Bioelectrical Impedance Changes of the Trunk are Opposite the Limbs Following Acute Hydration Change.

This study aimed to evaluate the changes in impedance and estimates of body composition variables obtained from segmental multi-frequency bioelectrical impedance analysis (SMFBIA) following acute hydration change. All participants (N = 11 active adults) had SMFBIA measurements at baseline (euhydration), post-dehydration, and post-hyperhydration in an experimental repeated-measures design. Dehydration and hyperhydration trials were randomized with the opposite treatment given 24 h later. Dehydration was achieved via a heat chamber of 40 °C and 60% relative humidity. Hyperhydration was achieved by drinking lightly-salted water (30 mmol·L-1 NaCl; 1.76 g NaCl·L-1) within 30 min. Post-measurements were taken 30 min after each treatment. Despite changes in mass post-dehydration (Δ = -2.0%, p < 0.001) and post-hyperhydration (Δ = 1.2%, p < 0.001), SMFBIA estimates of total body water (TBW) did not change significantly across trials (p = 0.507), leading to significant differences (p < 0.001) in SMFBIA-estimates of body fat percentage across trials. Dehydration resulted in a significant (p < 0.001) 8% decrease in limb impedances at both 20 kHz and 100 kHz. Hyperhydration increased limb impedances only slightly (1.5%, p > 0.05). Impedance changes in the trunk followed an opposite pattern of the limbs. SMFBIA failed to track acute changes in TBW. Divergent impedance changes suggest the trunk is influenced by fluid volume, but the limbs are influenced by ion concentration.

Ultrasound Measurements of Subcutaneous Fat Thickness Are Robust Against Hydration Changes.

Ultrasound is an appealing tool to assess body composition, combining the portability of a field method with the accuracy of a laboratory method. However, unlike other body composition methods, the effect of hydration status on validity is unknown. This study evaluated the impact of acute hydration changes on ultrasound measurements of subcutaneous fat thickness and estimates of body fat percentage. In a crossover design, 11 adults (27.1 ± 10.5 years) completed dehydration and hyperhydration trials to alter body mass by approximately ±2%. Dehydration was achieved via humid heat (40 °C, 60% relative humidity) with exercise, whereas hyperhydration was via ingestion of lightly salted water. Ultrasound measurements were taken at 11 body sites before and after each treatment. Participants lost 1.56 ± 0.58 kg (-2.0 ± 0.6%) during the dehydration trial and gained 0.90 ± 0.21 kg (1.2 ± 0.2%) during the hyperhydration trial even after urination. The sum of fat thicknesses as measured by ultrasound differed by <0.90 mm across trials (p = .588), and ultrasound estimates of body fat percentage differed by <0.5% body fat. Ultrasound measures of subcutaneous adipose tissue were unaffected by acute changes in hydration status by extents beyond which are rare and overtly self-correcting, suggesting that this method provides reliable and robust body composition results even when subjects are not euhydrated.

Interrater reliability of novice examiners using A-mode ultrasound and skinfolds to measure subcutaneous body fat.

Examiners with minimal training and skill are often called upon to make body composition assessments using field methods. This study compared the interrater reliability of novice examiners for the skinfold (SKF) and A-mode ultrasound (US) methods of body composition assessment. Undergraduate Kinesiology majors (48 males, 32 females) with minimal training took both SKF and US measurements at three sites (males: chest, abdomen, thigh; females: triceps, suprailiac, thigh). Interrater reliability was significantly better for US compared to SKF at the thigh (ICCUS = 0.975, ICCSKF = 0.912) and abdomen (ICCUS = 0.984, ICCSKF = 0.693) for men and suprailiac (ICCUS = 0.978, ICCSKF = 0.883) for women. Additionally, interrater reliability of the US method was superior to the SKF method for the estimate of male body fat percentage (ICCUS = 0.990, ICCSKF = 0.862). The 95% CI was generally narrower for the US method than the SKF method at each site. The interrater reliability of the US method was superior to or equal to the SKF method for measuring subcutaneous body fat when novice examiners took the measurements.

