Physiology Commons^™

Validation Of Piezorx Pedometer Derived Sedentary Time, Katelynn Donahoe, Dany Macdonald, Mark Tremblay, Travis Saunders

International Journal of Exercise Science

International Journal of Exercise Science 11(7): 552-560, 2018. Although pedometers are valid tools for measuring physical activity, to date they have not been used to assess sedentary time. The primary purpose of this study was to determine if the PiezoRx pedometer is a valid and reliable measure of sedentary time compared to the hip-worn Actical accelerometer. A secondary purpose was to compare sedentary time derived via the Fitbit Flex with that of the Actical. Finally, a third purpose was to compare sedentary time derived from the above devices, with that of the ActivPAL inclinometer. Thirty-five participants ages 11-69 years (M …

Validation Of The Piezorx® Step Count And Moderate To Vigorous Physical Activity Times In Free Living Conditions In Adults: A Pilot Study, Myles W. O'Brien, William R. Wojcik, Lisette D' Entremont, Jonathon R. Fowles

International Journal of Exercise Science

International Journal of Exercise Science 11(7): 541-551, 2018. The purpose of the study was to: 1) Validate the PiezoRx® for steps and intensity related physical activity in free-living conditions compared to the criterion measure. 2) Compare PiezoRx®’s steps and intensity related physical activity to physiological assessments. 3) To assess the utility of the PiezoRx® in a subsample of participants. Thirty-nine participants consisting of 28 females aged 54.9±10.6 (33-74) years and 11 males aged 63.9±10.9 (44-80) years wore the PiezoRx® physical activity monitor and the ActiGraph® accelerometer for one full week and completed a physical assessment. A subsample (n=24) wore the …

The Accuracy And Validity Of Ios-Based Heart Rate Apps During Moderate To High Intensity Exercise, Alexa M. Bouts, Lauren Brackman, Elizabeth Martin, Adam M. Subasic, Edward S. Potkanowicz

International Journal of Exercise Science

International Journal of Exercise Science 11(7): 533-540, 2018. People use their smartphones for everything from web browsing to tracking fitness metrics. However, it is unclear whether smartphone-based apps that use photoplethysmography to measure heart rate are an accurate or valid measure of exercise intensity. Purpose was to determine the accuracy and validity of two iOS-based heart rate monitors, Runtastic Heart Rate Monitor and Pulse Tracker PRO by Runtastic (Runtastic) and Instant Heart Rate+: Heart Rate and Pulse Monitor by Azumio (Instant Heart Rate), when compared to the electrocardiogram (ECG) and Polar® T31 uncoded heart rate monitor from moderate to vigorous …

A Descriptive Study Of Objectively Measured Pokémon Go Playtime In College Students, Charles J. Fountaine, Emily J. Springer, Jasmine R. Sward

International Journal of Exercise Science

International Journal of Exercise Science 11(7): 526-532, 2018. Since its debut in July 2016, Pokémon GO has been a wildly popular mobile gaming app. In contrast to many previous apps, Pokémon GO requires the user to be physically active. However, the extent to which Pokémon GO contributes to physical activity is unknown. Therefore, the purpose of this study was to investigate the physical activity profile of playing Pokémon GO for 60 minutes in recreationally active college students. College students (n=27, n=19 female) were fitted with an accelerometer, pedometer, and heart rate monitor to assess the activity demands during a 60-min …

Intraindividual Variability And Validity In Smart Apparel Muscle Activity Measurements During Exercise In Men, Jonathan Aquino, Jenevieve L. Roper

International Journal of Exercise Science

International Journal of Exercise Science 11(7): 516-525, 2018. The purpose of the study was to compare smart apparel (SA) muscle activity measurements to surface electromyography (sEMG) muscle activity measurements during exercise, and determine if any systematic bias of the apparel exists. Thirty-five male participants (Ages 23.1±2.92 yrs, height 178±0.09 cm, mass 81.14±10.59 kg, body fat percentage 15.4±4.79%) provided informed consent for participation. During two separate exercise sessions, participants performed three sets of 12 bodyweight squats and pushups in both SA and sEMG. Conditions (sEMG or SA) were randomly counterbalanced. During sEMG, sensors were placed at selected anatomical locations on the …

Current State Of Commercial Wearable Technology In Physical Activity Monitoring 2015-2017, Jennifer Bunn, James W. Navalta, Charles J. Fountaine, Joel Reece

