Boys demonstrate greater knee frontal moments than girls during the impact phase of cutting maneuvers, despite age-related increases in girls.

PURPOSE: Anterior cruciate ligament (ACL) injury rate is low among children, but increases during adolescence, especially in girls. Increases in the knee valgus moment within 70 ms of contact with the ground (KFM0-70) may explain the sex-specific increase in the risk of ACL injury. The purpose of the study was to investigate sex-dependent changes in the KFM0-70 from pre-adolescence to adolescence during a cutting maneuver (CM). METHODS: Kinematic and kinetic data during the CM task, performed before and after physical exertion, were recorded using a motion capture system and a force plate. A total of 293 team handball and soccer players, aged 9-12 years, were recruited. A number of those who continued sports participation (n = 103) returned five years later to repeat the test procedure. Three mixed-model analysis of variance (ANOVA) for repeated measures tests were used to determine the effects of sex and age period on the KFM0-70 (1: with no adjustment, 2: adjusted for repeated measurements, and 3: additionally adjusted with hip and knee joint frontal plane kinematics). RESULTS: Boys had significantly higher KFM0-70 than girls at both age periods (p < 0.01 for all models). Girls, not boys, demonstrated significantly increased KFM0-70 from pre-adolescence to adolescence. Importantly, this was fully explained by kinematic variables. CONCLUSION: Although the marked increase in KFM0-70 seen in girls may play a role in their risk of ACL rupture, the higher values demonstrated by boys during CM reflect the complexity of multifactorial biomechanical risk factor analysis. The role of kinematics in mediating the KFM0-70 provides means for modification of this risk factor, but as boys had higher joint moments, continued investigation into sex-dependent biomechanical risk factors is warranted. LEVEL OF EVIDENCE: II.

[Physique of children and adolescents in Northern Iceland then and now].

INTRODUCTION: In the first half of the 20th century, Icelandic doctors and teachers began documenting the health of school children, believing that physical measurements were important to monitoring physical development. The measurements could also be used for comparison in other areas and for reasearch. At the Reginonal Archives of Skagafjordur, rare data about the physique of children in Saudarkrokur in 1912-1953, measured by Jon Th. Bjornsson, is preserved. MATERIAL AND METHODS: Height, weight, grip strenght, thorax expansion and tidal volume were measured twice in 2018-2019 on 7-15-year-old children in elementary schools in Saudarkrokur and Varmahlid. These measurements were compared with similar measurements from 1912-1953. RESULTS: Children in 2018-2019 at ages 7-15 years were significantly taller, heavier, with greater thorax expansion and tidal volume than their peers in 1912-1953 (p<0,001-0,037). Children in 2018-2019 at ages 7-14 years had significantly higher body mass index than their peers in 1912-1953 (p<0,001-0,027). If adjusted for height and weight in thorax expansion and tidal volume measurements, similar results were found. Children in 2018-2019 had significantly less grip strength than their peers in 1912-1953 at ages 7 and 9-12-years when adjusted for height and weight (p<0,001-0,025). There was significant development in the physique of children over the years 1912-1953 in most measurements and age groups (p<0,001-0,040). CONCLUSIONS: A significant increase in measured factors in 2018-2019 compared to 1912-1953 can possibly be attributed to improved quality of life.

Predictive variables for poor long-term physical recovery after intensive care unit stay: An exploratory study.

BACKGROUND: Elucidating factors that influence physical recovery of survivors after an intensive care unit (ICU) stay is paramount in maximizing long-term functional outcomes. We examined potential predictors for poor long-term physical recovery in ICU survivors. METHODS: Based on secondary analysis of a trial of 50 ICU patients who underwent mobilization in the ICU and were followed for one year, linear regression analysis examined the associations of exposure variables (baseline characteristics, severity of illness variables, ICU-related variables, and lengths of ICU and hospital stay), with physical recovery variables (muscle strength, exercise capacity, and self-reported physical function), measured one year after ICU discharge. RESULTS: When the data were adjusted for age, female gender was associated with reduced muscle strength (P = .003), exercise capacity (P < .0001), and self-reported physical function (P = .01). Older age, when adjusted for gender, was associated with reduced exercise capacity (P < .001). After adjusting for gender and age, an association was observed between a lower score on one or two physical recovery variables and exposure variables, specifically, high body mass index, low functional independence, comorbidity and low self-reported physical function at baseline, muscle weakness at ICU discharge, and longer hospital stay. No adjustment was made for cumulative type I error rate due to small number of participants. CONCLUSION: Elucidating risk factors for poor long-term physical recovery after ICU stay, including gender, may be critical if mobilization and exercise are to be prescribed expediently during and after ICU stay, to ensure maximal long-term recovery.

