Showing papers in "Medicine and Science in Sports and Exercise in 2020"

Exercise Training Modulates Gut Microbiota Profile and Improves Endotoxemia.

Abstract: IntroductionIntestinal metabolism and microbiota profiles are impaired in obesity and insulin resistance. Moreover, dysbiotic gut microbiota has been suggested to promote systemic low-grade inflammation and insulin resistance through the release of endotoxins particularly lipopolysaccharides

A Critical Evaluation of Current Methods for Exercise Prescription in Women and Men.

Abstract: Common methods to prescribe exercise intensity are based on fixed percentages of maximum rate of oxygen uptake (V˙O2max), peak work rate (WRpeak), maximal HR (HRmax). However, it is unknown how these methods compare to the current models to partition the exercise intensity spectrum. PURPOSE Thus, the aim of this study was to compare contemporary gold-standard approaches for exercise prescription based on fixed percentages of maximum values to the well-established, but underutilized, "domain" schema of exercise intensity. METHODS One hundred individuals participated in the study (women, 46; men, 54). A cardiopulmonary ramp-incremental test was performed to assess V˙O2max, WRpeak, HRmax, and the lactate threshold (LT), and submaximal constant-work rate trials of 30-min duration to determine the maximal lactate steady-state (MLSS). The LT and MLSS were used to partition the intensity spectrum for each individual in three domains of intensity: moderate, heavy, and severe. RESULTS V˙O2max in women and men was 3.06 ± 0.41 L·min and 4.10 ± 0.56 L·min, respectively. Lactate threshold and MLSS occurred at a greater %V˙O2max and %HRmax in women compared with men (P < 0.05). The large ranges in both sexes at which LT and MLSS occurred on the basis of %V˙O2max (LT, 45%-74%; MLSS, 69%-96%), %WRpeak (LT, 23%-57%; MLSS, 44%-71%), and %HRmax (LT, 60%-90%; MLSS, 75%-97%) elicited large variability in the number of individuals distributed in each domain at the fixed-percentages examined. CONCLUSIONS Contemporary gold-standard methods for exercise prescription based on fixed-percentages of maximum values conform poorly to exercise intensity domains and thus do not adequately control the metabolic stimulus.

Velocity Loss as a Critical Variable Determining the Adaptations to Strength Training.

Abstract: PURPOSE This study aimed to compare the effects of four resistance training (RT) programs with different velocity loss (VL) thresholds: 0% (VL0), 10% (VL10), 20% (VL20), and 40% (VL40) on sprint and jump performance, muscle strength, neuromuscular, muscle hypertrophy, and architectural adaptations. METHODS Sixty-four young resistance-trained men were randomly assigned into four groups (VL0, VL10, VL20, and VL40) that differed in the VL allowed in each set. Subjects followed an RT program for 8 wk (two sessions per week) using the full-squat (SQ) exercise, with similar relative intensity (70%-85% 1-repetition maximum), number of sets (3), and interset recovery period (4 min). Before and after the RT program, the following tests were performed: 1) muscle hypertrophy and architecture of the vastus lateralis (VLA), 2) tensiomyography, 3) 20-m running sprint, 4) vertical jump, 5) maximal voluntary isometric contraction in SQ, 6) progressive loading test in SQ, and 7) fatigue test. RESULTS No between-group differences existed for RT-induced gains in sprint, jump, and strength performance despite the differences in the total volume performed by each group. VL20 and VL40 showed significant increases (P < 0.001) in muscle hypertrophy (group-time interaction, P = 0.06). However, only VL40 exhibited a significant slowing (P < 0.001) of the delay time in the VLA muscle (group-time interaction, P = 0.05). Moreover, VL40 showed a significant decrease in the early rate of force development (P = 0.04). CONCLUSIONS Higher VL thresholds (i.e., VL20 and VL40) maximized hypertrophic adaptations, although an excessive VL during the set (i.e., VL40) may also induce negative neuromuscular adaptations. Therefore, moderate VL thresholds should be chosen to maximize strength adaptations and to prevent negative neuromuscular adaptations.

Ultrasound-derived Biceps Femoris Long Head Fascicle Length: Extrapolation Pitfalls

Abstract: Purpose This study aimed to compare biceps femoris long head (BFlh) fascicle length (Lf) obtained with different ultrasound-based approaches: 1) single ultrasound images and linear Lf extrapolation, 2) single ultrasound images and one of two different trigonometric equations (termed equations A and B), and 3) extended field of view (EFOV) ultrasound images. Methods Thirty-seven elite alpine skiers (21.7 +/- 2.8 yr) without a previous history of hamstring strain injury were tested. Single ultrasound images were collected with a 5-cm linear transducer from BFlh at 50% femur length and were compared with whole muscle scans acquired by EFOV ultrasound. Results The intrasession reliability (intraclass correlation coefficient [ICC3,k]) of Lf measurements was very high for both single ultrasound images (i.e., Lf estimated by linear extrapolation; ICC3,k = 0.96-0.99, SEM = 0.18 cm) and EFOV scans (ICC3,k = 0.91-0.98, SEM = 0.19 cm). Although extrapolation methods showed cases of Lf overestimation and underestimation when compared with EFOV scans, mean Lf measured from EFOV scans (8.07 +/- 1.36 cm) was significantly shorter than Lf estimated by trigonometric equations A (9.98 +/- 2.12 cm, P < 0.01) and B (8.57 +/- 1.59 cm, P = 0.03), but not significantly different from Lf estimated with manual linear extrapolation (8.40 +/- 1.68 cm, P = 0.13). Bland-Altman analyses revealed mean differences in Lf obtained from EFOV scans and those estimated from equation A, equation B, and manual linear extrapolation of 1.91 +/- 2.1, 0.50 +/- 1.0, and 0.33 +/- 1.0 cm, respectively. Conclusions The typical extrapolation methods used for estimating Lf from single ultrasound images are reliable within the same session, but not accurate for estimating BFlh Lf at rest with a 5-cm field of view. We recommend that EFOV scans are implemented to accurately determine intervention-related Lf changes in BFlh.

