Medicine & Science in Sports & Exercise

Is the Normal Shoulder Rotation Strength Ratio Altered in Elite Swimmers? Introduction It is commonly believed that the shoulder external rotation (ER) to internal rotation (IR) strength ratio is decreased in swimmers due to predominant IR loading during the pull-through (propulsive) phase which predisposes to shoulder pain. However, the evidence supporting this hypothesis is inconclusive. Therefore, the aim of this study was to examine shoulder rotation strength parameters in elite swimmers and investigate potential associations with shoulder pain. Methods Sixty-eight (40 male; age = 19.9±3.2 years) elite swimmers provided demographic and shoulder pain history data prior to measurement of shoulder rotation strength. Mixed model analyses were used to examine differences in shoulder IR and ER strength normalised to body weight (BW) and the shoulder rotation strength ratio. A multinomial logistic regression model was utilised to examine associations between shoulder rotation strength parameters and shoulder pain. Results Mean shoulder IR strength (BW) was approximately 0.29 for male swimmers and 0.26 for females. Mean shoulder ER strength (BW) was approximately 0.19 for male swimmers and 0.18 for females. The shoulder ER: IR strength ratio was approximately 0.70 bilaterally for all swimmers. There were no significant differences between dominant and non-dominant shoulders in IR or ER strength normalized to body weight (p≥0.547). There were no associations between any shoulder strength parameters and shoulder pain (r2=0.032, p=0.107). Conclusion Despite the high IR loading, optimal swimming technique does not alter the normal ER:IR strength ratio at the shoulder. Elite swimmers who report current or a history of shoulder pain demonstrate normal shoulder rotation strength ratios. The finding of symmetrical shoulder rotation strength points to side-to-side strength comparisons as a valuable clinical tool in managing swimmers with unilateral shoulder pain. Corresponding Author: Professor Karen Ginn, School of Medical Sciences, Faculty of Medicine and Health, Room E316, Anderson Stuart Building (F13), The University of Sydney | NSW | 2006, Australia This study was supported by a Biomedical Research Initiative Grant, Discipline of Biomedical Science, The University of Sydney. The authors have no relationships with companies or manufacturers who will benefit from the results of the present study. The results of the present study do not constitute endorsement by ACSM. The authors declare that the results of the present study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for publication: 17 September 2019. © 2020 American College of Sports Medicine

Active Drag as a Criterion for Evidence-based Classification in Para Swimming Introduction Paralympic classification should provide athletes with an equitable starting point for competition by minimising the impact their impairment has on the outcome of the event. As swimming is an event conducted in water, the ability to overcome drag (active and passive) is an important performance determinant. It is plausible that the ability to do this is affected by type and severity of physical impairment, but the current World Para Swimming classification system does not objectively account for this component. The aim of this study was to quantify active and passive drag in Para swimmers and evaluate the strength of association between these measures and type of physical impairment, swimming performance and sport class. Methods Seventy-two highly-trained Para swimmers from sport classes S1 to S10 and fourteen highly-trained non-disabled swimmers were towed by a motorised winch whilst the towing force was recorded. Passive drag was measured with the arms held by the side; active drag was determined during freestyle swimming using an assisted towing method. Results Active and passive drag were higher in Para swimmers with central motor and neuromuscular impairments than for non-disabled swimmers and were associated with severity of swim-specific impairment (sport class) and maximal freestyle performance in these swimmers (r = -.40 to -.50, p ≤ .02). Para swimmers with anthropometric impairments showed similar active and passive drag to non-disabled swimmers, and between swimmers from different sport classes. Conclusion Para swimmers with central motor and neuromuscular impairments are predisposed to high active drag during freestyle swimming that impacts on their performance. It is recommended that drag measures be considered in revised classification for these swimmers, but not for those with anthropometric impairments. Corresponding author: Carl Payton, Musculoskeletal Science & Sports Medicine Research Centre, Manchester Metropolitan University, John Dalton Building, Chester Street, Manchester, M1 5GD, UK. Email: c.payton@mmu.ac.uk The authors would like to thank Manchester Metropolitan University for their technical support, and the International Paralympic Committee and UK Sport for their funding support. We declare that we have no financial or personal relationships with other people or organisations that could inappropriately influence (bias) our work. The results of the present study do not constitute endorsement by ACSM and are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for publication: 21 December 2019. © 2020 American College of Sports Medicine