Case study: Effect of surgical metal implant on single frequency bioelectrical impedance measures of an athlete.

This case study examined the influence of a surgical metal implant on the bioelectrical impedance analysis (BIA) readings of an athlete. Single-frequency BIA using a tetrapolar electrode configuration was applied to both the right and left sides of a 23-year-old female jumper who had an 8 × 345 mm titanium alloy nail implanted in her left tibia. The metal implant reduced BIA resistance and reactance on the implanted side by 27 and 6 ohms, respectively. This reduction in impedance resulted in a 0.4 kg-1.9 kg increase in the estimate of fat-free mass (FFM) depending on the prediction formula used. There was a concomitant decrease in the estimate of body fat percentage (%BF) with the underestimation ranging from 0.6% to 2.7% BF depending on the prediction formula. A metal implant of substantial size can alter the BIA reading. Technicians should apply BIA to the opposite side of the body when athletes present with a surgical implant in a limb.

Exercise in Thermal Inversions: PM2.5 Air Pollution Effects on Pulmonary Function and Aerobic Performance.

INTRODUCTION: Wintertime thermal inversions can lead to the accumulation of small particulate matter (PM2.5). Despite an association between respiratory hospital admissions and elevated PM2.5 levels, many people continue to exercise outdoors during inversions. This study compared pulmonary function and exercise performance during periods of low and high ambient PM2.5 concentrations. METHODS: Forced vital capacity and forced expiratory volume in 1 s were measured outdoors before and after two 3200 m running time trials: one with low ambient PM2.5 (0.6-14.7 microgram·m-3), and the other during high PM2.5 (19.1-42.5 micrograms·m-3). A 10 cm visual analog scale (VAS) administered postexercise quantified subjective ratings of respiratory discomfort. RESULTS: The PM2.5 differential between trials was ≥18 micrograms·m-3 for 10 healthy runners. Despite feeling more respiratory discomfort (P=0.044) during the bad air trial (VAS: 4.6±1.8 cm) compared with the good air trial (VAS: 2.9±1.8 cm), the 3200 m run time (low PM2.5: 13:54±1:34 min:s; high PM2.5: 14:07±1:44 min:s) was not different (P=0.261) between trials. Postexercise forced vital capacity was not significantly different (P=0.846) between the low (4.86±1.00 L) and high (4.84±0.95 L) PM2.5 conditions. Similarly, the difference in postexercise forced expiratory volume in 1 s was not significant (P=0.750) between trials (4.22±0.89 L vs 4.23±0.85 L). CONCLUSIONS: Neither run time nor pulmonary function of healthy adults were adversely affected by an acute bout of exercise in elevated ambient PM2.5, equivalent to yellow or orange on the air quality index.

Comparison of A-mode and B-mode Ultrasound for Measurement of Subcutaneous Fat.

With lower-cost devices and technologic advancements, ultrasound has been undergoing a resurgence as a method to measure subcutaneous adipose tissue. We aimed to determine whether a low-cost, 2.5-MHz amplitude (A-mode) ultrasound, designed specifically for body composition assessment, could produce subcutaneous fat thickness measurements comparable to an expensive, 12-MHz brightness (B-mode) device. Fat thickness was measured on 40 participants (20 female, 20 male; 29.7 ± 11.1 y of age; body mass index 24.9 ± 4.5 kg/m2) at 7 sites (chest, subscapula, mid-axilla, triceps, abdomen, suprailiac and thigh) with both devices. Intraclass correlations exceeded 0.75 at all measurement sites. Mean differences in fat thickness were not significantly different (p > 0.05) and within ± 1.0 mm. Variability between devices was greatest at the abdomen, the site with the greatest thickness. The low-cost, low-resolution A-mode ultrasound provides subcutaneous fat thickness measurements similar to the more expensive, high-resolution B-mode ultrasound.