Effect of Sex on Anterior Cruciate Ligament Injury-Related Biomechanics During the Cutting Maneuver in Preadolescent Athletes.

BACKGROUND: There are 2 movement patterns associated with an anterior cruciate ligament (ACL) injury: dynamic valgus and stiff landing. Although sex-dependent differences have been identified for adults, less is known for preadolescent athletes regarding movement patterns known to load the ACL. HYPOTHESIS: We hypothesized that girls would demonstrate greater vertical ground reaction forces and knee valgus angles. We further hypothesized that the exercise intervention would affect girls more than boys and that this would primarily be demonstrated in less sagittal plane excursions, increased vertical ground reaction forces and knee valgus moments for girls than for boys. STUDY DESIGN: Controlled laboratory study. METHODS: Male and female soccer and handball players (n = 288; age range, 9-12 years) were recruited. A motion capture system synchronized to a force platform was used to record 5 trials of a cutting maneuver before and after a 5-minute fatigue intervention. Linear mixed models were constructed, and analysis of variance was used to analyze differences in outcomes associated with the sex of the athletes. RESULTS: Boys showed greater peak knee valgus moment (0.26 vs 0.22 N·m/kg, respectively; P = .048), peak knee internal rotation moment (-0.13 vs -0.10 N·m/kg, respectively; P = .021), knee rotation excursion (-7.9° vs -6.9°, respectively; P = .014), and knee extension excursion (2.7° vs 1.4°, respectively; P < .001) compared with that in girls. A significant sex × fatigue intervention interaction (F = 7.6; P = .006) was found, which was caused by a greater increase in first peak vertical ground-reaction force (vGRF) from before to after the fatigue intervention for girls (15.3 to 16.0 N/kg) compared with boys (16.4 to 16.5 N/kg). CONCLUSION: Differences detected for biomechanical factors during the cutting maneuver do not point to a greater ACL injury risk for prepubescent or early pubescent girls than for boys. Nonetheless, girls go on to develop more detrimental movement patterns in adolescence than those in boys in terms of biomechanical risk factors. CLINICAL RELEVANCE: Early adolescence is a good target age to learn and develop muscular control; balance, strength; flexibility; and jumping, running, and landing control. This time of physical and athletic growth may therefore be an appropriate period to influence biomechanical factors and thereby task execution and the injury risk.

Needs, motivations, and identification with teaching: a comparative study of temporary part-time and tenure-track health science faculty in Iceland.

BACKGROUND: About 70% of teachers who instruct healthcare students are considered sessional (adjunct/temporary part-time) faculty and receive limited instruction in pedagogy. Sessional faculty may feel isolated and struggle with their teacher identity, and are often assumed to vary in their commitment, motivation, and ability to teach. However, research on teaching identity, motivations, and needs of sessional faculty is lacking. The aim of this study was to compare similarities and differences between sessional and tenure-track faculty across a health science school to guide faculty development for sessional faculty. METHODS: We developed an online needs assessment survey, based on informal interviews and literature reviews. Seventy-eight tenure-track faculty and 160 sessional faculty completed the survey (37, 25% response rate, respectively). We used validated scales to assess intrinsic motivation, identified regulated motivation, and identification with teaching, as well as developed scales (perceived connectedness, motivated by appreciation to try new teaching method) and single items. All scales demonstrated good internal consistency. We compared sessional and tenure-track faculty using t-tests/chi-square values. RESULTS: We found similarities between sessional and tenure-track faculty in intrinsic motivation, identified regulated motivation, and identification with teaching. However, sessional faculty perceived less department connectedness and were more motivated to improve instruction if shown appreciation for trying new teaching methods. Sessional faculty agreed more that they desired pedagogy instruction before starting to teach and that teachers should invest energy in improving their teaching. Admitting to less participation in activities to enhance teaching in the last year, sessional faculty were more interested in digital formats of faculty development. CONCLUSION: Our comparison suggested that sessional faculty value being a teacher as part of their self, similar to tenured faculty, but desired more appreciation for efforts to improve and perceived less connectedness to their university department than tenured faculty. They also preferred digital formats for pedagogy to improve accessibility, prior to and throughout their teaching career to support their development as teachers. Using this information as a guide, we provide suggestions for faculty development for sessional faculty. Supporting sessional faculty in the health sciences should improve the quality of teaching and positively affect student learning.

