Showing papers in "Scandinavian Journal of Medicine & Science in Sports in 2016"

A simple method for measuring power, force, velocity properties, and mechanical effectiveness in sprint running

Abstract: This study aimed to validate a simple field method for determining force– and power–velocity relationships and mechanical effectiveness of force application during sprint running. The proposed method, based on an inverse dynamic approach applied to the body center of mass, estimates the step-averaged ground reaction forces in runner's sagittal plane of motion during overground sprint acceleration from only anthropometric and spatio-temporal data. Force– and power–velocity relationships, the associated variables, and mechanical effectiveness were determined (a) on nine sprinters using both the proposed method and force plate measurements and (b) on six other sprinters using the proposed method during several consecutive trials to assess the inter-trial reliability. The low bias (<5%) and narrow limits of agreement between both methods for maximal horizontal force (638 ± 84 N), velocity (10.5 ± 0.74 m/s), and power output (1680 ± 280 W); for the slope of the force–velocity relationships ; and for the mechanical effectiveness of force application showed high concurrent validity of the proposed method. The low standard errors of measurements between trials (<5%) highlighted the high reliability of the method. These findings support the validity of the proposed simple method, convenient for field use, to determine power, force, velocity properties, and mechanical effectiveness in sprint running.

Emotional intelligence in sport and exercise: A systematic review.

Abstract: This review targets emotional intelligence (EI) in sport and physical activity. We systematically review the available literature and offer a sound theoretical integration of differing EI perspectives (the tripartite model of EI) before considering applied practice in the form of EI training. Our review identified 36 studies assessing EI in an athletic or physical activity context. EI has most often been conceptualized as a trait. In the context of sport performance, we found that EI relates to emotions, physiological stress responses, successful psychological skill usage, and more successful athletic performance. In the context of physical activity, we found that trait EI relates to physical activity levels and positive attitudes toward physical activity. There was a shortage of research into the EI of coaches, officials, and spectators, non-adult samples, and longitudinal and experimental methods. The tripartite model proposes that EI operates on three levels - knowledge, ability, and trait - and predicts an interplay between the different levels of EI. We present this framework as a promising alternative to trait and ability EI conceptualizations that can guide applied research and professional practice. Further research into EI training, measurement validation and cultural diversity is recommended.

Effects of resistance training with moderate vs heavy loads on muscle mass and strength in the elderly: A meta‐analysis

Abstract: The purpose of the present study was to perform a meta-analysis to compare the efficacy of heavy (∼80% of one repetition maximum, 1RM) vs light-moderate load (∼45% 1RM) resistance training (RT) programs in inducing strength gains and skeletal muscle hypertrophy in elderly people. To assess the role of training volumes, studies in which training protocols were matched for mechanical work were independently analyzed. In all 15 studies included (448 subjects, age 67.8 years), when comparing heavy with light-moderate loads, strength gains tended to be larger following RT with higher intensities of load, with the resulting total population effect being μ = 0.430 (P = 0.060). Effect sizes were substantially smaller in “work-matched” studies (μ = 0.297, P = 0.003). Training with higher loads also provoked marginally larger gains in muscle size, although the degree of training-induced muscle hypertrophy was generally small (0.056 < μ < 0.136). To conclude, provided a sufficient number of repetitions is performed, RT at lower than traditionally recommended intensities of load may suffice to induce substantial gains in muscle strength in elderly cohorts.

In-field gait retraining and mobile monitoring to address running biomechanics associated with tibial stress fracture.

Abstract: We sought to determine if an in-field gait retraining program can reduce excessive impact forces and peak hip adduction without adverse changes in knee joint work during running. Thirty healthy at-risk runners who exhibited high-impact forces were randomized to retraining [21.1 (± 1.9) years, 22.1 (± 10.8) km/week] or control groups [21.0 (± 1.3) years, 23.2 (± 8.7) km/week]. Retrainers were cued, via a wireless accelerometer, to increase preferred step rate by 7.5% during eight training sessions performed in-field. Adherence with the prescribed step rate was assessed via mobile monitoring. Three-dimensional gait analysis was performed at baseline, after retraining, and at 1-month post-retraining. Retrainers increased step rate by 8.6% (P < 0.0001), reducing instantaneous vertical load rate (-17.9%, P = 0.003), average vertical load rate (-18.9%, P < 0.0001), peak hip adduction (2.9° ± 4.2 reduction, P = 0.005), eccentric knee joint work per stance phase (-26.9%, P < 0.0001), and per kilometer of running (-21.1%, P < 0.0001). Alterations in gait were maintained at 30 days. In the absence of any feedback, controls maintained their baseline gait parameters. The majority of retrainers were adherent with the prescribed step rate during in-field runs. Thus, in-field gait retraining, cueing a modest increase in step rate, was effective at reducing impact forces, peak hip adduction and eccentric knee joint work.