International Journal of Exercise Science

International Journal of Exercise Science 11(7): 503-515, 2018. Wearable physical activity trackers are a popular and useful method to collect biometric information at rest and during exercise. The purpose of this systematic review was to summarize recent findings of wearable devices for biometric information related to steps, heart rate, and caloric expenditure for several devices that hold a large portion of the market share. Searches were conducted in both PubMed and SPORTdiscus. Filters included: humans, within the last 5 years, English, full-text, and adult 19+ years. Manuscripts were retained if they included an exercise component of 5-min or greater and …

Effect Of An 8-Week Eccentric Training Program On Strength And Balance In Older Adults, Samantha Johnson

International Journal of Exercise Science

International Journal of Exercise Science 11(3): 468-478, 2018. The purpose of the current study was to determine changes in balance and strength following an eccentric resistance training program in community-dwelling older adults who reported no history of falling. Participants (N = 14, 8 female, 6 male; age = 63.5 ± 2.0 years) completed an 8-week eccentric exercise training intervention on a commercially available eccentric step machine. Training included 2 training sessions per week, with a duration of 5 to 10 minutes and an intensity of 30 to 50% maximal eccentric strength. Single leg stance, 30-second repeated chair stand, timed …

The Relationship Between Athlete Identity And Career Exploration And Engagement In Division Ii Athletes, Jade M. Bell, Steven Prewitt, Vipa Bernhardt, Dean Culpepper

International Journal of Exercise Science

International Journal of Exercise Science 11(5): 493-502, 2018. There are over 480,000 individuals who compete under the governing of the National Collegiate Athletic Association (NCAA) but only a few of these student athletes continue to compete after college. The aim of this study was to assess whether there is an association between athlete identity and career exploration and engagement among current student athletes. Student athletes (N = 44) from various National Collegiate Athletic Association Division II institutions in the Southwest United States participated in the study. Participants were asked to complete an online survey consisting of demographic questions, the …

Effect Of Magnesium Carbonate Use On Repeated Open-Handed And Pinch Grip Weight-Assisted Pull-Ups, Nicholas T. Bacon, Greg A. Ryan, Jonathan E. Wingo, Mark T. Richardson, Tracey Pangallo, Phillip A. Bishop

International Journal of Exercise Science

International Journal of Exercise Science 11(4): 479-492, 2018. The purpose was to determine if pull-up performance was affected by the use of chalk (100% magnesium carbonate) during open-handed and pinch grip weight-assisted pull-ups (WAPU) in recreationally-trained rock climbers. Furthermore, the reliability of open-handed and pinch grip WAPU was also investigated. Recreationally-active volunteers (n = 9) completed six counterbalanced trials. Participants used chalk during four trials to determine the reliability (test-retest) of the open-handed and pinch grips. While two of the six trials were used to determine if open-handed and pinch grip WAPU performance was affected without using chalk. Three of …

Effects Of A 60 Minute On Ice Game Simulation On The Balance Error Scoring System, Philip Cameron, Noelle C. Soltero, Justin Byers

International Journal of Exercise Science

International Journal of Exercise Science 11(6): 462-467, 2018. Mild traumatic brain injuries (mTBIs) are common in contact sports. There is an association between mTBIs and altered motor function. BioSway technology measures individuals’ balance using the Balance Error Scoring System (BESS). Prior to incorporating BESS testing in concussion protocol, other variables that influence the BESS test require review. The objective of this study is to determine if game fatigue in hockey players also influences the BESS score. 23 male (21.08 ± 1.09) National Collegiate Athletic Association (NCAA) athletes were tested using the BioSway™ (Biodex, USA). The BESS test measures the Sway …

Adropin: An Endocrine Link Between The Biological Clock And Cholesterol Homeostasis, Sarbani Ghoshal, Joseph R. Stevens, Cyrielle Billon, Clemence Girardet, Sadichha Sitaula, Arthur S. Leon, D.C. Rao, James S. Skinner, Tuomo Rankinen, Claude Bouchard, Marinelle V. Nuñez, Kimber L. Stanhope, Deborah A. Howatt, Alan Daugherty, Jinsong Zhang, Matthew Schuelke, Edward P. Weiss, Alisha R. Coffey, Brian J. Bennett, Praveen Sethupathy, Thomas P. Burris, Peter J. Havel, Andrew A. Butler

Physiology Faculty Publications

Objective

Identify determinants of plasma adropin concentrations, a secreted peptide translated from the Energy Homeostasis Associated (ENHO) gene linked to metabolic control and vascular function.

