Showing papers in "Medicine and Science in Sports and Exercise in 2013"
TL;DR: The recent status of possible markers for the detection of overtraining syndrome is provided and it is generally thought that symptoms of OTS, such as fatigue, performance decline, and mood disturbances, are more severe than those of NFOR.
Abstract: Successful training not only must involve overload but also must avoid the combination of excessive overload plus inadequate recovery. Athletes can experience short-term performance decrement without severe psychological or lasting other negative symptoms. This functional overreaching will eventually lead to an improvement in performance after recovery. When athletes do not sufficiently respect the balance between training and recovery, nonfunctional overreaching (NFOR) can occur. The distinction between NFOR and overtraining syndrome (OTS) is very difficult and will depend on the clinical outcome and exclusion diagnosis. The athlete will often show the same clinical, hormonal, and other signs and symptoms. A keyword in the recognition of OTS might be "prolonged maladaptation" not only of the athlete but also of several biological, neurochemical, and hormonal regulation mechanisms. It is generally thought that symptoms of OTS, such as fatigue, performance decline, and mood disturbances, are more severe than those of NFOR. However, there is no scientific evidence to either confirm or refute this suggestion. One approach to understanding the etiology of OTS involves the exclusion of organic diseases or infections and factors such as dietary caloric restriction (negative energy balance) and insufficient carbohydrate and/or protein intake, iron deficiency, magnesium deficiency, allergies, and others together with identification of initiating events or triggers. In this article, we provide the recent status of possible markers for the detection of OTS. Currently, several markers (hormones, performance tests, psychological tests, and biochemical and immune markers) are used, but none of them meet all the criteria to make their use generally accepted.
884 citations
TL;DR: A classification algorithm using 13 features shows good classification into the four classes given the complexity of the activities in the original data set, and could be implemented in real time on mobile devices with only 4-s latency.
Abstract: AB Purpose: Large physical activity surveillance projects such as the UK Biobank and NHANES are using wrist-worn accelerometer-based activity monitors that collect raw data. The goal is to increase wear time by asking subjects to wear the monitors on the wrist instead of the hip, and then to use information in the raw signal to improve activity type and intensity estimation. The purposes of this work was to obtain an algorithm to process wrist and ankle raw data and to classify behavior into four broad activity classes: ambulation, cycling, sedentary, and other activities. Methods: Participants (N = 33) wearing accelerometers on the wrist and ankle performed 26 daily activities. The accelerometer data were collected, cleaned, and preprocessed to extract features that characterize 2-, 4-, and 12.8-s data windows. Feature vectors encoding information about frequency and intensity of motion extracted from analysis of the raw signal were used with a support vector machine classifier to identify a subject's activity. Results were compared with categories classified by a human observer. Algorithms were validated using a leave-one-subject-out strategy. The computational complexity of each processing step was also evaluated. Results: With 12.8-s windows, the proposed strategy showed high classification accuracies for ankle data (95.0%) that decreased to 84.7% for wrist data. Shorter (4 s) windows only minimally decreased performances of the algorithm on the wrist to 84.2%. Conclusions: A classification algorithm using 13 features shows good classification into the four classes given the complexity of the activities in the original data set. The algorithm is computationally efficient and could be implemented in real time on mobile devices with only 4-s latency.
368 citations
TL;DR: It is suggested that sufficient MVPA did not ameliorate the negative associations between SB and cardiometabolic risk factors or functional limitations in the current sample and that there was independence on a multiplicative scale in their associations with the outcomes examined.
Abstract: AB Introduction: The purpose of this study was to examine the association between sedentary behavior (SB), cardiometabolic risk factors, and self-reported physical function by level of moderate-vigorous physical activity (MVPA). Methods: Cross-sectional analysis was completed on 1914 older adults age >=65 yr from the 2003-2006 U.S. National Health and Nutrition Examination Survey. MVPA and SB were derived from ActiGraph accelerometers worn for 1 wk. MVPA was categorized as sufficient to meet the current U.S. guidelines (>=150 min[middle dot]wk-1) or not; SB was split into quartiles. Various biomarkers were examined in laboratory analyses and physical exams, and the number of functional limitations was self-reported. Statistical interaction between SB and MVPA on the biomarker associations was the primary analysis, followed by an examination of their independent associations with relevant covariate adjustment. Results: Average SB was 9.4 +/- 2.3 h[middle dot]d-1 (mean +/- SD), and approximately 35% were classified as sufficiently active. Overall, no significant meaningful statistical interactions were found between SB and MVPA for any of the outcomes; however, strong independent positive associations were found between SB and weight (P
252 citations
TL;DR: It is hypothesized that patterns of knee injuries in U.S. high school sports differ by sport and sex, and continuing efforts to develop preventive interventions could reduce the burden of these injuries.
