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ABSTRACT: Abstract Staab, Janet E., Beth A. Beidleman, Stephen R. Muza, Charles S. Fulco, Paul B. Rock, and Allen Cymerman. Efficacy of residence at moderate versus low altitude on reducing acute mountain sickness in men following rapid ascent to 4300 m. High Alt Med Biol 14:13-18, 2013.-To determine if residence at moderate (∼2000 m) compared to low (<50 m) altitude reduces acute mountain sickness (AMS) in men during subsequent rapid ascent to a higher altitude. Nine moderate-altitude residents (MAR) and 18 sea-level residents (SLR) completed the Environmental Symptoms Questionnaire (ESQ) at their respective baseline residence and again at 12, 24, 48, and 72 h at 4300 m to assess the severity and prevalence of AMS. AMS cerebral factor score (AMS-C) was calculated from the ESQ at each time point. AMS was judged to be present if AMS-C was ≥0.7. Resting end-tidal CO2 (PETco2) and arterial oxygen saturation (Sao2) were assessed prior to and at 24, 48, and 72 h at 4300 m. Resting venous blood samples were collected prior to and at 72 h at 4300 m to estimate plasma volume (PV) changes. MAR compared to SLR: 1) AMS severity at 4300 was lower (p<0.05) at 12 h (0.50±0.69 vs. 1.48±1.28), 24 h (0.15±0.19 vs. 1.39±1.19), 48 h (0.10±0.18 vs. 1.37±1.49) and 72 h (0.08±0.12 vs. 0.69±0.70); 2) AMS prevalence at 4300 was lower (p<0.05) at 12 h (22% vs. 72%), 24 h (0% vs. 56%), 48 h (0% vs. 56%), and 72 h (0% vs. 45%); 3) resting Sao2 (%) was lower (p<0.05) at baseline (95±1 vs. 99±1) but higher (p<0.05) at 4300 at 24 h (86±2 vs. 81±5), 48 h (88±3 vs. 83±6), and 72 h (88±2 vs. 83±5); and 4) PV (%) did not differ at 72 h at 4300 m in the MAR (4.5±6.7) but was reduced for the SLR (-8.1±10.4). These results suggest that ventilatory and hematological acclimatization acquired while living at moderate altitude, as indicated by a higher resting Sao2 and no reduction in PV during exposure to a higher altitude, is associated with greatly reduced AMS after rapid ascent to high altitude.
High altitude medicine & biology 03/2013; 14(1):13-8. · 1.58 Impact Factor
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ABSTRACT: PURPOSE: Despite decades of research, no predictive models of acute mountain sickness (AMS) exist which identify the time course of AMS severity and prevalence following rapid ascent to various altitudes. METHODS: Using general linear and logistic mixed models and a comprehensive database, we analyzed 1,292 AMS Cerebral factor scores in 308 unacclimatized men and women who spent between 4-48 h at altitudes ranging from 1659-4501 m under experimentally controlled conditions (low and high activity). Covariates included in the analysis were altitude, time at altitude, activity level, age, body-mass index (BMI), race, sex, and smoking status. RESULTS: AMS severity increased (P<0.05) nearly 2-fold (i.e., 179%) for every 1000 m increase in altitude at 20 h of exposure, peaked between 18-22 h of exposure, and returned to initial levels by 48 h of exposure regardless of sex or activity level. Peak AMS severity scores were 38% higher (P<0.05) in men compared to women at 20 h of exposure. High active men and women (> 50% of maximal oxygen uptake for > 45 min at altitude) demonstrated a 72% increase (P<0.05) in the odds (OR 1.72, CI 1.03-3.08) of AMS compared to low actives. There was also a tendency (P=0.10) for men to demonstrate greater odds of AMS (OR 1.65, CI 0.84-3.25) compared to women. Age, BMI, race, and smoking status were not significantly associated with AMS. CONCLUSION: These models provide the first quantitative estimates of AMS risk over a wide range of altitudes and time points and suggest that in addition to altitude and time at altitude, high activity increases the risk of developing AMS. In addition, men demonstrated increased severity but not prevalence of AMS.
Medicine and science in sports and exercise 11/2012; · 3.71 Impact Factor
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ABSTRACT: Acute mountain sickness (AMS) and large decrements in endurance exercise performance occur when unacclimatized individuals rapidly ascend to high altitude. Six altitude and hypoxia pre-acclimatization strategies were evaluated to determine their effectiveness for minimizing AMS and improving performance during altitude exposure. Strategies using hypobaric chambers or true altitude were much more effective overall than those using normobaric hypoxia (breathing <20.9% oxygen).