Methods

Associations between plasma adropin concentrations, demographics (sex, age, BMI) and circulating biomarkers of lipid and glucose metabolism were assessed in plasma obtained after an overnight fast in humans. The regulation of adropin expression was then assessed in silico, in cultured human cells, and in animal models.

Results

In humans, plasma adropin concentrations are inversely related to atherogenic LDL-cholesterol (LDL-C) levels in men (n = 349), but not in women (n = …

Rad Gtpase Deletion Atenuates Post-Ischemic Cardiac Dysfunction And Remodeling, Janet R. Manning, Lakshman Chelvarajan, Bryana R. Levitan, Catherine Nicole Kaminski Withers, Prabhakara R. Nagareddy, Christopher M. Haggerty, Brandon K. Fornwalt, Erhe Gao, Himi Tripathi, Ahmed Abdel-Latif, Douglas A. Andres, Jonathan Satin

Physiology Faculty Publications

The protein Rad interacts with the L-type calcium channel complex to modulate trigger Ca²⁺ and hence to govern contractility. Reducing Rad levels increases cardiac output. Ablation of Rad also attenuated the inflammatory response following acute myocardial infarction. Future studies to target deletion of Rad in the heart could be conducted to establish a novel treatment paradigm whereby pathologically stressed hearts would be given safe, stable positive inotropic support without arrhythmias and without pathological structural remodeling. Future investigations will also focus on establishing inhibitors of Rad and testing the efficacy of Rad deletion in cardioprotection relative to the time of …

An Evaluation Of Select Physical Activity Exercise Classes On Bone Metabolism, Tori M. Stone, Jonathan E. Wingo, John C. Young, James W. Navalta

International Journal of Exercise Science

International Journal of Exercise Science 11(2): 452-461, 2018. Weight-bearing physical activity can optimize bone mass early in life and prevent the development of osteoporosis. However, less is known about the potential benefits of non-weight-bearing activities. The purpose of this study was to assess the efficacy of structured physical activity classes on bone metabolism. Twenty-eight premenopausal women, aged 18–35 years who were either enrolled in a yoga class (n=14) or cardio-kickboxing class (n=14) voluntarily consented to participate. Both classes were introductory classes meeting twice per week for 50 min per session for 12 weeks. Anteroposterior spine (L1-L4), hip (dual femur), and …

Weekly Salivary Biomarkers Across A Season For Elite Men Collegiate Basketball Players, Matthew J. Andre, Andrew C. Fry, Paul E. Luebbers, Andrea Hudy, Patricia R. Dietz, Glenn J. Cain

International Journal of Exercise Science

International Journal of Exercise Science 11(6): 439-451, 2018. The purpose of this study was to monitor weekly the salivary free testosterone (FT), cortisol (C), and the FT/C ratio in elite men NCAA Division I basketball athletes across an entire season. Twelve athletes gave salivary samples for 30 consecutive weeks, beginning in the pre-season and ending one week after the end of post-season competition. Samples were assayed for FT and C. Additionally, a composite value (CBD) composed of Z-scores for weekly practice minutes, game minutes, resistance training repetitions, academic demands, and travel schedules was determined. One-way RM ANOVAs were used to …

Comparison Of Techniques For Tracking Body Composition Changes Across A Basketball Season, Ashley Ploudre, Jerry Mayhew

International Journal of Exercise Science

International Journal of Exercise Science 11(4): 425-438, 2018. Body composition assessment has become an integral part of athletes’ training schedules. Questions remain concerning the accuracy of various methods to track body composition changes over a competitive year cycle. The purpose of this study was to compare various methods of tracking body composition across a college women’s basketball season. Fourteen Division II women (age = 20.1 ± 1.2 y) were measured prior to the season (T1), after pre-season conditioning (T2), at mid-season (T3), and at the end of the season (T4) using skinfolds (SKF), two bioelectric impedance analysis (BIA) devices, and …

External Feedback Does Not Affect Running Pace In Recreational Runners, Nicholas A. Puleo, Kirk A. Abraham