Abstract: AB Purpose: U.S. high school athletes sustain millions of injuries annually. Detailed patterns of knee injuries, among the most costly sports injuries, remain largely unknown. We hypothesize that patterns of knee injuries in U.S. high school sports differ by sport and sex. Methods: U.S. high school sports-related injury data were collected for 20 sports using the National High School Sports-Related Injury Surveillance System, High School RIO(TM). Knee injury rates, rate ratios (RR), and injury proportion ratios were calculated. Results: From 2005/2006 to 2010/2011, 5116 knee injuries occurred during 17,172,376 athlete exposures (AE) for an overall rate of 2.98 knee injuries per 10,000 AE. Knee injuries were more common in competition than in practice (rate ratio = 3.53, 95% confidence interval [CI] = 3.34-3.73). Football had the highest knee injury rate (6.29 per 10,000 AE) followed by girls' soccer (4.53) and girls' gymnastics (4.23). Girls had significantly higher knee injury rates than boys in sex-comparable sports (soccer, volleyball, basketball, baseball/softball, lacrosse, swimming and diving, and track and field; RR = 1.52, 95% CI = 1.39-1.65). The most commonly involved structure was the medial collateral ligament (reported in 36.1% of knee injuries), followed by the patella/patellar tendon (29.5%), anterior cruciate ligament (25.4%), meniscus (23.0%), lateral collateral ligament (7.9%), and posterior cruciate ligament (2.4%). Girls were significantly more likely to sustain anterior cruciate ligament injuries in sex-comparable sports (RR = 2.38, 95% CI = 1.91-2.95). Overall, 21.2% of knee injuries were treated with surgery; girls were more often treated with surgery than boys in sex-comparable sports (injury proportion ratio = 1.30, 95% CI = 1.11-1.53). Conclusions: Knee injury patterns differ by sport and sex. Continuing efforts to develop preventive interventions could reduce the burden of these injuries.
246 citations
TL;DR: FFS exhibit both lower patellofemoral stress and knee frontal plane moment than RFS, which may reduce the risk of running-related knee injuries, and parallel increase in ankle plantarflexor and Achilles tendon loading may increase risk for ankle and foot injuries.
Abstract: AB Purpose: Knee pain and Achilles tendinopathies are the most common complaints among runners. The differences in the running mechanics may play an important role in the pathogenesis of lower limb overuse injuries. However, the effect of a runner's foot strike pattern on the ankle and especially on the knee loading is poorly understood. The purpose of this study was to examine whether runners using a forefoot strike pattern exhibit a different lower limb loading profile than runners who use rearfoot strike pattern. Methods: Nineteen female athletes with a natural forefoot strike (FFS) pattern and pair-matched women with rearfoot strike (RFS) pattern (n = 19) underwent 3-D running analysis at 4 m[middle dot]s-1. Joint angles and moments, patellofemoral contact force and stresses, and Achilles tendon forces were analyzed and compared between groups. Results: FFS demonstrated lower patellofemoral contact force and stress compared with heel strikers (4.3 +/- 1.2 vs 5.1 +/- 1.1 body weight, P = 0.029, and 11.1 +/- 2.9 vs 13.0 +/- 2.8 MPa, P = 0.04). In addition, knee frontal plane moment was lower in the FFS compared with heel strikers (1.49 +/- 0.51 vs 1.97 +/- 0.66 N[middle dot]m[middle dot]kg-1, P =0.015). At the ankle level, FFS showed higher plantarflexor moment (3.12 +/- 0.40 vs 2.54 +/- 0.37 N[middle dot]m[middle dot]kg-1; P = 0.001) and Achilles tendon force (6.3 +/- 0.8 vs 5.1 +/- 1.3 body weight; P = 0.002) compared with RFS. Conclusions: To our knowledge, this is the first study that shows differences in patellofemoral loading and knee frontal plane moment between FFS and RFS. FFS exhibit both lower patellofemoral stress and knee frontal plane moment than RFS, which may reduce the risk of running-related knee injuries. On the other hand, parallel increase in ankle plantarflexor and Achilles tendon loading may increase risk for ankle and foot injuries
231 citations
TL;DR: RT was shown to be associated with clinically important positive effects on muscular function and body composition in patients during treatment or in long-term follow-up.
Abstract: STRASSER, B., K. STEINDORF, J. WISKEMANN, and C. M. ULRICH. Impact of Resistance Training in Cancer Survivors: A MetaAnalysis. Med. Sci. Sports Exerc., Vol. 45, No. 11, pp. 2080–2090, 2013. Purpose: Current evidence suggests many health benefits from physical activity during and after cancer treatment. However, the optimal exercise program for cancer survivors has not yet been established. The purpose of this meta-analysis was to summarize evidence for the efficacy of resistance training (RT) interventions to improve muscle strength and body composition among adult cancer survivors. We also investigate potential dose–response relationships between intensity, duration, and frequency of RT and assessed outcomes. Methods: A systematic literature review of the Clinical Trial Register, Cochrane Trial Register, MEDLINE, and EMBASE literature databases was undertaken. Studies were included if they were randomized controlled trials (RCT) comparing RT with an exercise or nonexercise control group in cancer survivors during and after treatment. Thirteen articles from 11 RCT met our inclusion criteria. We performed a random-effects meta-analysis to determine weighted mean differences (WMD) with 95% confidence intervals using the Cochrane Review Manager 5.0.25. A random-effects metaregression model was performed to examine dose–response relationships between RT variables and assessed outcomes. Results: Quantitative evidence shows a large effect of RT on lower-limb and upper-limb muscle strength (WMD: +14.57 kg, P = 0.0005 and +6.90 kg, P G 0.00001, respectively) and moderate effects on lean body mass and percentage of body fat (WMD: +1.07 kg, P G 0.0001 and j2.08%, P = 0.003, respectively). A small positive effect of RT was noted on Functional Assessment of Cancer Therapy–Fatigue (P = 0.05). Upper-limb muscle strength and percentage of body fat improved to a greater extent when RT interventions were of low to moderate intensity (e75% one-repetition maximum, P = 0.042). Conclusions: RT was shown to be associated with clinically important positive effects on
226 citations
TL;DR: The prevalence of ED is higher in adolescent elite athletes than controls and higher in female than male athletes.