Wingate Anaerobic Test Reliability on the Velotron With Ice Hockey Players.

Bringhurst, RF, Wagner, DR, and Schwartz, S. Wingate anaerobic test reliability on the velotron with ice hockey players. J Strength Cond Res 34(6): 1716-1722, 2020-This study evaluated the test-retest reliability of the Wingate Anaerobic Test (WAnT) performed on a Velotron electromagnetically braked cycle ergometer for power-trained athletes and assessed whether a familiarization trial was necessary to achieve high test-retest reliability. Twenty-one male ice hockey players (age 23.5 ± 4.7 years, mass 86.3 ± 16.6 kg, height 180.9 ± 7.4 cm) from a collegiate club team (Club = 10) and a recreational league (Rec = 11) performed three 30-second WAnTs within 2 weeks and with at least 24 hours between visits. Mean power (MP), anaerobic capacity, peak power (PP), anaerobic power, maximum revolutions per minute, and fatigue index were assessed. Resistance was 8.5% of the participant's body mass. The effect of time on power output was moderated (p < 0.001, (Equation is included in full-text article.)= 0.24) such that a significant increase was observed after a practice trial, but not between subsequent trials for the Club players; no practice effect was observed among Rec players. Extremely high reliability (ICC1,1) was found between trials after excluding the practice trial (MP = 0.973, anaerobic capacity = 0.975, PP = 0.957, and anaerobic power = 0.890). Club players achieved higher outputs despite no significant differences in body size or age compared with Rec players. Ice hockey players performing the 30-second WAnT on the Velotron electromagnetically braked cycle ergometer had highly reliable data, and using a familiarization trial is recommended to increase reliability and achieve higher power outputs.

A-mode and B-mode ultrasound measurement of fat thickness: a cadaver validation study.

BACKGROUND/OBJECTIVES: With technological advances, there has been a resurgence in ultrasound as a method to measure subcutaneous fat thickness. Despite the increased interest in this methodology, research comparing A-mode and B-mode ultrasound devices is lacking. Subcutaneous fat thickness measured by a low resolution (2.5 MHz) A-mode ultrasound and a high resolution (12 MHz) B-mode ultrasound were compared to the actual fat thickness in dissected cadavers. SUBJECTS/METHODS: Subcutaneous fat thickness of six cadavers was measured at the abdomen, thigh, triceps, and calf (plus chest for males and suprailiac for females) with both ultrasound devices before the cadavers were dissected and site-specific thickness was measured. RESULTS: Correlations between both ultrasounds and the dissected measurement exceeded 0.90 at all sites with a few exceptions. At the abdomen, the relationship between the ultrasounds was 0.76, and the B-mode and dissected measurement was also 0.76. The correlation between dissection and A-mode was 0.75 for the suprailiac site, but it was not possible to discern the separation of tissue at this site when using the B-mode device. There were no significant differences (P > 0.05) between the devices and the dissected measurement at any of the six sites. The mean difference in fat thickness between A-mode and B-mode was <0.7 mm at all sites except the calf (1.2 mm) CONCLUSION: With the exception of the suprailiac site, both A-mode and B-mode ultrasound are equally capable of providing measurements of subcutaneous fat thickness with an accuracy of <1 mm at most sites.

Effects of isokinetic eccentric versus traditional lower body resistance training on muscle function: examining a multiple-joint short-term training model.