International Journal of Exercise Science

International Journal of Exercise Science 11(5): 384-390, 2018. Many runners receive external feedback, such as running pace, during training; however, it is unknown if this feedback increases the intensity of a given exercise session. Therefore, the purpose of this study was to examine the effect of the provision of pace feedback on self-selected submaximal running pace, heart rate, and perceived exertion in recreational runners. Ten runners (6 female, 4 male) completed four 30-min treadmill running bouts in random order, each on a separate day. In each session, participants adjusted their pace as desired; however, all treadmill display information was concealed …

Comparison Of Body Composition Measurements In Lean Female Athletes, Carly L. Houska, Jessica D. Kemp, Jamal S. Niles, Amy Morgan, Robin M. Tucker, Mary-Jon Ludy

International Journal of Exercise Science

International Journal of Exercise Science 11(4): 417-424, 2018. This study compared body composition measurements in lean female athletes. The primary objective was to compare the accuracy of percent body fat (%BF) determined by bioelectrical impedance analysis (BIA), air-displacement plethysmography (ADP), and underwater weighing (UWW) in female Division I cheerleaders (n = 10 bases, 6 back-spots, and 12 flyers) from two universities. The secondary objective was to compare health risk predicted by %BF to body mass index (BMI) categorizations. UWW was considered the gold standard for assessing %BF. Pearson correlation coefficients were used to determine associations between methods. Repeated measures …

Association Between Different Non-Invasively Derived Thresholds With Lactate Threshold During Graded Incremental Exercise., Conor J. Raleigh, Bernard Donne, Neil Fleming

International Journal of Exercise Science

International Journal of Exercise Science 11(4): 391-403, 2018. We compared lactate threshold (T_Lac)with non-invasive markers of an aerobic-anaerobic transition; namely, ventilatory (VT) and tissue saturation index (TSI_T) thresholds. While identification of a breakpoint in blood lactate concentration ([BLa]) is common for determination of an aerobic-anaerobic transition, non-invasive measures, VT and NIRS, have also received attention as a means of determining this critical exercise intensity. We hypothesised that one or other of these non-invasive measures would have a strong association with T_Lac. Thirty-one (n=31) competitive male athletes (mean ± SD, age 29±9 yr, height 1.81±0.1 …

Comparison Of A Pneumatic Compression Device To A Compression Garment During Recovery From Doms, Molly Winke, Shelby Williamson

International Journal of Exercise Science

International Journal of Exercise Science 11(3): 375-383, 2018. The purpose of this study was to determine the effects of a pneumatic compression device (PCD) compared to a continuously-worn compression sleeve (CS) during a five-day recovery period from delayed-onset muscle soreness (DOMS) of the elbow flexors. Eight college-aged students participated in this crossover design study. The muscle-damage protocol consisted of four sets of 25 repetitions of isokinetic concentric elbow flexion followed by eccentric elbow extension at 60 ^o/second. Immediately following the muscle-damage protocol, subjects either wore a CS continually for five days or completed daily, 20-minute PCD treatments for five …

The Effect Of Acute L-Carnitine And Carbohydrate Intake On Cycling Performance, Boe M. Burrus, Brian M. Moscicki, Tracey D. Matthews, Vincent J. Paolone

International Journal of Exercise Science

International Journal of Exercise Science 11(2): 404-416, 2018. Chronic supplementation of L-carnitine and carbohydrate has been reported to increase L-carnitine content in skeletal muscle and have positive influences on exercise variables and performance. This study investigated the acute intake of L-carnitine and carbohydrate on the exercise parameters of cycling. A total of 10 males (27.0 ± 4 years) completed two exercise sessions consisting of 40 min of cycling at 65% of VO_2peak, followed by cycling to exhaustion at 85% of VO_2peak. L-carnitine or a placebo was consumed 3 hours prior to exercise, and beverages consisting of …

Global Active Stretching (Sga®) Practice For Judo Practitioners’ Strength Enhancement, Heleno Almeida Jr., Raphael F. De Souza, Felipe J. Aidar, Alisson G. Da Silva, Ricardo P. Regi, Afranio A. Bastos

International Journal of Exercise Science

International Journal of Exercise Science 11(6): 364-374, 2018. In order to analyze the Global Active Stretching (SGA®) practice on the physical performance enhancement in judo-practitioner competitors, 12 male athletes from Judo Federation of Sergipe (Federação Sergipana de Judô), were divided into two groups: Experimental Group (EG) and Control Group (CG). For 10 weeks, the EG practiced SGA® self-postures and the CG practiced assorted calisthenic exercises. All of them were submitted to a variety of tests (before and after): handgrip strength, flexibility, upper limbs’ muscle power, isometric pull-up force, lower limbs’ muscle power (squat-jump – SJ and countermovement jump – CMJ) …