Factors predicting identity as educators and openness to improve: an exploratory study.

CONTEXT: Researchers suggest that teachers' work environment affects their sense of connectedness and appreciation, which affects their educator identity. However, sessional (also known as adjunct, clinical, contingent and non-tenured) faculty members may struggle with their educator identity. The purpose of this exploratory study was to examine the extent to which perceived connectedness and received appreciation predicted identity as a medical (health care science) educator and openness to improve in tenure-track and sessional faculty members. METHODS: We utilised an 'identification with teaching' scale to measure medical educator identity. We developed scales to measure perceived connectedness to university department, openness to improve teaching, and appreciation as a motivation to try a new teaching method. We then hypothesised a path model between these constructs. We surveyed faculty members at a health sciences school and performed confirmatory factor analyses and structural equation modelling using data from a sample of 73 tenure-track and 146 sessional faculty members to explore support for the hypothesised model. RESULTS: Connectedness and appreciation predicted identity as a medical educator and openness to improve in different ways for sessional and tenure-track faculty members. For tenure-track faculty members, appreciation predicted medical educator identity and openness to improve, whereas a sense of connectedness trended towards predicting an openness to improve. For sessional faculty members, connectedness to their department predicted their identity as a medical educator, which acted as a mediator to predict an openness to improve. DISCUSSION: Our data supported the hypothesised model, but the sessional and tenure-track faculty models differed in strength and focus. We explore reasons for these differences based on the working environment of each teacher type. We suggest that the two models partially explain the transformation from 'a clinician who teaches' to a medical educator. Finally, we make suggestions for how identity as a medical educator and openness to improve may be encouraged in both types of teachers.

Dynamic sitting: Measurement and associations with metabolic health.

Dynamic sitting, such as fidgeting and desk work, might be associated with health, but remains difficult to identify out of accelerometry data. We examined, in a laboratory study, whether dynamic sitting can be identified out of triaxial activity counts. Among 18 participants (56% men, 27.3 ± 6.5 years), up to 236 counts per minute were recorded in the anteroposterior and mediolateral axes during dynamic sitting using a hip-worn accelerometer. Subsequently, we examined in 621 participants (38% men, 80.0 ± 4.7 years) from the AGES-Reykjavik Study whether dynamic sitting was associated with cardio-metabolic health. Compared to participants who recorded the fewest dynamic sitting minutes (Q1), those with more dynamic sitting minutes had a lower BMI (Q2 = -1.39 (95%CI = -2.33;-0.46); Q3 = -1.87 (-2.82;-0.92); Q4 = -3.38 (-4.32;-2.45)), a smaller waist circumference (Q2 = -2.95 (-5.44;-0.46); Q3 = -3.47 (-6.01;-0.93); Q4 = -8.21 (-10.72;-5.71)), and a lower odds for the metabolic syndrome (Q2 = 0.74 [0.45;1.20] Q3 = 0.58 [0.36;0.95]; Q4 = 0.36 [0.22;0.59]). Our findings suggest that dynamic sitting might be identified using accelerometry and that this behaviour was associated with health. This might be important given the large amounts of time people spend sitting. Future studies with a focus on validation, causation and physiological pathways are needed to further examine the possible relevance of dynamic sitting.

Injury Pattern in Icelandic Elite Male Handball Players.

OBJECTIVE: To examine the incidence, type, location, and severity of injuries in Icelandic elite male handball players and compare across factors like physical characteristics and playing position. DESIGN: Prospective cohort study. SETTING: The latter part of the preseason and the competitive season of Icelandic male handball. PARTICIPANTS: Eleven handball teams (185 players) from the 2 highest divisions in Iceland participated in the study. Six teams (109 players) completed the study. VARIABLES MEASURED: Injuries were recorded by the players under supervision from their team physiotherapists or coaches. Coaches recorded training exposure, and match exposure was obtained from the Icelandic and European Handball Federations. The players directly recorded potential risk factors, such as age, height, weight, previous injuries, and player position. MAIN OUTCOME MEASURES: Injury incidence and injury location and number of injury days. RESULTS: Recorded time-loss injuries were 86, of which 53 (62%) were acute and 33 (38%) were due to overuse. The incidence of acute injuries was 15.0 injuries/1000 hours during games and 1.1 injuries/1000 hours during training sessions. No significant difference was found in injury incidence between teams, but number of injury days did differ between teams (P = 0.0006). Acute injuries were most common in knees (26%), ankles (19%), and feet/toes (17%), but overuse injuries occurred in low back/pelvic region (39%), shoulders (21%), and knees (21%). Previous knee injuries were the only potential risk factor found for knee injury. CONCLUSIONS: The results indicate a higher rate of overuse injuries in low back/pelvic region and shoulders than in comparable studies.

