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Background: There is a lack of a methodological standard to process accelerometer data to measures of physical activity, which impairs data quality and comparability. This study investigated the effect of different combinations of settings of multiple processing components, on the measure of physical activity and the association with measures of cardiometabolic health in an unselected population of middle‐aged individuals. Methods: Free‐living hip accelerometer data, aerobic fitness, body mass index, HDL:total cholesterol ratio, blood glucose, and systolic blood pressure were achieved from 4391 participants 50–64 years old included in The Swedish CArdioPulmonary bioImage Study (SCAPIS) baseline measurement (cross‐sectional). Lab data were also included for calibration of accelerometers to provide comparable measure of physical activity intensity and time spent in different intensity categories, as well as to enhance understanding. The accelerometer data processing components were hardware recalibration, frequency filtering, number of accelerometer axes, epoch length, wear time criterium, time composition (min/24 h vs. % of wear time). Partial least regression and ordinary least regression were used for the association analyses. Results: The setting of frequency filter had the strongest effect on the physical activity intensity measure and time distribution in different intensity categories followed by epoch length and number of accelerometer axes. Wear time criterium and recalibration of accelerometer data were less important. The setting of frequency filter and epoch length also showed consistent important effect on the associations with the different measures of cardiometabolic health, while the effect of recalibration, number of accelerometer axes, wear time criterium and expression of time composition was less consistent and less important. There was a large range in explained variance of the measures of cardiometabolic health depending on the combination of processing settings, for example, 12.1%–20.8% for aerobic fitness and 5.8%–14.0% for body mass index. Conclusions: There was a large variation in the physical activity intensity measure and the association with different measures of cardiometabolic health depending on the combination of settings of accelerometer data processing components. The results provide a fundament for a standard to process hip accelerometer data to assess the physical activity in middle‐aged populations. [ABSTRACT FROM AUTHOR]

Rationale: More research is needed to uncover the effectiveness of combined strength and foam‐rolling interventions to prevent running‐related injuries. Objectives: To evaluate effectiveness of an 18‐week general strength and foam‐rolling intervention on the incidence of running‐related injuries. Method: This is an 18‐week observational comparative study. A total of 433 recreational runners participated (n = 203 female). The intervention group (n = 228) performed general strength and foam‐rolling exercises twice weekly for 18 weeks, the control group (n = 205) maintained their regular training habits. Running volume and running‐related pain were reported weekly. Secondary analyses were performed on the subgroups of the intervention group based on compliance; low compliance (n = 100), intermediate compliance (n = 63), and high compliance (n = 65). Cumulative incidence proportions were calculated and time‐to‐event statistics were performed to compare survival times between groups. Univariate cox proportional hazards ratio was calculated to estimate the risk of running‐related injuries at 18 weeks. Results: A total of 100 running‐related injuries were sustained. The cumulative incidence proportion for the control and intervention groups was 27.1% (95% CI: 21.4–33.9) and 23.0% (95% CI: 17.8–29.4), respectively. No statistically significant difference was found between the overall intervention group and control group (log‐rank p = 0.31). A significant difference existed between the high‐compliance subgroup and the control group (log‐rank p = 0.00). Highly compliant runners were 85% less likely (hazard rate ratio = 0.15; 95% CI: 0.05–0.46) to sustain an injury during the study compared with controls. Conclusion: Recreational runners highly compliant with the intervention were 85% less likely and took on average 57 days longer to sustain a running‐related injury when compared with controls, with a cumulative incidence proportion of 4.6% after 18 weeks. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to investigate how rifle carriage and skiing speed during biathlon roller skiing affect range of motion (ROM) in joint angles and equipment (skis and poles), the vertical distance between shoulders and treadmill (vertdist), as well as possible sex differences associated with rifle carriage. Methods: Fourteen biathletes (6 women, 8 men) roller‐skied on a treadmill at submaximal and simulated race speeds, with (WR) and without (NR) a rifle, using gears 3 and 2. Kinematical data for the whole body, poles, roller‐skis, rifle, and treadmill were monitored using a 3D motion capture system. Movements determined as flexion/extension (x), abduction/adduction (y), and/or internal/external rotation (z) were analyzed for the hip, shoulder, thorax, knee, ankle, elbow, poles, and roller skis. ROM (the difference between maximal and minimal angles) in joints and equipment, and vertdist were analyzed over six skiing cycles during each condition (WR and NR) and speed. Results: The maximal vertdist was lower for WR compared with NR (gear 3: 1.53 ± 0.06 vs 1.54 ± 0.06 m; gear 2: 1.49 ± 0.06 vs 1.51 ± 0.06 m; both p < 0.001). ROM in the upper body was altered when roller skiing WR (movements decreased in thorax and shoulder (x) and increased in elbow (only gear 3) (x), thorax (only gear 2), and shoulder (y) and (z); all p < 0.05) and increased with speed, without differences between sexes (p > 0.05). Conclusion: Since rifle carriage and speed appear to affect the kinematics of roller skiing, coaches, and biathletes are advised to perform skiing technique training under competition‐like conditions (i.e., at race speeds while carrying the rifle). [ABSTRACT FROM AUTHOR]

