Medicine & Science in Sports & Exercise

High-Intensity Interval Training is Feasible in Women at High Risk for Breast Cancer Purpose This trial aimed to demonstrate feasibility of high-intensity interval training (HIIT) in post-menopausal, overweight/obese women at high-risk of invasive breast cancer, and explore HIIT on changes in cardiorespiratory fitness (CRF), body weight, and body mass index (BMI) compared to moderate-intensity continuous training (MICT) and usual care (UC). Methods Forty-four women were randomized to HIIT, MICT or UC for a 12-week, thrice weekly, supervised exercise intervention. HIIT included a 5-minute warm-up at 50-70% peak heart rate (HR), four cycles of four minutes at 90-100% peak HR followed by three minutes at 50-70% peak HR. MICT consisted of 41 minutes at 60-70% peak HR. Feasibility was assessed by consent, adherence, compliance and retention rates. CRF, body weight and BMI were measured at baseline and end-of-study. Repeated measures linear mixed models were used to assess within- and between-group differences. Results Average age was 63.9±8.8 years. BMI was 30.9±5.7 kg/m2. Participants completed 90% and 89% of HIIT and MICT workouts respectively, with 100% compliance to the exercise prescriptions. No serious adverse events were reported. Compared to MICT and UC, HIIT exhibited improvements in change in treadmill time (101 seconds greater than MICT, and 125 seconds greater than UC, respectively, p<0.001). Compared to UC, HIIT exhibited improvement in changes in absolute and relative VO2peak (a 0.15 increase in L/min, p=0.005; and 2.3 increase in ml/kg/min, p=0.004). There were no significant differences between groups for body weight or BMI (p>0.05). Conclusions HIIT is feasible, safe, and appears to promote greater improvements in CRF compared to MICT and UC in women at high risk for breast cancer. Correspondence: Susan C Gilchrist, MD; The University of Texas MD Anderson Cancer Center, 1155 Pressler Street, Unit 1360, Houston TX 77230-1439; Phone: 713-745-6251; Fax: 713-794-4403; sgilchrist@mdanderson.org The authors thank the NCI R25 Cancer Prevention Research Training Program (CA057730, PI: Shine Chang PhD), the MD Anderson Cancer Center/Energy Balance Assessment Supplemental Funding (PI: Susan Gilchrist MD), and the MD Anderson Cancer Center, Center for Energy Balance in Cancer Prevention and Survivorship. The authors declare that they have no conflicts of interest to disclose. The results of the present study do not constitute endorsement by the ACSM, and are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for publication: 10 May 2019. 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. © 2019 American College of Sports Medicine

Data-informed Intervention Improves Football Technique and Reduces Head Impacts Introduction Although sport participation is a key contributor to the physical and mental health of children and youth, exposure to sub-concussive head impacts in football has raised concerns about safety for athletes. Purpose To demonstrate the efficacy of incorporating targeted football drills into a team's practice routine with the goal of improving players' technique, and reduce exposure to sub-concussive head impacts. Methods Seventy high-school football players (age=16.4±1.1years) were tested PRE-season using a sport-specific functional assessment. Results from the testing were used to inform the design of a pre-practice intervention aimed at improving tackling and blocking techniques, while reducing exposure to head impacts. The assessment included drills which evaluated the players' ability to safely tackle, and block, while simulating game-like situations. Testing was repeated at MID-season (internal control) without an intervention, and again at POST-season (experimental), following introduction of the pre-practice intervention between these timepoints, administered twice weekly. All testing sessions were recorded, and subsequently reviewed by trained graders based on selected criteria defined by football coaches. A subset of nineteen participants wore in-helmet accelerometers to assess the effectiveness of the intervention in decreasing head impacts during practice. Results Significant improvements in blocking and tackling techniques were observed following the introduction of the intervention (P<0.0001). Participating athletes also showed better techniques when evaluated in new game-like situations, post-season, providing evidence for proper acquisition and generalizability of these safer habits. Finally, frequency of head impacts (>15g) per practice was significantly reduced by ~30% after one month of training. Conclusion Our results suggest that data-informed methods can be used to improve coaching practices, and promote safer play, which can have a positive public health impact moving forward. Corresponding author: Douglas J. Cook, Department of Surgery, Queen's University, Room 232, 18 Stuart St. Kingston, ON K7L 3N6. Phone: 613-549-6666 ext. 3696. Fax: 613-548-1346. dj.cook@queensu.ca Results from this study are presented clearly, honestly and without fabrication, falsification, or inappropriate data manipulation. Results of the present study do not constitute endorsement by the American College of Sports Medicine. The authors declare no conflict of interest. Funding from the Southeastern Ontario Academic Medical Organization (SEAMO) helped making this project possible. Accepted for publication: 7 May 2019. 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. © 2019 American College of Sports Medicine