Exercise and sport sciences reviews 05/2012; · 3.23 Impact Factor
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ABSTRACT: There is an expectation that repeated daily exposures to normobaric hypoxia (NH) will induce ventilatory acclimatization and lessen acute mountain sickness (AMS) and the exercise performance decrement during subsequent hypobaric hypoxia (HH) exposure. However, this notion has not been tested objectively. Healthy, unacclimatized sea-level (SL) residents slept for 7.5 h each night for 7 consecutive nights in hypoxia rooms under NH [n = 14, 24 ± 5 (SD) yr] or "sham" (n = 9, 25 ± 6 yr) conditions. The ambient percent O(2) for the NH group was progressively reduced by 0.3% [150 m equivalent (equiv)] each night from 16.2% (2,200 m equiv) on night 1 to 14.4% (3,100 m equiv) on night 7, while that for the ventilatory- and exercise-matched sham group remained at 20.9%. Beginning at 25 h after sham or NH treatment, all subjects ascended and lived for 5 days at HH (4,300 m). End-tidal Pco(2), O(2) saturation (Sa(O(2))), AMS, and heart rate were measured repeatedly during daytime rest, sleep, or exercise (11.3-km treadmill time trial). From pre- to posttreatment at SL, resting end-tidal Pco(2) decreased (P < 0.01) for the NH (from 39 ± 3 to 35 ± 3 mmHg), but not for the sham (from 39 ± 2 to 38 ± 3 mmHg), group. Throughout HH, only sleep Sa(O(2)) was higher (80 ± 1 vs. 76 ± 1%, P < 0.05) and only AMS upon awakening was lower (0.34 ± 0.12 vs. 0.83 ± 0.14, P < 0.02) in the NH than the sham group; no other between-group rest, sleep, or exercise differences were observed at HH. These results indicate that the ventilatory acclimatization induced by NH sleep was primarily expressed during HH sleep. Under HH conditions, the higher sleep Sa(O(2)) may have contributed to a lessening of AMS upon awakening but had no impact on AMS or exercise performance for the remainder of each day.
AJP Regulatory Integrative and Comparative Physiology 02/2011; 300(2):R428-36. · 3.34 Impact Factor
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ABSTRACT: Hypoxia often causes body water deficits (hypohydration, HYPO); however, the effects of HYPO on aerobic exercise performance and prevalence of acute mountain sickness (AMS) at high altitude (ALT) have not been reported. We hypothesized that 1) HYPO and ALT would each degrade aerobic performance relative to sea level (SL)-euhydrated (EUH) conditions, and combining HYPO and ALT would further degrade performance more than one stressor alone; and 2) HYPO would increase the prevalence and severity of AMS symptoms. Seven lowlander men (25 ± 7 yr old; 82 ± 11 kg; mean ± SD) completed four separate experimental trials. Trials were 1) SL-EUH, 2) SL-HYPO, 3) ALT-EUH, and 4) ALT-HYPO. In HYPO, subjects were dehydrated by 4% of body mass. Subjects maintained hydration status overnight and the following morning entered a hypobaric chamber (at SL or 3,048 m, 27°C) where they completed 30 min of submaximal exercise immediately followed by a 30-min performance time trial (TT). AMS was measured with the Environmental Symptoms Questionnaire-Cerebral Score (AMS-C) and the Lake Louise Scoring System (LLS). The percent change in TT performance, relative to SL-EUH, was -19 ± 12% (334 ± 64 to 278 ± 87 kJ), -11 ± 10% (334 ± 64 to 293 ± 33 kJ), and -34 ± 22% (334 ± 64 to 227 ± 95 kJ), for SL-HYPO, ALT-EUH, and ALT-HYPO, respectively. AMS symptom prevalence was 2/7 subjects at ALT-EUH for AMS-C and LLS and 5/7 and 4/7 at ALT-HYPO for AMS-C and LLS, respectively. The AMS-C symptom severity score (AMS-C score) tended to increase from ALT-EUH to ALT-HYPO but was not significant (P = 0.07). In conclusion, hypohydration at 3,048 m 1) degrades aerobic performance in an additive manner with that induced by ALT; and 2) did not appear to increase the prevalence/severity of AMS symptoms.