Above average increases in body fat from 9 to 15 years of age had a negative impact on academic performance, independent of physical activity.

AIM: The associations between body fat levels and physical activity with academic performance are inconclusive and were explored using longitudinal data. METHODS: We enrolled 134/242 adolescents aged 15, who were studied at the age of nine and agreed to be followed up from April to May 2015 for the Health behaviours of Icelandic youth study. Accelerometers measured physical activity, body mass indexes (BMI) were calculated and dual-energy X-ray absorptiometry scans assessed the participants' body composition at nine and 15. Their language and maths skills were compared to a growth model that estimated the academic performances of children born in 1999. RESULTS: Higher than normal body fat levels between the ages of nine and 15 were negatively associated with maths performance, but the same association was not found for Icelandic language studies. These were Pearson's r = -0.24 (p = 0.01) for BMI and Pearson's r = -0.34 (p = 0.01) for the percentage of body fat. No associations were found with changes in physical activity. CONCLUSION: Children who put on more body fat than normal between the ages of nine and 15 had an increased risk of adverse academic performance that was independent of changes in physical activity.

Preferred posture in lying and its association with scoliosis and windswept hips in adults with cerebral palsy.

Objective: The aim of this study was to clarify the association of scoliosis and windswept hips with immobility, lying position, and time in lying, in adults with cerebral palsy (CP).Methods: This cross-sectional study included 830 adults (469 males and 361 females) with a diagnosis of CP, 16-73 years, and classified at levels I-V according to the Gross Motor Function Classification System (GMFCS). Subjects' Gross motor function classification system level, presence and severity of scoliosis, hip and knee joint range of movement, lying position, postural ability in lying, and time in lying were used to identify connections between them.Results: Adults who are immobile in the lying position have higher odds of both scoliosis and windswept hips. Spending more than 8 h daily in the same lying position, increased the odds of having scoliosis, while lying solely in a supine position, resulted in higher odds of windswept hips.Conclusions: The "preferred" habitual posture frequently observed in immobile adults with CP, leads to established distortion of their body shape. The results indicate the need for early introduction of appropriate posture control, in immobile individuals with CP, from a young age.Implications for rehabilitationThe preferred posture, observed in immobile adults with cerebral palsy, leads to a distortion of their body shape.One in four adults with cerebral palsy use only one position when in bed.The results indicate the need for early introduction of appropriate posture control in individuals unable to change position.

Self-reported health problems and prioritized goals in community-dwelling individuals with spinal cord injury in Sweden.

OBJECTIVE: To explore self-reported health problems and functional goals in community-dwelling individuals with spinal cord injury in Sweden. DESIGN: Cross-sectional descriptive study that used a survey designed by an experienced peer mentor with spinal cord injury. SUBJECTS: Community-dwelling individuals with spinal cord injury from Sweden. METHODS: The survey was distributed online by the community peer-based organization RG Active Rehabilitation. RESULTS: A total of 203 individuals (55% males, 90% acquired spinal cord injury) from all regions in Sweden completed the survey. Of these, 33% reported living with > 2 unbearable physical or psychological problems. While some problems (e.g. problems related to bladder and balance) were consistently ranked to be common across all years since injury and type of spinal cord injury, distribution of some other unbearable problems (e.g. type of pain, excessive weight) varied between subgroups. Years since injury, level of acquired spinal cord injury and sex, but not age-group or type of spinal cord injury, explained some of the variation in the goals. CONCLUSION: The high proportion of reported "unbearable" problems point to the stronger need for systematic, comprehensive, life-long, multi-disciplinary follow-up for people with spinal cord injury. The high rate of goals related to improving strength and fitness across all participants independently of their characteristics highlight the important role of community organizations that offer such lifetime services.