Abstract: MARTINSEN, M., and J. SUNDGOT-BORGEN. Higher Prevalence of Eating Disorders among Adolescent Elite Athletes than Controls. Med. Sci. Sports Exerc., Vol. 45, No. 6, pp. 1188–1197, 2013. Purpose: The objective of this study is to examine the prevalence of eating disorders (ED) among female and male adolescent elite athletes and nonathletic controls. Methods: This was a two-phase study, including a self-report questionnaire (part I) followed by clinical interviews (part II). The total population of first-year students at 16 Norwegian Elite Sport High Schools (n = 677) and two randomly selected high schools (controls, n = 421) were invited to participate. The questionnaire was completed by 611 (90%) athletes and 355 (84%) controls. The subjects reporting symptoms associated with ED were classified as ‘‘at risk’’ for ED. In part II, all ‘‘at-risk’’ athletes (n = 153), a random sample of not ‘‘at risk’’ (n = 153), and a random sample of 50% of the controls classified as ‘‘at risk’’ (n = 91) and not ‘‘at risk’’ (n = 88) were invited to the clinical interview to screen for ED (i.e., meeting the Diagnostic and Statistical Manual of Mental Disorders criteria for anorexia nervosa, bulimia nervosa, or ED not otherwise specified). Results: In part I, more controls than athletes were classified as ‘‘at risk’’ for ED (50.7% vs 25.0%, P G 0.001). In part II, the prevalence of ED among the total population of athletes and controls was estimated to be 7.0% versus 2.3%, with a difference of 4.7% (95% confidence interval, 3.4–6.0; P = 0.001), with the ED prevalence being higher for female than male athletes (14.0% vs 3.2%, P G 0.001) and female and male controls (5.1% vs 0%, P G 0.001). No difference in the prevalence of ED was detected between the females in weight-sensitive and less weight-sensitive sport groups (19.7% vs 11.9%, P = 0.136). Conclusion: The prevalence of ED is higher in adolescent elite athletes than controls and higher in female than male athletes. Clinical interview is needed to determine accurate
224 citations
TL;DR: Healthy adults wore triaxial accelerometers on the hip and dominant wrist along with a portable metabolic unit to measure energy expenditure during 20 activities and the ROC for determining sedentary behavior and activity intensity had greater sensitivity and specificity at the hip than at the wrist.
Abstract: PurposePreviously, the National Health and Examination Survey measured physical activity with an accelerometer worn on the hip for 7 d but recently changed the location of the monitor to the wrist. This study compared estimates of physical activity intensity and type with an accelerometer on
218 citations
TL;DR: A positive association of MVPA with a healthier CVD risk factor profile is confirmed and indicate that accruing PA in bouts <10 min may favorably influence cardiometabolic risk.
Abstract: PurposeWhereas greater physical activity (PA) is known to prevent cardiovascular disease (CVD), the relative importance of performing PA in sustained bouts of activity versus shorter bouts of activity on CVD risk is not known. The objective of this study was to investigate the relationship b
200 citations
TL;DR: This study investigated associations between injuries and individual components of the Marine Corps physical fitness test (PFT), self-reported exercise and previous injury history, and Functional Movement Screen (FMS) scores to determine what combination of PFT and FMS tests are most suitable for predicting injuries.
Abstract: PURPOSE: This study investigated associations between injuries and individual components of the Marine Corps physical fitness test (PFT), self-reported exercise and previous injury history, and Functional Movement Screen (FMS) scores. METHODS: A cohort of 874 men enrolled in either 6 wk (n = 447) or 10 wk (n = 427) of Marine Corps officer candidate training was recruited. They completed an exercise history questionnaire, underwent an FMS during medical in-processing, and completed the standardized PFT (pull-ups, abdominal crunch, and 3-mile run) within 1 wk of training. Injury data were gathered throughout training from medical records and classified into overuse, traumatic, and any injury. RESULTS: Three-mile run time (RT) was the only PFT component predictive of injury: candidates with RT ≥20.5 min were 1.7 times (95% confidence interval = 1.29-2.31, P < 0.001) more likely to experience an injury compared with those with RT <20.5 min. Prior injury, frequency of general exercise and sport participation, and length of running history were predictive of any, overuse, and traumatic injuries, respectively. Combining slow RT and low FMS scores (≤14) increased the predictive value across all injury classifications: candidates scoring poorly on both tests were 4.2 times more likely to experience an injury. The pull-up to exhaustion test was related to four of the seven FMS tests and the only PFT test positively related to total FMS score, although correlations were generally low (r ≤ 0.11). CONCLUSION: Slow RT was associated with increased injury risk, and combining poor RT and low FMS scores significantly increased the injury predictive value. Additional research is warranted to further clarify what combination of PFT and FMS tests are most suitable for predicting injuries.