Burnout is a construct that has garnered considerable attention in sport psychology within recent years. Several hypothesized models regarding how the three dimensions (exhaustion, devaluation, and reduced sense of accomplishment) temporally relate to each other have been advanced. One proposal outlined by Maslach and Leiter suggests that exhaustion predicts devaluation which predicts reduced sense of accomplishment. However, there is no consensus among researchers as it has been argued that exhaustion predicts devaluation and reduced accomplishment separately. The aim of this study was to test multiple alternative hypotheses regarding the relationships of the burnout dimensions in athletes. Two samples of Swedish youth elite athletes with differing time spans between measurements were used. Specifically, one sample involved time‐intensive measures collected every week over an eight‐week period, and the other sample included four measurement points across an 18‐month period. Results showed that none of the previously proposed models outlining the temporal relations of burnout dimensions were supported. Statistical analysis of the models including the cross‐lagged predictions of dimensions did not have any statistically significant impact except when exhaustion negatively predicted devaluation between time 1 (month 0) and time 2 (month 6) in the 18‐month sample; this relation faded in the following time points. Further, issues regarding the stability of devaluation and reduced sense of accomplishment emerged as their autocorrelation were very weak in the time‐intensive sample. These findings raise a number of points for further theoretical and practical discussions about the athlete burnout construct. [ABSTRACT FROM AUTHOR]

The main aim of the Swedish physical activity and fitness cohort study ( SPAF-1958) was to describe physical fitness, physical activity, health, and lifestyle across part of the lifespan, and to assess the influences on these factors from the environment, personal factors, and genetics. There is inevitable dropout from longitudinal studies, and it may be systematic. The aim of this first paper of the second follow-up of SPAF-1958 was to provide a dropout analysis to consider to what extent the participants, at 52 years of age, remain a representative sample of the original adolescent study population. Additional aims were to provide an overview of the study protocol and the ongoing study population. Ongoing study participants in SPAF born in 1958 were, at the second follow-up at the age of 52, still representative of the study cohort in terms of sex, adolescent geographical area, upper secondary school program, adolescent body composition, muscular strength, and muscular endurance. However, a higher physical activity and, among women, a higher aerobic capacity in adolescence decreased the risk for dropout. It is important when interpreting results from longitudinal studies to adjust for the systematic dropout that could bias the conclusions drawn from the results. [ABSTRACT FROM AUTHOR]

