30 kg/m2 and 9/11 were female. The strongest relationships between anthropometric measurements and SDMD were with arm circumference (r = 0.76, P < 0.001) and BMI (r = 0.73, P < 0.001). Arm circumference and BMI were the best predictors of SDMD measurements with AUC for ROC curves of 0.99 and 0.94 above the 25 mm cut point, 0.97 and 0.89 above the 20 mm cut point respectively. Conclusions: The standard needle length of 25 mm is likely to be insufficient to ensure deposition of COVID-19 vaccine within the deltoid muscle in a small but important proportion of obese adults with diabetes. Arm circumference and BMI are simple measurements that could identify those that need a long needle to ensure successful intramuscular vaccine administration. Funding: Ruth Maud Ring Spencer Estate; Health Research Council of New Zealand (Independent Research Organisation).

Effects of inhaled JAK inhibitor GDC-4379 on exhaled nitric oxide and peripheral biomarkers of inflammation.

BACKGROUND: Janus Kinases (JAKs) mediate activity of many asthma-relevant cytokines. GDC-0214, an inhaled small molecule JAK1 inhibitor, has previously been shown to reduce fractional exhaled nitric oxide (FeNO) in patients with mild asthma, but required an excessive number of inhalations. AIM: To assess whether GDC-4379, a new inhaled JAK inhibitor, reduces FeNO and peripheral biomarkers of inflammation. METHODS: This study assessed the activity of GDC-4379 in a double-blind, randomized, placebo-controlled, Phase 1 study in patients with mild asthma. Participants included adults (18-65y) with a diagnosis of asthma for ≥6 months, forced expiratory volume in 1 s (FEV1)> 70% predicted, FeNO >40 ppb, using as-needed short-acting beta-agonist medication only. Four sequential, 14-day, ascending-dose cohorts (10 mg QD, 30 mg QD, 40 mg BID, and 80 mg QD) of 12 participants each were randomized 2:1 to GDC-4379 or placebo. The primary activity outcome was percent change from baseline (CFB) in FeNO to Day 14 compared to the pooled placebo group. Safety, tolerability, pharmacokinetics, and pharmacodynamic biomarkers, including blood eosinophils, serum CCL17, and serum CCL18, were also assessed. RESULTS: Of 48 enrolled participants, the mean age was 25 years and 54% were female. Median (range) FeNO at baseline was 79 (41-222) ppb. GDC-4379 treatment led to dose-dependent reductions in FeNO. Compared to placebo, mean (95% CI) percent CFB in FeNO to Day 14 was: -6 (-43, 32) at 10 mg QD, -26 (-53, 2) at 30 mg QD, -55 (-78, -32) at 40 mg BID and -52 (-72, -32) at 80 mg QD. Dose-dependent reductions in blood eosinophils and serum CCL17 were also observed. Higher plasma drug concentrations corresponded with greater FeNO reductions. No serious AEs occurred. The majority of AEs were mild to moderate. The most common AEs were headache and oropharyngeal pain. Minor changes in neutrophils were noted at 80 mg QD, but were not considered clinically meaningful. CONCLUSIONS: In patients with mild asthma, 14-day treatment with GDC-4379 reduced FeNO levels and peripheral biomarkers of inflammation. Treatment was well tolerated without any major safety concerns. AUSTRALIAN NEW ZEALAND CLINICAL TRIALS REGISTRY: ACTRN12619000227190.

Cannabis in Palliative Care: A Systematic Review of Current Evidence.

CONTEXT: Palliative care aims to improve the quality of life in patients with incurable illness. Medicinal cannabis (MC) has been used in the palliative care setting to address multiple symptoms in patients. OBJECTIVES: To evaluate the full scope of available literature investigating the effects and potential harms of MC on symptom management and quality of life in palliative care. METHODS: PubMed, Embase, The Cochrane Library and clinicaltrials.gov were searched for eligible articles, published between 1960 and September 9, 2021. Quality of the evidence was assessed in accordance with Grading of Recommendations, Assessment, Development and Evaluations. Risk of bias was assessed using the RoB 2 tool for randomised controlled trials and the Risk of Bias in Non-randomized Studies-of Interventions (ROBINS-I) tool for non-randomized trials. RESULTS: Fifty-two studies (20 randomised; 32 non-randomised) with 4786 participants diagnosed with cancer (n = 4491), dementia (n = 43), AIDS (n = 235), spasticity (n = 16), NORSE syndrome (n = 1) were included. The quality of evidence was 'very low' or 'low' for all studies, and low for only two randomised controlled trials. Positive treatment effects (statistical significance with P < 0.05) were seen for some MC products in pain, nausea and vomiting, appetite, sleep, fatigue, chemosensory perception and paraneoplastic night sweats in patients with cancer, appetite and agitation in patients with dementia and appetite, nausea and vomiting in patients with AIDS. Meta-analysis was unable to be performed due to the wide range of cannabis products used and the heterogeneity of the study outcomes. CONCLUSION: While positive treatment effects have been reported for some MC products in the palliative care setting, further high quality evidence is needed to support recommendations for its use in clinical practice.