200 citations
TL;DR: The finding of greater hip adduction in female runners who developed PFP is in agreement with previous cross-sectional studies and suggests that runners who develop PFP use a different proximal neuromuscular control strategy than those who remain healthy.
Abstract: PurposePatellofemoral pain (PFP) is the leading cause of knee pain in runners. Proximal and distal running mechanics have been linked to the development of PFP. However, the lack of prospective studies limits establishing a causal relationship of these mechanics to PFP. The purpose of this s
TL;DR: This study detected a progressive increase in the parasympathetic modulation of HR in endurance athletes led to F-OR, and revealed that due to a wide day-to-day variability, isolated, once per week HRV recordings may not detect training-induced autonomic modulations in F- OR athletes.
Abstract: PurposeWe analyzed HR variability (HRV) to detect alterations in autonomic function that may be associated with functional overreaching (F-OR) in endurance athletes.MethodsTwenty-one trained male triathletes were randomly assigned to either intensified training (n = 13) or normal training (n
TL;DR: These findings provide the first experimental evidence that prolonged mental exertion does not reduce maximal muscle activation and does not increase the extent of central fatigue induced by subsequent endurance exercise.
Abstract: Purpose: The aim of this study was to test the hypotheses that prolonged mental exertion i) reduces maximal muscle activation and ii) increases the extent of central fatigue induced by subsequent endurance exercise. Methods: Neuromuscular function of the knee extensor muscles was assessed in 10 male subjects in two different conditions: i) before and after prolonged mental exertion leading to mental fatigue; ii) before and after an easy cognitive task (control). Both cognitive tasks lasted 90 min and were followed by submaximal isometric knee extensor exercise until exhaustion (endurance task), and a third assessment of neuromuscular function. Results: Time to exhaustion was 13 ± 4% shorter in the mental fatigue condition (230 ± 22s) compared to the control condition (266 ± 26 s) (P<0.01). Prolonged mental exertion did not have any significant effect on maximal voluntary contraction (MVC) torque, voluntary activation level (VAL) and peripheral parameters of neuromuscular function. A similar significant decrease in MVC torque (mental fatigue condition: -26.7 ± 5.7%; control condition: -27.6 ± 3.3%, P<0.001), VAL (mental fatigue: - 10.6 ± 4.3%; control condition: - 11.2 ± 5.2%, P<0.05) and peripheral parameters of neuromuscular function occurred in both conditions following the endurance task. However, mentally fatigued subjects rated perceived exertion significantly higher during the endurance task compared to the control condition (P < 0.05). Conclusion: These findings provide the first experimental evidence that i) prolonged mental exertion does not reduce maximal muscle activation and ii) does not increase the extent of central fatigue induced by subsequent endurance exercise. The negative effect of mental fatigue on endurance performance seems to be mediated by higher perception of effort rather than impaired neuromuscular function.
TL;DR: Overall, students' FMS competency was low especially in the kick and overarm throw in girls, and Strategies to improve children's physical activity should consider ensuring children are taught FMS to competency level to enjoy being physically active.
Abstract: AB Purpose: The objective of this study is to describe 13-yr trends in children's fundamental movement skill (FMS) competency. Methods: Secondary analysis of representative, cross-sectional, Australian school-based surveys was conducted in 1997, 2004, and 2010 (n = 13,752 children age 9-15 yr). Five FMS (sprint run, vertical jump, catch, kick, and overarm throw) were assessed using process-oriented criteria at each survey and children's skills classified as competent or not competent. Covariates included sex, age, cardiorespiratory endurance (20-m shuttle run test), body mass index (kg[middle dot]m-2), and socioeconomic status (residential postcode). Results: At each survey, the children's FMS competency was low, with prevalence rarely above 50%. Between 1997 and 2004, there were significant increases in all students' competency in the sprint run, vertical jump, and catch. For boys, competency increased in the kick (primary) and the overarm throw (high school), but among high school girls, overarm throw competency decreased. Between 2004 and 2010, competency increased in the catch (all students), and in all girls, competency increased in the kick, whereas competency in the vertical jump decreased. Conclusions: Overall, students' FMS competency was low especially in the kick and overarm throw in girls. The observed increase in FMS competency in 2004 was attributed to changes in practice and policy to support the teaching of FMS in schools. In 2010, competency remained low, with improvements in only the catch (all) and kick (girls) and declines in vertical jump. Potentially, the current delivery of FMS programs requires stronger positioning within the school curriculum. Strategies to improve children's physical activity should consider ensuring children are taught FMS to competency level, to enjoy being physically active
TL;DR: Players sustained more impacts and impacts of higher severity on days of diagnosed concussion than on days without diagnosed concussion and those associated with peak linear acceleration are the best predictors of immediately diagnosed concussion.