Different cardiorespiratory fitness expressions based on the maximal cycle ergometer test show no effect on the relation of cardiorespiratory fitness to the academic achievement of nine-year-olds.

The relationship between cardiorespiratory fitness and academic achievement has been inconclusive. The results may depend on how cardiorespiratory fitness is expressed. The aim of this study is to explore the impact of different cardiorespiratory fitness expression methods, measured by the maximal cycle ergometer test, on the relationship between cardiorespiratory fitness and academic achievement. A cross-sectional study consisting of 303 Icelandic 4th grade students (163 girls) was conducted. Cardiorespiratory fitness was assessed using a graded maximal cycle ergometer test and scores of standardized tests in Icelandic and math obtained from the Icelandic National Examination Institute. Cardiorespiratory fitness was measured as absolute power output in watts in a maximal progressive cycle ergometer test. To adjust for different body sizes, the power output was scaled to body weight, body height, body surface area, and allometrically expressed body weight. In addition, linear regression scaling was also used to adjust for different body sizes. No significant relationship was found between any of the cardiorespiratory fitness expressions and academic achievement, using both univariate and multivariate linear regression analyses. The use of different methods to express cardiorespiratory fitness does not significantly affect the association with the academic achievement of fourth grade students.

Timing, not magnitude, of force may explain sex-dependent risk of ACL injury.

PURPOSE: The anterior cruciate ligament is loaded through valgus moment, vertical ground reaction force, and internal rotation moment. The aim of this study was to compare the timing of force peaks during early stance between youth girls and boys. METHODS: One-hundred and twenty-nine team sport athletes aged 9-12 completed a total of 2540 cutting maneuvers captured with an 8-camera motion capture system. Timing of early force peaks was analyzed within 100 ms after ground contact. RESULTS: Genders showed different mean (95% CI) time to peak valgus-(32 ms (30-33 ms) vs 37 ms (36-38 ms), P < 0.001) and time to peak internal rotation moments (36 ms (35-37 ms) vs 38 ms (37-39 ms), P = 0.029) but not time to peak vertical ground reaction force [38 ms (37-40 ms) vs 37 ms (36-38 ms, n.s.)]. Girls showed a smaller time between vertical ground reaction force and valgus moment peaks (mean (95% CI) of 1 ms (1-2 ms) vs 7 ms (5-9 ms), P < 0.001), and valgus- and internal rotation moment peaks (0 ms (- 2 to 1.0 ms) vs - 5 ms (- 6 to - 3 ms), P = 0.0003) but not between internal rotation moment and vertical ground reaction force. CONCLUSIONS: Concurrent force peaks are more common for girls compared with boys, leading to more frequent multi-planar loading of the knee. Timing may explain sex-dependent risk of ACL injuries. Exposure to repeated cutting movements may result in greater ACL injury risk due to timing of knee forces as well as magnitude. Such exposure should be minimized for at-risk athletes. LEVEL OF EVIDENCE: III.

Comparison of Summer and Winter Objectively Measured Physical Activity and Sedentary Behavior in Older Adults: Age, Gene/Environment Susceptibility Reykjavik Study.

In Iceland, there is a large variation in daylight between summer and winter. The aim of the study was to identify how this large variation influences physical activity (PA) and sedentary behavior (SB). Free living PA was measured by a waist-worn accelerometer for one week during waking hours in 138 community-dwelling older adults (61.1% women, 80.3 ± 4.9 years) during summer and winter months. In general, SB occupied about 75% of the registered wear-time and was highly correlated with age (ß = 0.36). Although the differences were small, more time was spent during the summer in all PA categories, except for the moderate-to-vigorous PA (MVPA), and SB was reduced. More lifestyle PA (LSPA) was accumulated in ≥5-min bouts during summer than winter, especially among highly active participants. This information could be important for policy makers and health professionals working with older adults. Accounting for seasonal difference is necessary in analyzing SB and PA data.

The effect of asymmetrical limited hip flexion on seating posture, scoliosis and windswept hip distortion.