Underestimation of COVID-19 mortality during the pandemic.

BACKGROUND: There has been considerable international variation in mortality during the COVID-19 pandemic. The objective of this study was to investigate the differences between mortality registered as due to COVID-19 and the excess all-cause mortality reported in countries worldwide during the COVID-19 pandemic. METHODS: Ecological analysis of 22 countries compared 5-year historical all-cause mortality, reported all-cause mortality and expected all-cause mortality (calculated as historical mortality plus the reported deaths attributed to COVID-19). Data available from the first week of January 2020 to that most recently available were analysed. RESULTS: Compared to the preceding 5 years, there was an excess of 716 616 deaths, of which 64.3% were attributed to COVID-19. The proportion of deaths registered as COVID-19-related/excess deaths varied markedly between countries, ranging between 30% and 197% in those countries that had an excess of deaths during the period of observation. In most countries where a definite peak in COVID-19-related deaths occurred, the increase in reported all-cause mortality preceded the increase in COVID-19 reported mortality. During the latter period of observation, a few countries reported fewer all-cause deaths than the historical figures. CONCLUSION: The increases in all-cause mortality preceded the increase in COVID-19 mortality in most countries that had definite spikes in COVID-19 mortality. The number of deaths attributed to COVID-19 was underestimated by at least 35%. Together these findings suggest that calculation of excess all-cause mortality is a better predictor of COVID-19 mortality than the reported rates, in those countries experiencing definite increases in mortality.

Medicinal applications of cannabis/cannabinoids.

Regulatory approvals for Epidiolex (purified cannabidiol) in the treatment of childhood drug resistant epilepsy have set a precedent for the use of cannabinoids as a prescribed medicine. Two common reasons cited for the use and prescription of cannabis-based products are pain and insomnia. Unlike drug resistant epilepsy, the level of evidence of efficacy in pain is poorly developed. The lowest quality trials with the greatest methodological shortcomings suggest some benefit, a level of evidence that is inconsistent with widespread prescribing. The evidence in insomnia is scant. Ongoing trial development and critical review of the literature should not be overshadowed by increasing permissiveness towards cannabis use and anecdotal reports of efficacy.

A systematic review of the label accuracy of cannabinoid-based products in regulated markets: is what's on the label what's in the product?

OBJECTIVES: To review the literature regarding label accuracy and contamination of medical cannabinoid-based products. METHODS: A systematic review with meta-analysis following PRISMA guidelines. This study is registered with PROSPERO (CRD42019131565). RESULTS: Five studies reported label accuracy data ranging between 17% and 86%. Four studies reported contaminants, including pesticides, solvents and AB-FUBINACA. Meta-analysis was limited to the proportion of pesticide-contaminated samples found in two studies (0.25 (95% CI [0.10, 0.40])) and displayed significant heterogeneity. CONCLUSIONS: Label inaccuracies and contaminants are found across a spectrum of cannabinoid-based products. The review highlights the paucity and heterogeneity of research relating to cannabinoid-based products in light of changing global legislation. Further robust research is required to support ongoing pharmacovigilance and patient safety.

The Effects of Anticipation and Visual and Sensory Performance on Concussion Risk in Sport: A Review.