Footwear and Cadence Affect Gait Variability in Runners with Patellofemoral Pain Purpose To examine the effects of increased cadence and minimalist footwear on lower limb variability in runners with patellofemoral pain (PFP). Methods Fifteen (12 female, 3 male) runners with PFP ran on an instrumented treadmill with 3-dimensional motion capture in three randomly ordered conditions: (i) standard shoe at preferred cadence; (ii) standard shoe +10% cadence; and (iii) minimalist shoe at preferred cadence. Vector coding was used to calculate coordination variability between strides for select lower limb joint couplings. Approximate entropy (ApEn) was calculated to assess continuous variability for segment kinematic and kinetic data and compared between conditions using repeated measures analysis of variance (ANOVA). One-dimensional statistical parametric mapping (SPM1D) repeated measures ANOVA was performed on the coordination variability data. Cohen’s d effect size was calculated for all comparisons. Results Larger ApEn values (i.e. greater variability) were observed for the standard shoe +10% cadence versus the standard shoe at preferred cadence for hip flexion/extension (p < 0.001; d = 1.12), hip adduction/abduction (p < 0.001; d = 0.99) and ankle dorsiflexion/plantarflexion (p < 0.001; d = 1.37) kinematics, and knee flexion/extension moments (p < 0.001; d = 0.93). Greater variability was also observed in the minimalist shoe versus the standard shoe at preferred cadence for hip internal/external rotation moments (p < 0.001; d = 0.76), knee adduction/abduction moments (p < 0.001; d = 0.51) and knee internal/external rotation moments (p < 0.001; d = 1.02). SPM1D repeated measures ANOVA revealed no significant differences in coordination variability between running conditions. Conclusion Greater hip and knee kinematic and kinetic variability observed with either increased cadence or minimalist footwear may be beneficial for those with patellofemoral pain. Corresponding Author: Dr. Jason Bonacci, Centre for Sports Research, School of Exercise and Nutrition Sciences, Deakin University, 75 Pigdons Road, Waurn Ponds, Victoria, Australia, 3216. Ph: +61 3 5227 2634 Fax: +61 3 9244 6017 E-mail: jason.bonacci@deakin.edu.au Disclosure of Funding: No external funding was received for the undertaking of this study or production of this manuscript. The authors declare that the results of this study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The results of this study do not constitute endorsement by the American College of Sports Medicine. Accepted for publication: 26 December 2019. © 2020 American College of Sports Medicine

Effects of Exercise Training on Anxious–Depressive-like Behavior in Alzheimer Rat 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 (WT) rats were divided into WT (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 (ELISA) analysis, and related assay kits were used to measure inflammatory cytokines, oxidative stress, amyloid-beta 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 Aβ 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. Chongyun Wu and Luodan Yang contributed equally to this work. Corresponding author: Quanguang Zhang, Ph. D., Associate Professor, Department of Neuroscience and Regenerative Medicine, Medical college of Georgia, Augusta University, 1120 15th Street, Augusta, GA 30912, USA. Phone: (706) 721-7025, Fax: (706) 721-8685. E-mail: qzhang@augusta.edu This study was supported by Research Grant AG058603 from National Institute on Aging,National Institutes of Health, and Innovation Project of Graduate School of South China Normal University (2018LKXM010). Statement of interest: The authors declare that there is no conflict of interest in the current study. The results of the study are presented clearly, honestly, and without fabrication or inappropriate data manipulation. The results of the present study do not constitute endorsement by ACSM. Accepted for publication: 25 November 2019. © 2020 American College of Sports Medicine