Resting Hormone Alterations And Injuries: Block Vs. Dup Weight-Training Among D-1 Track And Field Athletes, Keith B. Painter, G. Gregory Haff, N. Travis Triplett, Charles Stuart, Guy Hornsby, Mike W. Ramsey, Caleb D. Bazyler, Michael H. Stone

ETSU Faculty Works

Daily undulating periodization (DUP), using daily alterations in repetitions, has been advocated as a superior method of resistance training, while traditional forms of programming for periodization (Block) have been questioned. Nineteen Division I track and field athletes were assigned to either a 10-week Block or DUP training group. Year and event were controlled. Over the course of the study, there were four testing sessions, which were used to evaluate a variety of strength characteristics, including maximum isometric strength, rate of force development, and one repetition maximum (1RM). Although, performance trends favored the Block group for strength and rate of force …

No Observable Relative Age Effects In Professional Surfers: A Constraints-Based Evaluation, Michael Redd, David Fukuda, Kyle Beyer, Leonardo Oliveira

International Journal of Exercise Science

International Journal of Exercise Science 11(6): 355-363, 2018. With the recent inclusion of surfing in the 2020 Olympic Games in Japan, there will be a number of surfing athletes vying for one of the twenty total available spots for their respective gender. The purpose was to evaluate relative age effects (RAEs) in surfing with consideration for specific developmental constraints. Elite competitive male surfers (n = 1590) were examined by birth month and subcategorized by competitive level, age groups, and geographical regions. The observed quarterly distribution was not significantly different (using c²; p>0.05) from expected for the overall …

Central Hemodynamics Measured During 5 Repetition Maximum Free Weight Resistance Exercise, Jonathan S. Howard, Cherilyn N. Mclester, Thomas W. Evans, John R. Mclester, Jimmy P. Calloway

International Journal of Exercise Science

International Journal of Exercise Science 11(2): 342-354, 2018. The PhysioFlow™ is a piece of equipment that uses bioimpedance cardiography to measure central hemodynamics. The purpose of this research was to explore the novel approach of monitoring central hemodynamics during free weight resistance exercise using bioimpedance cardiography throughout a 5 repetition maximum (5RM). Thirty participants ranging from beginner to advanced lifters (16 males and 14 females) completed a 5RM for back squat, seated push press, and bicep curl while connected to the PhysioFlow™ to assess the response of heart rate (HR), stroke volume (SV), cardiac output (Q), and ejection fraction (EF). …

Novel Function Of Ceramide For Regulation Of Mitochondrial Atp Release In Astrocytes, Ji-Na Kong, Zhihui Zhu, Yutaka Itokazu, Guanghu Wang, Michael B. Dinkins, Liansheng Zhong, Hsuan-Pei Lin, Ahmed Elsherbini, Silvia Leanhart, Xue Jiang, Haiyan Qin, Wenbo Zhi, Stefka D. Spassieva, Erhard Bieberich

Physiology Faculty Publications

We reported that amyloid β peptide (Aβ₄₂) activated neutral SMase 2 (nSMase2), thereby increasing the concentration of the sphingolipid ceramide in astrocytes. Here, we show that Aβ₄₂ induced mitochondrial fragmentation in wild-type astrocytes, but not in nSMase2-deficient cells or astrocytes treated with fumonisin B1 (FB1), an inhibitor of ceramide synthases. Unexpectedly, ceramide depletion was concurrent with rapid movements of mitochondria, indicating an unknown function of ceramide for mitochondria. Using immunocytochemistry and super-resolution microscopy, we detected ceramide-enriched and mitochondria-associated membranes (CEMAMs) that were codistributed with microtubules. Interaction of ceramide with tubulin was confirmed by cross-linking to N-[9-(3-pent-4-ynyl-3-H-diazirine-3-yl)-nonanoyl]-D-erythro-sphingosine …

Impact Of Occupational Footwear And Workload On Lower Extremity Muscular Exertion, Alana J. Turner, Jonathan C. Swain, Katherine L. Mcwhirter, Adam C. Knight, Daniel W. Carruth, Harish Chander