Athlete: a working definition for medical and health sciences research

Abstract: It is largely recognized that being physically fit (Blair et al., 1989; Myers et al., 2002; Barry et al., 2014; Brito et al., 2014; Feldman et al., 2015) and adopting a regular exercise routine (Stofan et al., 1998; Blair & Haskell, 2006; Arem et al., 2015) are relevant attributes to a healthy status. While a conceptual distinction between physical activity and exercise was presented 30 years ago (Caspersen et al., 1985), a clear definition of the term athlete for scientific research is still missing. Therefore, it is our aim to provide an unambiguous working definition of the term “athlete”, so that data obtained from scientific experiments performed on “athletes” by different researchers can be compared and contrasted. Because of the lack of an agreed definition of the term “athlete”, cross comparisons between laboratories is presently not readily possible, and it is unsure, where and when the term “athlete” originated. Most likely, the term “athlete” comes from the Greek root “athlos” which means achievement, and therefore it is related to perform exceedingly well. In general, it has been often used in the context of sport competition in ancient and modern Olympic Games as well as World Championships. In essence, athletes are supposedly to be very fit as compared with general population of same sex and age group. Furthermore, athletes have always attracted considerable interest from general population and media and tend to be considered as a model of optimal health. On the other hand, although very rare, an athlete’s death during sport training or competition (Risgaard et al., 2014; Chugh & Weiss, 2015) demonstrates the vulnerability of an apparently very fit and healthy individual. As it could be exemplified by a Sumo wrestler, not all athletes should be expected to be very aerobically fit and to conform to an idealized stereotype. Indeed, in general, athletes tend to represent a very inhomogeneous group in several aspects, including morphological, physiological, psychological, and clinical terms. Searching PubMed in April 5, 2015, we found that 0.13% or 33,372 of the almost 26 million citations include the term athlete(s) in papers’ titles or abstracts. Nevertheless, when searching in the same database by “athlete definition” OR “definition of athlete”, not a single citation was found. Therefore, it seems that health professionals are not, in principle, concerned about the need to define what is meant by the term “athlete”. In addition, we found several criteria or types for classification of athletes in medical and health sciences literature. These types appear as descriptors and are placed before the term “athlete”. After being linked with a given sport or modality (e.g., basketball, football, tennis, swimming, track and field, etc.) or even within position or characteristic (e.g., goalkeeper, defender, etc.), the most frequent criteria were: sex (male and female), age or age categories (young, adult, master, middleaged, old, college, etc.), nature of participation (recreational and competitive), and type of predominant metabolic pathway for energy production or muscle action (strength and endurance). However, when we start to more carefully revise the scientific studies about athletes, it became obvious that there was a lot of misunderstanding and inappropriate use of the term “athlete”, which could influence the differences among institutional guidelines about eligibility of athletes for sport participation (Mitchell et al., 1985; Maron et al., 2001, 2004, 2015; Maron & Zipes, 2005; Pelliccia et al., 2008). Other common classification criteria were “nationality and/or ethnical groups” or “level of performance or competition”. Furthermore, sport participation in an earlier period of the life of the subject may be added as an additional criterion (i.e., former athlete). Another relevant descriptor to be taken into account is the age of the athlete and the corresponding sport modality (Wylleman & Reints, 2010), as the age of peak sport performance was found to be inversely related to increase event duration for explosive power/sprint-type events and to be directly related to increasing duration for endurancetype events (Allen & Hopkins, 2015). In this context, peak performance age was about 20 years to swimmers and 39 years to ultra-distance cyclists. Notwithstanding, it is interesting to point out that athletes’ career seems to be much longer in most recent times.

A pilot study of active rehabilitation for adolescents who are slow to recover from sport‐related concussion

Abstract: The purpose of this study was to examine the effectiveness of an active rehabilitation intervention for adolescents who are slow-to-recover after a sport-related concussion. Ten adolescents (three girls and seven boys) seen at the Montreal Children's Hospital Concussion Clinic participated in this case series. Adolescents who were symptomatic more than 4 weeks after the injury were provided with an active rehabilitation intervention (M = 7.9 weeks following injury; range = 3.7 to 26.2 weeks). The rehabilitation program includes gradual, closely monitored light aerobic exercise, general coordination exercises, mental imagery, as well as reassurance, normalization of recovery, and stress/anxiety reduction strategies. The program continued until complete symptom resolution and readiness to begin stepwise return to activities. The primary outcome of the study was evolution of post-concussion symptoms. Secondary outcomes included mood, energy, balance, and cognition. After the intervention, post-concussion symptoms significantly decreased for the group of participants. They also had decreased fatigue and improved mood after 6 weeks of initiating the rehabilitation intervention. This case series shows that postconcussive symptoms and functioning in adolescents following sports-related concussion can be improved after participation in an active rehabilitation intervention. The introduction of graded light intensity exercise in the post-acute period following concussion is safe, feasible and appears to have a positive impact on adolescents' functioning.

