Showing papers in "Scandinavian Journal of Medicine & Science in Sports in 2018"

Muscle thickness correlates to muscle cross‐sectional area in the assessment of strength training‐induced hypertrophy

Abstract: Muscle thickness (MT) measured by ultrasound has been used to estimate cross-sectional area (measured by CT and MRI) at a single time point. We tested whether MT could be used as a valid marker of MRI determined muscle anatomical cross-sectional area (ACSA) and volume changes following resistance training (RT). Nine healthy, young, male volunteers (24 ± 2 y.o., BMI 24.1 ± 2.8 kg/m(2) ) had vastus lateralis (VL) muscle volume (VOL) and ACSAmid (at 50% of femur length, FL) assessed by MRI, and VL MT measured by ultrasound at 50% FL. Measurements were taken at baseline and after 12 weeks of isokinetic RT. Differences between baseline and post-training were assessed by Student's paired t test. The relationships between MRI and ultrasound measurements were tested by Pearson's correlation. After RT, MT increased by 7.5 ± 6.1% (P .05). These data support evidence that MT is a reliable index of muscle ACSAmid and VOL at a single time point. MT changes following RT are associated with parallel changes in muscle ACSAmid but not with the changes in VOL, highlighting the impact of RT on regional hypertrophy.

A comparison of injuries in elite male and female football players: A five-season prospective study.

Abstract: The aim was to compare the epidemiology of injuries between elite male and female football players from the same club. Injuries and individual exposure time in a male team and a female team, both playing in the Spanish first division, were prospectively recorded by the club's medical staff for five seasons (2010-2015) following the FIFA consensus statement. Total, training, and match exposure hours per player-season were 20% higher for men compared to women (P<.01). Total, training, and match injury incidence were 30%-40% higher in men (P≤.04) mainly due to a 4.82 (95% confidence interval [CI] 2.30-10.08) times higher incidence of contusions, as there were no differences in the incidence of muscle and joint/ligament injuries (P≥.44). The total number of absence days was 21% larger in women owing to a 5.36 (95% CI 1.11-25.79) times higher incidence of severe knee and ankle ligament injuries. Hamstring strains and pubalgia cases were 1.93 (95% CI 1.16-3.20) and 11.10 (95% CI 1.48-83.44) times more frequent in men, respectively; whereas quadriceps strains, anterior cruciate ligament ruptures, and ankle syndesmosis injuries were 2.25 (95% CI 1.22-4.17), 4.59 (95% CI 0.93-22.76), and 5.36 (95% CI 1.11-25.79) times more common in women, respectively. In conclusion, prevention strategies should be tailored to the needs of male and female football players, with men more predisposed to hamstring strains and hip/groin injuries, and women to quadriceps strains and severe knee and ankle ligament injuries.

Can chronic stretching change the muscle-tendon mechanical properties? A review.

Abstract: It is recognized that stretching is an effective method to chronically increase the joint range of motion. However, the effects of stretching training on the muscle-tendon structural properties remain unclear. This systematic review with meta-analysis aimed to determine whether chronic stretching alter the muscle-tendon structural properties. Published papers regarding longitudinal stretching (static, dynamic and/or PNF) intervention (either randomized or not) in humans of any age and health status, with more than 2 weeks in duration and at least 2 sessions per week, were searched in PubMed, PEDro, ScienceDirect and ResearchGate databases. Structural or mechanical variables from joint (maximal tolerated passive torque or resistance to stretch) or muscle-tendon unit (muscle architecture, stiffness, extensibility, shear modulus, volume, thickness, cross-sectional area, and slack length) were extracted from those papers. A total of 26 studies were selected, with a duration ranging from 3 to 8 weeks, and an average total time under stretching of 1165 seconds per week. Small effects were seen for maximal tolerated passive torque, but trivial effects were seen for joint resistance to stretch, muscle architecture, muscle stiffness, and tendon stiffness. A large heterogeneity was seen for most of the variables. Stretching interventions with 3- to 8-week duration do not seem to change either the muscle or the tendon properties, although it increases the extensibility and tolerance to a greater tensile force. Adaptations to chronic stretching protocols shorter than 8 weeks seem to mostly occur at a sensory level.

Effect of an acute exercise bout on immediate post-exercise irisin concentration in adults: A meta-analysis.

Abstract: Irisin is a recently discovered myokine that increases adipocyte metabolism, induces further "browning" of white adipose tissue, and enhances glucose metabolism. No study has ever determined how an acute bout of exercise impacts immediate post-exercise irisin concentration using a meta-analytic approach. The purpose of this study is to determine the impact of an acute bout of exercise on the magnitude of post-exercise irisin concentration in adults using meta-analytic procedures. Searches were performed on PubMed, EMBASE, CINAHL, PEDro, SCOPUS, and SPORTDiscus databases. Effect summaries were obtained using random-effects models. Random-effects single and multiple meta-regressions were performed to determine relationships between, and potential confounding effects of, variables of interest. Ten articles were retained for the final meta-analysis, producing 21 study estimates. An acute bout of exercise was accompanied by a post-exercise average increase in irisin concentration of 15.0 (95% CI: 10.8%-19.3%). There was no significant relationship between post-exercise irisin concentration and age, intensity of aerobic exercise, or type of exercise training session (resistance vs aerobic training). Fitness level and body mass index were identified as significant predictive variables for post-exercise irisin concentration. However, a multiple meta-regression model identified fitness level as the single best predictor, with being fit (21.1%±2.2%) associated with a nearly twofold increase in post-exercise irisin concentration, compared with being unfit (11.8%±2.1%). Immediately following an acute bout of exercise, irisin concentration increases substantially in adults, with fitness level as an important modifier for the effect.

Reliable recognition of lying, sitting, and standing with a hip-worn accelerometer.