To improve current understanding of energy contributions and determinants of sprint-skiing performance, 11 well-trained male cross-country skiers were tested in the laboratory for VO2max, submaximal gross efficiency ( GE), maximal roller skiing velocity, and sprint time-trial ( STT) performance. The STT was repeated four times on a 1300-m simulated sprint course including three flat (1°) double poling ( DP) sections interspersed with two uphill (7°) diagonal stride ( DS) sections. Treadmill velocity and VO2 were monitored continuously during the four STTs and data were averaged. Supramaximal GE during the STT was predicted from the submaximal relationships for GE against velocity and incline, allowing computation of metabolic rate and O2 deficit. The skiers completed the STT in 232 ± 10 s (distributed as 55 ± 3% DP and 45 ± 3% DS) with a mean power output of 324 ± 26 W. The anaerobic energy contribution was 18 ± 5%, with an accumulated O2 deficit of 45 ± 13 mL/kg. Block-wise multiple regression revealed that VO2, O2 deficit, and GE explained 30%, 15%, and 53% of the variance in STT time, respectively (all P < 0.05). This novel GE-based method of estimating the O2 deficit in simulated sprint-skiing has demonstrated an anaerobic energy contribution of 18%, with GE being the strongest predictor of performance. [ABSTRACT FROM AUTHOR]

Low or reduced energy availability ( LEA) is linked to functional hypothalamic oligomenorrhea/amenorrhea ( FHA), which is frequently reported in weight-sensitive sports. This makes LEA a major nutritional concern for female athletes. The aim of this study was to describe dietary characteristics of athletes with LEA and/or FHA. Endurance athletes ( n = 45) were recruited from national teams and competitive clubs. Protocols included gynecological examination, body composition, eating disorder evaluation, and 7-day dietary intake and EA assessment. Athletes with disordered eating behavior/eating disorders ( n = 11), menstrual dysfunction other than FHA ( n = 5), and low dietary record validity ( n = 4) were excluded. Remaining subjects ( n = 25) were characterized by EA [optimal: ≥ 45 kcal (188 kJ)/kg fat-free mass ( FFM)/day ( n = 11), LEA: < 45 kcal (188 kJ)/kg FFM/day ( n = 14)] and reproductive function [eumenorrhea ( EUM; n = 10), FHA ( n = 15)]. There was no difference in EA between FHA and EUM subjects. However, FHA and LEA subjects shared the same dietary characteristics of lower energy density ( ED) [( P = 0.012; P = 0.020), respectively], and fat content [( P = 0.047; P = 0.027), respectively]. Furthermore, FHA subjects had a lower intake of carbohydrate-rich foods ( P = 0.019), higher fiber content ( P < 0.001), and drive for thinness score ( P = 0.003). Conclusively, low ED together with high fiber content may constitute targets for dietary intervention in order to prevent and treat LEA and FHA in female athletes. [ABSTRACT FROM AUTHOR]

Physical activity in children is associated with several positive health outcomes such as decreased cardiovascular risk factors, improved lung function, enhanced motor skill development, healthier body composition, and also improved defense against inflammatory diseases. We examined how high physical activity vs a sedentary lifestyle in young children influences the immune response with focus on autoimmunity. Peripheral blood mononuclear cells, collected from 55 5-year-old children with either high physical activity ( n = 14), average physical activity ( n = 27), or low physical activity ( n = 14), from the All Babies In Southeast Sweden ( ABIS) cohort, were stimulated with antigens (tetanus toxoid and beta-lactoglobulin) and autoantigens ( GAD65, insulin, HSP60, and IA-2). Immune markers (cytokines and chemokines), C-peptide and proinsulin were analyzed. Children with high physical activity showed decreased immune activity toward the autoantigens GAD65 ( IL-5, P < 0.05), HSP60 and IA-2 ( IL-10, P < 0.05) and also low spontaneous pro-inflammatory immune activity ( IL-6, IL-13, IFN-γ, TNF-α, and CCL2 ( P < 0.05)) compared with children with an average or low physical activity. High physical activity in young children seems to have positive effects on the immune system by altering autoantigen-induced immune activity. [ABSTRACT FROM AUTHOR]