Motor Strategies Learned during Pain Are Sustained upon Pain-free Re-exposure to Task Introduction Pain affects movement planning and execution, and may interfere with the ability to learn new motor skills. Variations among previous studies suggest task-specific effects of pain on the initial acquisition and subsequent retention of motor strategies. Methods The present study assessed how acute pain in the anterior deltoid muscle affects movement accuracy of fast arm-reaching movements during force field perturbations, and upon immediate pain-free repetition of the same task. Results Despite having slower initial rate of improvement, individuals who experienced pain during training achieved the same final performance as pain-free controls. However, pain altered the strategy of muscle activation adopted to perform the task, which involved less activity of the shoulder and arm muscles. Strikingly, motor strategies developed during the first exposure to the force field were retained upon re-exposure to the same perturbation, after resolution of pain. Conclusion Although reduced muscle activation may be interpreted as metabolically efficient, it reduces joint stability and can have negative consequences for joint integrity. These results demonstrate that alternative motor strategies developed in the presence of pain can be maintained when training is resumed after resolution of pain. This effect could have deleterious consequences if it applies when learning motor skills in sports training and rehabilitation. Corresponding author: Dr Paul W. Hodges, School of Health and Rehabilitation Sciences, The University of Queenslandm, Brisbane QLD 4072, Australia, Phone: +61 7 3365 2008, E-mail: p.hodges@uq.edu.au Disclosures and Acknowledgements This study was funded by a Program Grant (APP1091302), a Senior Principal Research Fellowship (APP1102905) from the National Health and Medical Research Council (NHMRC) of Australia, and a Future Fellowship grant to TC (FT120100391). The authors have no conflicts of interest to declare. All the authors are properly listed, and all have contributed substantially to the manuscript. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation, and statement that results of the present study do not constitute endorsement by ACSM. Accepted for Publication: 29 May 2019 © 2019 American College of Sports Medicine