Sports-related concussions pose a significant public health concern, and preventative measures are needed to help reduce risk in sport. Vision training could be a suitable prevention strategy for sports-related concussion to help improve athletes' abilities to scan the visual field for oncoming objects or opponents and thus anticipate head impacts. By accurately anticipating impacts, athletes can prepare for impact or attempt to avoid the collision altogether. The purpose of this review is to explore the relationships between anticipation, visual and sensorimotor performance and head accelerations, as well as to examine the efficacy of vision training programmes in reducing concussion risk in sport. Anticipation of head impacts has been shown to help reduce linear and rotational head accelerations, particularly for mild-to-moderate severity head impacts, but less so for severe head impacts. There is conflicting evidence regarding the influences visual and sensorimotor performance and oculomotor behaviour have on concussion risk. However, preliminary research indicates vision training may help reduce concussion rates in collegiate American Football players. Therefore, this promising area of research warrants further investigation, particularly the role of anticipation and visual and sensory performance on reducing concussion risk in non-helmeted contact sports.

Cannabinoids in the Treatment of Insomnia Disorder: A Systematic Review and Meta-Analysis.

BACKGROUND: Insomnia is associated with significant comorbidity, disability and impact on quality of life and, despite advances in pharmacotherapy and psychotherapy, remains a significant burden to society. Cannabinoids are gaining acceptance for use as medicines in the treatment of insomnia disorder. OBJECTIVE: We conducted a systematic review and meta-analysis to evaluate the efficacy of cannabinoids in the treatment of insomnia disorder. METHODS: We performed a systematic review of the PubMed, Cochrane Library, MEDLINE, and Cumulative Index to Nursing and Allied Health Literature Complete databases from inception to 5 December 2019, and again prior to data abstraction, for studies of cannabis-based products for the treatment of insomnia disorder in adults. Inclusion criteria were (1) clinical studies, (2) participants aged ≥ 18 years, (3) insomnia disorder either formally diagnosed against contemporaneous diagnostic criteria or quantified with validated instruments and (4) compared cannabis-based products with the standard of care, placebo or a sedative. No language restrictions were imposed. Non-primary research, animal studies and studies of cannabis-induced insomnia were excluded. Risk of bias was assessed using the RoB 2 tool for randomised controlled trials (RCTs) and Risk of Bias in Non-randomized Studies-of Interventions (ROBINS-I) tool for non-randomized trials. Heterogeneity was assessed with the I2 statistic. RESULTS: A total of five studies (two RCTs and three non-randomised studies) with 219 study participants were included, of which three could be combined. The three non-randomised studies contributed data on the Pittsburgh Sleep Quality Index Questionnaire score, showing a favourable effect of cannabinoids at ≤ 4 weeks of follow-up (mean difference - 1.89 [95% confidence interval {CI} - 2.68 to - 1.10]; n = 176) and at 8 weeks of follow-up (mean difference - 2.41 [95% CI - 3.36 to - 1.46]; n = 166). One double-blind crossover RCT (n = 32) reported that, compared with amitriptyline, nabilone-a synthetic analogue to tetrahydrocannabinol (THC)-improved Insomnia Severity Index scores after 2 weeks of treatment (adjusted difference - 3.25 [95% CI - 5.26 to - 1.24]) and resulted in a more restful sleep as a sub-measure of the Leeds Sleep Evaluation Questionnaire (LSEQ) (difference 0.48 [95% CI 0.01-0.95]) but with no effect on overall sleep quality as measured by the LSEQ. In a single ascending-dose RCT (n = 9), THC reduced sleep-onset latency compared with placebo at 10 mg, 20 mg and 30 mg doses (mean difference - 43.00 min [95% CI - 82.76 to - 3.24], - 62.00 [95% CI - 103.60 to - 20.40] and - 54.00 [95% CI - 103.93 to - 4.07], respectively). All the included studies were assessed as poor quality, mainly due to small sample sizes, short treatment periods, uncertain clinical significance and high risk of bias. CONCLUSIONS: Few studies have examined the efficacy of cannabinoids in the treatment of insomnia disorder. Despite some possible signals for efficacy, the heterogeneity of participants, interventions, efficacy outcomes and results, and the high risk of bias across included trials, do not reliably inform evidence-based practice. This review highlights shortcomings in the existing literature, including lack of diagnostic clarity, poorly defined participant groups, non-standardised interventions and studies of inappropriate design, duration and power to detect clinically meaningful outcomes. Further research in the form of high-quality RCTs are required before drawing any conclusions about the efficacy of cannabinoids in the treatment of insomnia disorder. TRIAL REGISTRATION: PROSPERO registration number, CRD42020161043.

Age-Related Differences in Perceived Exertion While Walking and Running Near the Preferred Transition Speed.