Abstract: PURPOSE: This study compares the frequency and severity of head impacts sustained by American-football players on days with and without diagnosed concussion and to identify the sensitivity and specificity of single impact severity measures to diagnosed injury. METHODS: 1,208 players from eight collegiate and six high school football teams wore instrumented helmetsto measure head impacts during all team sessions, of which 95 players were diagnosed with concussion. Eight players sustained two injuries and one three, providing 105 injury cases. Measures of head kinematics (peak linear and rotational acceleration, Gadd Severity Index (GSI), Head Injury Criteria (HIC15), change in head velocity (Δv)) and the number of head impacts sustained by individual players were compared between days with and without diagnosed concussion. Receiver operator characteristic curves were generated to evaluate the sensitivity and specificity of each kinematic measure to diagnosed concussion using only those impacts that directly preceded diagnosis. RESULTS: Players sustained a higher frequency of impacts and impacts with more severe kinematic properties on days of diagnosed concussion than on days without diagnosed concussion. Forty-five injury cases were immediately diagnosed following head impact. For these cases, peak linear acceleration and HIC15 were most sensitive to immediately diagnosed concussion (AUC = 0.983). Peak rotational acceleration was less sensitive to diagnosed injury than all other kinematic measures (p = 0.01) which are derived from linear acceleration (peak linear, HIC15, GSI, and Δv). CONCLUSION: Players sustain more impacts and impacts of higher severity on days of diagnosed concussion than on days without diagnosed concussion. Additionally, of historical measures of impact severity, those associated with peak linear acceleration are the best predictors of immediately diagnosed concussion. Language: en
TL;DR: Low-volume HIT provides an alternative to the current, more time-intensive prescription for cardiac rehabilitation, and elicited similar improvements in fitness and FMD as END, despite differences in exercise duration and intensity.
Abstract: AB Purpose: Isocaloric interval exercise training programs have been shown to elicit improvements in numerous physiological indices in patients with CAD Low-volume high-intensity interval exercise training (HIT) is effective in healthy populations; however, its effectiveness in cardiac rehabilitation has not been established This study compared the effects of 12-wk of HIT and higher-volume moderate-intensity endurance exercise (END) on brachial artery flow-mediated dilation (FMD) and cardiorespiratory fitness (V[spacing dot above]O2peak) in patients with CAD Methods: Twenty-two patients with documented CAD were randomized into HIT (n = 11) or END (n = 11) based on pretraining FMD Both groups attended two supervised sessions per week for 12 wk END performed 30-50 min of continuous cycling at 58% peak power output (PPO), whereas HIT performed ten 1-min intervals at 89% PPO separated by 1-min intervals at 10% PPO per session Results: Relative FMD was increased posttraining (END, 44% +/- 26% vs 59% +/- 36%; HIT, 46% +/- 36% vs 61% +/- 34%, P
TL;DR: A review of studies that determined the prevalence of clinical or subclinical Triad conditions in exercising women and in women participating in lean (LS) versus nonlean sports (NLS) using self-report and/or objective measures demonstrates that additional research on the prevalence is necessary to more accurately describe the extent of the problem.
Abstract: PurposeThe female athlete triad (Triad) is a syndrome linking low energy availability (EA) with or without disordered eating (DE), menstrual disturbances (MD), and low bone mineral density (BMD) in exercising women. The prevalence of Triad conditions (both clinical and subclinical) has not b
TL;DR: Conussed adolescents have difficulty recovering executive function after injury and may require extended recuperation time before full recovery is achieved, and evaluations focusing on attention and executive function can be useful additions in the assessment and follow-up after head injury.
Abstract: BACKGROUND: Head trauma in adolescents has been linked with deficits in attention and executive function that can compromise the performance of everyday tasks. Although previous research has examined this issue using computerized neuropsychological testing, little work has been done using laboratory-based measurements of attention and executive function in this population. A longitudinal analysis of recovery patterns of these measures among adolescents is central to understanding the effects of concussions across the age spectrum. PURPOSE: This study prospectively and longitudinally examined laboratory-based measures of attention and executive function in concussed adolescents sequentially over a 2-month period following injury. METHODS: Two measures of attention and executive function: the Attentional Network Test (ANT) and Task-Switching Test (TST) were administered to 20 concussed adolescents within 72 hours post injury as well as at one week, two weeks, one month, and two months post injury. Twenty healthy, matched control subjects were similarly assessed at the same time intervals. Data were analyzed by two-way, mixed effects analyses of variance to determine the effect of group and time on the dependent variables. RESULTS: Compared with control subjects, the concussed group exhibited a significantly greater switch cost on the TST (p = .038, mean difference value = 38 ms) and a significantly greater reaction time for the ANT conflict effect component (p = .015, mean difference value = 34 ms) for up to two months after injury. CONCLUSIONS: Concussed adolescents have difficulty recovering executive function after injury and may require extended recuperation time before full recovery is achieved. Evaluations focusing on attention and executive function can be useful additions in the assessment and follow-up after head injury. Language: en
TL;DR: Prior fracture represents the most robust predictor of stress fractures in both sexes and low body mass index, late menarche, and prior participation in gymnastics and dance are identifiable risk factors for stress fracture in girls.
Abstract: PurposeAdolescent females and males participating in running represent a population at high risk of stress fracture. Few investigators have evaluated risk factors for prospective stress fracture in this population.MethodsTo better characterize risk factors for and incidence of stress fractur
TL;DR: In athletes with unexplained respiratory symptoms, EILO is an important differential diagnosis not discerned from other etiologies by clinical features, which has important implications for the assessment and management of athletes presenting with persistent respiratory symptoms despite asthma therapy.