Abstract: Hip-worn accelerometers are widely used to estimate physical activity (PA), but the accuracy of acceleration threshold-based analysis is compromised when it comes to identifying stationary and sedentary behaviors, let alone classifying body postures into lying, sitting, or standing. The purpose of this study was to devise a novel method for accurate classification of body posture using triaxial data from hip-worn accelerometer and to evaluate its performance in free-living conditions against a thigh-worn accelerometer. The posture classification rested on 2 facts: constant Earth's gravity vector and upright walking posture. Thirty healthy adults wore a hip-mounted accelerometer and underwent an array of lying, sitting, standing, and walking tasks. Task type, their order, and length were randomly assigned to each participant. During walking, the accelerometer orientation in terms of gravity vector was taken as reference, and the angle for posture estimation (APE) was determined from the incident accelerometer orientation in relation to the reference vector. Receiver operating characteristic (ROC) curve yielded an optimal cut-point APE of 64.9° (sensitivity 100% and specificity 100%) for lying and sitting and 11.6° (94.2%; 94.5%) for sitting and standing. In free-living conditions, high agreement (89.2% for original results and 90.4% for median-filtered results) in identifying sedentary periods (sitting and lying) was observed between the results from hip- and thigh-worn accelerometers. Walking provides a valid reference activity to determine the body posture. The proposed APE analysis of the raw data from hip-worn triaxial accelerometer gives accurate and specific information about daily times spent lying, sitting, and standing.

Achilles and patellar tendinopathy display opposite changes in elastic properties: A shear wave elastography study.

Abstract: To compare tendon elastic and structural properties of healthy individuals with those with Achilles or patellar tendinopathy. Sixty-seven participants (22 Achilles tendinopathy, 17 patellar tendinopathy, and 28 healthy controls) were recruited between March 2015 and March 2016. Shear wave velocity (SWV), an index of tissue elastic modulus, and tendon thickness were measured bilaterally at mid-tendon and insertional regions of Achilles and patellar tendons by an examiner blinded to group. Analysis of covariance, adjusted for age, body mass index, and sex was used to compare differences in tendon thickness and SWV between the two tendinopathy groups (relative to controls) and regions. Tendon thickness was included as a covariate for analysis of SWV. Compared to controls, participants with Achilles tendinopathy had lower SWV at the distal insertion (Mean difference MD; 95% CI: -1.56; -2.49 to -0.62 m/s; P < .001) and greater thickness at the mid-tendon (MD 0.19; 0.05-0.33 cm; P = .007). Compared to controls, participants with patellar tendinopathy had higher SWV at both regions (MD 1.25; 0.40-2.10 m/s; P = .005) and greater thickness proximally (MD 0.17; 0.06-0.29 cm; P = .003). Compared to controls, participants with Achilles and patellar tendinopathy displayed lower Achilles tendon elastic modulus and higher patellar tendon elastic modulus, respectively. More research is needed to explore whether maturation, aging, or chronic load underlie these findings and whether current management programs for Achilles and patellar tendinopathy need to be tailored to the tendon.

Secular and longitudinal physical activity changes in population-based samples of children and adolescents.

Abstract: The aims of this study were to investigate whether physical activity (PA) and sedentary time (ST) in 9- and 15-year-olds differed between 2005-2006 and 2011-2012 (secular change), and to investigate changes in PA and ST from age 9 to 15 (longitudinal change). In 2005-2006, we invited nationally representative samples of Norwegian 9- (n=1470) and 15-year-olds (n=1348) to participate. In 2011-2012, we invited a new nationally representative sample of 9-year-olds (n=1945), whereas 15-year-olds (n=1759) were invited to participate either based on previous participation in 2005-2006 or from a random sample of schools. We assessed PA and ST objectively using accelerometers. In 2011-2012, both 9- and 15-year-olds spent more time sedentary (≥35.7 min/d, P 2 h/d (P<.011). We observed an adverse secular change in PA from 2005-2006 to 2011-2012 among 9- and 15-year-olds, and a large decline in PA in the participants followed longitudinally from age 9 to 15 years.

Validity of activity trackers, smartphones, and phone applications to measure steps in various walking conditions.

Abstract: To examine the validity of popular smartphone accelerometer applications and a consumer activity wristband compared to a widely used research accelerometer while assessing the impact of the phone's position on the accuracy of step detection. Twenty volunteers from 2 different age groups (Group A: 18-25 years, n = 10; Group B 45-70 years, n = 10) were equipped with 3 iPhone SE smartphones (placed in pants pocket, shoulder bag, and backpack), 1 Samsung Galaxy S6 Edge (pants pocket), 1 Garmin Vivofit 2 wristband, and 2 ActiGraph wGTX+ devices (worn at wrist and hip) while walking on a treadmill (1.6, 3.2, 4.8, and 6.0 km/h) and completing a walking course. All smartphones included 6 accelerometer applications. Video observation was used as gold standard. Validity was evaluated by comparing each device with the gold standard using mean absolute percentage errors (MAPE). The MAPE of the iPhone SE (all positions) and the Garmin Vivofit was small (<3) for treadmill walking ≥3.2 km/h and for free walking. The Samsung Galaxy and hip-worn ActiGraph showed small MAPE only for treadmill walking at 4.8 and 6.0 km/h and for free walking. The wrist-worn ActiGraph showed high MAPE (17-47) for all walking conditions. The iPhone SE and the Garmin Vivofit 2 are accurate tools for step counting in different age groups and during various walking conditions, even during slow walking. The phone's position does not impact the accuracy of step detection, which substantially improves the versatility for physical activity assessment in clinical and research settings.

Kinetic risk factors of running-related injuries in female recreational runners.