Ultrasonography of Lumbar Multifidus Muscle in University American Football Players Purpose The primary objective of this study was to examine and compare lumbar multifidus (LM) muscle size, asymmetry and function in university football players with and without low back pain (LBP). A secondary objective was to examine the relationship between LM characteristics and body composition in football players. Methods Ultrasound assessments of the LM muscle were performed in 41 university football players during the preseason. LM muscle cross-sectional area (CSA), echo-intensity (e.g. indicator of fatty infiltration and connective tissue), thickness at rest, and thickness during submaximal contraction (e.g. contralateral arm lift) measurements in prone and standing positions were obtained bilaterally at the L5-S1 level. Body composition measures were acquired using dual X-ray absorptiometry (DEXA). A self-administered questionnaire was used to obtain LBP history data. Results The LM muscle thickness at rest in prone and in standing was significantly smaller in football players who reported the presence of LBP in the previous 3-months. The LM CSA in prone was significantly and positively correlated with weight, height, lean body mass, total fat mass, and total % body fat. LM echo-intensity was strongly correlated with total % body fat and total fat mass and negatively correlated with the % thickness change during contraction. Conclusion The results of this study provide novel information on LM muscle morphology and activation in football players in prone and standing and suggest that players with LBP in the previous 3-months had smaller LM muscle thickness. LM morphology was strongly correlated with body composition measurements. Corresponding author: Maryse Fortin, Concordia University, 7141 Sherbrooke St W, L-SP 165-29, H4B 1R6, email: maryse.fortin@concordia.ca, Ph: 514-848-2424, ext. 8642. The PERFORM Centre (Concordia University) and the R. Howard Webster Foundation provided funding for this project. Conflict of Interest: The authors declare that there are no conflicts of interest. There exist no professional relationships with companies or manufacturers who will benefit from the results of this study. The results of the present study do not constitute endorsement by ACSM. The results of this study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for publication: 24 January 2020. © 2020 American College of Sports Medicine

Exercise Training Rapidly Increases Hepatic Insulin Extraction in NAFLD Purpose We aimed to determine the immediacy of exercise intervention on liver-specific metabolic processes in Non-alcoholic fatty liver disease (NAFLD). Methods We undertook a short-term (7-day) exercise training study (60 min/day treadmill walking at 80-85% of maximum heart rate) in obese adults (N=13, 58±3 years, 34.3±1.1 kg/m2, >5% hepatic lipid by 1H-MR spectroscopy). Insulin sensitivity (ISI) was estimated by oral glucose tolerance test using the Soonthorpun model. Hepatic insulin extraction (HIE) was calculated as the molar difference in AUC for insulin and C-peptide (HIE= 1-(AUCInsulin÷AUCC-Pep)). Results The increase in HIE, VO2max and ISI following the intervention was 9.8%, 9.8% and 34%, respectively (all P<0.05). Basal fat oxidation increased (Pre: 47±6 Vs Post: 65±6 mg/min, P<0.05) and carbohydrate oxidation decreased (Pre: 160±20 Vs Post: 112±15 mg/min, P<0.05) with exercise training. After the intervention, HIE correlated positively with adiponectin (r=0.56, P<0.05) and negatively with TNF-α (r=-0.78, P<0.001). Conclusions By increasing hepatic insulin extraction along with peripheral insulin sensitivity, aerobic exercise training rapidly reverses some of the underlying physiological mechanisms associated with NAFLD, in a weight-loss independent manner. This reversal could potentially act through adipokine-related pathways. Keywords: Aerobic Exercise Training; NAFLD; Hepatic Insulin Extraction Address for Correspondence: John P. Kirwan, PhD., FACSM Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, Louisiana 70808 Phone: (225) 763-2500; Fax: (225) 763-2525; Email: John.Kirwan@pbrc.edu The authors declare that they have no conflict of interest. The results of this study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The authors report that results of the present study do not constitute endorsement by ACSM. This research was supported by National Institute of Health (NIH) Grants R01-AG-12834 (J. P. K) and was supported in part by the NIH National Center for Research Resources, CTSA-1UL1-RR-024989, and the Case Center for Imaging Research, Case Western Reserve University, Cleveland, OH. Accepted for publication: 26 December 2019. © 2020 American College of Sports Medicine