Abstract: IntroductionUnexplained respiratory symptoms reported by athletes are often incorrectly considered secondary to exercise-induced asthma. We hypothesized that this may be related to exercise-induced laryngeal obstruction (EILO). This study evaluates the prevalence of EILO in an unselected coh
TL;DR: Runners interested in transitioning to minimalist running shoes, such as Vibram FiveFingers, should transition very slowly and gradually to avoid potential stress injury in the foot.
Abstract: AB Purpose: Minimalist running shoes are becoming a more popular choice for runners in the past few years. However, there is little conclusive evidence about the advantages or disadvantages of running in these shoes. Although performance benefits may exist, injury may also occur from the added stress of running without the benefit of cushioning under the foot. Bone marrow edema can be a manifestation of added stress on the foot. This study measured bone marrow edema in runners' feet before and after a 10-wk period of transitioning from traditional to minimalist running shoes. Methods: Thirty-six experienced recreational runners underwent magnetic resonance imaging (MRI) before and after a 10-wk period. Seventeen subjects were in the control group (ran in their traditional shoes only for 10 wk), whereas the other 19 were in the experimental group (gradually transitioned to Vibram FiveFinger running shoes for 10 wk). The severity of the bone marrow edema was scored on a range of 0-4 (0 = no bone marrow edema, 4 = edema in more than 50% of the length of the bone). A score of 4 represented a stress fracture. Results: Pretraining MRI scores were not statistically different between the groups. The posttraining MRI scores showed that more subjects in the Vibram group (10 of 19) showed increases in bone marrow edema in at least one bone after 10 wk of running than that in the control group (P = 0.009). Conclusion: Runners interested in transitioning to minimalist running shoes, such as Vibram FiveFingers, should transition very slowly and gradually to avoid potential stress injury in the foot.
TL;DR: In this study, self-reported physical activity was directly, and screen time inversely, associated with academic achievement, andObjectively measured physical activity and sedentary time were not associated withademic achievement.
Abstract: AB Purpose: This study aimed to determine the relationships between objectively measured and self-reported physical activity, sedentary behavior, and academic performance in Finnish children. Methods: Two hundred and seventy-seven children from five schools in the Jyvaskyla school district in Finland (58% of the 475 eligible students, mean age = 12.2 yr, 56% girls) participated in the study in the spring of 2011. Self-reported physical activity and screen time were evaluated with questions used in the WHO Health Behavior in School-Aged Children study. Children's physical activity and sedentary time were measured objectively by using an ActiGraph GT1M/GT3X accelerometer for seven consecutive days. A cutoff value of 2296 counts per minute was used for moderate-to-vigorous physical activity (MVPA) and 100 counts per minute for sedentary time. Grade point averages were provided by the education services of the city of Jyvaskyla. ANOVA and linear regression analysis were used to analyze the relationships among physical activity, sedentary behavior, and academic performance. RESULTS: Objectively measured MVPA (P = 0.955) and sedentary time (P = 0.285) were not associated with grade point average. However, self-reported MVPA had an inverse U-shaped curvilinear association with grade point average (P = 0.001), and screen time had a linear negative association with grade point average (P = 0.002), after adjusting for sex, children's learning difficulties, highest level of parental education, and amount of sleep. Conclusions: In this study, self-reported physical activity was directly, and screen time inversely, associated with academic achievement. Objectively measured physical activity and sedentary time were not associated with academic achievement. Objective and subjective measures may reflect different constructs and contexts of physical activity and sedentary behavior in association with academic outcomes.
TL;DR: Evidence from epidemiological studies conducted in the United States, Canada, and Scandinavia on the benefits of LTPA and exercise during pregnancy with regard to maternal health, pregnancy outcomes, and child health is synthesized.
Abstract: MUDD, L. M., K. M. OWE, M. F. MOTTOLA, and J. M. PIVARNIK. Health Benefits of Physical Activity during Pregnancy: An International Perspective. Med. Sci. Sports Exerc., Vol. 45, No. 2, pp. 268–277, 2013. While early studies on the effects of leisure time physical activity (LTPA) during pregnancy were concerned about possible harm to the mother or fetus, these fears have not been substantiated. Instead, a growing body of literature has documented several health benefits related to pregnancy LTPA. The purpose of this article was to synthesize evidence from epidemiological studies conducted in the United States, Canada, and Scandinavia on the benefits of LTPA and exercise during pregnancy with regard to maternal health, pregnancy outcomes, and child health. We focused on studies evaluating relations between pregnancy LTPA and gestational diabetes, hypertensive disorders, excessive gestational weight gain, birth weight, timing of delivery, and child body composition. The bulk of evidence supports beneficial effects of pregnancy LTPA on each outcome; however, most previous studies have been observational and used self-reported LTPA at only one or two time points in pregnancy. Limitations of the current knowledge base and suggestions for future research on the health benefits of LTPA during
TL;DR: The shoe-based physical activity monitor provides a valid estimate of EE, whereas the other physical activity monitors tested have a wide range of validity when estimating EE.