This observational study investigated skydiver neck muscle activity during parachute opening shock ( POS), as epidemiological data recently suggested neck pain in skydivers to be related to POS. Twenty experienced skydivers performed two terminal velocity skydives each. Surface electromyography quantified muscle activity bilaterally from the anterior neck, the upper and lower posterior neck, and the upper shoulders; and two triaxial accelerometers sampled deceleration. Muscle activity was normalized as the percentage of reference maximum voluntary electrical activity (% MVE); and temporal muscle activity onset was related to POS onset. Our results showed that neck muscle activity during POS reached mean magnitudes of 53-104% MVE, often exceeding reference activity in the lower posterior neck and upper shoulders. All investigated muscle areas' mean temporal onsets occurred <50 ms after POS onset (9-34 ms latencies), which is consistent with anticipatory motor control. The high muscle activity observed supports that the neck is under substantial strain during POS, while temporal muscle activation suggests anticipatory motor control to be a strategy used by skydivers to protect the cervical spine from POS. This study's findings contribute to understanding the high rates of POS-related neck pain, and further support the need for evaluation of neck pain preventative strategies. [ABSTRACT FROM AUTHOR]

Cardiac biomarker release after exercise is well documented in endurance sports, but neither the impact of intermittent high-intensity exercise nor the reproducibility has yet been established. Floorball, a popular sport in Scandinavia, involves intermittent periods of high-intensity exercise. This study aimed to determine the prevalence and reproducibility of elevated cardiac marker levels among elite floorball players after two games. Twenty-three healthy male elite floorball players of median age 19 years (range 16-34 years) participated in two standard games. Blood was drawn at three time points: pregame, immediately after, and 2 h after the game. Creatine kinase MB ( CK- MB), myoglobin, and high-sensitivity cardiac troponin T (hs- cTnT) were measured. The results showed significantly elevated median postgame values in all markers. In both games, hs- cTnT exceeded the cutoff for myocardial damage (≥ 14 ng/L) 2 h postgame in the same six players. The major findings were that postgame cardiac hs- cTnT values among elite floorball players were significantly elevated and reproducible. The findings imply that extended investigations should incorporate evaluation of myocardial function and myocardial perfusion during exercise to seek the clinical significance and underlying mechanisms of elevated cardiac troponin after high-intensity exercise. [ABSTRACT FROM AUTHOR]

The long-term consequences on knee muscle strength some decades after rupture of the anterior cruciate ligament ( ACL) are not established. The aims of our study were to examine peak torque more than 20 years after ACL injury and to compare their knee muscle strength to that of healthy controls. We tested 70 individuals with unilateral ACL injury 23 ± 2 years after injury, whereof 33 (21 men) were treated with physiotherapy in combination with ACL reconstruction ( ACLR) and 37 (23 men) with physiotherapy alone ( ACLPT). These were compared with 33 age- and gender-matched controls (21 men). A Kin- Com® dynamometer (90°/s) was used to measure peak torque in knee flexion and extension in both concentric and eccentric contractions. Knee extension peak torque, concentric and eccentric, was ∼10% lower for the injured leg compared with the non-injured leg for both ACLR ( P < 0.001; P < 0.001) and ACLPT ( P = 0.007; P = 0.002). The ACLPT group also showed reduced eccentric knee flexion torque of the injured leg ( P = 0.008). The strength of the non-injured leg in both ACL groups was equal to that of controls. No difference was seen for those with no-or-low degree of knee osteoarthritis compared to those with moderate-to-high degree of osteoarthritis. ACL injury may lead to a persistent reduction of peak torque in the injured leg, which needs to be considered across the lifespan. [ABSTRACT FROM AUTHOR]