The Mechanics of Seated and Nonseated Cycling at Very-High-Power Output: A Joint-level Analysis Cyclists frequently use a non-seated posture when accelerating, climbing steep hills, and sprinting; yet, the biomechanical difference between seated and non-seated cycling remains unclear. Purpose To test the effects of posture (seated and non-seated) and cadence (70 rpm and 120 rpm) on joint power contributions, effective mechanical advantage, and muscle activations within the leg during very-high-power output cycling. Methods Fifteen male participants rode on an instrumented ergometer at 50% of their individualised instantaneous maximal power (10.74 ± 1.99 W⋅kg-1; above the reported threshold for seated to non-seated transition) in different postures (seated and non-seated) and at different cadences (70 rpm and 120 rpm); whilst leg muscle activity, full body motion capture, and crank radial and tangential forces were recorded. A scaled, full-body model was used to solve inverse kinematics and inverse dynamics to determine joint displacements and net joint moments. Statistical comparisons were made using repeated measure, two-way analyses of variance (posture x cadence). Results There were significant main effects of posture and cadence on joint power contributions. A key finding was that the non-seated posture increased negative power at the knee, with an associated significant decrease of net power at the knee. The contribution of knee power decreased by 15% at both 70 and 120 rpm (~=0.8 W·kg-1) when non-seated compared to seated. Subsequently, hip power and ankle power contributions were significantly higher when non-seated compared to seated at both cadences. In both postures, knee power was 9% lower at 120 rpm compared to 70 rpm (~=0.4 W·kg-1). Conclusion These results evidenced that the contribution of knee joint power to leg power was reduced by switching from a seated to non-seated posture during very-high-power output cycling, however the size of the reduction is cadence dependent. Corresponding author: Ross D. Wilkinson, The University of Queensland, School of Human Movement and Nutrition Sciences, Brisbane, QLD, 4072, Australia. ross.wilkinson@uqconnect.edu.au Ross D. Wilkinson was supported by an Australian Government Research Training Program Scholarship. The authors report no conflicts of interest. The results of the present study do not constitute endorsement by ACSM. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for Publication: 19 January 2020. © 2020 American College of Sports Medicine

Dual-Task Gait Recovery after Concussion among Female and Male Collegiate Athletes Purpose Few studies have investigated recovery between sexes using objective outcome measures. Our purpose was to examine the independent association between biological sex and recovery of post-concussion gait among collegiate athletes. Methods We evaluated participants with a diagnosed concussion <7 days post-injury, and approximately 1.5 months and 3.5 months post-injury. Participants completed a single/dual-task gait evaluation and symptom inventory. During dual-task trials, they completed a mental task (backwards subtraction, spelling, or month recitation). The primary outcome measure was height-adjusted gait velocity recovery, defined as achieving normal gait velocity using established values: >0.56 and >0.50 gait velocity (m·s−1)/height (m) under single and dual-task conditions, respectively. We used a multivariable Cox proportional hazard model to identify associations between sex and dual-task recovery, controlling for age, concussion history, symptom severity, and loss of consciousness at the time of injury. Results Ninety-four individuals participated in the study: 47 (50%) were female athletes (mean age=20.1, SD=1.3 years) and 47 (50%) were male athletes (mean age=20.3, SD=1.3 years). Sex was not independently associated with height-adjusted single-task gait velocity recovery after controlling for potential confounders (hazard ratio=1.62, 95% confidence interval=0.87, 3.01). However, male sex was independently associated with longer dual-task gait recovery time after controlling for potential confounders (hazard ratio=2.43, 95% confidence interval=1.11, 5.35). Conclusion Male athletes required a longer duration of time after concussion to achieve dual-task gait recovery than female athletes. Thus, functional dual-task abilities after concussion may be affected differentially by sex, and should be accounted for within individualized concussion management strategies. Corresponding author: David R. Howell, PhD, Sports Medicine Center, Children’s Hospital Colorado, University of Colorado School of Medicine, 13123 E. 16th Avenue, B060 Aurora, CO, USA 80045, Email: David.Howell@CUAnschutz.edu Funding Sources and Conflicts of interest disclosure: Research reported in this work was supported by the National Institute of Neurological Disorders And Stroke of the National Institutes of Health under Award Number R01NS100952. Unrelated to this work, Dr. Howell has received research support from the National Institutes of Health (R03HD094560 and R41NS103698). Dr. Meehan receives royalties from 1) ABC-Clio publishing for the sale of his books, Kids, Sports, and Concussion: A guide for coaches and parents, and Concussions; 2) Springer International for the book Head and Neck Injuries in the Young Athlete and 3) Wolters Kluwer for working as an author for UpToDate. His research is funded, in part, by philanthropic support from the National Hockey League Alumni Association through the Corey C. Griffin Pro-Am Tournament and a grant from the National Football League. The remaining authors have conflicts to disclose. Accepted for Publication: 5 November 2019 © 2020 American College of Sports Medicine