A Machine Learning Approach to Assess Injury Risk in Elite Youth Football Players.

Abstract: Purpose To assess injury risk in elite-level youth football (soccer) players based on anthropometric, motor coordination and physical performance measures with a machine learning model. Methods A total of 734 players in the U10 to U15 age categories (mean age, 11.7 ± 1.7 yr) from seven Belgian youth academies were prospectively followed during one season. Football exposure and occurring injuries were monitored continuously by the academies' coaching and medical staff, respectively. Preseason anthropometric measurements (height, weight, and sitting height) were taken and test batteries to assess motor coordination and physical fitness (strength, flexibility, speed, agility, and endurance) were performed. Extreme gradient boosting algorithms (XGBoost) were used to predict injury based on the preseason test results. Subsequently, the same approach was used to classify injuries as either overuse or acute. Results During the season, half of the players (n = 368) sustained at least one injury. Of the first occurring injuries, 173 were identified as overuse and 195 as acute injuries. The machine learning algorithm was able to identify the injured players in the hold-out test sample with 85% precision, 85% recall (sensitivity) and 85% accuracy (f1 score). Furthermore, injuries could be classified as overuse or acute with 78% precision, 78% recall, and 78% accuracy. Conclusions Our machine learning algorithm was able to predict injury and to distinguish overuse from acute injuries with reasonably high accuracy based on preseason measures. Hence, it is a promising approach to assess injury risk among elite-level youth football players. This new knowledge could be applied in the development and improvement of injury risk management strategies to identify youth players with the highest injury risk.

Temporal Muscle-specific Disuse Atrophy during One Week of Leg Immobilization.

Abstract: Purpose Musculoskeletal injuries necessitate periods of disuse (i.e., limb immobilization) during which rapid skeletal muscle atrophy occurs. The relative susceptibility of different muscles of the thigh to disuse atrophy remains uninvestigated. We assessed muscle disuse atrophy of individual thigh muscles throughout 1 wk of unilateral knee immobilization. Methods Thirteen healthy, young (20.2 ± 0.6 yr) men underwent 7 d of unilateral leg immobilization via knee bracing. Magnetic resonance imaging scans were performed bilaterally prior to, and following 2 and 7 d of immobilization to determine the volume and anatomical cross-sectional area of the individual muscle groups of the upper legs. Results In contrast to the control leg, total thigh muscle volume had decreased by 1.7% ± 0.3% (P < 0.01) and 5.5% ± 0.6% (P < 0.001) in the immobilized leg after 2 and 7 d of disuse, respectively. Muscle loss was significantly greater in the Musculus quadriceps (day 2; 1.7% ± 0.3% (P < 0.05) and day 7; 6.7% ± 0.6%) when compared with the Musculus hamstrings (day 2; 1.4% ± 0.2% (P < 0.01) and day 7; 3.5% ± 0.3%) after 7 d of disuse (P < 0.001). Individual muscles of the thigh exhibited different atrophy rates with the Musculus vastus lateralis anatomical cross-sectional area showing the greater (2.6% ± 0.4% and 7.2% ± 0.8%), and the Musculus gracilis the lesser (1.1% ± 0.7% and 2.3% ± 1.0%) decline following 2 and 7 d of immobilization, respectively (P < 0.01). Conclusions Thigh muscle disuse atrophy occurs rapidly and is already evident within 2 d of leg immobilization and progresses at a similar rate over the next 5 d (~0.8% muscle loss per day). M. quadriceps muscle shows more atrophy when compared with the M. hamstrings.

Ergogenic Effect of Nitrate Supplementation: A Systematic Review and Meta-analysis.

Abstract: Although over 100 studies and reviews have examined the ergogenic effects of dietary nitrate (NO3) supplementation in young, healthy men and women, it is unclear if participant and environmental factors modulate the well-described ergogenic effects-particularly relevant factors include biological sex, aerobic fitness, and fraction of inspired oxygen (FiO2) during exercise. To address this limitation, the literature was systematically reviewed for randomized, crossover, placebo-controlled studies reporting exercise performance outcome metrics with NO3 supplementation in young, healthy adults. Of the 2033 articles identified, 80 were eligible for inclusion in the meta-analysis. Random-effects meta-analysis demonstrated that exercise performance improved with NO3 supplementation compared with placebo (d = 0.174; 95% confidence interval (CI), 0.120-0.229; P < 0.001). Subgroup analyses conducted on biological sex, aerobic fitness, and FiO2 demonstrated that the ergogenic effect of NO3 supplementation was as follows: 1) not observed in studies with only women (n = 6; d = 0.116; 95% CI, -0.126 to 0.358; P = 0.347), 2) not observed in well-trained endurance athletes (≥65 mL·kg·min; n = 26; d = 0.021; 95% CI, -0.103 to 0.144; P = 0.745), and 3) not modulated by FiO2 (hypoxia vs normoxia). Together, the meta-analyses demonstrated a clear ergogenic effect of NO3 supplementation in recreationally active, young, healthy men across different exercise paradigms and NO3 supplementation parameters; however, the effect size of NO3 supplementation was objectively small (d = 0.174). NO3 supplementation has more limited utility as an ergogenic aid in participants with excellent aerobic fitness that have optimized other training parameters. Mechanistic research and studies incorporating a wide variety of subjects (e.g., women) are needed to advance the study of NO3 supplementation; however, additional descriptive studies of young, healthy men may have limited utility.

Review of High-Intensity Interval Training for Cognitive and Mental Health in Youth.