The aim was to study long-term effects on motor skills and school performance of increased physical education (PE). All pupils born 1990-1992 from one school were included in a longitudinal study over nine years. An intervention group ( n = 129) achieved daily PE (5 × 45 min/week) and if needed one extra lesson of adapted motor training. The control group ( n = 91) had PE two lessons/week. Motor skills were evaluated by the Motor Skills Development as Ground for Learning observation checklist and school achievements by marks in Swedish, English, Mathematics, and PE and proportion of pupils who qualified for upper secondary school. In school year 9 there were motor skills deficits in 7% of pupils in the intervention group compared to 47% in the control group ( P < 0.001), 96% of the pupils in the intervention group compared to 89% in the control group ( P < 0.05) qualified for upper secondary school. The sum of evaluated marks was higher among boys in the intervention group than in the control group ( P < 0.05). The sum of marks was also higher in pupils with no motor skills deficit than among pupils with motor skills deficits ( P < 0.01), as was the proportion of pupils who qualified for upper secondary school (97% vs 81%, P < 0.001). Daily PE and adapted motor skills training during the compulsory school years is a feasible way to improve not only motor skills but also school performance and the proportion of pupils who qualify for upper secondary school. [ABSTRACT FROM AUTHOR]

Studies have shown that reduced neuromuscular control or strength increases the risk of acute injuries. It is hypothesized that a non-functional movement pattern can predispose for injuries. In the present paper a detailed description of a test battery consisting of nine different tests to screen athletic movement pattern is provided. The aim was to evaluate the inter- and intra-rater reliability of the test battery on a group of male elite soccer players. Twenty-six healthy elite soccer players (17-28 years) were screened. Eighteen participated at a second occasion 7 days later. No significant difference ( P=0.31) was found between test occasion 1 (LS means 18.3, 95% confidence interval 14.9-21.7) and test occasion 2 (18.0, 14.4-21.7) in the mean total score of the test battery. No significant difference in the inter-rater reliability was found between the eight physiotherapists at the two test occasions. The intra-class correlation coefficient was 0.80 and 0.81, respectively. The test battery showed good inter- and intra-rater reliability. The screening battery is easy to use for familiarized professionals and requires minimal equipment. However, further studies are needed to confirm the validity of the test battery in injury prevention, rehabilitation and performance enhancement. [ABSTRACT FROM AUTHOR]

The aim was to investigate injury risk factors in junior tennis players. Fifty-five players, 35 boys and 20 girls, answered a questionnaire about training habits, time of exposure, previous injuries and equipment factors. A battery of clinical tests and functional performance tests were also carried out. All tennis-related injuries that occurred during a 2-year period were identified and recorded. An injury was defined as an injury if it was impossible to participate in regular tennis training or playing matches during at least one occasion, a time loss injury. Potential injury risk factors were tested in a forward stepwise logistic regression model for injury. Thirty-nine players sustained totally 100 new and recurrent injuries. Injuries to the lower extremity were the most common ones (51%) followed by the upper extremity (24%) and the trunk (24%). Injured players performed more singles per week ( P<0.0001) and played more tennis hours per year ( P=0.016) than the uninjured players. Playing tennis more than 6 h/week was found to be a risk factor for back pain. A previous injury regardless of location was identified as an injury risk factor, and a previous injury to the back was a risk factor for back pain. [ABSTRACT FROM AUTHOR]

Osteoarthritis (OA) of the knee can be defined as primary (non-traumatic) or secondary (post-traumatic). Both non-traumatic OA and post-traumatic OA have been described predominantly in the medial compartment of the knee. The objective of this study was to compare the location of structural radiographic changes in non-traumatic OA and post-traumatic OA. A non-traumatic cohort, consisting of 155 patients suffering from chronic knee pain without known major injuries, was compared with a post-traumatic cohort, consisting of 176 patients, all of whom had sustained an anterior cruciate ligament injury while playing soccer. A standardized weight-bearing knee radiography of the tibiofemoral joint was performed. Joint space narrowing (JSN) and osteophytes were graded according to the radiographic atlas of the Osteoarthritis Research Society International. JSN and osteophytes were located predominantly in the medial compartment in the non-traumatic cohort. In the post-traumatic cohort, structural changes were evenly distributed between the lateral and the medial compartments. We were thus able to demonstrate radiological differences between post-traumatic and non-traumatic OA. [ABSTRACT FROM AUTHOR]