Early adaptations in eccentric training show several advantages over those in concentric training. The purpose of this study was to quantify the effects of 4 weeks of multiple-joint eccentric versus traditional leg press (TLP) training on muscle strength, rate of torque development (RTD), and jump and sprint performance adaptations. Twenty-six resistance-trained adults performed either an eccentric or a TLP resistance-training program twice per week for 4 weeks. Single-joint isometric maximal and rapid strength (peak torque and RTD, respectively) and isokinetic strength of the knee extensors and flexors, multiple-joint eccentric strength, leg press strength (1-repetition maximum), 40-m sprint, and vertical and long jump were measured before, at the midpoint, and after a 4-week training period. Four weeks of isokinetic multiple-joint eccentric training elicited greater test-specific strength gains (effect size (ES) = 1.06) compared with TLP training (ES = 0.11). The eccentric group also yielded moderate improvements in the middle-late phase RTD (RTD100-200; ES = 0.51 and 0.54 for the knee flexors and extensors, respectively), whereas the TLP group showed small-moderate improvements (ES = 0.37). The majority of the single-joint strength variables showed negligible improvements. Performance tests showed no (broad jump) to small (vertical jump; sprint for the leg press) improvements. Multiple-joint eccentric training induced significant improvements in lower body strength in a short amount of time in a recreationally trained population. These accelerated adaptations along with the lower energy requirements of eccentric exercise, may be useful for clinicians or practitioners when prescribing training programs for those who are injured, sedentary, or elderly as a means to elicit time- and metabolically efficient muscle function improvements.

Effect of a Flying Versus Stationary Start on Wingate Test Outcomes Using an Electromagnetically-Braked Cycle Ergometer in Advanced Resistance-Trained Males.

The purpose of this study was to compare power outputs of the flying start to the stationary start method on an electromagnetically-braked cycle ergometer. Twenty advanced resistance-trained men (age 24.6 ± 4.5 years; 25.4 ± 2.5 kg/m2) volunteered to participate in this study. A counter-balanced, repeated-measures design was utilized to randomly assign participants to either the flying start or the stationary start for their first Wingate test. Paired t tests were used to evaluate mean differences between start methods. Peak power (PP), mean power (MP), total work (TW), peak cadence (PC), mean cadence (MC), and time to reach peak power (TPP) were recorded. Start method revealed significant differences for PP (p<0.01; flying start = 1,111 ± 42 W vs. stationary start = 854 ± 41 W) and PC attainment (p<0.01; flying start = 167 ± 7 RPM vs. stationary start = 128 ± 5 RPM). Start method did not significantly affect MP (p=0.73; flying start 673 ± 30 W vs. stationary start 657 ± 34 W) or MC (p=0.61; flying start 102 ± 5 RPM vs. 99 ± 4 RPM). The flying start method allowed for not only a greater PP but also a faster TPP (0.24 ± 0.02 seconds). In contrast, TPP was not attained until approximately one-third of the stationary start test (10.3 ± 0.4 seconds). This study showed that the traditional flying start allowed higher PP and PC outputs when compared to the alternative stationary start method in a sample of advanced resistance-trained male participants.

Influence of Velotron chainring size on Wingate anaerobic test.

OBJECTIVES: This study compared an 85-tooth versus the standard 62-tooth chainring for power outputs during a Wingate test using a Velotron electromagnetically-braked cycle ergometer. DESIGN: All participants completed trials using both chainring sizes in a repeated-measures cross-over design. METHODS: Resistance-trained male participants (n=20, 24.6±4.5years) performed two Wingate tests separated by at least 48h. Peak power (PP), mean power (MP), fatigue index (FI), peak cadence, mean cadence, and total work (TW) were recorded. RESULTS: Peak power was not significantly different (p=0.10) between trials (62-tooth=1111±187W vs. 85-tooth=1188±103W). However, MP, mean cadence, and TW were significantly greater (p<0.01) for the 85-tooth trial (869±114W, 131±16rpm, and 26,063±3418J) compared to the 62-tooth test (673±136W, 102±24rpm, and 20,199±4066J). Fatigue index was reduced during the 85-tooth trial (49.9±9.1% vs. 61.6±8.8%; p<0.01). Agreement was poor with most ICCs≈0.19 and large SEMs. CONCLUSIONS: The two options for chainrings on Velotron cycle ergometers should not be interchangeably used with the Wingate test software; the 62-tooth ring is recommended for most applications. Individuals who can attain peak cadence >180rpm have less variability and tend to achieve higher power outputs on the 62-tooth ring. We suspect that the manufacturer's software limits peak cadence to 182rpm when using the 85-tooth chainring.