BACKGROUND: Postural asymmetries with seating problems are common in adults with cerebral palsy. AIMS: To analyse the prevalence of asymmetrical limited hip flexion (<90°) in adults with CP, and to evaluate the association between asymmetrical limited hip flexion and postural asymmetries in the sitting position. METHODS AND PROCEDURES: Cross-sectional data of 714 adults with CP, 16-73 years, GMFCS level I-V, reported to CPUP, the Swedish cerebral palsy national surveillance program and quality registry, from 2013 to 2015. Hip range of motion was analysed in relation to pelvic obliquity, trunk asymmetry, weight distribution, scoliosis and windswept hip distortion. OUTCOMES AND RESULTS: The prevalence of asymmetrical limited hip flexion increased as GMFCS level decreased. Of adults at GMFCS level V, 22% had asymmetrical limited hip flexion (<90°). The odds of having an oblique pelvis (OR 2.6, 95% CI:1.6-2.1), an asymmetrical trunk (OR 2.1, 95% CI:1.1-4.2), scoliosis (OR 3.7, 95% CI:1.3-9.7), and windswept hip distortion (OR 2.6, 95% CI:1.2-5.4) were higher for adults with asymmetrical limited hip flexion compared with those with bilateral hip flexion>90°. CONCLUSIONS AND IMPLICATIONS: Asymmetrical limited hip flexion affects the seating posture and is associated with scoliosis and windswept hip distortion.

Organized leisure-time sport participation and academic achievement in preadolescents.

AIMS: The aims of this study were to study the correlation between lifestyle-related factors, such as organized leisure-time sport participation (OLSP), cardiorespiratory fitness, and adiposity, and academic achievement among preadolescents. METHODS: A cross-sectional study involving 248 nine-year-old school children was carried out. OLSP was self-reported with parental assistance, categorized as ≤ 1× a week, 2-3× a week, and ≥ 4× times a week or more. Academic achievement was estimated with results from standardized test scores in Icelandic and math. Cardiorespiratory fitness was estimated using a maximal cycle ergometer test. The sum of four skinfolds was used to estimate adiposity. RESULTS: Tests of between-subjects effect indicated that OLSP significantly correlated with achievement in math only (F(2,235) = 3.81, p = 0.024). Further analysis showed that the two less active groups had significantly lower scores in math compared to the most active group with OLSP ≥ 4× times a week or more (2-3× times a week, unstandardized coefficient (b) = -4.08, 95% confidence interval (CI) [-7.09, -1.07]; ≤ 1× a week, b = -3.84, 95% CI [-7.59, -0.08]), independent of sex, age, maturity level (age to/from peak height velocity), family structure, and parental education. Neither cardiorespiratory fitness nor adiposity significantly correlated with academic achievements. CONCLUSIONS: The study's result indicates that frequent (four times per week or more often) sport participation is not harmful but may be beneficial to learning. However, further intervention-based study of this topic is needed to determine if this relationship is causal.

Effects of Sex and Fatigue on Biomechanical Measures During the Drop-Jump Task in Children.

BACKGROUND: Female athletes have a higher rate of anterior cruciate ligament (ACL) injury than males from adolescence and into maturity, which is suggested to result from sex-specific changes in dynamic movement patterns with maturation. Few studies have studied movement strategies and response to fatigue in children. PURPOSE: To evaluate the effect of fatigue on biomechanical variables associated with increased risk for ACL injury during a drop-jump (DJ) performance in children. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 116 children (mean age, 10.4 years) were recruited from local sports clubs and performed 5 repetitions of a DJ task before and after a fatigue protocol. Kinematic and kinetic data from initial contact (IC) to the first peak vertical ground reaction force (vGRF) were analyzed for both limbs, including limb and fatigue as within-subject factors for analyses between boys and girls. Pearson correlation coefficients were calculated to identify associations between variables of interest. RESULTS: Girls demonstrated greater peak vGRF values than boys (by 8.1%; P < .05), there were greater peak vGRF values for the right limb than the left (by 6.2%; P < .001), and fatigue led to slightly greater values (P < .05). Although weak, the correlation between peak vGRF values and knee flexion excursion was stronger for girls (r = -0.20) than boys (r = -0.08) (P < .006). Fatigue resulted in greater knee flexion angles at IC and less excursion during landing, more so for girls (by 6.1° vs 1.4°; interaction, P < .001), although the knee flexion moment was generally lowered by fatigue (P < .001). Limb asymmetry in knee flexion moments was more pronounced for boys than for girls (interaction, P < .05), contrary to that seen in frontal plane knee moments, where asymmetry was much greater in girls than boys (interaction, P < .001). CONCLUSION: Even as young athletes, girls and boys seem to adopt dissimilar movement strategies and are differently affected by fatigue. CLINICAL RELEVANCE: Injury prevention programs should be considered at an earlier age in an effort to lower the risk of ACL injury in athletes.