Journal of Applied Physiology 12/2010; 109(6):1792-800. · 3.75 Impact Factor
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ABSTRACT: For many low-altitude (<1500 m) residents, their travel itineraries may cause them to ascend rapidly to high (>2400 m) altitudes without having the time to develop an adequate degree of altitude acclimatization. Prior to departing on these trips, low-altitude residents can induce some degree of altitude acclimatization by ascending to moderate (>1500 m) or high altitudes during either continuous or intermittent altitude preexposures. Generally, the degree of altitude acclimatization developed is proportional to the altitude attained and the duration of exposure. The available evidence suggests that continuous residence at 2200 m or higher for 1 to 2 days or daily 1.5- to 4-h exposures to >4000 m induce ventilatory acclimatization. Six days at 2200 m substantially decreases acute mountain sickness (AMS) and improves work performance after rapid ascent to 4300 m. There is evidence that 5 or more days above 3000 m within the last 2 months will significantly decrease AMS during a subsequent rapid ascent to 4500 m. Exercise training during the altitude preexposures may augment improvement in physical performance. The persistence of altitude acclimatization after return to low altitude appears to be proportional to the degree of acclimatization developed. The subsequent ascent to high altitude should be scheduled as soon as possible after the last altitude preexposure.
High altitude medicine & biology 01/2010; 11(2):87-92. · 1.58 Impact Factor
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ABSTRACT: This study determined the effectiveness of 6 days (d) of staging at 2200 m on physiologic adjustments and acute mountain sickness (AMS) during rapid, high-risk ascent to 4300 m. Eleven sea-level (SL) resident men (means +/- SD; 21 +/- 3 yr; 78 +/- 13 kg) completed resting measures of end-tidal CO(2) (Petco(2)), arterial oxygen saturation (Sao(2)), heart rate (HR), and mean arterial pressure (MAP) at SL and within 1 h of exposure to 4300 m in a hypobaric chamber prior to 6 d of staging at 2200 m (preSTG) and on the summit of Pikes Peak following 6 d of staging at 2200 m (postSTG). Immediately following resting ventilation measures, all performed submaximal exercise ( approximately 55% of altitude-specific maximal oxygen uptake) for approximately 2 h on a bicycle ergometer to induce higher levels of AMS. AMS-C, calculated from the Environmental Symptoms Questionnaire, was measured following 4 h and 8 h of exposure at preSTG and postSTG, and the mean was calculated. Resting Petco(2) (mmHg) was unchanged from SL (39.8 +/- 2.6) to preSTG (39.3 +/- 3.0), but decreased (p < 0.05) from preSTG to postSTG (32.8 +/- 2.6). Resting Sao(2) (%) decreased (p < 0.05) from SL (97 +/- 2) to preSTG (80 +/- 4) and increased (p < 0.05) from preSTG to postSTG (83 +/- 3). Resting HR (bpm) and MAP (mmHg) did not change in any of the test conditions. The incidence and severity of AMS-C decreased (p < 0.05) from preSTG (91 +/- 30%; 1.05 +/- 0.56) to postSTG (45 +/- 53%; 0.59 +/- 0.43), respectively. These results suggest that modest physiologic adjustments induced by staging for 6 d at 2200 m reduced the incidence and severity of AMS during rapid, high-risk ascent to 4300 m.