Cytokine and Sclerostin Response to High-Intensity Interval Running versus Cycling Purpose This study examined whether the exercise-induced changes in inflammatory cytokines differ between impact and no-impact high intensity interval exercise, and whether they are associated with post-exercise changes in sclerostin. Methods Thirty-eight females (n=19, 22.6±2.7 years) and males (n=19, 22.3±2.4 years) performed two high-intensity interval exercise trials in random order (cross-over design): running on a treadmill and cycling on a cycle ergometer. Trials consisted of eight repetitions of 1 min running or cycling at ≥90% maximal heart rate, separated by 1 min passive recovery intervals. Blood was collected pre-exercise, and 5 min, 1h, 24h and 48h post-exercise, and was analyzed for serum levels of interleukins (IL-1β, IL-6, IL-10), tumor necrosis factor alpha (TNF-α) and sclerostin. Results Inflammatory cytokines significantly increased over time in both sexes with some differences between trials. Specifically, IL-1β significantly increased from pre- to 5 min after both trials (23%, p<0.05), IL-6 increased 1h following both trials (39%, p<0.05), IL-10 was elevated 5 min after running (20%, p<0.05) and 1h after both running and cycling (41% and 64%, respectively, p<0.05), and TNF-α increased 5 min after running (10%, p<0.05). Sclerostin increased 5 min following both trials, with a greater increase in males than in females (62 vs 32 pg/ml in running, p=0.018; 63 vs 30 pg/ml in cycling, p=0.004). In addition, sclerostin was significantly correlated with the corresponding changes in inflammatory cytokines and 34% of the variance in its post-exercise gain score (Δ) was explained by sex and the corresponding gain scores in TNF-α, which was the strongest predictor. Conclusion A single bout of either impact or no-impact high-intensity exercise induces changes in inflammatory cytokines, which are associated with the post-exercise increase in sclerostin. Corresponding author: Panagiota Klentrou Department of Kinesiology Faculty of Applied Health Sciences Brock University 1812 Sir Isaac Brock Way St. Catharines, ON, L2S 3A1, Canada E-mail: nklentrou@brocku.ca This study was funded by a National Science Engineer Research Council of Canada (NSERC) grant to P. Klentrou (grant # 2015-04424). R. Kouvelioti holds an Ontario Trillium Scholarship. N. Kurgan holds an NSERC Doctoral Scholarship. W. Wards holds a Canada Research Chair in Bone and Muscle Development. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The results of the present study do not constitute endorsement by ACSM. Conflicts of interest: The authors have no conflict of interest to declare. Accepted for publication: 14 June 2019. © 2019 American College of Sports Medicine

Extended Sleep Maintains Endurance Performance better than Normal or Restricted Sleep Purpose The cumulative influence of sleep time on endurance performance remains unclear. This study examined effects of three consecutive nights of both sleep extension and restriction on endurance cycling performance. Methods Endurance cyclists/triathletes (n=9) completed a counterbalanced crossover experiment with three conditions; sleep restriction (SR), normal sleep (NS), and sleep extension (SE). Each condition comprised seven days/nights of data collection (-2, -1, D1, D2, D3, D4, +1). Sleep was monitored using actigraphy throughout. Participants completed testing sessions on days D1-D4 that included an endurance time-trial (TT), mood, and psychomotor vigilance assessment. Perceived exertion (RPE) was monitored throughout each TT. Participants slept habitually prior to D1, however, time in bed was reduced by 30% (SR), remained normal (NS), or extended by 30% (SE) on nights D1, D2, and D3. Data were analysed using Generalised Estimating Equations. Results On nights D1, D2, and D3, total sleep time was longer (P<0.001) in the SE condition (8.6±1.0; 8.3±0.6; 8.2±0.6h, respectively), and shorter (P<0.001) in the SR condition (4.7±0.8; 4.8±0.8; 4.9±0.4h) compared with NS (7.1±0.8; 6.5±1.0; 6.9±0.7h). Compared with NS, TT performance was slower (P<0.02) on D3 of SR (58.8±2.5 vs 60.4±3.7min) and faster (P<0.02) on D4 of SE (58.7±3.4 vs 56.8±3.1min). RPE was not different between or within conditions. Compared with NS, mood disturbance was higher-, and psychomotor vigilance impaired, following SR. Compared with NS, psychomotor vigilance improved following SE. Conclusion Sleep extension for three nights led to better maintenance of endurance performance compared with normal and restricted sleep. Sleep restriction impaired performance. Cumulative sleep time affects performance by altering the perceived exertion of a given exercise intensity. Endurance athletes should sleep >8 hours per night to optimise performance. Corresponding author: Spencer S. H. Roberts, PhD Candidate School of Exercise and Nutrition Sciences, Deakin University. 221 Burwood Hwy, Burwood, Victoria, Australia, 3125 Email: rspen@deakin.edu.au The results of this study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Results do not constitute endorsement by the American College of Sports Medicine. Spencer Roberts, Wei-Peng Teo, Brad Aisbett, and Stuart Warmington declare they have no conflict of interest. The authors acknowledge the School of Exercise and Nutrition Sciences at Deakin University for funding the study. Accepted for publication: 9 June 2019. © 2019 American College of Sports Medicine