Abstract: PURPOSE High-intensity interval training (HIIT) has emerged as a time-efficient strategy to improve children's and adolescents' health-related fitness in comparison to traditional training methods. However, little is known regarding the effects on cognitive function and mental health. Therefore, the aim of this systematic review was to evaluate the effect of HIIT on cognitive function (basic information processing, executive function) and mental health (well-being, ill-being) outcomes for children and adolescents. METHODS A systematic search was conducted, and studies were eligible if they 1) included a HIIT protocol, 2) examined cognitive function or mental health outcomes, and 3) examined children or adolescents (5-18 yr). Separate meta-analyses were conducted for acute and chronic studies, with potential moderators (i.e., study duration, risk of bias, participant age, cognitive demand, and study population) also explored. RESULTS A total of 22 studies were included in the review. In acute studies, small to moderate effects were found for executive function (standardized mean difference [SMD], 0.50, 95% confidence interval [CI], 0.03-0.98; P = 0.038) and affect (SMD, 0.33; 95% CI, 0.05-0.62; P = 0.020), respectively. For chronic studies, small significant effects were found for executive function (SMD, 0.31; 95% CI, 0.15-0.76, P < 0.001), well-being (SMD, 0.22; 95% CI, 0.02-0.41; P = 0.029), and ill-being (SMD, -0.35; 95% CI, -0.68 to -0.03; P = 0.035). CONCLUSIONS Our review provides preliminary review evidence suggesting that participation in HIIT can improve cognitive function and mental health in children and adolescents. Because of the small number of studies and large heterogeneity, more high-quality research is needed to confirm these findings.

Effects of Exercise Training on Anxious-Depressive-like Behavior in Alzheimer Rat.

Abstract: Purpose This study aimed to examine the effects of treadmill training on anxious-depressive-like behaviors of transgenic Alzheimer rats in the early stage of Alzheimer's disease (AD) and provided evidence of exercise in alleviating fear-avoidance behavior deficits. Methods Male 2-month-old TgF344-AD and wild-type rats were divided into wild-type (n = 9), AD (n = 8), and AD + treadmill exercise (Exe) groups (n = 12). After 8 months of exercise, the passive avoidance test, Barnes maze task, novel object recognition test, and object location test were used to measure learning and memory function. The open-field test, elevated plus maze, sucrose preference test, and forced swim test were conducted to determine the anxious-depressive-like behavior of AD rats. Immunofluorescence staining, Western blot analysis, enzyme-linked immunosorbent assay analysis, and related assay kits were used to measure inflammatory cytokines, oxidative stress, amyloid-β production, and tau hyperphosphorylation. Results Behavioral tests revealed that 12-month-old animals did not show any spatial learning and memory deficits but did display anxious-depressive-like behavior (open field, center time: P = 0.008; center entries: P = 0.009; line crossings: P = 0.001). However, long-term exercise significantly inhibited anxious-depressive-like behavior in AD rats (center time: P = 0.016; center entries: P = 0.004; line crossings: P = 0.033). In addition, these animals displayed increased amyloid-β deposition, tau hyperphosphorylation, microgliosis, inflammatory cytokines release, and oxidative damage, which were attenuated significantly by long-term exercise training. Conclusion Long-term exercise training alleviated anxious-depressive-like behavior and improved fear-avoidance behavior in transgenic AD rats, supporting exercise training as an effective approach to prevent anxiety, depression, and fear-avoidance behavior deficits in the early stages of AD pathogenesis.

Acute Exercise Effects Predict Training Change in Cognition and Connectivity.

Abstract: PurposePrevious studies report memory and functional connectivity of memory systems improve acutely after a single aerobic exercise session or with training, suggesting that the acute effects of aerobic exercise may reflect initial changes that adapt over time. In this trial, for the first t

Moderators of exercise effects on cancer-related fatigue: A meta-analysis of individual patient data

Abstract: PURPOSE: Fatigue is a common and potentially disabling symptom in patients with cancer. It can often be effectively reduced by exercise. Yet, effects of exercise interventions might differ across subgroups. We conducted a meta-analysis using individual patient data of randomized controlled trials (RCT) to investigate moderators of exercise intervention effects on cancer-related fatigue. METHODS: We used individual patient data from 31 exercise RCT worldwide, representing 4366 patients, of whom 3846 had complete fatigue data. We performed a one-step individual patient data meta-analysis, using linear mixed-effect models to analyze the effects of exercise interventions on fatigue (z score) and to identify demographic, clinical, intervention- and exercise-related moderators. Models were adjusted for baseline fatigue and included a random intercept on study level to account for clustering of patients within studies. We identified potential moderators by testing their interaction with group allocation, using a likelihood ratio test. RESULTS: Exercise interventions had statistically significant beneficial effects on fatigue (β = -0.17; 95% confidence interval [CI], -0.22 to -0.12). There was no evidence of moderation by demographic or clinical characteristics. Supervised exercise interventions had significantly larger effects on fatigue than unsupervised exercise interventions (βdifference = -0.18; 95% CI -0.28 to -0.08). Supervised interventions with a duration ≤12 wk showed larger effects on fatigue (β = -0.29; 95% CI, -0.39 to -0.20) than supervised interventions with a longer duration. CONCLUSIONS: In this individual patient data meta-analysis, we found statistically significant beneficial effects of exercise interventions on fatigue, irrespective of demographic and clinical characteristics. These findings support a role for exercise, preferably supervised exercise interventions, in clinical practice. Reasons for differential effects in duration require further exploration.

Can Creatine Combat the Mental Fatigue-associated Decrease in Visuomotor Skills?

Abstract: PurposeThe importance of the brain in sports was recently confirmed by the negative effect of mental fatigue (MF) on sport-specific psychomotor skills. Creatine supplementation improves strength but can also improve cognitive functioning. To explore the role of creatine in combating MF, we e

Bilateral Gait 6 and 12 Months Post-Anterior Cruciate Ligament Reconstruction Compared with Controls.