High altitude medicine & biology 01/2009; 10(3):253-60. · 1.58 Impact Factor
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ABSTRACT: The purpose of this study was to determine in sea-level residents if 6 to 7 consecutive days of normobaric intermittent hypoxic exposure (IHE) (hypoxia room: 2-h ambient PO2=90 mmHg sedentary and 1-h ambient PO2=110 mmHg exercising at 80+/-5% of maximum heart rate) improved sleep quality (awakenings per hour) and quantity at altitude (4300 m). We hypothesized that IHE would improve sleep arterial oxygen saturation (SaO2) levels and decrease desaturation events, thereby contributing to improvements in sleep quality and quantity during subsequent exposure to high altitude. Ten sea-level residents (mean+/-SE: 22+/-1 yr, 179+/-2 cm, 79+/-3 kg) were assigned to an IHE group and six to a SHAM group (20+/-0.5 yr, 180+/-3 cm, 77+/-4 kg). Sleep quantity, SaO2, and heart rate (HR) were monitored at sea level and during high altitude (i.e., 4300 m in a hypobaric chamber) before pretest (PRE-T) and 60 h after posttest (POST-T) for the last IHE or SHAM treatment. Over the 6 to 7 days of IHE, resting SaO2 increased from 75+/-1% to 81+/-3% in the IHE group, while the SHAM group remained at 98+/-1%. From PRE-T to POST-T at 4300-m exposure, both the IHE and SHAM groups had significantly higher sleep SaO2, fewer desaturation events per hour, and an increase in the percentage of time asleep while sleeping (sleep percent). The IHE group, but not the SHAM group, had significantly lower sleep HR and a trend to more awakenings during the POST-T 4300-m exposure. These results indicate that although IHE treatment induced significant ventilatory acclimatization, relative to the SHAM group, IHE did not further improve sleep SaO2 quality and quantity following rapid ascent to 4300 m. Rather, it is likely that the acquired ventilatory acclimatization was lost in the 60 h between the last IHE session and the POST-T altitude exposure.
High Altitude Medicine & Biology 02/2008; 9(4):281-7. · 1.77 Impact Factor
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01/2008: pages 444 - 465; , ISBN: 9780470757826
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ABSTRACT: The purpose of this study was to determine whether seven intermittent altitude exposures (IAE), in combination with either rest or exercise training, improves time-trial exercise performance and induces physiologic adaptations consistent with chronic altitude adaptation at 4300 m.
Ten adult lowlanders (26 +/- 2 yr; 78 +/- 4 kg; means +/- SE) completed cycle endurance testing during an acute exposure to a 4300-m-altitude equivalent (446 mm Hg) once before (pre-IAE) and once after (post-IAE) 7 d of IAE (4h x d(-1), 5 d x wk(-1), 4300 m). Cycle endurance testing consisted of two consecutive 15-min constant-work rate exercise bouts followed immediately by a time-trial exercise performance test. During each IAE, five subjects performed exercise training, and the other group of five subjects rested.
Both groups demonstrated similar improvements in time-trial cycle exercise performance and physiologic adaptations during constant-work rate exercise from pre-IAE to post-IAE. Thus, data from all subjects were combined. Seven days of IAE resulted in a 16% improvement (P < 0.05) in time-trial cycle exercise performance (min) from pre-IAE (35 +/- 3) to post-IAE (29 +/- 2). During the two constant-work rate exercise bouts, there was an increase (P < 0.05) in exercise arterial O2 saturation (%) from pre-IAE (77 +/- 2; 75 +/- 1) to post-IAE (80 +/- 2; 79 +/- 1), a decrease (P < 0.05) in exercise heart rate (bpm) from pre-IAE (136 +/- 6; 162 +/- 5) to post-IAE (116 +/- 6; 153 +/- 5), and a decrease (P < 0.05) in exercise ratings of perceived exertion from pre-IAE (10 +/- 1; 14+/- 1) to post-IAE (8 +/- 1; 11 +/- 1).
Our findings indicate that 7 d of IAE, in combination with either rest or exercise training, improves time-trial cycle exercise performance and induces physiologic adaptations during constant-work rate exercise consistent with chronic altitude adaptation at 4300 m.
Medicine & Science in Sports & Exercise 01/2008; 40(1):141-8. · 4.43 Impact Factor
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ABSTRACT: The purpose of this study was to validate a shortened (11-item) electronic version of the 67-item paper and pencil Environmental Symptoms Questionnaire (ESQ-III) to assess acute mountain sickness (AMS). Thirty-three volunteers (means +/- SE; 28 +/- 1 yr; 74 +/- 2 kg) were given both the paper and pencil and electronic versions of the ESQ (IPAQ 5550, Hewlett Packard, Palo Alto, CA) to complete one after the other at residence altitude (RA) and after 24-h (PP24), 48-h (PP48), and 72-h (PP72) exposure to 4300 m on the summit of Pikes Peak (PP). The AMS-Cerebral (AMS-C) weighted factor score was calculated from responses to the same 11 items for each version of the ESQ. If AMS-C was >or=0.7, then the individual was classified as having AMS. There were no differences in the AMS-C scores between the paper and pencil and electronic versions of the ESQ at RA (0.05 +/- 0.01 vs. 0.05 +/- 0.02), PP24 (0.76 +/- 0.16 vs. 0.74 +/- 0.15), PP48 (0.61 +/- 0.15 vs. 0.53 +/- 0.14), and PP72 (0.34 +/- 0.09 vs. 0.34 +/- 0.09). There were no differences in the incidence of AMS between the paper and pencil and electronic versions of the ESQ at RA (0% vs. 0%), PP24 (33% vs. 36%), PP48 (27% vs. 27%), and PP72 (21% vs. 21%). The relationships between AMS-C calculated from the two versions of the ESQ at RA (r = 0.43; p = 0.01), PP24 (r = 0.92; p = 0.0001), PP48 (r = 0.82; p = 0.0005), and PP72 (r = 0.95; p = 0.0001) were significant. The relationships between the incidence of AMS calculated from the two version of the ESQ at RA (k = 0.90; p = 0.01), PP24 (k = 0.90; p = 0.01), PP48 (k = 0.91; p = 0.01), and PP72 (k = 0.92; p = 0.01) were significant. Our findings suggest that the shortened electronic version can be substituted for the paper and pencil version of the ESQ to assess AMS.