Fundamental movement skills and physical fitness as predictors of physical activity: A 6-year follow-up study

Abstract: The purpose of this study was to examine the extent to which fundamental movement skills and physical fitness scores assessed in early adolescence predict self-reported physical activity assessed 6 years later. The sample comprised 333 (200 girls, 133 boys; M age = 12.41) students. The effects of previous physical activity, sex, and body mass index (BMI) were controlled in the main analyses. Adolescents’ fundamental movement skills, physical fitness, self-report physical activity, and BMI were collected at baseline, and their self-report energy expenditure (metabolic equivalents: METs) and intensity of physical activity were collected using the International Physical Activity Questionnaire 6 years later. Results showed that fundamental movement skills predicted METs, light, moderate, and vigorous intensity physical activity levels, whereas fitness predicted METs, moderate, and vigorous physical activity levels. Hierarchical regression analyses also showed that after controlling for previous levels of physical activity, sex, and BMI, the size of the effect of fundamental movement skills and physical fitness on energy expenditure and physical activity intensity was moderate (R2 change between 0.06 and 0.15), with the effect being stronger for high intensity physical activity.

Neuromuscular and athletic performance following core strength training in elite youth soccer: Role of instability

Abstract: Cross-sectional studies revealed that inclusion of unstable elements in core-strengthening exercises produced increases in trunk muscle activity and thus potential extra stimuli to induce more pronounced performance enhancements in youth athletes. Thus, the purpose of the study was to investigate changes in neuromuscular and athletic performance following core strength training performed on unstable (CSTU) compared with stable surfaces (CSTS) in youth soccer players. Thirty-nine male elite soccer players (age: 17 ± 1 years) were assigned to two groups performing a progressive core strength-training program for 9 weeks (2–3 times/week) in addition to regular in-season soccer training. CSTS group conducted core exercises on stable (i.e., floor, bench) and CSTU group on unstable (e.g., Thera-Band® Stability Trainer, Togu© Swiss ball) surfaces. Measurements included tests for assessing trunk muscle strength/activation, countermovement jump height, sprint time, agility time, and kicking performance. Statistical analysis revealed significant main effects of test (pre vs post) for trunk extensor strength (5%, P < 0.05, d = 0.86), 10–20-m sprint time (3%, P < 0.05, d = 2.56), and kicking performance (1%, P < 0.01, d = 1.28). No significant Group × test interactions were observed for any variable. In conclusion, trunk muscle strength, sprint, and kicking performance improved following CSTU and CSTS when conducted in combination with regular soccer training.

A one‐season prospective study of injuries and illness in elite junior tennis

Abstract: the course of the study, 67 players reported a total of 187 health problems. The average weekly prevalence of all health problems was 21.3% (95% CI: 19.2–22.9), of which 12.1% (95% CI: 10.9–13.3) constituted overuse injuries and 5.8% (95% CI: 4.6–6.9) illnesses. The incidence of acute injuries was 1.2/1000 h of tennis play (95% CI: 0.7–1.7). The high occurrence of overuse injuries among elite junior tennis players suggests that an early focus on preventative measures is warranted, with a particular focus on the monitoring and management of workload.

Pathological tendons maintain sufficient aligned fibrillar structure on ultrasound tissue characterization (UTC).

Abstract: Structural disorganization in the tendon is associated with tendinopathy, with little research investigating whether disorganization overwhelms the overall structural integrity of the tendon. This study investigated the mean cross-sectional area (CSA) of aligned fibrillar structure as detected by ultrasound tissue characterization (UTC) in the pathological and normal Achilles and patellar tendons. Ninety-one participants had their Achilles and/or patellar tendons scanned using UTC to capture a three-dimensional image of the tendon and allow a semi-quantification of the echopattern. The mean CSA of aligned fibrillar structure (echo type I + II) and disorganized structure (echo type III + IV) was calculated based on UTC algorithms. Each tendon was classified as either pathological or normal based solely on gray-scale ultrasound. The mean CSA of aligned fibrillar structure was significantly greater (P ≤ 0.001) in the pathological tendon compared with the normal tendon, despite the pathological tendon containing greater amounts of disorganized structure (P ≤ 0.001). A significant relationship was observed between the mean CSA of disorganized structure and anteroposterior diameter of the Achilles (R(2) = 0.587) and patellar (R(2) = 0.559) tendons. This study is the first to show that pathological tendons have sufficient levels of aligned fibrillar structure. Pathological tendons may compensate for areas of disorganization by increasing in tendon thickness.

Is repetition failure critical for the development of muscle hypertrophy and strength

Abstract: This investigation sought to determine the effect of resistance training to failure on functional, structural and neural elbow flexor muscle adaptation. Twenty-eight males completed a 4-week familiarization period and were then counterbalanced on the basis of responsiveness across; non-failure rapid shortening (RS; rapid concentric, 2 s eccentric), non-failure stretch-shortening (SSC; rapid concentric, rapid eccentric), and failure control (C, 2 s concentric, 2 s eccentric), for a 12-week unilateral elbow flexor resistance training regimen, 3 × week using 85% of one repetition maximum (1RM). 1RM, maximal voluntary contraction (MVC), muscle cross-sectional area (CSA), and muscle activation (EMG(RMS)) of the agonist, antagonist, and stabilizer muscles were assessed before and after the 12-week training period. The average number of repetitions per set was significantly lower in RS 4.2 [confidence interval (CI): 4.2, 4.3] and SSC 4.2 (CI: 4.2, 4.3) compared with C 6.1 (CI: 5.8, 6.4). A significant increase in 1RM (30.5%), MVC (13.3%), CSA (11.4%), and agonist EMG(RMS) (22.1%) was observed; however, no between-group differences were detected. In contrast, antagonist EMG(RMS) increased significantly in SSC (40.5%) and C (23.3%), but decreased in RS (13.5%). Similar adaptations across the three resistance training regimen suggest repetition failure is not critical to elicit significant neural and structural changes to skeletal muscle.