PURPOSE: To investigate whether youth and adults can perceive differences in exertion between walking and running at speeds near the preferred transition speed (PTS) and if there are age-related differences in these perceptions. METHODS: A total of 49 youth (10-12 y, n = 21; 13-14 y, n = 10; 15-17 y, n = 18) and 13 adults (19-29 y) completed a walk-to-run transition protocol to determine PTS and peak oxygen uptake. The participants walked and ran on a treadmill at 5 speeds (PTS-0.28 m·s-1, PTS-0.14 m·s-1, PTS, PTS+0.14 m·s-1, PTS+0.28 m·s-1) and rated perceived exertion using the OMNI Perceived Exertion (OMNI-RPE) scale. Oxygen consumption was measured during the walk-to-run transition protocol to obtain the relative intensity (percentage of peak oxygen uptake) at PTS. OMNI-RPE scores at all speeds and percentage of peak oxygen uptake at PTS were compared between age groups. RESULTS: The 10- to 12-year-olds transitioned at a higher percentage of peak oxygen uptake than adults (64.54 [10.18] vs 52.22 [11.40], respectively; P = .035). The 10- to 14-year-olds generally reported higher OMNI-RPE scores than the 15- to 17-year-olds and adults (P < .050). In addition, the 10- to 14-year-olds failed to distinguish differences in OMNI-RPE between walking and running at PTS and PTS+0.14 m·s-1. CONCLUSIONS: Children aged 10-14 years are less able to distinguish whether walking or running requires less effort at speeds near the PTS compared with adults. The inability to judge which gait mode is less demanding could hinder the ability to minimize locomotive demands.

Age-dependent variability in spatiotemporal gait parameters and the walk-to-run transition.

Adolescents tend to exhibit more variability in their gait patterns than adults, suggesting a lack of gait maturity during this period of ongoing musculoskeletal growth and development. However, there is a lack of consensus over the age at which mature gait patterns are achieved and the factors contributing to gait maturation. Therefore, the purpose of this study was to investigate gait control and maturity in adolescents by determining if differences existed between adolescents and adults in a) the amount of spatiotemporal variability of walking and running patterns across a range of speeds, and b) how swiftly gait patterns are adapted to increasing gait speed during the walk-to-run transition. Forty-six adolescents (10-12-year-olds, n = 17; 13-14-year-olds, n = 12; and 15-17-year-olds, n = 17) and 12 young adults completed an incrementally ramped treadmill test (+0.2 km·h-1 every 30 s) to determine the preferred transition speed (PTS) during a walk-to-run transition. Age-related differences in the variability of stride lengths and stride durations were assessed across 4 speeds (self-selected walking speed, PTS - 0.06 m·s-1, PTS + 0.06 m·s-1, PTS + 0.83 m·s-1). Repeated measures ANOVAs (p < 0.05) compared coefficients of variation for these spatiotemporal parameters, while a one-way ANOVA compared the numbers of gait transitions and speed increments used to identify PTS between the adolescent groups and young adults. Compared to adults, 10-12yo exhibited more spatiotemporal variability during all gait conditions, while 13-17yo only exhibited more variability at PTS + 0.06 m·s-1. No age-dependent pattern was observed in PTS values, but 10-12yo completed more gait transitions over more speed increments than 15-17yo and adults. The development of mature gait patterns is thus a progressive process, with walking maturing at an earlier age than running. As 10-12yo were unable to swiftly adapt gait patterns to the changing task demands, their control mechanisms of gait may not have fully matured yet.

What factors determine the preferred gait transition speed in humans? A review of the triggering mechanisms.

Human locomotion is a fundamental skill that is required for daily living, yet it is not completely known how human gait is regulated in a manner that seems so effortless. Gait transitions have been analyzed to gain insight into the control mechanisms of human locomotion since there is a known change that occurs as the speed of locomotion changes. Specifically, as gait speed changes, there is a spontaneous transition between walking and running that occurs at a particular speed. Despite the growing body of research on the determinants of this preferred transition speed and thus the triggering mechanisms of human gait transitions, a clear consensus regarding the control mechanisms of gait is still lacking. Therefore, this article reviews the determinants of the preferred transition speed using concepts of the dynamic systems theory and how these determinants contribute to four proposed triggers (i.e. metabolic efficiency, mechanical efficiency, mechanical load and cognitive and perceptual) of human gait transitions. While individual anthropometric and strength characteristics influence the preferred transition speed, they do not act to trigger a gait transition. The research has more strongly supported the mechanical efficiency and mechanical load determinants as triggering mechanisms of human gait transitions. These mechanical determinants, combined with cognitive and perceptual processes may thus be used to regulate human gait patterns through proprioceptive and perceptual feedback as the speed of locomotion changes.