Abstract: Our objective was to prospectively investigate the association of kinetic variables with running-related injury (RRI) risk. Seventy-four healthy female recreational runners ran on an instrumented treadmill while 3D kinetic and kinematic data were collected. Kinetic outcomes were vertical impact transient, average vertical loading rate, instantaneous vertical loading rate, active peak, vertical impulse, and peak braking force (PBF). Participants followed a 15-week half-marathon training program. Exposure time (hours of running) was calculated from start of program until onset of injury, loss to follow-up, or end of program. After converting kinetic variables from continuous to ordinal variables based on tertiles, Cox proportional hazard models with competing risks were fit for each variable independently, before analysis in a forward stepwise multivariable model. Sixty-five participants were included in the final analysis, with a 33.8% injury rate. PBF was the only kinetic variable that was a significant predictor of RRI. Runners in the highest tertile (PBF < -0.27 BW) were injured at 5.08 times the rate of those in the middle tertile and 7.98 times the rate of those in the lowest tertile. When analyzed in the multivariable model, no kinetic variables made a significant contribution to predicting injury beyond what had already been accounted for by PBF alone. Findings from this study suggest PBF is associated with a significantly higher injury hazard ratio in female recreational runners and should be considered as a target for gait retraining interventions.

The effect of Nordic hamstring exercise training volume on biceps femoris long head architectural adaptation.

Abstract: The aim of this study was to determine the time course of architectural adaptations in the biceps femoris long head (BFLH ) following high or low volume eccentric training. Twenty recreationally active males completed a two week standardized period of eccentric Nordic hamstring exercise (NHE) training, followed by four weeks of high (n = 10) or low volume (n = 10) training. Eccentric strength was assessed pre- and post intervention and following detraining. Architecture was assessed weekly during training and after two and four weeks of detraining. After six weeks of training, BFLH fascicles increased significantly in the high (23% ± 7%, P < .001, d = 2.87) and low volume (24% ± 4%, P < .001, d = 3.46) groups, but reversed following two weeks of detraining (high volume: -17% ± 5%, P < .001, d = -2.04; low volume: -15% ± 3%, P < .001, d = -2.56) after completing the intervention. Both groups increased eccentric strength after six weeks of training (high volume: 28% ± 20%, P = .009, d = 1.55; low volume: 34% ± 14%, P < .001, d = 2.09) and saw no change in strength following a four week period of detraining (high volume: -7% ± 7%, P = .97, d = -0.31; low volume: -2% ± 5%, P = .99, d = -0.20). Both low and high volume NHE training stimulate increases in BFLH fascicle length and eccentric knee flexor strength. Architectural adaptations reverted to baseline levels within two weeks after ceasing training, but eccentric strength was maintained for at least four weeks. These observations provide novel insight into the effects of training volume and detraining on BFLH architecture and may provide guidance for the implementation of NHE programs.

Comparability of published cut‐points for the assessment of physical activity: Implications for data harmonization

Abstract: This study aimed to compare estimations of sedentary time (SED) and time spent in physical activity (PA) intensities in children with overweight/obesity across different age-appropriate cut-points based on different body-worn attachment sites and acceleration metrics. A total of 104 overweight/obese children (10.1 ± 1.1 years old, 43 girls) concurrently wore ActiGraph GT3X+ accelerometers on their right hip and non-dominant wrist for 7 days (24 hours). Euclidean norm -1 g (ENMO) and activity counts from both vertical axis (VACounts) and vector magnitude (VMCounts) were derived. We calculated estimates of SED and light, moderate, vigorous, and moderate-to-vigorous (MVPA) intensity PA using different published cut-points for children. The prevalence of children meeting the recommended 60 min/d of MVPA was calculated. The time spent in SED and the different PA intensities largely differed across cut-points based on different attachment sites and acceleration metrics (ie, SED = 11-252 min/d; light PA = 10-217 min/d; moderate PA = 1-48 min/d; vigorous PA = 1-35 min/d; MVPA = 4-66 min/d). Consequently, the prevalence of children meeting the recommended 60 min/d of MVPA varied from 8% to 96% of the study sample. The present study provides a comprehensive comparison between available cut-points for different attachment and acceleration metrics in children. Furthermore, our data clearly show that it is not possible (and probably will never be) to know the prevalence of meeting the PA guidelines based on accelerometer data since apparent differences range from almost zero to nearly everyone meeting the guidelines.

Exercise training in overweight and obese children: Recreational football and high-intensity interval training provide similar benefits to physical fitness.