Effect of short-term heat acclimation with permissive dehydration on thermoregulation and temperate exercise performance.

Abstract: We examined the effect of short-term heat acclimation with permissive dehydration (STHADe) on heat acclimation (HA) and cycling performance in a temperate environment. Ten trained male cyclists [mean (SD) maximal oxygen uptake: 63.3(4.0) mL/kg/min; peak power output (PPO): 385(40) W; training: 10 (3) h/week] underwent a STHADe program consisting of 5 days of exercise (maximum 90 min/day) in a hot environment (40 °C, 50% RH) to elicit isothermic heat strain [rectal temperature 38.64(0.27) °C]. Participants abstained from fluids during, and 30 min after, HA sessions. Pre- and post-STHADe HA was evaluated during euhydrated fixed-intensity exercise (60 min) in hot conditions; the effect of STHADe on thermoregulation was also examined under temperate conditions (20 min fixed-intensity exercise; 22 °C, 60% RH). Temperate cycling performance was assessed by a graded exercise test (GXT) and 20-km time trial (TT). STHADe reduced thermal and cardiovascular strain in hot and temperate environments. Lactate threshold [Δ = 16 (17) W] and GXT PPO [Δ = 6 (7) W] were improved following STHADe (P 0.05), although there was a trend for a higher mean power (P = 0.06). In conclusion, STHADE can reduce thermal and cardiovascular strain under hot and temperate conditions and there is some evidence of ergogenic potential for temperate exercise, but longer HA regimens may be necessary for this to meaningfully influence performance.

Vitamin C and E supplementation blunts increases in total lean body mass in elderly men after strength training.

Abstract: The aim of this study was to investigate the effects of vitamin C and E supplementation on changes in muscle mass (lean mass and muscle thickness) and strength during 12 weeks of strength training in elderly men. Thirty-four elderly males (60-81 years) were randomized to either an antioxidant group (500 mg of vitamin C and 117.5 mg vitamin E before and after training) or a placebo group following the same strength training program (three sessions per week). Body composition was assessed with dual-energy X-ray absorptiometry and muscle thickness by ultrasound imaging. Muscle strength was measured as one-repetition maximum (1RM). Total lean mass increased by 3.9% (95% confidence intervals: 3.0, 5.2) and 1.4% (0, 5.4) in the placebo and antioxidant groups, respectively, revealing larger gains in the placebo group (P = 0.04). Similarly, the thickness of m. rectus femoris increased more in the placebo group [16.2% (12.8, 24.1)] than in the antioxidant group [10.9% (9.8, 13.5); P = 0.01]. Increases of lean mass in trunk and arms, and muscle thickness of elbow flexors, did not differ significantly between groups. With no group differences, 1RM improved in the range of 15-21% (P < 0.001). In conclusion, high-dosage vitamin C and E supplementation blunted certain muscular adaptations to strength training in elderly men.

Post-exercise hot water immersion induces heat acclimation and improves endurance exercise performance in the heat

Abstract: We examined whether daily hot water immersion (HWI) after exercise in temperate conditions induces heat acclimation and improves endurance performance in temperate and hot conditions. Seventeen non-heat-acclimatized males performed a 6-day intervention involving a daily treadmill run for 40 min at 65% VO2max in temperate conditions (18 °C) followed immediately by either HWI (N = 10; 40 °C) or thermoneutral (CON, N = 7; 34 °C) immersion for 40 min. Before and after the 6-day intervention, participants performed a treadmill run for 40 min at 65% VO2max followed by a 5-km treadmill time trial (TT) in temperate (18 °C, 40% humidity) and hot (33 °C, 40% humidity) conditions. HWI induced heat acclimation demonstrated by lower resting rectal temperature (Tre , mean, -0.27 °C, P < 0.01), and final Tre during submaximal exercise in 18 °C (-0.28 °C, P < 0.01) and 33 °C (-0.36 °C, P < 0.01). Skin temperature, Tre at sweating onset and RPE were lower during submaximal exercise in 18 °C and 33 °C after 6 days in HWI (P < 0.05). Physiological strain and thermal sensation were also lower during submaximal exercise in 33 °C after 6 days in HWI (P < 0.05). HWI improved TT performance in 33 °C (4.9%, P < 0.01) but not in 18 °C. Thermoregulatory measures and performance did not change in CON. Hot water immersion after exercise on 6 days presents a simple, practical, and effective heat acclimation strategy to improve endurance performance in the heat.