International Journal of Exercise Science

International Journal of Exercise Science 11(1): 331-341, 2018. Footwear worn and workload performed can influence muscular exertion, which is critical in occupational environments. The purpose of the study was to assess the impact of two occupational footwear, steel-toed (SWB) and tactical (TWB) work boots, on muscular exertion when exposed to a physical workload. Eighteen healthy male participants (age: 21.27 ± 1.7 years; height: 177.67 ± 6.0 cm; mass: 87.95 ± 13.8 kg) were tested for maximal voluntary isometric contraction (MVIC) using electromyography (EMG) and pressure pain threshold (PPT) using an algometer for four lower extremity muscles prior to (pre-test) and …

Does Body Mass Index Influence The Physiological And Perceptual Demands Associated With Defensive Tactics Training In State Patrol Officers?, J. Jay Dawes, Charles Kornhauser, Diana Crespo, Craig L. Elder, Keston Lindsay, Ryan J. Holmes

International Journal of Exercise Science

International Journal of Exercise Science 11(6): 319-330, 2018. The purpose of this investigation was to determine the physiological and perceptual demands associated with defensive tactics (DEFTAC) training among state patrol officers of different BMI (body mass index) categories. Twenty-four male state patrol officers (n = 24, age 36.00 + 7.86 yrs) voluntarily agreed to participate in data collection during a DEFTAC gauntlet. Anthropometric information (height (HT) 182.19 + 7.43 cm and weight (WT) 96.31 + 17.45 kg), body mass index (BMI), peak and average heart rates, duty weight, BLa, and RPE, were recorded. Officers were then divided into two-groups (Healthy …

Rate Of Performance Change In American Female Weightlifters Over Ten Years Of Competition, Jason Miller, Heidi Ventresca, Lindsay Bracken

International Journal of Exercise Science

International Journal of Exercise Science 11(6): 290-307, 2018. The purpose of this study was to evaluate the rates of performance change for American female weightlifters over 10 years of competition. Athlete performance results were gathered from the United States Weightlifting open access, results archive, database. Data was delimited to athletes (N ≥ 750) that competed in Youth or Junior Nationals to ensure athletes were <21yrs old at the first recorded competition. Competition results were converted to strength to mass (SM) ratios to control for the effect of bodyweight on performance. Starting with the first competition date, the highest SM for the snatch (SNT), clean and jerk (CJ) and combined total (T), in three month segments for three years, and six month segments over 10 years, were recorded. Observed percentage change in SM and Cohen’s d effect size (ES) between each 3- and 6-month segment and the first competition (baseline), for the SNT, CJ and T, was determined. Positive change in rate of …

Sex And Age Differences In Trail Half Marathon Running, James W. Navalta, Jeffrey Montes, Elizabeth A. Tanner, Nathaniel Bodell, John C. Young

International Journal of Exercise Science

International Journal of Exercise Science 11(6): 281-289, 2018. Female participation is growing in trail running races. The purpose was to evaluate sex and age differences in top finishers of a trail running half marathon. Velocity differences between males (M) and females (F) were determined for the top 10 finishers of the Moab Trail Half Marathon from 2012 - 2015 across age, and by finishing place. Differences between age category and between sexes were determined through ANOVA with significance accepted at P < 0.05. A significant difference for running velocity was present between sexes at each age category (20-29 yr F = 2.9±0.3, M = 3.4±0.4 m·sec^-1; 30-39 yr F = 2.8±0.3, M = 3.3±0.3; 40-49 yr F = 2.7±0.3, M = 3.0±0.5; 50-59 …

Simulated Altitude Via Re-Breathing Creates Arterial Hypoxemia But Fails To Improve Elements Of Running Performance, Matthew J. Garver, Cory M. Scheadler, Logan M. Smith, Sarah J. Taylor, Chase M. Harbach

International Journal of Exercise Science

International Journal of Exercise Science 11(6): 187-197, 2018. Acclimatization to altitude has been shown to improve elements of performance. Use of simulated altitude is popular among athletes across the sports spectrum. This work was on a handheld, re-breathing device touted to enhance performance. Seven recreationally-trained athletes used the device for 18 hours over the course of the 37-day intervention trial. The elevations simulated were progressively increased from 1,524m to 6,096m. To ascertain potential efficacy, four performance trials were included (familiarization, baseline, and 2 follow-ups). Hematological (hematocrit, hemoglobin, and lactate), physiological (respiratory exchange ratio, heart rate, and oxygen consumption), and perceptual …