Abstract: Purpose To compare gait biomechanics throughout stance phase 6 and 12 months after unilateral anterior cruciate ligament reconstruction (ACLR) between ACLR and contralateral limbs and compared with controls. Methods Vertical ground reaction force (vGRF), knee flexion angle (KFA), and internal knee extension moment (KEM) were collected bilaterally 6 and 12 months post-ACLR in 30 individuals (50% female, 22 ± 3 yr, body mass index = 23.8 ± 2.2 kg·m) and at a single time point in 30 matched uninjured controls (50% female, 22 ± 4 yr, body mass index = 23.6 ± 2.1 kg·m). Functional analyses of variance were used to evaluate the effects of limb (ACLR, contralateral, and control) and time (6 and 12 months) on biomechanical outcomes throughout stance. Results Compared with the uninjured controls, the ACLR group demonstrated bilaterally lesser vGRF (ACLR, 9% body weight [BW]; contralateral, 4%BW) during early stance and greater vGRF during midstance (ACLR, 5%BW; contralateral, 4%BW) 6 months post-ACLR. Compared to the uninjured controls, the ACLR group demonstrated bilaterally lesser vGRF (ACLR, 10%BW; contralateral, 8%BW) during early stance and greater vGRF during midstance (ACLR, 5%BW; contralateral, 5%BW) 12 months post-ACLR. Compared with controls, the ACLR limb demonstrated lesser KFA during early stance at 6 (2.3°) and 12 months post-ACLR (2.0°), and the contralateral limb demonstrated lesser KFA during early stance at 12 months post-ACLR (2.8°). Compared with controls, the ACLR limb demonstrated lesser KEM during early stance at both 6 months (0.011BW × height) and 12 months (0.007BW × height) post-ACLR, and the contralateral limb demonstrated lesser KEM during early stance only at 12 months (0.006BW × height). Conclusions Walking biomechanics are altered bilaterally after ACLR. During the first 12 months post-ACLR, both the ACLR and contralateral limbs demonstrate biomechanical differences compared with control limbs. Differences between the contralateral and control limbs increase from 6 to 12 months post-ACLR.

Reporting of Resistance Training Dose, Adherence, and Tolerance in Exercise Oncology

Abstract: This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.

Proximal Adaptations in Chronic Ankle Instability: Systematic Review and Meta-analysis.

Abstract: INTRODUCTION Chronic ankle instability (CAI) is known to induce impairments throughout the lower quarter kinetic chain, however there is currently no synthesized information on proximal adaptations of the trunk, hip, thigh, and knee for neuromuscular and biomechanical outcomes during strength, balance, jumping, and gait among CAI patients. The purpose of this systematic review and meta-analysis was to synthesize trunk, hip, thigh and knee neuromuscular and biomechanical outcome measures during functional assessments when comparing CAI to healthy groups. METHODS Cumulative Index of Nursing and Allied Health Literature and Medical Literature Analysis and Retrieval System Online with PubMed databases were searched on June 3, 2019. Studies comparing outcomes at the trunk, hip, thigh, or knee regardless of assessment type in CAI versus healthy groups were considered for inclusion. Assessment categories were used to differentiate adaptations by assessment type after inclusion. Two independent reviewers assessed methodological quality using the Physiotherapy Evidence Database scoring criteria. Data pertaining to study methodology and primary proximal adaptation outcomes were extracted. Separate random effects meta-analyses were performed for consistently reported outcome measures. RESULTS Pooled estimates reflected that CAI patients had decreased triplanar isometric hip strength outcomes (P < 0.001, effect size range: 0.52-0.93). Knee kinematics did not differ from healthy groups during dynamic balance testing (P = 0.26). Few studies found CAI patients have altered knee kinematics during jumping tasks. The remaining findings were isolated to individual studies and thus inconclusive. CONCLUSIONS The CAI groups demonstrated triplanar hip strength deficits and altered knee flexion angles during jumping assessments. Clinicians should consider proximal evaluations and interventions for CAI patients.

Does Eccentric-only and Concentric-only Activation Increase Power Output?

Abstract: PURPOSE The aim of study was to evaluate changes in power output and bar velocity in the bench press throw (BPT) following the bench press (BP) exercise as a conditioning activity (CA) with concentric only (CONONLY) and eccentric only (ECCONLY) contractions. METHODS Thirty-two (n = 32) healthy strength-trained men participated in this study (age, 28.4 ± 4.5 yr; height, 177 ± 7.6 cm; body mass, 93.5 ± 9.3 kg; BP one-repetition maximum (1RM), 143.6 ± 17.5 kg). The experiment was performed following a randomized crossover design, where each participant performed 2 sets of 2 repetitions using the BP exercise as the CA at 90% 1RM ECCONLY, 90% 1RM CONONLY, 110% 1RM ECCONLY, or 130% 1RM ECCONLY contraction. The BPT was performed to assess changes in peak power (PP), mean power (MP), and peak velocity (PV), mean velocity (MV) before and after CA. The differences between analyzed variables before and after the CA were verified using ANOVA with repeated measures. Statistical significance was set at P < 0.05. RESULTS There were statistically significant differences between baseline and postactivation value of PP and PV in the BPT (P < 0.05) after the CA with ECCONLY contraction at 110% 1RM and at 130% 1RM as well between baseline and postactivation value of MV in the BPT (P < 0.05) after CA with contraction at 110% 1RM. There were no significant differences between baseline and postactivation values of PP, MP, PV, and MV in the BPT after the CA with CONONLY contraction at 90% 1RM and CA with ECCONLY contraction at 90% 1RM. CONCLUSIONS Partial movement with ECCONLY contraction is effective in short-term power output development, but only when the load used in the CA exceeds 100% 1RM.