Running performance and thermal sensation in the heat are improved with menthol mouth rinse but not ice slurry ingestion.

Abstract: The purpose of this study was to compare the effects of a cooling strategy designed to predominately lower thermal state with a strategy designed to lower thermal sensation on endurance running performance and physiology in the heat. Eleven moderately trained male runners completed familiarization and three randomized, crossover 5-km running time trials on a non-motorized treadmill in hot conditions (33 °C). The trials included ice slurry ingestion before exercise (ICE), menthol mouth rinse during exercise (MEN), and no intervention (CON). Running performance was significantly improved with MEN (25.3 ± 3.5 min; P = 0.01), but not ICE (26.3 ± 3.2 min; P = 0.45) when compared with CON (26.0 ± 3.4 min). Rectal temperature was significantly decreased with ICE (by 0.3 ± 0.2 °C; P < 0.01), which persisted for 2 km of the run and MEN significantly decreased perceived thermal sensation (between 4 and 5 km) and ventilation (between 1 and 2 km) during the time trial. End-exercise blood prolactin concentration was elevated with MEN compared with CON (by 25.1 ± 24.4 ng/mL; P = 0.02). The data demonstrate that a change in the perception of thermal sensation during exercise from menthol mouth rinse was associated with improved endurance running performance in the heat. Ice slurry ingestion reduced core temperature but did not decrease thermal sensation during exercise or improve running performance.

Short-term low-intensity blood flow restricted interval training improves both aerobic fitness and muscle strength.

Abstract: The present study aimed to analyze and compare the effects of four different interval-training protocols on aerobic fitness and muscle strength. Thirty-seven subjects (23.8 ± 4 years; 171.7 ± 9.5 cm; 70 ± 11 kg) were assigned to one of four groups: low-intensity interval training with (BFR, n = 10) or without (LOW, n = 7) blood flow restriction, high-intensity interval training (HIT, n = 10), and combined HIT and BFR (BFR + HIT, n = 10, every session performed 50% as BFR and 50% as HIT). Before and after 4 weeks training (3 days a week), the maximal oxygen uptake (VO2max ), maximal power output (Pmax ), onset blood lactate accumulation (OBLA), and muscle strength were measured for all subjects. All training groups were able to improve OBLA (BFR, 16%; HIT, 25%; HIT + BFR, 22%; LOW, 6%), with no difference between groups. However, VO2max and Pmax improved only for BFR (6%, 12%), HIT (9%, 15%) and HIT + BFR (6%, 11%), with no difference between groups. Muscle strength gains were only observed after BFR training (11%). This study demonstrates the advantage of short-term low-intensity interval BFR training as the single mode of training able to simultaneously improve aerobic fitness and muscular strength.

Time trends in physical activity from 1982 to 2012 in Finland.

Abstract: The aim of this study was to examine population trends from 1982 to 2012 in Finland for leisure time physical activity (LTPA), commuting physical activity (CPA), occupational physical activity (OPA), and total physical activity. Furthermore, time trends in physical activity by educational levels and body mass index (BMI) categories were explored. Data were collected in independent cross-sectional population surveys, implemented every 5 years from 1982 to 2012. The data comprised 21 903 men and 24 311 women. Participants underwent a health examination and filled in questionnaires. Information on LTPA, CPA, and OPA was used both separately and combined to create an index of total physical activity. Between 1982 and 2012, high LTPA has increased in men (from 21% to 33%) and women (from 12% to 27%). High CPA and high OPA have decreased in men (from 17% to 12% and from 48% to 36%, respectively) and women (from 30% to 20% and from 26% to 21%, respectively). Total physical activity has remained fairly stable. Differences by education and BMI have increased, particularly for LTPA. Marked changes in physical activity have taken place over time. Differences in LTPA and OPA have grown wider across educational groups and BMI categories.

The role of the anterolateral ligament in ACL insufficient and reconstructed knees on rotatory stability: A biomechanical study on human cadavers.

Abstract: Studies suggest that the anterolateral ligament (ALL) is important for knee stability. The purpose was to clarify ALL's effect on rotatory and anterior-posterior stability in the anterior cruciate ligament (ACL)-insufficient and reconstructed knees and the effect of reconstruction of an insufficient ALL. Eighteen cadaveric knees were included. Stability was tested for intact (+ALL), detached (-ALL) and reconstructed (+ reALL) ALL, with ACL removed (-ACL) and reconstructed (+ACL) in six combinations. All were tested in 0, 30, 60, and 90 °C flexion. Anterior-posterior stability was measured with a rolimeter. Rotation with a torque of 8.85 Nm was measured photographically. The ALL was well defined in 78% of knees. ACL reconstruction had a significant effect on anterior-posterior stability. Detaching the ALL had a significant effect on internal rotatory stability and on anterior-posterior stability in ACL-insufficient knees. Reconstruction of ACL and ALL reestablished knee stability. The appearance of the ALL was not uniform. The ALL was an internal rotational stabilizer. Anatomical ALL reconstruction in combination with ACL reconstruction could reestablish stability. ALL reconstruction might be considered in patients with combined ACL and ALL tears, but the clinical effect should be established in a controlled clinical study.