Changes in Lower Extremity Kinematics and Temporal Parameters of Adolescent Baseball Pitchers During an Extended Pitching Bout.

BACKGROUND: Few studies have investigated detailed 3-dimensional lower extremity kinematics during baseball pitching in adolescent athletes during extended play. Changes in these parameters may affect performance outcomes. PURPOSE: To investigate whether adolescent baseball pitchers experience changes in lower extremity kinematics and event timing during a simulated game-length pitching bout. STUDY DESIGN: Descriptive laboratory study. METHODS: Twelve male adolescent pitchers (aged 14-16 years) threw 6 sets of 15 fastball pitches from an artificial pitching mound to a target at regulation distance. Joint angles and angular velocities at the hip, knee, and ankle of both legs were collected throughout the phases of the pitching cycle as well as stride length, pelvis orientation, pitch duration, timing of foot contact and ball release, ball speed, and pitching accuracy. Paired t tests ( P < .05) were used to compare the dependent variables between the last 5 pitches of the second (baseline) and sixth (final) sets. RESULTS: During the stride phase, decreased maximum angular excursions for hip extension (baseline: 14.7° ± 9.8°; final: 11.6° ± 10.3°; P < .05) and ankle plantar flexion (baseline: 30.2° ± 14.5°; final: 24.2° ± 15.3°; P < .05) as well as maximum angular velocity for knee extension (baseline: 144.9 ± 63.3 deg·s-1; final: 121.7 ± 62.0 deg·s-1; P < .05) were observed between sets in the trailing leg. At foot contact, pitchers had decreased hip flexion (baseline: 69.5° ± 10.1°; final: 66.5° ± 11.8°; P < .05) and increased hip abduction (baseline: 20.7° ± 8.9°; final: 25.4° ± 6.0°; P < .05) in the leading leg in the final set. Compared with the baseline set, ball speed significantly decreased in the final set (29.5 ± 2.5 m·s-1 vs 28.3 ± 2.5 m·s-1, respectively; P < .05). CONCLUSION: Kinematic changes and decreased ball speeds observed in the final set suggest that adolescent pitchers are unable to maintain lower extremity kinematics and performance as a result of extended play. CLINICAL RELEVANCE: The results from this study may warrant further investigation into how altered lower extremity kinematics may affect trunk and upper extremity function, performance, and risk of injuries during pitching in adolescent athletes, particularly during actual game play.

Does adiposity affect muscle function during walking in children?

The biomechanical mechanisms responsible for the altered gait in obese children are not well understood, particularly as they relate to increases in adipose tissue. The purpose of this study was to test the hypotheses that as body-fat percentage (BF%) increased: (1) knee flexion during stance would decrease while pelvic obliquity would increase; (2) peak muscle forces normalized to lean-weight would increase for gluteus medius, gastrocnemius, and soleus, but decrease for the vasti; and (3) the individual muscle contributions to center of mass (COM) acceleration in the direction of their primary function(s) would not change for gluteus medius, gastrocnemius, and soleus, but decrease for the vasti. We scaled a musculoskeletal model to the anthropometrics of each participant (n=14, 8-12 years old, BF%: 16-41%) and estimated individual muscle forces and their contributions to COM acceleration. BF% was correlated with average knee flexion angle during stance (r=-0.54, p=0.024) and pelvic obliquity range of motion (r=0.78, p<0.001), as well as with relative vasti (r=-0.60, p=0.023), gluteus medius (r=0.65, p=0.012) and soleus (r=0.59, p=0.026) force production. Contributions to COM acceleration from the vasti were negatively correlated to BF% (vertical-- r=-0.75, p=0.002, posterior-- r=-0.68, p=0.008), but there were no correlation between BF% and COM accelerations produced by the gastrocnemius, soleus and gluteus medius. Therefore, we accept our first, partially accept our second, and accept our third hypotheses. The functional demands and relative force requirements of the hip abductors during walking in pediatric obesity may contribute to altered gait kinematics.