High Altitude Medicine & Biology 01/2007; 8(3):192-9. · 1.77 Impact Factor
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ABSTRACT: Recent studies have demonstrated that brief daily IAE (intermittent altitude exposure) was equally as effective as continuous altitude residence in inducing physiological adaptations consistent with altitude acclimatization. Although the positive benefits of IAE have been clearly defined, the potential negative consequences of IAE on health, specifically the immune system, remain undefined. The present study determined the effects of IAE on WBC (white blood cell) and hormonal responses during rest and exercise at 4300 m altitude. Six lowlanders (age, 23+/-2 years; body weight, 77+/-6 kg; values are means+/-S.E.M.) completed a VO(2)max (maximal O(2) uptake) and submaximal cycle ergometer test during a 30-h SL (sea level) exposure and during a 30 h exposure to 4300 m altitude-equivalent once before (PreIAE) and once after (PostIAE) a 3-week period of IAE (4 hxday(-1), 5 daysxweek(-1), 4300 m). The submaximal cycle ergometer test consisted of two consecutive 15-min work bouts at 40% and 70% of altitude-specific VO(2)max. Blood samples were obtained at rest and during both exercise work bouts for measurements of WBC count, leucocyte subset counts, cortisol, adrenaline (epinephrine) and noradrenaline (norepinephrine). WBC, neutrophil and lymphocyte counts increased significantly (P<0.05) during rest and exercise from SL to PreIAE and decreased (P<0.05) during rest and exercise from PreIAE to PostIAE. Monocyte counts decreased (P<0.05) during rest and exercise from PreIAE to PostIAE, but eosinophil and basophil counts did not change. Cortisol, adrenaline and noradrenaline did not change during rest or exercise from SL to PreIAE or PostIAE, but all increased significantly (P<0.05) from rest during the two work bouts. In conclusion, this type of IAE stimulus did not induce a hormonal stress response and did no harm in terms of activation of the immune system at altitude, as measured by WBC and leucocyte subset counts. This method of pre-acclimatization can therefore be highly recommended for inducing altitude acclimatization without the 'altitude residency' requirement.