Muscle activation patterns in the Nordic hamstring exercise: Impact of prior strain injury

Abstract: This study aimed to determine: (a) the spatial patterns of hamstring activation during the Nordic hamstring exercise (NHE); (b) whether previously injured hamstrings display activation deficits during the NHE; and (c) whether previously injured hamstrings exhibit altered cross-sectional area (CSA). Ten healthy, recreationally active men with a history of unilateral hamstring strain injury underwent functional magnetic resonance imaging of their thighs before and after six sets of 10 repetitions of the NHE. Transverse (T2) relaxation times of all hamstring muscles [biceps femoris long head (BFlh); biceps femoris short head (BFsh); semitendinosus (ST); semimembranosus (SM)] were measured at rest and immediately after the NHE and CSA was measured at rest. For the uninjured limb, the ST's percentage increase in T2 with exercise was 16.8%, 15.8%, and 20.2% greater than the increases exhibited by the BFlh, BFsh, and SM, respectively (P < 0.002 for all). Previously injured hamstring muscles (n = 10) displayed significantly smaller increases in T2 post-exercise than the homonymous muscles in the uninjured contralateral limb (mean difference −7.2%, P = 0.001). No muscles displayed significant between-limb differences in CSA. During the NHE, the ST is preferentially activated and previously injured hamstring muscles display chronic activation deficits compared with uninjured contralateral muscles.

Caffeine and 3-km cycling performance: Effects of mouth rinsing, genotype, and time of day.

Abstract: We assessed the efficacy of caffeine mouth rinsing on 3-km cycling performance and determined whether caffeine mouth rinsing affects performance gains influenced by the CYP1A2 polymorphism. Thirty-eight recreational cyclists completed four simulated 3-km time trials (TT). Subjects ingested either 6 mg/kg BW of caffeine or placebo 1 h prior to each TT. Additionally, 25 mL of 1.14% caffeine or placebo solution were mouth rinsed before each TT. The treatments were Placebo, caffeine Ingestion, caffeine Rinse and Ingestion+Rinse. Subjects were genotyped and classified as AA homozygotes or AC heterozygotes for the rs762551 polymorphism of the CYP1A2 gene involved in caffeine metabolism. Magnitude-based inferences were used to evaluate treatment differences in mean power output based on a predetermined meaningful treatment effect of 1.0%. AC heterozygotes (4.1%) and AA homozygotes (3.4%) benefited from Ingestion+Rinse, but only AC performed better with Ingestion (6.0%). Additionally, Rinse and Ingestion+Rinse elicited better performance relative to Placebo among subjects that performed prior to 10:00 h (Early) compared with after 10:00 h (Late). The present study provides additional evidence of genotype and time of day factors that affect the ergogenic value of caffeine intake that may allow for more personalized caffeine intake strategies to maximize performance.

Motivational climate, goal orientation, perceived sport ability, and enjoyment within Finnish junior ice hockey players.

Abstract: The aim of this study was to investigate the relations among situational motivational climate, dispositional approach and avoidance achievement goals, perceived sport ability, and enjoyment in Finnish male junior ice hockey players. The sample comprised 265 junior B-level male players with a mean age of 17.03 years (SD = 0.63). Players filled questionnaires tapping their perceptions of coach motivational climate, achievement goals, perceived sport ability, and enjoyment. For the statistical analysis, players were divided into high and low perceived sport ability groups. Multigroup structural equation modeling (SEM) revealed an indirect path from task-involving motivational climate via task-approach goal to enjoyment. Additionally, SEM demonstrated four other direct associations, which existed in both perceived ability groups: from ego-involving motivational climate to ego-approach and ego-avoidance goals; from ego-approach goal to ego-avoidance goal; and from task-avoidance goal to ego-avoidance goal. Additionally, in the high perceived sport ability group, there was an association from task-involving motivational climate to enjoyment. The results of this study reveal that motivational climate emphasizing effort, personal development and improvement, and achievement goal mastering tasks are significant elements of enjoyment in junior ice hockey.

Health and economic burden of running-related injuries in runners training for an event: A prospective cohort study

Abstract: Prospective running-related injury (RRI) data from runners training for an event are scarce, especially with regard to RRI-associated costs. Therefore, the aim of this study was to investigate the prevalence and economic burden of RRIs in runners participating in an organized training program preparing them for an event. This was a prospective cohort study with 18 weeks of follow-up. Individuals aged 18 or older and registered to participate in an organized running program were eligible. Follow-up surveys were sent every 2 weeks to collect data about running exposure, RRIs, and costs. Of the 161 potential participants, 53 (32.9%) were included in this study. A total of 32 participants reported 41 RRIs. The mean prevalence during follow-up was 30.8% [95% confidence interval (CI) 25.6–36.0%]. Overuse was the main mechanism of RRI (85.4%, n = 35). An RRI was estimated to have an economic burden of €57.97 (95% CI €26.17–94.00) due to healthcare utilization (direct costs) and €115.75 (95% CI €10.37–253.73) due to absenteeism from paid work (indirect costs). These results indicate that the health and economic burden of RRIs may be considered significant for public health. Therefore, prevention programs are needed for runners participating in organized training programs.