The Effect of Exercise Timing on Glycemic Control: A Randomized Clinical Trial

Abstract: Despite the acknowledgment of exercise as a cornerstone in the management of type 2 diabetes (T2D), the importance of exercise timing has only recently been considered. PURPOSE This study sought to determine the effect of diurnal exercise timing on glycemic control in individuals enrolled in a 12-wk supervised multimodal exercise training program. A secondary aim was to determine the effect of diurnal exercise timing on the circadian rhythm of wrist skin temperature. METHODS Forty sedentary, overweight adults (mean ± SD, age = 51 ± 13 yr; body mass index = 30.9 ± 4.2 kg·m; women, n = 23) with and without (n = 20) T2D diagnosis were randomly allocated to either a morning (amEX) or an evening (pmEX) exercise training group. The supervised 12-wk (3 d·wk) program, comprised 30 min of moderate-intensity walking and 4 resistance-based exercises (3 sets, 12-18 repetitions each). Glycemic outcomes (glycated hemoglobin, fasting glucose, postprandial glucose) and wrist skin temperature were assessed at baseline and postintervention. RESULTS Exercise training improved (main effect of time, all P < 0.01) all glycemic outcomes; however, this was independent of allocation to either the amEX (Hedge's g, 0.23-0.90) or the pmEX (Hedge's g, 0.16-0.90) group. Accordingly, the adopted exercise training program did not alter the circadian rhythm of skin temperature. When only T2D individuals were compared, amEX demonstrated greater effects (all Hedge's g) on glycated hemoglobin (amEX, 0.57; pmEX, 0.32), fasting glucose (amEX, 0.91; pmEX, 0.53), and postprandial glucose (amEX, 1.12; pmEX, 0.71) but was not statistically different. CONCLUSIONS Twelve weeks of multimodal exercise training improved glycemic control and postprandial glycemic responses in overweight non-T2D and T2D individuals. However, no distinct glycemic benefits or alterations in circadian rhythm were associated with morning versus evening exercise, when performed three times per week in this cohort.

Physiological Evidence That the Critical Torque Is a Phase Transition, Not a Threshold.

Abstract: Introduction: Distinct physiological responses to exercise occur in the heavy and severe-intensity domains, which are separated by the critical power or critical torque (CT). However, how the transition between these intensity domains actually occurs is not known. We tested the hypothesis that CT is a sudden threshold, with no gradual transition from heavy- to severe-intensity behavior within the confidence limits associated with the CT. Methods: Twelve healthy participants performed four exhaustive severe-intensity trials for the determination of CT, and four 30-minute trials in close proximity to CT (one or two standard errors above or below each participant’s CT estimate; CT–2, CT–1, CT+1, CT+2). Muscle O2 uptake (mV[Combining Dot Above]O2), rectified EMG and torque variability and complexity were monitored throughout each trial, and maximal voluntary contractions with femoral nerve stimulation were performed before and after each trial to determine central and peripheral fatigue responses. Results: The rates of change in fatigue-related variables, mV[Combining Dot Above]O2, EMG amplitude and torque complexity were significantly faster in the severe trials compared to CT–2. For example, the fall in maximal voluntary contraction (MVC) torque was –1.5 ± 0.8 N.m.min-1 in CT–2 vs. –7.9 ± 2.5 N.m.min-1 in the lowest severe-intensity trial (S1; P < 0.05). Individual analyses showed a low frequency of severe responses even in the circa-CT trials ostensibly above the CT, but also the rare appearance of severe-intensity responses in all circa-CT trials. Conclusion: These data demonstrate that the transition between heavy- and severe-intensity exercise occurs gradually rather than suddenly.

Exercise Effects on Multiple Sclerosis Quality of Life and Clinical-Motor Symptoms.

Abstract: Introduction Different therapies can improve clinical and motor symptoms of multiple sclerosis (MS) similarly, but studies comparing the effects of different exercise therapies on clinical and motor outcomes are scant. We compared the effects of exergaming (EXE), balance (BAL), cycling (CYC), proprioceptive neuromuscular facilitation (PNF), and a standard care wait-listed control group (CON) on clinical and motor symptoms and quality of life (QoL) in people with MS (PwMS). Methods PwMS (n = 68, 90% female; age, 47.0 yr; Expanded Disability Status Scale score 5-6) were randomized into five groups. Before and after the interventions (five times a week for 5 wk), PwMS were tested for MS-related clinical and motor symptoms (Multiple Sclerosis Impact Scale-29 (MSIS-29), primary outcome), QoL (EuroQol Five Dimensions Questionnaire), symptoms of depression, gait and balance ability (Tinetti Assessment Tool), static and dynamic balance and fall risk (Berg Balance Scale), walking capacity (6-min walk test), and standing posturography on a force platform. Results EXE, BAL, and CYC improved the MSIS-29 scores similarly. EXE and CYC improved QoL and walking capacity similarly but more than BAL. Only EXE improved gait and balance scores (Tinetti Assessment Tool). EXE and BAL improved fall risk and standing balance similarly but more than CYC. PNF and CON revealed no changes. The EuroQol Five Dimensions Questionnaire moderated the exercise effects on the MSIS-29 scores only in EXE. Changes in QoL and changes in the MSIS-29 scores correlated (R = 0.73) only in EXE. Conclusion In conclusion, BAL and CYC but EXE in particular, but not PNF, can improve clinical and motor symptoms and QoL in PwMS (Expanded Disability Status Scale score 5 to 6), expanding the evidence-based exercise options to reduce mobility limitations in PwMS.

Associations between Range of Motion and Tissue Stiffness in Young and Older People.