Clinical Science 09/2006; 111(2):163-9. · 4.61 Impact Factor
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Medicine & Science in Sports & Exercise 04/2006; 38(5):S526. · 4.43 Impact Factor
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Charles S. Fulco,
Michael Zupan,
Tamara Payn,
Megan Hannon,
Kenneth Kambis,
Ellen Glickman,
Stephen Muza,
Paul B. Rock,
Leonard Elliot,
Janet Staab,
Michael Tapia,
Dennis Rufolo, Beth A. Beidleman,
Allen Cymerman
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ABSTRACT: This study determined the effect of living at moderate altitude on endurance exercise performance, with and without carbohydrate supplementation (CHOS), during the first 3 days of residence at 4300 m. The experimental trials were conducted in a double-blind manner. Subjects were healthy Air Force Academy (AFA) active duty members (9 men and 6 women; age: 30 +/- 30 yrs; mean +/- SE) who had been living at 1800 to 2200 m for at least 3 months prior to the start of the study. All performed a maximal effort 720 kJ cycle time trial at the AFA and at the summit of Pikes Peak (PP), CO, (4300 m) on Days 1 (PP1) and 3 (PP3). At the start of the time trials at PP, and then every 15 min thereafter, nine subjects drank a 10% CHO solution (0.175 g*kgEXP -1 body weight) and six fitness-matched subjects drank a placebo (PLA) solution. All subjects freely adjusted power outputs and drank water ad libitum. Blood glucose, heart rate, arterial oxygen saturation, and ratings of perceived exertion were recorded frequently during exercise. Cycle time did not differ between groups at the AFA (CHOS vs. PLA; 85 +/- 8 vs. 93 +/- 8 min), PP1 (101 +/- 8 vs. 116 +/- 10 min), or PP3 (95 +/- 8 vs. 107 +/- 12 min). For both groups, cycle times on PP1 and PP3 were longer compared to the AFA (P<0.01) and were improved from PP1 to PP3 (P<0.03). There were no between-group differences in any of the measurements during exercise, other than blood glucose (1.5 to 2.0 mmol*Lexp -1 higher for CHOS vs. PLA P<0.01). It was concluded that (1) moderate altitude residents had improved endurance performance from PP1 to PP3; (2) CHOS during exercise provided no additional performance benefit; and (3) endurance performance during initial exposure to 4300 m for moderate altitude residents was more than 50% better compared to previously studied low-altitude residents.
03/2005;
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ABSTRACT: Acute mountain sickness (AMS) commonly occurs at altitudes exceeding 2000-2500 m and usually resolves after acclimatization induced by a few days of chronic residence at the same altitude. Increased ventilation and diuresis may contribute to the reduction in AMS with altitude acclimatization. The aim of the present study was to examine the effects of intermittent altitude exposures (IAE), in combination with rest and exercise training, on the incidence and severity of AMS, resting ventilation and 24-h urine volume at 4300 m. Six lowlanders (age, 23 +/- 2 years; body weight, 77 +/- 6 kg; values are means +/- S.E.M.) completed an Environmental Symptoms Questionnaire (ESQ) and Lake Louise AMS Scoring System (LLS), a resting end-tidal partial pressure of CO2 ( PETCO2) test and a 24-h urine volume collection at sea level (SL) and during a 30 h exposure to 4300 m altitude-equivalent (barometric pressure=446 mmHg) once before (PreIAE) and once after (PostIAE) a 3-week period of IAE (4 h.day(-1), 5 days.week(-1), 4300 m). The previously validated factor score, AMS cerebral score, was calculated from the ESQ and the self-report score was calculated from the LLS at 24 h of altitude exposure to assess the incidence and severity of AMS. During each IAE, three subjects cycled for 45-60 min.day(-1) at 60-70% of maximal O2 uptake (VO2 max) and three subjects rested. Cycle training during each IAE did not affect any of the measured variables, so data from all six subjects were combined. The results showed that the incidence of AMS (%), determined from both the ESQ and LLS, increased (P<0.05) from SL (0 +/- 0) to PreIAE (50 +/- 22) at 24 h of altitude exposure and decreased (P<0.05) from PreIAE to PostIAE (0 +/- 0). The severity of AMS (i.e. AMS cerebral symptom and LLS self-report scores) increased (P<0.05) from SL (0.02 +/- 0.02 and 0.17 +/- 0.17 respectively) to PreIAE (0.49 +/- 0.18 and 4.17 +/- 0.94 respectively) at 24 h of altitude exposure, and decreased (P<0.05) from PreIAE to PostIAE (0.03 +/- 0.02 and 0.83 +/- 0.31 respectively). Resting PETCO2 (mmHg) decreased (i.e. increase in ventilation; P<0.05) from SL (38 +/- 1) to PreIAE (32 +/- 1) at 24 h of altitude exposure and decreased further (P<0.05) from PreIAE to PostIAE (28 +/- 1). In addition, 24-h urine volumes were similar at SL, PreIAE and PostIAE. In conclusion, our findings suggest that 3 weeks of IAE provide an effective alternative to chronic altitude residence for increasing resting ventilation and reducing the incidence and severity of AMS.