We will be champions: Leaders' confidence in 'us' inspires team members' team confidence and performance.

Abstract: The present research examines the impact of leaders' confidence in their team on the team confidence and performance of their teammates. In an experiment involving newly assembled soccer teams, we manipulated the team confidence expressed by the team leader (high vs neutral vs low) and assessed team members' responses and performance as they unfolded during a competition (i.e., in a first baseline session and a second test session). Our findings pointed to team confidence contagion such that when the leader had expressed high (rather than neutral or low) team confidence, team members perceived their team to be more efficacious and were more confident in the team's ability to win. Moreover, leaders' team confidence affected individual and team performance such that teams led by a highly confident leader performed better than those led by a less confident leader. Finally, the results supported a hypothesized mediational model in showing that the effect of leaders' confidence on team members' team confidence and performance was mediated by the leader's perceived identity leadership and members' team identification. In conclusion, the findings of this experiment suggest that leaders' team confidence can enhance members' team confidence and performance by fostering members' identification with the team.

Large eccentric strength increase using the Copenhagen Adduction exercise in football: A randomized controlled trial.

Abstract: Hip adductor injuries are frequent in football, and players with low adductor strength appear to be at increased risk of injury. High adductor muscle activity has been shown in the Copenhagen Adduction exercise (CA); however, an associated strength gain has not been investigated. This study aims to examine the eccentric hip adduction strength (EHAD) gain using the CA in-season. Two U-19 sub-elite football teams, including 24 football players, were randomized to either an 8-week supervised progressive training program in addition to the usual training (intervention) or to continue training as usual (control). EHAD, eccentric hip abduction strength (EHAB), and side-bridge endurance were measured using reliable test procedures at baseline and follow-up by a blinded tester. There was a significant interaction between group and time on EHAD, EHAB, and EHAD/EHAB ratio (P 0.335). Compliance was 91.25%, and median muscle soreness ranged from 0 to 2. The CA implemented in-season with an 8-week progressive training program elicited a large significant increase in EHAD, EHAB, and EHAD/EHAB ratio.

Urinary incontinence and other pelvic floor dysfunctions in female athletes in Brazil: A cross-sectional study.

Abstract: The pelvic floor (PF) provides support to all pelvic organs, as well as appropriately closure/opening mechanism of the urethra, vagina, and anus. Therefore, it is likely that female athletes involved in high-impact and in strong-effort activities are at risk for the occurrence of urinary incontinence (UI). This study aimed to investigate the occurrence of UI and other PF dysfunctions (PFD) [anal incontinence (AI), symptoms of constipation, dyspareunia, vaginal laxity, and pelvic organ prolapse] in 67 amateur athletes (AT) compared with a group 96 of nonathletes (NAT). An ad hoc survey based on questions from reliable and valid instruments was developed to investigate the occurrence of PFD symptoms. The risk of UI was higher in AT group (odds ratio: 2.90; 95% CI: 1.50-5.61), mostly among artistic gymnastics and trampoline, followed by swimming and judo athletes. Whereas, AT group reported less straining to evacuate (OR: 0.46; 95% CI: 0.22-0.96), manual assistance to defecate (OR: 0.24; 95% CI: 0.05-1.12), and a higher stool frequency (OR: 0.29; 95% CI: 0.13-0.64) than NAT group. The occurrence of loss of gas and sexual symptoms was high for both groups when compared with literature, although with no statistical difference between them. Pelvic organ prolapse was only reported by nonathletes. Athletes are at higher risk to develop UI, loss of gas, and sexual dysfunctions, either practicing high-impact or strong-effort activities. Thus, pelvic floor must be considered as an entity and addressed as well. Also, women involved in long-term high-impact and strengthening sports should be advised of the impact of such activities on pelvic floor function and offered preventive PFD strategies as well.

"Exercise as medicine" in chronic kidney disease.

Abstract: Exercise and physical activity are increasingly becoming key tools in the treatment and prevention of several medical conditions including arthritis and diabetes; this notion has been termed "exercise as medicine". Exercise has favorable effects on reducing cardiovascular risk, inflammation, cachexia, and hypertension, in addition to increasing physical functioning, strength, and cardio-respiratory capacity. Chronic kidney disease, a condition that affects around 10% of the population, is often overlooked as a target for exercise-based therapy. Despite the vast range of severity in kidney disease (e.g., pre-dialysis, dialysis, transplant), exercise has a potential role in all patients suffering from the condition. In this review, we summarise the important role exercise may have in the clinical management of kidney disease and how this form of 'medicine' should be best administered and 'prescribed'.