Abstract: This study compared the effects of recreational football and high-intensity interval training (HIIT) on body composition, muscular fitness, and cardiorespiratory fitness in overweight and obese children. Forty-two overweight/obese males aged 11-13 years [body mass index (BMI) >20.5 kg/m2 ] were randomly assigned to a recreational football training group (n = 14; 157.9 ± 5.8 cm; 63.7 ± 12.6 kg), HIIT group (n = 14; 163.8 ± 9.4 cm; 71.5 ± 10.5 kg), or nontraining control group (n = 14; 162.7 ± 9.3 cm; 67.4 ± 16.1 kg). Physical fitness components were measured at baseline and after 12 weeks of training at the same time of the day and under similar conditions, including body composition, muscular fitness (lower-body power, change-of-direction speed, and flexibility), and cardiovascular fitness (Yo-Yo Intermittent Endurance test distance, resting heart rate, and blood pressure). Lean body mass (4.3%, ES = 0.40; 95% CI: -0.48, 1.29; P = .382) and muscle mass 4.4% (ES = 0.40; 95% CI: -0.48, 1.29; P = .378) very likely increased in the recreational football group, while possible improvements were observed in the HIIT group (lean body mass: 2.5%, ES = 0.22; 95% CI: -0.62, 1.06; P = .607, muscle mass: 2.8%, ES = 0.23; 95% CI: -0.61, 1.07; P = .594). Only trivial increases were observed in the control group for lean body mass (0.5%, ES = 0.05; 95% CI: -0.70, 0.79; P = .906) and muscle mass (1.1%, ES = 0.09; 95% CI: -0.65, 0.83; P = .814). Significant differences were found between the recreational football and control groups in post-training body mass (P = .034) and body mass index (P = .017). Body fat very likely decreased in the recreational football group (-7.7%, ES = -0.41; 95% CI: -1.29, 0.48; P = .376) and possibly decreased in the HIIT group (-5.2%, ES = -0.22; 95% CI: -1.05, 0.62; P = .607), with a trivial reduction in the control group (-1.1%, ES = -0.04; 95% CI: -0.78, 0.70; P = .914). Very likely increases in lower-body power were evident in the recreational football (17.0%, ES = 0.76; 95% CI: -0.15, 1.66; P = .107) and control groups (16.1%, ES = 0.55; 95% CI: -0.20, 1.31; P = .156), while small improvements were observed in the HIIT group (6.0%, ES = 0.24; 95% CI: -0.60, 1.08; P = .580, possible). Likely to most likely improvements in Yo-Yo Intermittent Endurance test performance and change-of-direction speed were noted in the recreational football group (Yo-Yo: 79.8%, ES = 1.09; 95% CI: 0.16, 2.03; P = .025, change-of-direction speed: -10.6%, ES = -1.05; 95% CI: -1.98, -0.12; P = .031) and the HIIT group (Yo-Yo: 81.2%, ES = 1.03; 95% CI: 0.15, 1.92; P = .025, change-of-direction speed: -5.4%, ES = -0.91; 95% CI: -1.79, -0.04; P = .045). Diastolic blood pressure likely decreased in the recreational football (-8.6%, ES = -0.74; 95% CI: -1.64, 0.17; P = .116) and HIIT groups (-9.8%, ES = -0.57; 95% CI: -1.40, 0.30; P = .195), with a possible increase in the control group (1.2%, ES = 0.21; 95% CI: -0.53, 0.96; P = .068). Recreational football and HIIT elicited improvements in all muscular and cardiorespiratory fitness measures. In contrast, the control group, which performed only physical education classes, increased body mass, BMI, and fat mass. Therefore, additional activities such as recreational football or HIIT might counter the prevalence of overweight and obesity in children.

Changes in muscle architecture of biceps femoris induced by eccentric strength training with nordic hamstring exercise.

Abstract: Eccentric strength training alters muscle architecture, but it is also an important factor for the prevention of hamstring injuries. The purpose was to determine the architectural adaptations of the biceps femoris long head (BFlh) after eccentric strength training with nordic hamstring exercise (NHE), followed by a subsequent detraining period. The participants in this intervention (n=23) completed a period of 13 weeks consisting of a first week of control and prior training, followed by 8 weeks of eccentric strength training with NHE, and concluding with a 4-week period of detraining. The architectural characteristics of the BFlh were measured at rest using two-dimensional ultrasound before (M1—week 1) and after (M2—week 9) the eccentric strength training, and at the end of the detraining period (M3—week 13). The muscle fascicle length significantly increased (t=−7.73, d=2.28, P<.001) in M2 compared to M1, as well as the muscle thickness (t=−5.23, d=1.54, P<.001), while the pennation angle presented a significant decrease (t=7.81, d=2.3, P<.001). The muscle fascicle length decreased significantly (t=6.07, d=1.79, P<.001) in M3 compared to M2, while the pennation angle showed a significant increase (t=−4.63, d=1.36, P<.001). The results provide evidence that NHE may cause alterations in the architectural conditions of the BFlh and may have practical implications for injury prevention and rehabilitation programs.

Hamstring Injury Prevention in Soccer: Before or After Training?

Abstract: We examined the effects of a 12-week program of Nordic hamstring exercises (NHE), administered before or after football training, upon eccentric hamstring strength, muscle activity, and architectural adaptations. Amateur soccer players were randomized into three groups. The control group (CON; n=11) undertook core stability exercises, whereas a periodized NHE program was delivered either before (NHEBEF ; n=10) or after (NHEAFT ; n=14) biweekly training sessions. Outcome measures included peak torque and concomitant normalized peak surface electromyography signals (sEMG) of the biceps femoris (BF) and medial hamstring (MH) muscles during knee flexor maximal eccentric contractions, performed at 30°·s-1 . Ultrasonography was used to determine BF muscle thickness, muscle fiber pennation angle, and fascicle length. Performing the NHE derived likely moderate peak torque increases in both NHEBEF (+11.9%; 90% confidence interval: 3.6%-20.9%) and NHEAFT (+11.6%; 2.6%-21.5%) vs CON. Maximum sEMG increases were moderately greater in the BF of both NHE training groups vs CON. There were likely moderate increases in BF muscle thickness (+0.17 cm; 0.05-0.29 cm) and likely small pennation angle increases (+1.03°; -0.08° to 2.14°) in NHEAFT vs CON and NHEBEF . BF fascicle length increases were likely greater in NHEBEF (+1.58 cm; 0.48-2.68 cm; small effect) vs CON and NHEAFT . A 12-week eccentric hamstring strengthening program increased strength and sEMG to a similar magnitude irrespective of its scheduling relative to the football training session. However, architectural adaptations to support the strength gains differed according to the timing of the injury prevention program.

Kinetic demands of sprinting shift across the acceleration phase: Novel analysis of entire force waveforms.

Abstract: A novel approach of analyzing complete ground reaction force waveforms rather than discrete kinetic variables can provide new insight to sprint biomechanics. This study aimed to understand how these waveforms are associated with better performance across entire sprint accelerations. Twenty-eight male track and field athletes (100-m personal best times: 10.88 to 11.96 seconds) volunteered to participate. Ground reaction forces produced across 24 steps were captured during repeated (two to five) maximal-effort sprints utilizing a 54-force-plate system. Force data (antero-posterior, vertical, resultant, and ratio of forces) across each contact were registered to 100% of stance and averaged for each athlete. Statistical parametric mapping (linear regression) revealed specific phases of stance where force was associated with average horizontal external power produced during that contact. Initially, antero-posterior force production during mid-late propulsion (eg, 58%-92% of stance for the second ground contact) was positively associated with average horizontal external power. As athletes progressed through acceleration, this positive association with performance shifted toward the earlier phases of contact (eg, 55%-80% of stance for the eighth and 19%-64% for the 19th ground contact). Consequently, as athletes approached maximum velocity, better athletes were more capable of attenuating the braking forces, especially in the latter parts of the eccentric phase. These unique findings demonstrate a shift in the performance determinants of acceleration from higher concentric propulsion to lower eccentric braking forces as velocity increases. This highlights the broad kinetic requirements of sprinting and the conceivable need for athletes to target improvements in different phases separately with demand-specific exercises.