Abstract: DANNECKER, K. L., N. A. SAZONOVA, E. L. MELANSON, E. S. SAZONOV, and R. C. BROWNING. A Comparison of Energy Expenditure Estimation of Several Physical Activity Monitors. Med. Sci. Sports Exerc., Vol. 45, No. 11, pp. 2105–2112, 2013. Introduction: Accurately and precisely estimating free-living energy expenditure (EE) is important for monitoring energy balance and quantifying physical activity. Recently, single and multisensor devices have been developed that can classify physical activities, potentially resulting in improved estimates of EE. Purpose: This study aimed to determine the validity of EE estimation of a footwear-based physical activity monitor and to compare this validity against a variety of research and consumer physical activity monitors. Methods: Nineteen healthy young adults (10 men, 9 women) completed a 4-h stay in a room calorimeter. Participants wore a footwear-based physical activity monitor as well as Actical, ActiGraph, IDEEA, DirectLife, and Fitbit devices. Each individual performed a series of postures/activities. We developed models to estimate EE from the footwear-based device, and we used the manufacturer’s software to estimate EE for all other devices. Results: Estimated EE using the shoe-based device was not significantly different than measured EE (mean T SE; 476 T 20 vs 478 T 18 kcal, respectively) and had a root-mean-square error of 29.6 kcal (6.2%). The IDEEA and the DirectLlife estimates of EE were not significantly different than the measured EE, but the ActiGraph and the Fitbit devices significantly underestimated EE. Root-mean-square errors were 93.5 (19%), 62.1 kcal (14%), 88.2 kcal (18%), 136.6 kcal (27%), 130.1 kcal (26%), and 143.2 kcal (28%) for Actical, DirectLife, IDEEA, ActiGraph, and Fitbit, respectively. Conclusions: The shoe-based physical activity monitor provides a valid estimate of EE, whereas the other physical activity monitors tested have a wide range of validity when estimating EE. Our results also demonstrate that estimating EE based on classification of physical activities can be more accurate and precise than
TL;DR: The results suggest that nonuniform muscle hypertrophy after training intervention is due to the region-specific muscle activation during the training session.
Abstract: AB Purpose: Muscle hypertrophy in response to resistance training has been reported to occur nonuniformly along the length of the muscle. The purpose of the present study was to examine whether the regional difference in muscle hypertrophy induced by a training intervention corresponds to the regional difference in muscle activation in the training session. Methods: Twelve young men participated in a training intervention program for the elbow extensors with a multijoint resistance exercise for 12 wk (3 d[middle dot]wk-1). Before and after the intervention, cross-sectional areas of the triceps brachii along its length were measured with magnetic resonance images. A series of transverse relaxation time (T2)-weighted magnetic resonance images was recorded before and immediately after the first session of training intervention. The T2 was calculated for each pixel within the triceps brachii. In the images recorded after the session, the number of pixels with a T2 greater than the threshold (mean + 1 SD of T2 before the session) was expressed as the ratio to the whole number of pixels within the muscle and used as an index of muscle activation (percent activated area). Results: The percent activated area of the triceps brachii in the first session was significantly higher in the middle regions than that in the most proximal region. Similarly, the relative change in cross-sectional area induced by the training intervention was also significantly greater in the middle regions than the most proximal region. Conclusion: The results suggest that nonuniform muscle hypertrophy after training intervention is due to the region-specific muscle activation during the training session.
TL;DR: Prolonged resistance-type exercise training increases skeletal muscle mass and strength, augments functional capacity, improves glycemia and lipidemia, and reduces blood pressure in healthy elderly men and women.
Abstract: IntroductionResistance training has been well established as an effective treatment strategy to increase skeletal muscle mass and strength in the elderly. We assessed whether dietary protein supplementation can further augment the adaptive response to prolonged resistance-type exercise train
TL;DR: Lower ventilatory responses to a similar hypoxic stimulus during rest and exercise in HH versus NH were sustained for 24 h and associated with lower plasma pH level, exaggerated oxidative stress, and impaired NO bioavailability.
Abstract: FAISS, R., V. PIALOUX, C. SARTORI, C. FAES, O. DERIAZ, and G. P. MILLET. Ventilation, Oxidative Stress, and Nitric Oxide in Hypobaric versus Normobaric Hypoxia. Med. Sci. Sports Exerc., Vol. 45, No. 2, pp. 253-260, 2013. Purpose: Slight differences in physiological responses and nitric oxide (NO) have been reported at rest between hypobaric hypoxia (HH) and normobaric hypoxia (NH) during short exposure. Our study reports NO and oxidative stress at rest and physiological responses during moderate exercise in HH versus NH. Methods: Ten subjects were randomly exposed for 24 h to HH (3000 m; FIO2, 20.9%; BP, 530 T 6 mm Hg) or to NH (FIO2, 14.7%; BP, 720 T 1 mm Hg). Before and every 8 h during the hypoxic exposures, pulse oxygen saturation (SpO2), HR, and gas exchanges were measured during a 6-min submaximal cycling exercise. At rest, the partial pressure of exhaled NO, blood nitrate and nitrite (NOx), plasma levels of oxidative stress, and pH levels were additionally measured. Results: During exercise, minute ventilation was lower in HH compared with NH (j13% after 8 h, P G 0.05). End-tidal CO2 pressure was lower (P G 0.01) than PRE both in HH and NH but decreased less in HH than that in NH (j25% vs j37%, P G 0.05). At rest, exhaled NO and NOx decreased in HH (j46% and j36% after 24 h, respectively, P G 0.05) whereas stable in NH. By contrast, oxidative stress was higher in HH than that in NH after 24 h (P G 0.05). The plasma pH level was stable in HH but increased in NH (P G 0.01). When compared with prenormoxic values, SpO2, HR, oxygen consumption, breathing frequency, and end-tidal O2 pressure showed similar changes in HH and NH. Conclusion: Lower ventilatory responses to a similar hypoxic stimulus during rest and exercise in HH versus NH were sustained for 24 h and associated with
TL;DR: A dose of 3 mg · kg(-1) is enough to improve high-velocity muscle actions against low loads, whereas a higher caffeine dose is necessary against high loads, despite the appearance of adverse side effects.