Profiles of perfectionism, parental climate, and burnout among competitive junior athletes.

Abstract: Recent research suggests that groups of athletes which differ in terms of perfectionism and perceptions of achievement climate can be identified. Moreover, these groups also differ in terms of burnout symptoms. The purpose of the current study was to extend this research by examining whether discernible groups can be identified based on scores of perfectionism and perceptions of parent-initiated climate and, then, whether these groups differ in terms of burnout. Two-hundred and thirty-seven Swedish junior athletes (124 males and 113 females aged 16-19) from a variety of sports completed measures of athlete burnout, multidimensional perfectionism, and parent-initiated motivational climate. Latent profile analysis identified four groups: non-perfectionistic athletes in a task-involving climate, moderately perfectionistic athletes in a task-involving climate, highly perfectionistic athletes in a task-involving climate, and highly perfectionistic athletes in a mixed climate. The latter two groups reported higher levels of burnout in comparison to other groups. The findings suggest that junior athletes high in perfectionism may be at comparatively greater risk to burnout and that this may especially be the case when they perceive their parents to emphasize concerns about failure and winning without trying one's best.

Determinants of elite-level air rifle shooting performance

Abstract: This study focused on identifying the most important factors determining performance in elite-level air rifle shooting technique. Forty international- and national-level shooters completed a simulated air rifle shooting competition series. From a total of 13 795 shots in 319 tests, shooting score and 17 aiming point trajectory variables were measured with an optoelectronic device and six postural balance variables were measured with force platform. Principal component analysis revealed six components in the air rifle shooting technique: aiming time, stability of hold, measurement time, cleanness of triggering, aiming accuracy, and timing of triggering. Multiple regression analysis identified four of those, namely stability of hold, cleanness of triggering, aiming accuracy, and timing of triggering as the most important predictors of shooting performance, accounting for 81% of the variance in shooting score. The direct effect of postural balance on performance was small, accounting for less than 1% of the variance in shooting score. Indirectly, the effect can be greater through a more stable holding ability, to which postural balance was correlated significantly (R = 0.55, P < 0.001). The results of the present study can be used in assessing athletes' technical strengths and weaknesses and in directing training programs on distinct shooting technical components.

Associations of cardiorespiratory fitness, physical activity, and adiposity with arterial stiffness in children.

Abstract: Associations of cardiorespiratory fitness (CRF), physical activity (PA), sedentary behavior, and body fat percentage (BF%) with arterial stiffness and dilation capacity were investigated in 160 prepubertal children (83 girls) 6-8 years of age We assessed CRF (watts/lean mass) by maximal cycle ergometer exercise test, total PA, structured exercise, unstructured PA, commuting to and from school, recess PA and total and screen-based sedentary behavior by questionnaire, BF% using dual-energy X-ray absorptiometry, and arterial stiffness and dilation capacity using pulse contour analysis Data were adjusted for sex and age Poorer CRF (standardized regression coefficient β = -0297, P < 0001), lower unstructured PA (β = -0162, P = 0042), and higher BF% (β = 0176, P = 0044) were related to higher arterial stiffness When CRF, unstructured PA, and BF% were in the same model, only CRF was associated with arterial stiffness (β = -0246, P = 0006) Poorer CRF was also related to lower arterial dilation capacity (β = 0316, P < 0001) Children with low CRF (< median) and high BF% (≥ median; P = 0002), low CRF and low unstructured PA (< median; P = 0006) or children with low unstructured PA and high BF% (P = 0005) had higher arterial stiffness than children in the opposite halves of these variables Poor CRF was independently associated with increased arterial stiffness and impaired arterial dilation capacity among children

The biomechanics of running in athletes with previous hamstring injury: A case-control study.

Abstract: Hamstring injury is prevalent with persistently high reinjury rates. We aim to inform hamstring rehabilitation by exploring the electromyographic and kinematic characteristics of running in athletes with previous hamstring injury. Nine elite male Gaelic games athletes who had returned to sport after hamstring injury and eight closely matched controls sprinted while lower limb kinematics and muscle activity of the previously injured biceps femoris, bilateral gluteus maximus, lumbar erector spinae, rectus femoris, and external oblique were recorded. Intergroup comparisons of muscle activation ratios and kinematics were performed. Previously injured athletes demonstrated significantly reduced biceps femoris muscle activation ratios with respect to ipsilateral gluteus maximus (maximum difference -12.5%, P = 0.03), ipsilateral erector spinae (maximum difference -12.5%, P = 0.01), ipsilateral external oblique (maximum difference -23%, P = 0.01), and contralateral rectus femoris (maximum difference -22%, P = 0.02) in the late swing phase. We also detected sagittal asymmetry in hip flexion (maximum 8°, P = 0.01), pelvic tilt (maximum 4°, P = 0.02), and medial rotation of the knee (maximum 6°, P = 0.03) effectively putting the hamstrings in a lengthened position just before heel strike. Previous hamstring injury is associated with altered biceps femoris associated muscle activity and potentially injurious kinematics. These deficits should be considered and addressed during rehabilitation.