Return to play, performance, and career duration after anterior cruciate ligament rupture: A case-control study in the five biggest football nations in Europe.

Abstract: A media-based collection and further analysis of relative return to play (RTP) rates and the corresponding quality of play after anterior cruciate ligament (ACL) rupture in top-level football was the aim of our study. In the 5-year case-control study, male players from the first two leagues of the five top leagues in Europe, who sustained a total ACL rupture during the season 2010/11 and/or 2011/12, were included. For them and a matched control sample (ratio 1:2), data were retrieved from the publicly available and validated media-based platforms (transfermarkt.de & whoscored.com) until the end of season 2016/17. Injury and return to play-specific data were calculated as rate ratios (RR) to compare the injured and matched control athletes rates and as a survival analysis (log-rank test; career duration). Overall, 132 ACL-injuries in 125 players occurred. The RTP rate was 98.2%, and the RTP to the same level was 59.4%. Five years post-RTP, 69.9% of the ACL group were still engaged in football (RR = 87%), 40.9% at the same level (RR = 72%). Survival analysis revealed a systematic group difference in career duration compared to controls (Cox-Mantel's χ2 = 5.8; P = 0.016). Game performance (scoring points, P < 0.001; rates/number of completed passes, P = 0.048; and minutes played, P < 0.001) was lower in the ACL athletes than in the matching group in the RTP and post-RTP seasons. Although absolute and relative RTP rates after ACL reconstruction are high in professional football, career duration and game performance are lower than in the reference group.

Within-day energy deficiency and reproductive function in female endurance athletes

Abstract: We aimed to estimate and compare within-day energy balance (WDEB) in athletes with eumenorrhea and menstrual dysfunction (MD) with similar 24-hour energy availability/energy balance (EA/EB). Furthermore, to investigate whether within-day energy deficiency is associated with resting metabolic rate (RMR), body composition, S-cortisol, estradiol, T3 , and fasting blood glucose. We reanalyzed 7-day dietary intake and energy expenditure data in 25 elite endurance athletes with eumenorrhea (n = 10) and MD (n = 15) from a group of 45 subjects where those with disordered eating behaviors (n = 11), MD not related to low EA (n = 5), and low dietary record validity (n = 4) had been excluded. Besides gynecological examination and disordered eating evaluation, the protocol included RMR measurement; assessment of body composition by dual-energy X-ray absorptiometry, blood plasma analysis, and calculation of WDEB in 1-hour intervals. Subjects with MD spent more hours in a catabolic state compared to eumenorrheic athletes; WDEB < 0 kcal: 23.0 hour (20.8-23.4) vs 21.1 hour (4.7-22.3), P = .048; WDEB < -300 kcal: 21.8 hour (17.8-22.4) vs 17.6 hour (3.9-20.9), P = .043, although similar 24-hour EA: 35.6 (11.6) vs 41.3 (12.7) kcal/kg FFM/d, (P = .269), and EB: -659 (551) vs -313 (596) kcal/d, (P = .160). Hours with WDEB <0 kcal and <-300 kcal were inversely associated with RMRratio (r = -.487, P = .013, r = -.472, P = .018), and estradiol (r = -.433, P = .034, r = -.516, P = .009), and positively associated with cortisol (r = .442, P = .027, r = .463, P = .019). In conclusion, although similar 24-hour EA/EB, the reanalysis revealed that MD athletes spent more time in a catabolic state compared to eumenorrheic athletes. Within-day energy deficiency was associated with clinical markers of metabolic disturbances.

The prevalence and severity of health problems in youth elite sports: a 6-month prospective cohort study of 320 athletes.

Abstract: Little is known regarding the overall health of youth elite athletes. Our aim was to describe the prevalence and severity of health problems in a cohort of youth elite athletes representing a variety of endurance, team, and technical sports. Elite sport athletes (N = 260, 16.2 years) from different Sport Academy High Schools in Norway, and a group of their teammates (N = 60, 16.4 years) attending regular high schools, were included in the study. The Oslo Sports Trauma Research Centre (OSTRC) questionnaire on health problems was used to self-report injuries and illnesses for 26 weeks. At any given time, an average of 43% [95% CI: 37%-49%] of the elite sport athletes had some form of health problem and 25% [20%-31%] had substantial health problems. The prevalence of health problems was similar between the elite team sport athletes and their teammates, except for substantial injuries (22% [16%-30%] vs 10% [5%-20%]). Endurance sport athletes reported more illnesses (23% [15%-35%]) than technical and team sport athletes (10% [5%-20%] and 8% [4%-14%]). In contrast, technical and team sport athletes reported more injuries (36% [95% CI: 25-48] and 37% [95% CI 29-45]) compared to endurance sport athletes (15% [8%-25%]). The total impact of health problems was roughly split in thirds between overuse injuries (37%), acute injuries (34%), and illnesses (30%). This is the first prospective study to present self-reported injury and illness data in a large heterogeneous group of youth elite athletes, documenting a substantial impact of both injuries and illnesses on the health of this population.

Effects of fasted vs fed-state exercise on performance and post-exercise metabolism: A systematic review and meta-analysis.