Effects of ambient particulate matter on aerobic exercise performance.

BACKGROUND/OBJECTIVE: Wintertime thermal inversions in narrow mountain valleys create a ceiling effect, increasing concentration of small particulate matter (PM2.5). Despite potential health risks, many people continue to exercise outdoors in thermal inversions. This study measured the effects of ambient PM2.5 exposure associated with a typical thermal inversion on exercise performance, pulmonary function, and biological markers of inflammation. METHODS: Healthy, active adults (5 males, 11 females) performed two cycle ergometer time trials outdoors in a counterbalanced design: 1) low ambient PM2.5 concentrations (<12 µg/m3), and 2) an air quality index (AQI) ranking of "yellow." Variables of interest were exercise performance, exhaled nitric oxide (eNO), c-reactive protein (CRP), forced vital capacity (FVC), and forced expiratory volume in 1 s (FEV1). RESULTS: Despite a significant difference in mean PM2.5 concentration of 9.3 ±â€¯3.0 µg/m3 between trials (p < .001), there was no significant difference (p = .424) in the distance covered during low PM2.5 conditions (9.9 ±â€¯1.7 km) compared to high PM2.5 conditions (10.1 ±â€¯1.5 km). There were no clinically significant differences across time or between trials for eNO, CRP, FVC, or FEV1. Additionally, there were no dose-response relationships (p > .05) for PM2.5 concentration and the measured variables. CONCLUSION: An acute bout of vigorous exercise during an AQI of "yellow" did not diminish exercise performance in healthy adults, nor did it have a negative effect on pulmonary function or biological health markers. These variables might not be sensitive to small changes from acute, mild PM2.5 exposure.

Normobaric Hypoxia Effects on Balance Measured by Computerized Dynamic Posturography.

Wagner, Dale R., Skyler Saunders, Brady Robertson, and John E. Davis. Normobaric hypoxia effects on balance measured by computerized dynamic posturography. High Alt Med Biol. 17:222-227, 2016.-Background/Aim: Equilibrium was measured by computerized dynamic posturography at varying levels of normobaric hypoxia before and after exercise. METHODS: Following a familiarization trial, 12 males (27.3 ± 7.1 years) completed three sessions in random order on a NeuroCom SMART Balance Master: a sham trial at the ambient altitude of 1500 m and simulated altitudes of 3000 and 5000 m created by a hypoxic generator. The NeuroCom provided composite scores for a sensory organization test of equilibrium and a motor control test to assess the appropriate motor response. Additional information on somatosensory, visual, and vestibular responses was obtained. Each session consisted of 20 minutes of rest followed by the NeuroCom test, then 10 minutes of exercise, and 10 minutes of recovery followed by a second NeuroCom test, all while connected to the hypoxic generator. Mean differences were identified with a two-way (pre/postexercise and altitude condition), repeated-measures analysis of variance. RESULTS: The composite sensory score was significantly lower (p < 0.001) during the 5000 m trial (73.4 ± 12.0) compared to the 1500 m (80.8 ± 7.0) and 3000 m (84.1 ± 5.0) altitudes. The inability to ignore inaccurate visual cues in a situation of visual conflict was the most common sensory error. Motor control was not affected by altitude or exercise. DISCUSSION: These results suggest that moderate hypoxia does not affect balance, but severe hypoxia significantly reduces equilibrium. Furthermore, it appears that the alterations in equilibrium are primarily from impairments in visual function.

Validity and Reliability of A-Mode Ultrasound for Body Composition Assessment of NCAA Division I Athletes.