Methodological Recommendations for Menstrual Cycle Research in Sports and Exercise Introduction The aim of this review is to provide methodological recommendations for menstrual cycle research in exercise science and sports medicine based on a review of recent literature. Research in this area is growing, but often reports conflicting results and it is proposed that some of this may be explained by methodological issues. Methods This review examined the menstrual cycle verification methodologies used in recent literature on exercise performance over the menstrual cycle identified through a literature search of PubMed and SportDiscus from 2008 until 2018. Results Potential changes over the menstrual cycle are likely related to hormone fluctuations, however, only 44% of the selected studies measured the actual concentrations of the female steroid hormones estrogen and progesterone. It was shown that the likely inclusion of participants with anovulatory or luteal phase deficient cycles in combination with small participant numbers has impacted results in recent menstrual cycle research and consequently our understanding of this area. Conclusion To improve the quality of future menstrual cycle research it is recommended that a combination of three methods is used to verify menstrual cycle phase: the calendar-based counting method combined with urinary luteinizing hormone surge testing and the measurement of serum estrogen and progesterone concentrations at the time of testing. A strict luteal phase verification limit of >16 nmol·L-1 for progesterone should be set. It is also recommended that future research focusses on the inclusion of the late follicular estrogen peak. It is envisaged that these methodological recommendations will assist in clarifying some of the disagreement around the effects of the menstrual cycle on exercise performance and other aspects of exercise science and sports medicine. Corresponding author: Xanne Janse de Jonge Exercise & Sport Science Faculty of Science The University of Newcastle, Australia Central Coast Campus PO Box 127 Ourimbah NSW 2258 Australia E: X.Jansedejonge@newcastle.edu.au ORCID 0000-0003-3657-5298 Xanne Janse de Jonge, Belinda Thompson and Ahreum Han declare that they have no conflicts of interest relevant to the content of this review. The results of the present study do not constitute endorsement by ACSM. The results of this review are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. No funding was received for this review. Accepted for publication: 22 May 2019. © 2019 American College of Sports Medicine

Estimated Cardiorespiratory Fitness and Risk of Atrial Fibrillation: The HUNT Study Purpose To investigate the association between estimated cardiorespiratory fitness (eCRF) and risk of atrial fibrillation (AF), and examine how long-term changes in eCRF affects the AF risk. Methods This prospective cohort study includes data of 39 844 men and women from the HUNT2 (August 15, 1995 - June 18, 1997) and the HUNT3 study (October 3, 2006 – June 25, 2008). The follow-up period was from HUNT3 until AF diagnosis or November 30, 2015. AF diagnoses were retrieved from hospital registers and validated by medical doctors. A non-exercise test based on age, waist circumference, resting heart rate and self-reported physical activity was used to estimate CRF. Cox regression was performed to assess the association between eCRF and AF. Results The mean age was 50.6 ± 14.6 years for men and 50.2 ± 15.2 years for women. Mean follow-up time was 8.1 years. 1 057 cases of AF were documented. For men, the highest risk reduction of AF was 31% in the 4th quintile of eCRF when compared to the 1st quintile (HR, 0.69; 95% CI, 0.53-0.89). For women, the highest risk reduction was 47% in the 5th quintile when compared to the 1st quintile (HR, 0.53; 95% CI, 0.38-0.74). One metabolic equivalent increase in eCRF over a 10-year period was associated with 7% lower risk of AF (HR, 0.93; 95% CI, 0.86-1.00) Participants with improved eCRF had 44% lower AF risk compared to those with decreased eCRF (HR, 0.56; 95% CI, 0.36-0.87). Conclusion eCRF was inversely associated with AF, and participants with improved eCRF over a 10-year period had less risk of AF. These findings support the hypothesis that fitness may prevent AF. Correspondence and reprints to: Lars E. Garnvik, Department of Circulation and Medical Imaging, NTNU, Medisinsk Teknisk Forskningssenter, Post box 8905, 7491 Trondheim, Norway. E-mail: lars.e.garnvik@ntnu.no This work was supported by grants from the The Liaison Committee for education, research and innovation in Central Norway. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation, and statement that results of the present study do not constitute endorsement by ACSM. The Nord-Trøndelag Health Study (The HUNT Study) is a collaboration between HUNT Research Centre, (Faculty of Medicine and Health Sciences, NTNU, Norwegian University of Science and Technology), Trøndelag County Council, Central Norway Regional Health Authority, and the Norwegian Institute of Public Health. We would like to thank all the participants and technicians of the HUNT study for their contributions. Conflict of interest: None declared. Accepted for publication: 14 June 2019. © 2019 American College of Sports Medicine