Abstract: The effects of nutrition on exercise metabolism and performance remain an important topic among sports scientists, clinical, and athletic populations. Recently, fasted exercise has garnered interest as a beneficial stimulus which induces superior metabolic adaptations to fed exercise in key peripheral tissues. Conversely, pre-exercise feeding augments exercise performance compared with fasting conditions. Given these seemingly divergent effects on performance and metabolism, an appraisal of the literature is warranted. This review determined the effects of fasting vs pre-exercise feeding on continuous aerobic and anaerobic or intermittent exercise performance, and post-exercise metabolic adaptations. A search was performed using the MEDLINE and PubMed search engines. The literature search identified 46 studies meeting the relevant inclusion criteria. The Delphi list was used to assess study quality. A meta-analysis and meta-regression were performed where appropriate. Findings indicated that pre-exercise feeding enhanced prolonged (P = .012), but not shorter duration aerobic exercise performance (P = .687). Fasted exercise increased post-exercise circulating FFAs (P = .023) compared to fed exercise. It is evidenced that pre-exercise feeding blunted signaling in skeletal muscle and adipose tissue implicated in regulating components of metabolism, including mitochondrial adaptation and substrate utilization. This review's findings support the hypothesis that the fasted and fed conditions can divergently influence exercise metabolism and performance. Pre-exercise feeding bolsters prolonged aerobic performance, while seminal evidence highlights potential beneficial metabolic adaptations that fasted exercise may induce in peripheral tissues. However, further research is required to fully elucidate the acute and chronic physiological adaptations to fasted vs fed exercise.

Exercise-mediated modulation of autophagy in skeletal muscle.

Abstract: Although exercise exerts multiple beneficial health effects, it may also damage cellular structures. Damaged elements are continuously degraded and its constituents recycled to produce renovated structures through a process called autophagy, which is essential for the adaptation to training. Autophagy is particularly active in skeletal muscle, where it can be evaluated using specific molecular markers of activation (unc-51-like kinase 1 [ULK1] phosphorylation) and specific proteins indicating increased autophagosome content (increased total LC3, LC3-II, LC3-II/LC3-I ratio). Studies in humans are technically limited but have provided evidence suggesting the activation of autophagy in skeletal muscle through AMP-activated protein kinase (AMPK) and its downstream target ULK1. Autophagy activation is more likely when the intensity is elevated and the exercise performed in the fasted state. The autophagy-gene program and autophagosome content are upregulated after ultraendurance running competitions. However, autophagosome content is reduced after endurance exercise at moderate intensities (50% and 70% of VO2 max) for 60-120 minutes. Autophagosome content is decreased within the first few hours after resistance training. The effects of regular endurance and strength training on basal autophagy remain to be established in humans. One study has reported that acute severe hypoxia increases autophagosome content in human skeletal muscle, which is reverted by 20 minutes of low-intensity exercise. Experiments with transgenic mice have shown that autophagy is necessary for skeletal muscle adaptation to training. Little is known on how genetic factors, environment, nutrition, drugs and diseases may interact with exercise to modulate autophagy at rest and during exercise in humans.

Comparison of time‐matched aerobic, resistance, or concurrent exercise training in older adults

Abstract: A supervised 12-week intervention of time-matched aerobic vs resistance versus concurrent exercise training was employed to investigate mode- and time course-specific effects of exercise training in older adults. Community-dwelling men and women (n = 84; M/F, 45/39; 69.3 ± 3.5 years; 26.4 ± 3.8 kg m-2 ) were randomly assigned (n = 21 each) to either non-exercise control (CON), aerobic exercise only (AER), resistance exercise only (RES), or concurrent aerobic and resistance exercise (CEX). Training groups trained three times per week, each performing 72 minutes of active exercise time per week. Body composition, physical and cognitive function, and markers of metabolic health were assessed before (PRE), and after 6 (MID) and 12 (POST) weeks of exercise training. Hand-grip strength, 1RM chest press, and arm LBM were improved by both RES and CEX, but not AER. Aerobic fitness increased in AER and RES, but not CEX. Cognitive function improved in all groups, but occurred earlier (ie, at MID) in AER. CEX improved gait speed and lower limb strength and reduced trunk fat compared to either AER or RES. Leg LBM was unchanged in any group. Temporal patterns were observed as early as 6 weeks of training (gait speed, upper and lower limb strength, aerobic fitness), whereas others were unchanged until 12 weeks (hand-grip strength, timed up-and-go, sit-to-stand). Compared to either aerobic or resistance exercise training alone, concurrent exercise training is as efficacious for improving a range of health-related parameters and is more efficacious for increasing gait speed and lower limb strength, and decreasing trunk fat in older adults.

Region‐dependent hamstrings activity in Nordic hamstring exercise and stiff‐leg deadlift defined with high‐density electromyography

Abstract: Recent studies suggest region-specific metabolic activity in hamstring muscles during injury prevention exercises, but the neural representation of this phenomenon is unknown. The aim of this study was to examine whether regional differences are evident in the activity of biceps femoris long head (BFlh) and semitendinosus (ST) muscles during two common injury prevention exercises. Twelve male participants without a history of hamstring injury performed the Nordic hamstring exercise (NHE) and stiff-leg deadlift (SDL) while BFlh and ST activities were recorded with high-density electromyography (HD-EMG). Normalized activity was calculated from the distal, middle, and proximal regions in the eccentric phase of each exercise. In NHE, ST overall activity was substantially higher than in BFlh (d = 1.06 ± 0.45), compared to trivial differences between muscles in SDL (d = 0.19 ± 0.34). Regional differences were found in NHE for both muscles, with different proximal-distal patterns: The distal region showed the lowest activity level in ST (regional differences, d range = 0.55-1.41) but the highest activity level in BFlh (regional differences, d range = 0.38-1.25). In SDL, regional differences were smaller in both muscles (d range = 0.29-0.67 and 0.16-0.63 in ST and BFlh, respectively) than in NHE. The use of HD-EMG in hamstrings revealed heterogeneous hamstrings activity during typical injury prevention exercises. High-density EMG might be useful in future studies to provide a comprehensive overview of hamstring muscle activity in other exercises and high-injury risk tasks.