Clinical Science 03/2004; 106(3):321-8. · 4.61 Impact Factor
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ABSTRACT: The purpose of this study was to evaluate the user acceptability of four design concepts (e.g., textile chest belt, rubber chest belt, vest, and adhesive patch) for a LSDS in four groups of 15 soldiers (i.e., 60 soldiers). During the six days of testing, soldiers participated in a diverse set of military activities as part of their participation in the U.S. Army Expert Infantryman Badge (EIB) course. On the first day of testing, soldiers filled out a demographic survey and were fitted for each LSDS design concept. Over the next four days of testing (Days 2-5), each soldier wore each of the four design concepts for 24 h and completed a user acceptability survey containing yes/no and 9-point hedonic scale questions. On Day 6 of testing, each soldier completed a comparison survey comparing the four design concepts against one another on a 4-point rank order scale, with 1 as the best rank and 4 as the worst rank. A counter-balanced study design was used so that each group wore a different design concept on Days 2-5 of testing. The ambient environmental conditions were recorded each day of testing. In the user acceptability survey, 90% found the textile chest belt acceptable, 83% found the adhesive patch acceptable, 73% found the rubber chest belt acceptable, and 29% found the vest acceptable. The percentage that found the vest acceptable was lower (P <0.05) than all other design concepts. The percentage that found the rubber chest belt acceptable was also lower (P <0.05) than the percentage that found the textile chest belt acceptable. There were no differences between the textile chest belt and adhesive patch in overall user acceptability. In the comparison survey, the textile chest belt (mean LSD) (l.7+/-0.7) and adhesive patch (2.1 +/- 1.2) were ranked the best in the overall user acceptability category and the rubber chest belt (2.6+/-0.7) and vest (3.5+/-0.9) were ranked the worst.
11/2003;
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Beth A Beidleman,
Stephen R Muza,
Charles S Fulco,
Allen Cymerman,
Dan T Ditzler,
Dean Stulz,
Janet E Staab,
Scott R Robinson,
Gary S Skrinar,
Steven F Lewis,
Michael N Sawka
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ABSTRACT: Chronic altitude residence improves muscular performance at altitude, but the effect of intermittent altitude exposures (IAE) on muscular performance at altitude has not been defined. The purpose of this study was to determine the effects of 3 wk of IAE, in combination with rest and cycle training, on muscular performance at altitude. Six lowlanders (23 +/- 2 yr, 77 +/- 6 kg; means +/- SE) completed a cycle time trial and adductor pollicis endurance test at sea level and during a 30-h acute exposure to 4,300 m altitude equivalent (barometric pressure = 446 mmHg) once before (pre-IAE) and once after (post-IAE) a 3-wk period of IAE (4 h/day, 5 days/wk, 4,300 m). During each IAE, three subjects cycled for 45-60 min/day at 60%-70% of maximal O2 uptake and three subjects rested. Cycle training during each IAE did not appear to affect muscular performance at altitude. Thus data from all six subjects were combined. Three weeks of IAE resulted in 1) a 21 +/- 6% improvement (P < 0.05) in cycle time-trial performance (min) from pre-IAE (32.8 +/- 3.7) to post-IAE (24.8 +/- 1.2), 2) a 63 +/- 26% improvement (P < 0.05) in adductor pollicis endurance (min) from pre-IAE (9.2 +/- 2.8) to post-IAE (14.8 +/- 4.2), and 3) a 10 +/- 4% increase (P < 0.05) in resting arterial O2 saturation (%) from pre-IAE (82 +/- 2) to post-IAE (90 +/- 1). These improvements in muscular performance after IAE correlated strongly with increases in resting arterial O2 saturation and were comparable to those reported previously after chronic altitude residence. IAE may therefore be used as an alternative to chronic altitude residence to facilitate improvements in muscular performance in athletes, soldiers, mountaineers, shift workers, and others that are deployed to altitude.
Journal of Applied Physiology 11/2003; 95(5):1824-32. · 3.75 Impact Factor
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ABSTRACT: The purpose of this study was to determine whether substrate oxidation during submaximal exercise in women is affected by an acute exposure to 4300-m altitude and menstrual cycle phase.
Eight female lowlanders (mean +/- SD; 33 +/- 3 yr, 58 +/- 6 kg, 163 +/- 8 cm) completed a peak oxygen uptake (VO2peak) and submaximal exercise to exhaustion (EXH) test at 70% of their altitude-specific VO2peak at sea level (SL) and during an acute altitude (AA) exposure to 4300 m in a hypobaric chamber (446 mm Hg) in their early-follicular and midluteal menstrual cycle phase. The respiratory exchange ratio (RER) was calculated from oxygen uptake and carbon dioxide output measurements made during the EXH tests, and used to estimate the percent contribution of fat and carbohydrate to energy metabolism. Blood samples were taken at rest and every 15 min during the EXH tests. Blood samples were evaluated for glucose, lactate, glycerol, free fatty acids, insulin, growth hormone, cortisol, glucagon, epinephrine, norepinephrine, estradiol, and progesterone concentrations.