Influence of Day Length and Physical Activity on Sleep Patterns in Older Icelandic Men and Women.

STUDY OBJECTIVES: To identify cross-sectional and seasonal patterns of sleep and physical activity (PA) in community-dwelling, older Icelandic adults using accelerometers. METHODS: A seven-day free-living protocol of 244 (110 female) adults aged 79.7 ± 4.9 years was conducted as part of a larger population-based longitudinal observational-cohort study in the greater Reykjavik area of Iceland. A subpopulation (n = 72) repeated the 7-day measurement during seasonal periods with greater (13.4 ± 1.4 h) and lesser (7.7 ± 1.8 h) daylight. RESULTS: Cross-sectional analyses using multiple linear regression models revealed that day length was a significant independent predictor of sleep duration, mid-sleep, and rise time (all p < 0.05). However, the actual within-individual differences in sleep patterns of the repeaters were rather subtle between periods of longer and shorter day-lengths. Compared to women, men had a shorter sleep duration (462 ± 80 vs. 487 ± 68 minutes, p = 0.008), earlier rise time, and a greater number of awakenings per night (46.5 ± 18.3 vs. 40.2 ± 15.7, p = 0.007), but sleep efficiency and onset latency were similar between the two sexes. Daily PA was also similar between men and women and between periods of longer and shorter day-lengths. BMI, age, gender, and overall PA all contributed to the variations in sleep parameters using multiple regression analysis. CONCLUSIONS: The sleep and PA characteristics of this unique population revealed some gender differences, but there was limited variation in response to significant daylight changes which may be due to long-term adaptation.

Association of change in brain structure to objectively measured physical activity and sedentary behavior in older adults: Age, Gene/Environment Susceptibility-Reykjavik Study.

Many studies have examined the hypothesis that greater participation in physical activity (PA) is associated with less brain atrophy. Here we examine, in a sub-sample (n=352, mean age 79.1 years) of the Age, Gene/Environment Susceptibility-Reykjavik Study cohort, the association of the baseline and 5-year change in magnetic resonance imaging (MRI)-derived volumes of gray matter (GM) and white matter (WM) to active and sedentary behavior (SB) measured at the end of the 5-year period by a hip-worn accelerometer for seven consecutive days. More GM (ß=0.11; p=0.044) and WM (ß=0.11; p=0.030) at baseline was associated with more total physical activity (TPA). Also, when adjusting for baseline values, the 5-year change in GM (ß=0.14; p=0.0037) and WM (ß=0.11; p=0.030) was associated with TPA. The 5-year change in WM was associated with SB (ß=-0.11; p=0.0007). These data suggest that objectively measured PA and SB late in life are associated with current and prior cross-sectional measures of brain atrophy, and that change over time is associated with PA and SB in expected directions.

The association of cardiorespiratory fitness to health independent of adiposity depends upon its expression.

BACKGROUND: The strong relation between cardiorespiratory fitness (CRF) and adiposity renders their independent associations to metabolic risk factors difficult to ascertain. AIM: To determine the associations of CRF and CRF relative to fat-free mass (CRFFFM) to total cholesterol, high-density lipoprotein, low-density lipoprotein, triglycerides, glucose, insulin and homeostasis model assessment (HOMA) and distinguish these relations from the association to adiposity. SUBJECTS AND METHODS: Anthropometrics, body fat percentage (%Fat) and fat-free mass (from dual energy X-ray absorptiometry) were measured in 127 (66 females) 17 and 23 year-olds. CRF from a maximal workload on a graded bicycle test and fasting blood samples were obtained. RESULTS: CRF was significantly related to total cholesterol, triglycerides, insulin and HOMA (r = -0.24 to -0.49, p < 0.03), as were all adiposity measures (r = 0.21-0.53, p < 0.05). Correcting CRF for %Fat rendered the relation to metabolic risk factors non-significant (p = 0.09-0.21); however, CRFFFM was significantly related to the metabolic risk factors (r = -0.25 to -0.32, p < 0.02). CONCLUSIONS: CRFFFM, where adiposity has been removed, is associated with metabolic risk factors, whereas CRF, which is related to adiposity, is not after adjustment for fatness. Previously, independent effects of CRF on health may have been underestimated by using an expression of CRF strongly related to the adiposity measures.