Whole-body biomechanical differences between limbs exist 9 months after ACL reconstruction across jump/landing tasks

Abstract: **Introduction** Previous studies examining jump tasks after anterior cruciate ligament reconstruction (ACLR) have focused on performance measures without examining joint kinematic and kinetic variables. The aim of this study was to identify differences in biomechanical and performance measures between limbs across tests nine months after surgery. **Methods** Four jump tests (double leg drop jump (DLDJ), single leg drop jump (SLDJ), single leg hop for distance (SLHD) and hurdle hop (HH)) were carried out on 156 male subjects in a 3D‐motion capture laboratory nine months after surgery. Statistical parametric mapping was used to identify differences in jump performance and biomechanical variables between limbs. **Results** Biomechanical measures were lower on the ACLR‐side across all four tests for internal knee valgus moment (Effect Size (ES) 0.77 – 0.92), knee internal rotation angle (ES 0.59 – 0.8) and ankle external rotation moment (ES 0.59 – 0.73), with the centre of mass less posterior to the knee during the single leg tests (ES 0.61 – 0.82). The timing of the largest difference between limbs was not at the same % stance between variables within a test or for any variable across tests. Large ES differences were observed in performance in the SLDJ (ES 0.73‐0.81; LSI 78%) and small differences in the SLHD (ES 0.36; LSI 94%) between the limbs. **Conclusion** Findings highlighted biomechanical differences between limbs which are consistent for jump tasks suggesting insufficient rehabilitation at 9 months post. Results indicate that the SLDJ may identify greater performance deficits between limbs than SLHD, which may over‐estimate rehabilitation status.

Characteristics of acute groin injuries in the hip flexor muscles a detailed MRI study in athletes

Abstract: Acute adductor injuries account for the majority of acute groin injuries; however, little is known about specific injury characteristics, which could be important for the understanding of etiology and management of these injuries. The study aim was to describe acute adductor injuries in athletes using magnetic resonance imaging (MRI). Male athletes with acute groin pain and an MRI confirmed acute adductor muscle injury were prospectively included. MRI was performed within 7 days of injury using a standardized protocol and a reliable assessment approach. 156 athletes presented with acute groin pain of which 71 athletes were included, median age 27 years (range 18-37). There were 46 isolated muscle injuries and 25 athletes with multiple adductor injuries. In total, 111 acute adductor muscle injuries were recorded; 62 adductor longus, 18 adductor brevis, 17 pectineus, 9 obturator externus, 4 gracilis, and 1 adductor magnus injury. Adductor longus injuries occurred at three main injury locations; proximal insertion (26%), intramuscular musculo-tendinous junction (MTJ) of the proximal tendon (26%) and the MTJ of the distal tendon (37%). Intramuscular tendon injury was seen in one case. At the proximal insertion, 12 of 16 injuries were complete avulsions. This study shows that acute adductor injuries generally occur in isolation from other muscle groups. Adductor longus is the most frequently injured muscle in isolation and in combination with other adductor muscle injuries. Three characteristic adductor longus injury locations were observed on MRI, with avulsion injuries accounting for three-quarters of injuries at the proximal insertion, and intramuscular tendon injury was uncommon.

Effects of home‐based exergaming on child social cognition and subsequent prediction of behavior

Abstract: The use of exergames may be one viable way to increase child physical activity, but investigation of its effects on motivation over time and prediction of adherence have seen little research attention. The purpose of this study was to compare the effect of two cycling exergame interventions (single-player, multi-player) among children aged 9-12 years on motivational variables (theory of planned behavior) and to explore whether these variables could predict objective assessment of playtime across 6 weeks. Sixty-nine insufficiently active children were recruited through advertisements within the community/schools and randomized to either the single play condition (n = 30) or multi-player condition (n = 39). Exergaming use was recorded objectively via game logs and motivational variables were assessed after a familiarization session, at 2 weeks, and at 4 weeks. Participants played the exergames M = 133.45 (SD = 81.27) minutes in week 1 to M = 77.23 (SD = 84.09) minutes in week 6. The two exergame conditions did not result in differences among theory of planned behavior variables (P > .05). Mean levels of these constructs declined across the first 4 weeks (P < .05), with the exception of injunctive norm. Positive bivariate associations (P < .05) between game play and perceived control (0-6 weeks), and intention (weeks 3-4 and weeks 5-6) were identified, but only affective attitude (assessed at week 2) predicted (P < .05) game play (3-4 weeks) in a multivariate examination of the theory of planned behavior model. The results demonstrate that social cognitive motives wane across time when exposed to repeated exergame play.

A prospective investigation to evaluate risk factors for lower extremity injury risk in male youth soccer players

Abstract: This article was published in Scandinavian Journal of Medicine and Science in Sports on 26 February 2018, available https://doi.org/10.1111/sms.13013

Analgesic and anti-inflammatory drugs in sports: Implications for exercise performance and training adaptations.

Abstract: Over-the-counter analgesics, such as anti-inflammatory drugs (NSAIDs) and paracetamol, are widely consumed by athletes worldwide to increase pain tolerance, or dampen pain and reduce inflammation from injuries. Given that these drugs also can modulate tissue protein turnover, it is important to scrutinize the implications of acute and chronic use of these drugs in relation to exercise performance and the development of long-term training adaptations. In this review, we aim to provide an overview of the studies investigating the effects of analgesic drugs on exercise performance and training adaptations relevant for athletic development. There is emerging evidence that paracetamol might acutely improve important endurance parameters as well as aspects of neuromuscular performance, possibly through increased pain tolerance. Both NSAIDs and paracetamol have been demonstrated to inhibit cyclooxygenase (COX) activity, which might explain the reduced anabolic response to acute exercise bouts. Consistent with this, NSAIDs have been reported to interfere with muscle hypertrophy and strength gains in response to chronic resistance training in young individuals. Although it remains to be established whether any of these observations also translate into detriments in sport-specific performance or reduced training adaptations in elite athletes, the extensive use of these drugs certainly raises practical, ethical, and important safety concerns that need to be addressed. Overall, we encourage greater awareness among athletes, coaches, and support staff on the potential adverse effects of these drugs. A risk-benefit analysis and professional guidance are strongly advised before the athlete considers analgesic medicine for training or competition.