Despite increased (P < 0.05) estradiol and progesterone levels in the midluteal phase, substrate oxidation, energy substrates, and metabolic hormones were not affected by cycle phase at SL or AA. However, free fatty acids and cortisol were increased (P < 0.05) whereas RER was decreased (P < 0.05) during exercise upon AA exposure compared with SL in both cycle phases.
These data suggest that substrate oxidation is altered in women during exercise at AA compared with SL but is not affected by cycle phase. Whether increased fat or protein oxidation accounts for the lower RER values during the AA exposure cannot be determined from this study but warrants further investigation.
Medicine & Science in Sports & Exercise 03/2002; 34(3):430-7. · 4.43 Impact Factor
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ABSTRACT: This study examined the effects of 3 wk of intermittent exposures (4 h/d, 5 d/wk) to 4,300 m altitude-equivalent, in combination with either passive sitting or exercise training, on the process of altitude acclimatization. Physiological, hematological, physical work performance, and acute mountain sickness (AMS) responses elicited by intermittent exposures to altitude were compared to previously published data from chronic altitude residence. Six adult lowlanders (30 +/- 2 yrs; 70 +/- 3 kg) were acutely exposed (i.e., 30 h) to 4,300 m altitude-equivalent once before (PreAc) and once after (PostAc) a 3-wk period of intermittent altitude exposures. Exercise training during intermittent exposures to altitude did not enhance the magnitude of altitude acclimatization. Thus, data from both groups were combined. Three weeks of intermittent altitude exposures resulted in an 11% increase in resting ventilation, 18% increase in maximal oxygen uptake (VO2(sub max)), 21% improvement in whole-body submaximal endurance performance, 26% increase in small-muscle endurance performance, and elimination of AMS symptoms from PreAc to PostAc. Intermittent altitude exposures accomplished 50%-100% of the expected adaptation to altitude, based on improvements in submaximal endurance performance and absence of altitude illness, when compared to previous chronic altitude residence studies. These large improvements in physical work performance and AMS symptomatology appear to be related to the large degree of ventilatory acclimatization achieved after 3 wk of intermittent altitude exposures. Our findings suggest that 3 wk of intermittent altitude exposures is a useful tool for enhancing physical work performance and eliminating symptoms of AMS in less total exposure hours than chronic altitude residence.
10/2001;
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ABSTRACT: The objective of this study was to determine if the magnitude of the sea level pre-ascent resting ventilation and hypoxic ventilatory depression (HVD) are selective in identifying subjects who are susceptible to AMS. We hypothesized that individuals with lower effective alveolar ventilation, i.e., high resting end-tidal carbon dioxide partial pressure (PETCO2), and high HVD will be more likely to develop AMS during subsequent exposure to 4300 m. Twenty volunteers spent 24 h in a hypobaric chamber at sea level undergoing baseline measurements. During this baseline period, the subjects completed sea level resting ventilation and HVD procedures. The next morning, the chamber was decompressed to simulated altitude (PB 430 or 446 mmHg) for approximately 32 h. Resting ventilation was measured after about 4 hours exposure to high altitude and AMS assessed using the Environmental Symptoms Questionnaire at 8-hour intervals throughout the altitude exposure. At sea level, all subjects had normal levels of ventilation and exhibited no evidence of hypoxemia. There was a wide distribution in the resting PETCO2, and HVD. At about 4 hours exposure to high altitude, both SaO2 and PETCO2 were lower (p < 0.002) compared to sea level. The distribution of PETCO2 and particularly SaO2 widened at high altitude. The sea-level normoxic PETCO2 was positively correlated to the high altitude PETCO2. Sixty percent of the volunteers developed AMS (AMS+) at some point during their altitude exposure. The resting SaO2 in the AMS+ group tended (p = 0.193) to be lower than the 40% not developing AMS (AMS-). The sea level HVD was significantly higher in the AMS+ group compared to the AMS- group; but there was a wide overlap in its distribution between the groups. None of the other sea level ventilatory measurements were meaningfully different between the AMS+ and AMS- groups.
04/2000;