Abstract: Purpose The purpose of this study was to investigate differences in the associations between passive ankle dorsiflexion range of motion (RoM) and stiffness of the triceps surae, sciatic nerve and deep fascia located in the posterior leg between young and older people. Methods Twenty young and twenty older males were recruited and were placed in a prone position with their hip and knee fully extended. Passive ankle dorsiflexion RoM was determined based on the onset of pain during passive dorsiflexion at 1°/s using an isokinetic dynamometer. Shear wave speeds (as a stiffness index) of the triceps surae, the sciatic nerve and the deep fascia in the posterior leg were evaluated by ultrasound shear wave elastography. Results The shear wave speeds of the medial and lateral gastrocnemius measured at 15° dorsiflexion correlated negatively with passive RoM in young but not in older participants. The shear wave speed of the sciatic nerve measured at 15° dorsiflexion correlated negatively with passive RoM only in older participants. No association was observed between passive RoM and shear wave speed of the deep fascia in the posterior leg. For data measured at maximal dorsiflexion angle (as an index of stretch tolerance), shear wave speeds of the triceps surae and passive joint torque correlated positively with passive RoM in both groups. Conclusion These results suggest that the tissues limiting passive ankle dorsiflexion RoM is muscle and nerve for young and older people, respectively, while stretch tolerance influences passive RoM for both groups. This implies that the relative contribution of non-muscular tissues to joint flexibility become stronger than that of muscles with age.

Contralateral Effects by Unilateral Eccentric versus Concentric Resistance Training.

Abstract: PURPOSE Unilateral resistance training increases muscle strength of the contralateral homologous muscle by the cross-education effect. Muscle damage induced by second eccentric exercise bout is attenuated, even when it is performed by the contralateral limb. The present study compared the effects of unilateral eccentric training (ET) and concentric training (CT) of the elbow flexors (EF) on maximal voluntary isometric contraction (MVC) strength and muscle damage of the contralateral untrained EF. METHODS Young men were placed into ET, CT, ipsilateral repeated bout (IL-RB), and contralateral repeated bout (CL-RB) groups (n = 12 per group). The ET and CT groups performed unilateral EF training consisting of five sets of six eccentric and concentric contractions, respectively, once a week for 5 wk by increasing the intensity from 10% to 100% of MVC, followed by 30 maximal eccentric contractions (30MaxEC) of the opposite EF 1 wk later. The IL-RB group performed two bouts of 30MaxEC separated by 2 wk using the nondominant arm, and CL-RB group performed two bouts of 30MaxEC with a different arm for each bout in 1-wk apart. RESULTS The MVC increased (P < 0.05) greater for the trained (19% ± 8%) and untrained (11% ± 5%) arms in ET when compared with those in CT (10% ± 6%, 5% ± 2%). The magnitude of changes in muscle damage markers was reduced by 71% ± 19% after the second than the first bout for IL-RB group, and by 48% ± 21% for CL-RB group. Eccentric training and CT attenuated the magnitude by 58% ± 25% and 13% ± 13%, respectively, and the protective effect of ET was greater (P < 0.05) than CL-RB, but smaller (P < 0.05) than IL-RB. CONCLUSIONS These results showed that cross-education effect was stronger for ET than CT, and progressive ET produced greater contralateral muscle damage protective effect than a single eccentric exercise bout.

Aerobic Exercise for Sport-related Concussion: A Systematic Review and Meta-analysis.

Abstract: INTRODUCTION Approximately 25% of people with sport-related concussion (SRC) experiences persistent symptoms. The 2016 Berlin consensus on SRC recommends symptom-limited aerobic exercise as a rehabilitation option for persistent symptoms after concussion. However, this recommendation is based on a limited body of knowledge because there is uncertainty about the effectiveness of such interventions. The objective of this systematic review is to assess the effects of symptom-limited aerobic exercise programs compared with control interventions on symptom intensity in individuals with SRC. METHODS A structured search was conducted in MEDLINE, EMBASE, CINHAL, and EBM reviews. Randomized clinical trials (RCT) including aerobic exercise programs as an intervention for SRC were included. After selection, the risk of bias and Grading of Recommendations, Assessment, Development and Evaluation recommendations were applied to pooled studies for quantitative analysis. Standard mean differences (SMD) and 95% confidence interval (CI) were calculated. A descriptive analysis was also performed. RESULTS Seven RCT (326 participants) in adolescent populations were included. Three of seven RCT had a high risk of bias. Symptom-limited aerobic exercise programs have a significant beneficial effect on the perception of symptoms (6 studies, 277 participants, low-quality evidence; pooled SMD, -0.44; 95% CI, -0.68 to -0.19). When introduced in the acute phase, symptom-limited aerobic exercise programs have a significant beneficial effect on symptomatic recovery compared with control interventions (3 studies, 206 participants, moderate quality evidence, pooled SMD, -0.43; 95% CI, -0.71 to -0.15). CONCLUSIONS Symptom-limited aerobic exercise programs are beneficial in improving symptoms of adolescents after an SRC. Good-quality studies are needed to determine effects on adults and on other outcomes.

Exercise Intensity and Recovery on Circulating Brain-derived Neurotrophic Factor.

Abstract: Introduction Brain-derived neurotrophic factor (BDNF) is an exercise-induced neurotropin mediating neuroprotection and synaptic plasticity. Although exercise intensity is implicated as a potentially important mediator of BNDF release after exercise, the optimal exercise stimulus (interval vs continuous) and intensity (submaximal vs supramaximal) for augmenting circulating BDNF levels remains unknown. Irisin, an exercise-driven myokine, may also contribute to neuroprotection by upregulating BDNF. Purpose To examine the response and recovery of plasma BDNF and irisin after acute exercise of differing intensities. Methods Eight males (23.1 ± 3.0 yr of age; V˙O2max 51.2 ± 4.4 mL·kg·min) completed four acute exercise sessions: 1) moderate-intensity continuous training (MICT, 65% V˙O2max); 2) vigorous-intensity continuous training (VICT, 85% V˙O2max); 3) sprint interval training (SIT, "all out"); and 4) no exercise (CTRL). Blood was collected preexercise as well as immediately, 30 min, and 90 min postexercise. Plasma BDNF and irisin were assessed with commercially available enzyme-linked immunosorbent assay kits. Results Plasma BDNF levels increased immediately after exercise in the SIT group (P 0.9999). Conclusions Plasma BDNF levels increased in an intensity-dependent manner with SIT eliciting the highest BDNF concentration immediately postexercise. These results identify SIT as a time-efficient exercise modality to promote brain health through BDNF release.