Two weeks of repetitive gut-challenge reduce exercise-associated gastrointestinal symptoms and malabsorption

Abstract: Debilitating gastrointestinal symptoms are a common feature of endurance running, and may be exacerbated by and (or) limit the ability to tolerate carbohydrate intake during exercise The study aimed to determine whether two weeks of repetitive gut-challenge during running can reduce exercise associated gastrointestinal symptoms and carbohydrate malabsorption Endurance runners (n= 18) performed an initial gut-challenge trial (GC1) comprising 2 h running exercise at 60% VO2max (steady state) whilst consuming a formulated gel-disc containing 30 g carbohydrates (2:1 glucose-fructose, 10% w/v) every 20 min, followed by a 1 h running effort bout Gastrointestinal symptoms, feeding tolerance, and breath hydrogen (H2) were determined along the gut-challenge trial After GC1, participants were randomly assigned to a blinded carbohydrate (CHO, 90 gCHO·h−1) or placebo (PLA, 0 gCHO·h−1) gut-training group This comprised of consuming the group specific feeding intervention during 1 h running exercise at 60% VO2max equivalent, daily over a period of two weeks Participants then repeated the gut-challenge trial (GC2) In GC2, a reduced gut discomfort (P= 0012), total (P= 0009), upper- (P= 0015) and lower-gastrointestinal (P= 0008) symptoms, and nausea (P= 005) were observed on CHO, but not PLA Feeding tolerance did not differ between GC1 and GC2 on CHO and PLA H2 peak was attenuated in GC2 (6 ± 3 ppm) compared to GC1 (13 ± 6 ppm) on CHO (P= 0004), but not on PLA (GC1 11 ± 7 ppm, and GC2 10 ± 10 ppm) The effort bout distance was greater in GC2 (123 ± 13 km) compared with GC1 (117 ± 15 km) on CHO (P= 0035) only Two weeks of repetitive gut-challenge improves gastrointestinal symptoms and reduces carbohydrate malabsorption during endurance running, which may have performance implications This article is protected by copyright All rights reserved

Longitudinal physical activity trajectories from childhood to adulthood and their determinants: The Young Finns Study.

Abstract: Determining lifelong physical activity (PA) trajectories and their determinants is essential to promote a physically active lifestyle throughout the life-course. We aimed to identify PA trajectories from childhood to midlife and their determinants in a longitudinal population-based cohort. This study is a part of the Cardiovascular Risk in Young Finns Study. From 1980, a population-based cohort (N = 3596; 1764 boys/1832 girls, age 3-18 years) has been followed up for 31 years. PA indices were formed based on self-reported data (between age 9-49 years) on frequency, duration, and intensity of leisure (during childhood) or high-intensity (at later age) PA and on sports club participation/competitions. PA trajectories were analyzed using group-based trajectory modeling. Childhood (age 12 years), young adulthood (age 24 years), and early midlife (age 37 years) determinants were analyzed. Five PA trajectories were identified: persistently active (6.6%), decreasingly active (13.9%), increasingly active (13.5%), persistently low active (51.4%, reference group), persistently inactive (14.6%). In childhood, rural residential area (OR 0.45, 95% CI 0.21-0.96) and high academic performance (OR 2.18; 95% CI 1.58-3.00) associated with persistently active group. In early midlife, smoking (OR 1.66; 95% CI 1.07-2.58) associated with persistently inactive group, regular alcohol drinking (OR 2.91; 95% CI 1.12-7.55) with persistently active group and having children (OR 2.07; 95% CI 1.27-3.38) with decreasingly active group. High adulthood education associated with both decreasingly (OR 1.87; 95% CI 1.05-3.35) and increasingly (OR 2.09; 95% CI 1.19-3.68) active groups. We identified five PA trajectories from childhood into midlife. Most prominent determinants were academic achievement, education, having children and health habits (i.e. smoking/alcohol use).

Pitfalls in accelerometer‐based measurement of physical activity: The presence of reactivity in an adult population

Abstract: Objective When a behavior is monitored, it is likely to change, even if no change may be intended. This phenomenon is known as measurement reactivity. We investigated systematic changes in accelerometer-based measures over the days of monitoring as an indicator of measurement reactivity in an adult population. Methods One hundred seventy-one participants from the general population (65% women; mean age = 55 years, range: 42–65 years) wore accelerometers for seven consecutive days to measure sedentary behavior and physical activity. Latent growth models were used (i) to investigate changes in accelerometer wear time over the measurement days and (ii) to identify measurement reactivity indicated by systematic changes in sedentary time (ST), light physical activity (LPA), and moderate-to-vigorous physical activity (MVPA). Results Over the measurement days, participants reduced accelerometer wear time by trend (rate of change [b] = -4.7 min/day, p = 0.051, Cohen's d = 0.38), increased ST (b = 2.4 min/day, p = 0.018, d = 0.39), and reduced LPA (b = -2.4 min/day, p = 0.015, d = 0.38). Participants did not significantly reduce MVPA (p = 0.537). Conclusion Accelerometry might generate reactivity. Our data indicated small effects on ST and LPA. Thus, the validity of accelerometer-based data on ST and LPA may be compromised. Systematic changes observed in accelerometer wear time may further bias accelerometer-based measures. MVPA seems to be less altered due to the presence of an accelerometer. This article is protected by copyright. All rights reserved.