Exposure to natural altitude using the "live high-train low" method improves athletic endurance performance at sea level by 1-2%. This method can also be employed with hypoxic devices that simulate altitude, but there is limited and conflicting research on their efficacy. Consequently, three studies were undertaken to investigate changes in sea level performance of endurance runners following exposure to altitude simulated with hypoxic tents. The device was chosen because of its potential for incorporation into the athlete's routine. In Study 1, 10 runners received altitude simulated with hypoxic tents (~9 h overnight at 2500-3500 m) and trained at sea level, while 10 runners in the control group performed usual training. Athletes in both groups performed a lactate-threshold test, but only the altitude group performed a run to exhaustion. The effect on 4-mM lactate speed was unclear, owing to poor reliability of this measure. There was a 16% increase in time to exhaustion in the hypoxic conditioning group, equivalent to a 1.9% (90% likely limits, ±1.4%) increase in speed in a time trial. Effects on performance were not apparent four and eight weeks after use of the tents. To improve precision of the effect of the tents and to determine the effects on performance of different durations, a further controlled trial was performed. A reliability study (Study 2) was first conducted to investigate the potential for runs to exhaustion to provide reliable measures of performance. Eight runners performed a test consisting of three runs to exhaustion lasting ~2, ~4 and ~8 min on six occasions over 14 wk. The critical power and log-log models were used to provide factors for converting variability in time to exhaustion into variability in equivalent time-trial time. Variabilities in time to exhaustion expressed as coefficients of variation for predicted 800-3000 m timetrial times were ~1-3%. A crossover study (Study 3) was then conducted in which 11 athletes performed usual (control) training and usual training with altitude exposure by using tents for 25 ± 3 days (mean ± SD) for 8.1 ± 0.6 h.d-1, progressing from a simulated altitude of 2500 m to 3500 m above sea level. Washout period between control and altitude treatments was four weeks. Performance was assessed with treadmill runs to exhaustion as in Study 2. Improvements in mean predicted times (altitude-control) for standard competition distances of 800, 1500 and 3000 m derived from the runs to exhaustion were 1.0% (±1.3%), 1.4% (±1.2%) and 1.9% (±1.5%) respectively. There was some evidence that hypoxic exposure favoured those athletes carrying the I allele for angiotensin converting enzyme. In summary, the main finding from the series of studies is that hypoxic tents are likely to enhance sea level endurance running performance by ~1-2%.

Athletes commonly use various forms of real and simulated altitude exposure combined with sea level training to enhance sea-level performance. Altitude can be simulated through use of apartments, tents and masks that allow athletes to breathe air containing less oxygen. There is clear evidence that altitude exposure combined with sea-level training enhances endurance performance especially when the altitude is real. It is unclear what the optimum level of altitude and length of exposure is to enhance performance, although researchers generally adopt 3-4 weeks at moderate altitude (~3000m). There is also little evidence to suggest how long the performance effect persists for. Large gains in VO2max have been reported following actual altitude exposure that may be partly mediated via an increase in red cell volume or haemoglobin mass. However, exposure to simulated altitude appears to have a little effect on VO2max probably due to differences in daily exposure time. The effects of altitude exposure on sprint performance are limited to several investigations that demonstrate a tendency for improved performance, especially in repeated sprints.

Exposure to natural altitude using the "live high-train low" method improves athletic endurance performance at sea level by 1-2%. This method can also be employed with hypoxic devices that simulate altitude, but there is limited and conflicting research on their efficacy. Consequently, three studies were undertaken to investigate changes in sea level performance of endurance runners following exposure to altitude simulated with hypoxic tents. The device was chosen because of its potential for incorporation into the athlete's routine. In Study 1, 10 runners received altitude simulated with hypoxic tents (~9 h overnight at 2500-3500 m) and trained at sea level, while 10 runners in the control group performed usual training. Athletes in both groups performed a lactate-threshold test, but only the altitude group performed a run to exhaustion. The effect on 4-mM lactate speed was unclear, owing to poor reliability of this measure. There was a 16% increase in time to exhaustion in the hypoxic conditioning group, equivalent to a 1.9% (90% likely limits, ±1.4%) increase in speed in a time trial. Effects on performance were not apparent four and eight weeks after use of the tents. To improve precision of the effect of the tents and to determine the effects on performance of different durations, a further controlled trial was performed. A reliability study (Study 2) was first conducted to investigate the potential for runs to exhaustion to provide reliable measures of performance. Eight runners performed a test consisting of three runs to exhaustion lasting ~2, ~4 and ~8 min on six occasions over 14 wk. The critical power and log-log models were used to provide factors for converting variability in time to exhaustion into variability in equivalent time-trial time. Variabilities in time to exhaustion expressed as coefficients of variation for predicted 800-3000 m timetrial times were ~1-3%. A crossover study (Study 3) was then conducted in which 11 athletes performed usual (control) training and usual training with altitude exposure by using tents for 25 ± 3 days (mean ± SD) for 8.1 ± 0.6 h.d-1, progressing from a simulated altitude of 2500 m to 3500 m above sea level. Washout period between control and altitude treatments was four weeks. Performance was assessed with treadmill runs to exhaustion as in Study 2. Improvements in mean predicted times (altitude-control) for standard competition distances of 800, 1500 and 3000 m derived from the runs to exhaustion were 1.0% (±1.3%), 1.4% (±1.2%) and 1.9% (±1.5%) respectively. There was some evidence that hypoxic exposure favoured those athletes carrying the I allele for angiotensin converting enzyme. In summary, the main finding from the series of studies is that hypoxic tents are likely to enhance sea level endurance running performance by ~1-2%.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves [179]-198).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Humans can only survive the low barometric pressure of altitudes above 6000m by making a complex series of adaptations. The energetics of human survival at such extreme altitudes have not been widely studied. Objectives were to compare the doubly labelled water (DLW) and intake-balance (IB) methods to estimate daily energy expenditure while climbing between 6000 and 8046m and to investigate the putative metabolic cost involved with the process of acclimatization to extreme altitude. Reliability of the DLW method to provide an accurate and portable means to measure human energy expenditure depends upon a series of assumptions regarding the flux of tracer and tracee across the physiological compartments of measurement. Additional objectives were to review and examine the proficiency of these assumptions to account for perturbations experienced while using DLW while climbing at extreme altitude. Findings suggest that the use of DLW at extreme altitudes requires special consideration towards elevated rates of fractional isotope loss, inter-subject isotope transfer, alterations in total body water, changes in background isotopic abundance, and choice of sampling technique. Revised strategies directed at achieving these aims are calculated. Results from extreme altitude indicate that IB and DLW techniques each provide similar estimates of group mean energy expenditure despite substantial changes in body weight and composition and that the metabolic cost for the process of acclimatization accounts for roughly 12% of total daily energy expenditure. Problems associated with maintaining energy balance while climbing at extreme altitude are related to low energy intakes, approximately only 70% of energy demands, and energy expenditure values that are comparable to those of highly trained endurance athletes at sea-level.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Thesis (Honors)--College of William and Mary, 2009. / Includes bibliographical references (leaves 58-66). Also available via the World Wide Web.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 113-118).