No Clinical Predictors of Postconcussion Musculoskeletal Injury in College Athletes.

Abstract: PURPOSE This study aimed to identify clinical predictors of postconcussion subsequent musculoskeletal (MSK) injuries. METHODS We recruited 66 National Collegiate Athletic Association intercollegiate student-athletes with a diagnosed concussion as well as 36 National Collegiate Athletic Association student-athletes without a concussion. All participants completed a multifaceted concussion baseline consisting of 1) 22-item 0-6 self-reported symptom checklist with outcomes including both the number of symptoms endorsed (0-22) and 2) total symptom score (0-132), 3) Standard Assessment of Concussion, 4) Balance Error Scoring System, 5) Immediate Post-Concussion Assessment and Cognitive Testing, 6) clinical reaction time, and 7) the King-Devick as well as demographic and injury characteristics. The concussion participants completed the same examination acutely postconcussion, and binary logistic regression was used to identify predictors of subsequent MSK from the change scores (acute minus baseline). From the 66 concussed student-athletes, a subset 36, matched with the healthy athletes, compared the risk of subsequent MSK in the year before and year after their concussion. RESULTS The concussion participants were 1.78 times (95% confidence interval, 1.12-2.84; P = 0.015) more likely to suffer a lower extremity MSK in the year after their concussion than the control participants. The participant demographics and injury characteristics (P = 0.318) and concussion clinical outcomes (P = 0.461) did not predict subsequent MSK. CONCLUSION The concussion participants were 1.78 times more likely to sustain a subsequent MSK; however, no demographic, injury characteristic, or concussion assessments predicted the MSK. Thus, clinicians are not able to utilize common neurological measures or participant demographics to identify those at risk for subsequent lower extremity MSK. Injury prevention strategies should be considered for collegiate student-athletes upon premature return to participation after a concussion to reduce the subsequent MSK.

Clinical and Device-based Metrics of Gait and Balance in Diagnosing Youth Concussion

Abstract: Purpose Evaluate the discriminatory ability of two clinical measures and one device-based measure of gait and balance for concussed youth. Methods We enrolled 81 cases and 90 controls age 14-18 yr old from August 2017 to June 2018. Controls were recruited from a suburban high school, and cases were recruited from the concussion program of an academic pediatric tertiary care center. Tests included two clinical measures: 1) complex tandem gait, scored as sway/errors walking forward and backward eyes open and closed; 2) Modified Balance Error Scoring System (mBESS), scored as total number of errors on three standing tasks; and one device-based measure; 3) Modified Clinical Test of Sensory Interaction and Balance (mCTSIB) using the Biodex Biosway Balance System, scored as a sway index. Sensitivity, specificity, ideal cutpoint, and area under the receiver operating characteristic curve (AUC) were calculated for all test components. Results Ideal cutpoint for total number of sway/errors for tandem gait = 5, sensitivity 41%, specificity 90%. Ideal cutpoint for total mBESS errors = 4, sensitivity 55%, specificity 75%. Ideal cutpoint for mCTSIB = 1.37, sensitivity 37%, specificity 88%. Among each test, some individual components outperformed overall composites, in particular tandem gait (specificity forward eyes open = 99%, sensitivity backward eyes closed = 81%). Among the 40 cases and 65 controls with all three assessments, AUC (95% CI) for tandem gait = 0.63 (0.52,0.75), mBESS = 0.70 (0.60,0.81), and mCTSIB = 0.54 (0.42,0.66). Conclusions A device-based measure of balance did not produce better discriminatory ability than two clinical assessments. Complex tandem gait has the additional benefit of being an easy-to-perform and graded test with highly sensitive and specific individual components.

Muscle Metabolism and Fatigue during Simulated Ice Hockey Match-Play in Elite Players.

Abstract: PURPOSE The present study investigated muscle metabolism and fatigue during simulated elite male ice hockey match-play. METHODS Thirty U20 male national team players completed an experimental game comprising three periods of 8 × 1-min shifts separated by 2-min recovery intervals. Two vastus lateralis biopsies were obtained either during the game (n = 7) or pregame and postgame (n = 6). Venous blood samples were drawn pregame and at the end of the first and last periods (n = 14). Activity pattern and physiological responses were continuously monitored using local positioning system and heart rate recordings. Further, repeated-sprint ability was tested pregame and after each period. RESULTS Total distance covered was 5980 ± 199 m with almost half the distance covered at high skating speeds (>17 km·h). Average and peak on-ice heart rate was 84% ± 2% and 97% ± 2% of maximum heart rate, respectively. Muscle lactate increased (P ≤ 0.05) more than fivefold and threefold, whereas muscle pH decreased (P ≤ 0.05) from 7.31 ± 0.04 pregame to 6.99 ± 0.07 and 7.13 ± 0.11 during the first and last periods, respectively. Muscle glycogen decreased by 53% postgame (P ≤ 0.05) with ~65% of fast- and slow-twitch fibers depleted of glycogen. Blood lactate increased sixfold (P ≤ 0.05), whereas plasma free fatty acid levels increased 1.5-fold and threefold (P ≤ 0.05) after the first and last periods. Repeated-sprint ability was impaired (~3%; P ≤ 0.05) postgame concomitant with a ~10% decrease in the number of accelerations and decelerations during the second and last periods (P ≤ 0.05). CONCLUSIONS Our findings demonstrate that a simulated ice hockey match-play scenario encompasses a high on-ice heart rate response and glycolytic loading resulting in a marked degradation of muscle glycogen, particularly in specific sub-groups of fibers. This may be of importance both for fatigue in the final stages of a game and for subsequent recovery.