New On-Water Test for the Assessment of Blood Lactate Response to Exercise in Elite Kayakers Purpose Lactate thresholds are physiological parameters used to train athletes and monitor performance or training. Currently, the assessment of lactate thresholds in kayakers is performed in a laboratory setting utilizing specific ergometers; however, laboratory tests differ from on-water evaluation for several reasons. The aim of this study was to assess reliability and validity of a new on-water incremental test for the assessment of blood lactate response to exercise in flat-water kayakers. Maximal lactate steady state test (MLSS) was used as criterion measurement. Methods Eleven junior (16.5±1.9yr) élite flat-water kayakers performed: i) an incremental cardiopulmonary test up to voluntary exhaustion on a stationary kayak ergometer to determine peak oxygen uptake; ii) an on-water 1000m distance trial (T1000) to record best performance time and average speed (S1000); iii) two repetitions of on-water incremental kayaking test (WIK-test); iv) several repetitions of on-water constant speed tests to determine MLSS. Speed, heart rate and blood lactate concentrations were determined during on-water tests. Results The best performance time in T1000 was 262±13s, corresponding to an S1000 of 3.82±0.19m·s-1. Lactate threshold determined by modified Dmax method (LTDmod) during WIK-test was 2.78±1.02mmol·L-1 and the corresponding speed (SLT) was 3.34±0.16m·s-1. Test-retest reliability, calculated on SLT, was strong (ICC=0.95 and r=0.93). MLSS corresponded to 3.06±0.68mmol·L-1 and was reached at a speed (SMLSS) of 3.36±0.14m·s-1. Correlation coefficient between SLT and SMLSS was 0.90 (p=0.0001). Interestingly, a significant correlation (r=0.96, p<0.0001) was observed between SLT and S1000. Conclusions WIK-test showed good reliability and validity for the assessment of speed corresponding to LTDmod in flat-water kayakers and it could be a useful tool to monitor athletic performance. The speed value at LTDmod nicely predicted performance on 1000m. Corresponding Author: Simone Porcelli Institute of Biomedical Technologies National Research Council Via Fratelli Cervi, 93 – Segrate 20090 (MI), Italy simone.porcelli@itb.cnr.it The authors have no conflicts of interest, source of founding, or financial ties to disclose and the results of the present study do not constitute endorsement by the American College of Sport Medicine. The results of this study are presented clearly, honestly, and without fabrication, or inappropriate data manipulation. Accepted for publication: 18 June 2019. © 2019 American College of Sports Medicine