Abstract: PALLARES, J. G., V. E. FERNANDEZ-ELIAS, J. F. ORTEGA, G. MUNOZ, J. MUNOZ-GUERRA, and R. MORA-RODRIGUEZ. Neuromuscular Responses to Incremental Caffeine Doses: Performance and Side Effects. Med. Sci. Sports Exerc., Vol. 45, No. 11, pp. 2184-2192, 2013. Purpose: The purpose of this study was to determine the oral dose of caffeine needed to increase muscle force and power output during all-out single multijoint movements. Methods: Thirteen resistance-trained men underwent a battery of muscle strength and power tests in a randomized, double-blind, crossover design, under four different conditions: (a) placebo ingestion (PLAC) or with caffeine ingestion at doses of (b) 3 mgIkg j1 body weight (CAFF3mg), (c) 6 mgIkg j1 (CAFF6mg), and (d) 9 mgIkg j1 (CAFF9mg). The muscle strength and power tests consisted in the measurement of bar displacement velocity and muscle power output during free- weight full-squat (SQ) and bench press (BP) exercises against four incremental loads (25%, 50%, 75%, and 90% one-repetition maxi- mum (1RM)). Cycling peak power output was measured using a 4-s inertial load test. Caffeine side effects were evaluated at the end of each trial and 24 h later. Results: Mean propulsive velocity at light loads (25%-50% 1RM) increased significantly above PLAC for all caffeine doses (5.4%-8.5%, P = 0.039-0.003). At the medium load (75% 1RM), CAFF3mg did not improve SQ or BP muscle power or BP velocity. CAFF9mg was needed to enhance BP velocity and SQ power at the heaviest load (90% 1RM) and cycling peak power output (6.8%-11.7%, P = 0.03-0.05). The CAFF9mg trial drastically increased the frequency of the adverse side effects (15%-62%). Conclusions: The ergogenic dose of caffeine required to enhance neuromuscular performance during a single all-out contraction depends on the magnitude of load used. A dose of 3 mgIkg j1 is enough to improve high-velocity muscle actions against low loads, whereas a higher
TL;DR: The results of this study suggest that three bouts of 2-min SS of the plantar flexors is useful for preventing muscle injury, improving muscle condition, and maintaining muscle strength, and that the acute effects of SS on the muscle hardness of MG and LG are of the same degree.
Abstract: AB Purpose: The objective of this study is to investigate the acute effects of static stretching (SS) on muscle hardness of the gastrocnemius medialis (MG) and gastrocnemius lateralis (LG). Methods: Twenty young men participated in this study. MG and LG hardness was measured using shear wave ultrasound elastography before and after three bouts of 2-min SS. The measurement site of muscle hardness was at 30% of the lower leg length from the popliteal crease to the lateral malleolus. Similarly, the passive range of motion (ROM) of dorsiflexion, musculotendinous unit (MTU) stiffness determined by the slope of the portion of the passive torque-angle curve from 15[degrees] to 25[degrees], and joint torque developed during isometric maximal voluntary plantarflexion at 0[degrees] of ankle joint angle were also measured before and after SS. Results: SS increased ROM and decreased MTU stiffness significantly but did not change joint torque. The main effects of test time and muscle group on muscle hardness were significant without a significant interaction of these variables. Both differences between the relative changes in the MG and LG hardness and between the muscle hardness ratios before and after SS were not significant. A significant correlation between the muscle hardness ratios before and after SS was found. Conclusion: The results of this study suggest that three bouts of 2-min SS of the plantar flexors is useful for preventing muscle injury, improving muscle condition, and maintaining muscle strength, and that the acute effects of SS on the muscle hardness of MG and LG are of the same degree
TL;DR: In this paper, the authors provide evidence that some individuals adopt compensatory behaviors, that is, increased energy intake and/or reduced activity, that offset the exercise energy expenditure and limit weight loss.
Abstract: In many interventions that are based on an exercise program intended to induce weight loss, the mean weight loss observed is modest and sometimes far less than what the individual expected. The individual responses are also widely variable, with some individuals losing a substantial amount of weight, others maintaining weight, and a few actually gaining weight. The media have focused on the subpopulation that loses little weight, contributing to a public perception that exercise has limited utility to cause weight loss. The purpose of the symposium was to present recent, novel data that help explain how compensatory behaviors contribute to a wide discrepancy in exercise-induced weight loss. The presentations provide evidence that some individuals adopt compensatory behaviors, that is, increased energy intake and/or reduced activity, that offset the exercise energy expenditure and limit weight loss. The challenge for both scientists and clinicians is to develop effective tools to identify which individuals are susceptible to such behaviors and to develop strategies to minimize their effect.