Hypoxic Training Is Beneficial in Elite Athletes.

Abstract: There is no doubt that many hypoxic conditions or prolonged exposures to altitude result in “biological costs of hypoxic adaptations that outweigh their benefits” (1), particularly in endurance athletes exposed to a) exercise-induced arterial hypoxemia leading to a larger decrease in VO2max and aerobic endurance; b) increased sympathetic activity and decreased baroreflex sensitivity; and c) increased pulmonary arterial pressure. There is also no doubt that sleeping in moderate altitude (2000-3000 m) as performed by the athletes using either live high-train high (LHTH) or live high-train low (LHTL) methods leads to periodic breathing, intermittent hypoxia (IH) and increase in desaturation periods; e.g. 3% oxygen desaturation index, but to a larger extent in hypobaric hypoxia (HH, real altitude) than in normobaric hypoxia (NH, simulated altitude), as shown at 2250 m (2). The three main questions debated in the present contrasting perspective are however different: 1. Are there any evidences showing if the “counteracting maladaptation” (reported above) outweigh the benefits of the different hypoxic methods at short- or long-term in elite athletes? ; 2. Are there any robust data supporting that hypoxic training is beneficial in elite athletes? ; 3. Contradictory, are there robust data showing that hypoxic training is not beneficial in elite athletes?

A "Step-Ramp-Step" Protocol to Identify the Maximal Metabolic Steady State.

Abstract: The oxygen uptake (V[Combining Dot Above]O2) at the respiratory compensation point (RCP) closely identifies with the maximal metabolic steady state. However, the power output (PO) at RCP cannot be determined from contemporary ramp-incremental exercise protocols. Purpose This study aimed to test the efficacy of a "step-ramp-step" (SRS) cycling protocol for estimating the PO at RCP and the validity of RCP as a maximal metabolic steady-state surrogate. Methods Ten heathy volunteers (5 women; age: 30 ± 7 yr; V[Combining Dot Above]O2max: 54 ± 6 mL·kg·min) performed in the following series: a moderate step transition to 100 W (MOD), ramp (30 W·min), and after 30 min of recovery, step transition to ~50% POpeak (HVY). Ventilatory and gas exchange data from the ramp were used to identify the V[Combining Dot Above]O2 at lactate threshold (LT) and RCP. The PO at LT was determined by the linear regression of the V[Combining Dot Above]O2 versus PO relationship after adjusting ramp data by the difference between the ramp PO at the steady-state V[Combining Dot Above]O2 from MOD and 100 W. Linear regression between the V[Combining Dot Above]O2-PO values associated with LT and HVY provided, by extrapolation, the PO at RCP. Participants then performed 30-min constant-power tests at the SRS-estimated RCP and 5% above this PO. Results All participants completed 30 min of constant-power exercise at the SRS-estimated RCP achieving steady-state V[Combining Dot Above]O2 of 3176 ± 595 mL·min that was not different (P = 0.80) from the ramp-identified RCP (3095 ± 570 mL·min) and highly consistent within participants (bias = -26 mL·min, r = 0.97, coefficient of variation = 2.3% ± 2.8%). At 5% above the SRS-estimated RCP, four participants could not complete 30 min and all, but two exhibited non-steady-state responses in blood lactate and V[Combining Dot Above]O2. Conclusions In healthy individuals cycling at their preferred cadence, the SRS protocol and the RCP are capable of accurately predicting the PO associated with maximal metabolic steady state.

The Acute: Chronic Workload Ratio Is Associated with Injury in Junior Tennis Players.

Abstract: This is the author accepted manuscript version of an article published in Medicine And Science In Sports And Exercise.

Impact of High-Intensity Interval Training, Moderate-Intensity Continuous Training, and Resistance Training on Endothelial Function in Older Adults.

Abstract: Purpose It is unclear if high-intensity interval training (HIIT) elicits superior improvements in brachial artery (BA) flow-mediated dilation (FMD) responses (i.e., endothelial-dependent vasodilation) than moderate-intensity continuous training (MICT) or resistance training (RT) in otherwise healthy older adults. Whether HIIT enhances lower-limb FMD responses and/or augments low flow-mediated constriction (L-FMC) (endothelial-dependent vasoconstriction) responses more than MICT or RT is also unknown. We tested the hypothesis that HIIT would improve BA and popliteal artery (POP) FMD and L-FMC responses more than MICT or RT in healthy older adults. Methods Thirty-eight older adults (age, 67 ± 6 yr) performed 6 wk of either HIIT (2 × 20 min bouts alternating between 15-s intervals at 100% of peak power output [PPO] and passive recovery [0% PPO]; n = 12), MICT (34 min at 60% PPO; n = 12), or whole-body RT (8 exercises, 2 × 10 repetitions; n = 14). The L-FMC and FMD were measured before and after training using high-resolution ultrasound and quantified as the percent change in baseline diameter during distal cuff occlusion and after cuff release, respectively. Results Resting BA blood flow and vascular conductance (both, P 0.20). Conclusions HIIT and MICT, but not RT, similarly improved lower-limb vasodilator and vasoconstrictor endothelial function in older adults. Although HIIT and MICT groups enhanced BA vasodilator function, only HIIT improved resting conductance and endothelial sensitivity to low-flow in the BA. In the short-term, HIIT may be most effective at improving peripheral vascular endothelial function in older adults.