The Physiology of Auto Racing: A Brief Review Introduction Auto racing poses a unique set of physiologic challenges for athletes who compete in this sport. These challenges are not widely recognized due to the limited amount of original research in this field and the diffuse nature of this literature. The purpose of this article is to review the major physiologic challenges of auto racing and summarize what is currently known about athletes in this sport. Conclusions The physical stressors of either driving or servicing the race car are overlaid with particular environmental challenges associated with racing (e.g. thermal, noise, carbon monoxide exposure) that increase the physiological stress on motorsport athletes. Physical stress reflects the muscular work required for car control and control of posture during high gravitational (g) loads: factors that predispose athletes to fatigue. The physiologic effects of these stressors include cardiovascular stress as reflected by prolonged elevation of heart rate, cardiac output, and oxygen consumption in both driver and pit athletes during competition. Psychological stress is evident in autonomic and endocrine responses of athletes during competition. The thermal stress of having to compete wearing multi-layer fire suits and closed helmets in ambient temperatures of 50-60o C results in the ubiquitous risk of dehydration. Published data show that both drivers and pit crew members are accomplished athletes with distinct challenges and abilities. There are gaps in the literature, especially in regard to female, older adult, and child participants. Additionally, minimal literature is available on appropriate training programs to offset the physiological challenges of auto racing. Address for correspondence: Michael B. Reid, Ph.D., College of Health & Human Performance, University of Florida, 1864 Stadium Rd., Suite 200, Gainesville, FL 32611; Tel.: 352-294-1601; Fax: 352-392-3186; E-mail: michael.reid@ufl.edu. This work was supported by the University of Florida and Texas A&M University. The authors have no conflicts of interest related to this article. The facts in this article are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Content of the article does not constitute endorsement by ACSM. Accepted for Publication: 10 April 2019 © 2019 American College of Sports Medicine

Fuel Use During Exercise At Altitude In Women With Glucose–Fructose Ingestion Purpose: This study compared the co-ingestion of glucose and fructose on exogenous and endogenous substrate oxidation during prolonged exercise at terrestrial high altitude (HA) versus sea level, in women. Method Five women completed two bouts of cycling at the same relative workload (55% Wmax) for 120 minutes on acute exposure to HA (3375m) and at sea level (~113m). In each trial, participants ingested 1.2 g.min-1 of glucose (enriched with 13C glucose) and 0.6 g.min-1 of fructose (enriched with 13C fructose) before and every 15 minutes during exercise. Indirect calorimetry and isotope ratio mass spectrometry were used to calculate fat oxidation, total and exogenous carbohydrate oxidation, plasma glucose oxidation and endogenous glucose oxidation derived from liver and muscle glycogen. Results The rates and absolute contribution of exogenous carbohydrate oxidation was significantly lower at HA compared with sea level (ES>0.99, P<0.024), with the relative exogenous carbohydrate contribution approaching significance (32.6±6.1 vs. 36.0±6.1%, ES=0.56, P=0.059) during the second hour of exercise. In comparison, no significant differences were observed between HA and sea level for the relative and absolute contributions of liver glucose (3.2±1.2 vs. 3.1±0.8%, ES=0.09, P=0.635 and 5.1±1.8 vs. 5.4±1.7 grams, ES=0.19, P=0.217), and muscle glycogen (14.4±12.2% vs. 15.8±9.3%, ES=0.11, P=0.934 and 23.1±19.0 vs. 28.7±17.8 grams, ES=0.30, P=0.367). Furthermore, there was no significant difference in total fat oxidation between HA and sea level (66.3±21.4 vs. 59.6±7.7 grams, ES=0.32, P=0.557). Conclusion In women, acute exposure to HA reduces the reliance on exogenous carbohydrate oxidation during cycling at the same relative exercise intensity. Keys Words Acute Hypoxia, Carbon Isotope, Exogenous Carbohydrate Oxidation, Liver Glycogen, Muscle Glycogen, Plasma Glucose Oxidation Address for Correspondence: John O'Hara, Research Institute for Sport, Physical Activity and Leisure, School of Sport, Leeds Beckett University, Headingley Campus, Leeds, LS6 3QS, UK. Email: J.OHara@leedsbeckett.ac.uk The authors would like to thank all the participants for their time and effort, as well as Leeds Beckett University for funding this research. The authors declared that the results of this study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The results of the present study do not constitute endorsement by ACSM. The authors report no conflict of interest. Accepted for publication: 10 June 2019. © 2019 American College of Sports Medicine

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