Modification of Neuromuscular Junction Protein Expression by Exercise and Doxorubicin PURPOSE Doxorubicin (DOX) is a highly effective antitumor agent widely used in cancer treatment. However, it is well established that DOX induces muscular atrophy and impairs force production. While no therapeutic interventions exist to combat DOX-induced muscle weakness, endurance exercise training has been shown to reduce skeletal muscle damage caused by DOX administration. Numerous studies have attempted to identify molecular mechanisms responsible for exercise-induced protection against DOX myotoxicity. Nevertheless, the mechanisms by which endurance exercise protects against DOX-induced muscle weakness remain elusive. In this regard, impairments to the neuromuscular junction (NMJ) are associated with muscle wasting, and studies indicate that physical exercise can rescue NMJ fragmentation. Therefore, we tested the hypothesis that exercise protects against DOX-induced myopathy by preventing detrimental changes to key proteins responsible for maintenance of the NMJ. METHODS Female Sprague-Dawley rats were assigned to sedentary or exercise trained groups. Exercise training consisted of a 5-day treadmill habituation period followed by 10 days of running (60min/day, 30m/min, 0% grade). After the last training bout exercise and sedentary animals were paired with either placebo (saline) or DOX (20 mg/kg i.p.) treatment. Two days after drug treatment the soleus muscle was excised for subsequent analyses. RESULTS Our results indicate that endurance exercise training prevents soleus muscle atrophy and contractile dysfunction in DOX treated animals. These adaptations were associated with increased expression of the neurotrophic factors BDNF, GNDF, NGF and NT-3. In addition, exercise enhanced the expression of Rapsyn and the acetylcholine receptor (AChR) subunits AChRβ, AChRδ and AChRγ in DOX treated animals. CONCLUSION Therefore, upregulating neurotrophic factor and NMJ protein expression may be an effective strategy to prevent DOX-induced skeletal muscle dysfunction. Matthew Hinkey, Present address: Translational Research Institute for Metabolism and Diabetes, Florida Hospital, Orlando, FL Corresponding author: Ashley J. Smuder, Department of Applied Physiology and Kinesiology, University of Florida, PO Box 118205, Gainesville, FL 32611, Email: asmuder@ufl.edu This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. ABM was supported by NIH T32 HD043730. CONFLICT OF INTEREST. No conflicts of interest, financial or otherwise, are declared by the authors. The results of the present study do not constitute endorsement by ACSM, and are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for Publication: 20 January 2020 © 2020 American College of Sports Medicine

Cumulative Metrics of Tendon Load and Damage Vary Discordantly with Running Speed Purpose Cumulative load has become a popular metric in running biomechanics research to account for potential spatiotemporal changes associated with different locomotion strategies. This study investigated how incorporating mechanical fatigue principles into Achilles tendon cumulative load measurements affected their relationship with running speed. Methods Achilles tendon forces and strains were estimated from a dynamometry/ultrasound session followed by a motion capture session, where participants ran at three speeds. Three cumulative measures of increasing complexity were calculated using Achilles tendon force/strain: (1) cumulative load, defined as the product of the stance phase time integral of Achilles tendon force/strain and the stride count for 1-km of running; (2) cumulative damage, which accounted for the non-linear relationship between load magnitude and fatigue life by exponentially weighting the time integral of Achilles tendon force/strain prior to multiplication with stride count; and (3) the probability of fatigue failure, which expanded upon the cumulative damage measure of Achilles tendon strain by fitting a probabilistic Weibull model to existing fatigue life data to account for the inherent variability that exists in the fatigue life of biological samples. Results Cumulative load measures significantly decreased with running speed, while the cumulative damage and probabilistic measures either increased or did not change significantly with running speed. Conclusions The choice of cumulative metric has an important influence on the interpretation of overuse injury risk with changes in running speed. While cumulative load metrics certainly provide meaningful information about the load experienced over a given distance, they do not account for the tissue damage incurred by such load. Cumulative load metrics should therefore be interpreted with caution when making inferences to overuse injury risk. Corresponding Author: Colin Firminger, KNB 219, Human Performance Laboratory, University of Calgary, 2500 University Drive NW, Calgary, AB Canada, T2N 1N4, Email:cfirming@ucalgary.ca The authors acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC; RGPIN 01029-2015, CGSD3 504212-2017), as well as support from an Alberta Innovates Graduate Studentship. The authors report no conflicts of interest. The results of this study do not constitute endorsement by the American College of Sports Medicine. The authors declare that the results of this study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for Publication: 20 January 2020 © 2020 American College of Sports Medicine