This study evaluated the validity and reliability of the BodyMetrix™ BX2000 A-mode ultrasound for estimating percent body fat (%BF) in athletes by comparing it to skinfolds and the BOD POD. Forty-five (22 males, 23 females) National Collegiate Athletic Association (NCAA) Division-I athletes volunteered for this study. Subjects were measured once in the BOD POD then twice by two technicians for skinfolds and ultrasound. A one-way repeated-measures ANOVA revealed significant differences between body composition methods (F = 13.24, p < 0.01, η² = 0.24). This difference was further explained by a sex-specific effect such that the mean difference between ultrasound and BOD POD was large for females (~ 5% BF) but small for males (~ 1.5% BF). Linear regression using the %BF estimate from ultrasound to predict %BF from BOD POD resulted in an R2 = 0.849, SEE = 2.6% BF and a TE = 4.4% BF. The inter-rater intraclass correlation (ICC) for skinfold was 0.966 with a large 95% confidence interval (CI) of 0.328 to 0.991. The inter-rater ICC for ultrasound was 0.987 with a much smaller 95% CI of 0.976 to 0.993. Both skinfolds and ultrasound had test-retest ICCs ≥ 0.996. The BX2000 ultrasound device had excellent test-retest reliability, and its inter-rater reliability was superior to the skinfold method. The validity of this method is questionable, particularly for female athletes. However, due to its excellent reliability, coaches and trainers should consider this portable and easy to use A-mode ultrasound to assess body composition changes in athletes.

Similar results for face mask versus mouthpiece during incremental exercise to exhaustion.

Investigations in the 1990s evaluated the influence of breathing assemblies on respiratory variables at rest and during exercise; however, research on new models of breathing assemblies is lacking. This study compared metabolic gas analysis data from a mouthpiece with a noseclip (MOUTH) and a face mask (MASK). Volunteers (7 males, 7 females; 25.1 ± 2.7 years) completed two maximal treadmill tests within 1 week, one MOUTH and one MASK, in random order. The difference in maximal oxygen consumption (VO2max) between MOUTH (52.7 ± 11.3 ml · kg(-1) · min(-1)) and MASK (52.2 ± 11.7 ml · kg(-1) · min(-1)) was not significant (P = 0.53). Likewise, the mean MOUTH-MASK differences in minute ventilation (VE), fraction of expired oxygen (FEO2) and carbon dioxide (FECO2), respiration rate (RR), tidal volume (Vt), heart rate (HR), and rating of perceived exertion (RPE) at maximal and submaximal intensities were not significant (P > 0.05). Furthermore, there was no systematic bias in the error scores (r = -0.13, P = 0.66), and 12 of the 14 participants had a VO2max difference of ≤3 ml · kg(-1) · min(-1) between conditions. Finally, there was no clear participant preference for using the MOUTH or MASK. Selection of MOUTH or MASK will not affect the participant's gas exchange or breathing patterns.

Predicted versus measured thoracic gas volumes of collegiate athletes made by the BOD POD air displacement plethysmography system.

Measured (TGVm) and predicted (TGVp) thoracic gas volumes from the BOD POD were compared in 33 lean, university athletes. On average, TGVp (3.529 L) was not significantly different (p = 0.343) from TGVm (3.628 L); however, there was a bias (r = -0.703, p < 0.001). The difference in the percentage of body fat (BF) was within ±2% BF for 76% of the sample, but athletes at the extremes of height should have TGV measured.

Cognitive and psychomotor responses to high-altitude exposure in sea level and high-altitude residents of Ecuador.

BACKGROUND: High-altitude inhabitants have cardiovascular and respiratory adaptations that are advantageous for high-altitude living, but they may have impaired cognitive function. This study evaluated the influence of altitude of residence on cognitive and psychomotor function upon acute exposure to very high altitude. FINDINGS: Ecuadorians (31 residing at 0-1,500 m [LOW], 78 from 1,501-3,000 m [MOD], and 23 living >3,000 m [HIGH]) were tested upon their arrival to a hut at 4,860 m on Mount Chimborazo. Cognitive/psychomotor measurements included a go-no-go test (responding to a non-visual stimulus), a verbal fluency test (verbalizing a series of words specific to a particular category), and a hand movement test (rapidly repeating a series of hand positions). Mean differences between the three altitude groups on these cognitive/psychomotor tests were evaluated with one-way ANOVA. There were no significant differences (p = 0.168) between LOW, MOD, and HIGH for the verbal fluency test. However, the go-no-go test was significantly lower (p < 0.001) in the HIGH group (8.8 ± 1.40 correct responses) than the LOW (9.8 ± 0.61) or MOD (9.8 ± 0.55) groups, and both MOD (97.9 ± 31.2) and HIGH (83.5 ± 26.7) groups completed fewer correct hand movements than the LOW (136.6 ± 37.9) subjects (p < 0.001). CONCLUSIONS: Based on this field study, high-altitude residents appear to have some impaired cognitive function suggesting the possibility of maladaptation to long-term exposure to hypobaric hypoxia.

Session rating of perceived exertion following resistance exercise with blood flow restriction.

Session ratings of perceived exertion (SRPE) provide a valid and reliable indicator of resistance exercise session intensity. However, there is a lack of studies on the effects of resistance exercise with blood flow restriction (BFR) on SRPE. Thus, the aim of this study is to compare the effects of resistance exercise at high intensity versus low intensity with BFR on internal training load measured by SRPE. Thirteen young (22.2 ± 3.8 years) resistance-trained men (training experience 3.2 ± 2.4 years) participated in the study protocol. After determining one maximum repetition (1-RM), the subjects were assigned to two groups in a counterbalanced design (i) high-intensity exercise (HIE, performed one training session at 80% of 1-RM) and (ii) low intensity with BFR (BFR, performed an exercise session at 50% of 1-RM with BFR). During each session, subjects performed three sets of unilateral elbow flexion leading to concentric failure with a 1-min rest interval between sets. A cuff around the arm, inflated at 110 mmHg, was used continuously for BFR. The SRPE was reported 30 min after the end of the session. The low intensity with BFR showed lower total work (197.13 ± 63.49 versus 300.92 ± 71.81 kg; P = 0.002) and higher SRPE (9 versus 6; P = 0.007) than high-intensity resistance exercise. The present results indicate that BFR is an important factor to increase internal training load. Future studies should investigate the physiological stress imposed by different training methods rather than just quantify the external training load such as intensity or volume.

Orthostatic responses at 4860 m in low, moderate, and high altitude residents.

This study evaluated the influence of altitude of residence on orthostatic responses when exposed to high altitude. Data collection took place at the Carrel hut (4860 m) on Chimborazo in Ecuador. After being transported to the hut by vehicle, 69 people volunteered for the study. A 3-min stand test (rapid change from supine to standing) provided an orthostatic challenge while resting heart rate (RHR), systolic (SBP) and diastolic (DBP) blood pressures, and arterial oxygen saturation (SpO2) were measured. Participants were separated into four groups based on altitude of residence and ethnicity: LOW (<1500 m; n=15), MOD (1500-3000 m, n=30), and HIGH (>3000 m, n=11) Ecuadorians, and non-Ecuadorian lowlanders (NE-LOW, n=13). Supine and standing RHRs were lower (p<0.05) for HIGH compared to other groups. Furthermore, standing increased RHR in LOW, MOD, and NE-LOW by 11.9 ± 5.3, 9.5 ± 4.1, and 11.6 ± 7.4 bpm, respectively, while HIGH stayed the same (0.6 bpm increase ± 3.3). Additionally, mean arterial pressure decreased slightly but not significantly upon standing in all groups except HIGH. The difference in Spo2 among groups was not significant (p>0.05). Altitude of residence influences the cardiovascular responses to orthostatic stress with HIGH having blunted responses and greater tolerance.