Thesis (M.S.)--Montana State University--Bozeman, 2007. / Typescript. Chairperson, Graduate Committee: Daniel P. Heil. Includes bibliographical references (leaves 65-68).

Thesis (M.S.)--Eastern Illinois University, 1987. / Includes bibliographical references (leaves 27-28).

Thesis (Ph.D.)--Baylor University, 2006. / Includes bibliographical references (p. 131-139).

Thesis (Ph.D.)--Baylor University, 2006. / Includes bibliographical references (p. 121-127).

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xi, 137 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

Thesis (M.S.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 66-75). Also available via the Internet.

During dynamic exercise, the response of the cardiorespiratory system is structured to maintain homeostasis at the cellular level. The rate at which homeostasis is established is largely dependent on the system's structural and physiological integrity. Evidence suggests that any impairment in the functioning of the system might be reflected in a determination of oxygen uptake (VO[2]) kinetics. The kinetics of VO[2] have been quantified in response to step, impulse, ramp and sinusoidal changes in work rate (WR). An alternative approach uses a technique in which the WR is perturbed according to a pseudorandom binary signal. Pseudorandom binary sequence (PRBS) WR forcings have the advantage of being able to provide a determination of vo2 kinetics from a single test session of ~30 min duration. The assessment of VO[2]kinetics using PRBS WR forcings demands that the controlling process behaves in a linear manner. To minimise the contribution of non-linear influences, changes in work intensity must be constrained to the sub-lactate threshold domain. When examining clinical, untrained or young subjects, the necessary reduction in the upper work limit of a PRBS forcing can effect a fall in the distribution of power across the bandwidth of the sequence. If the distribution of power should fall below a critical level, then it can become difficult to elicit discernible responses from the forcing. To resolve this problem, this thesis investigated the potential for developing a multifrequent WR forcing altered to enhance identification of the underlying VO[2] response. The multifrequent WR forcing developed for use in this thesis took the form of a binary sequence. Binary transitions were determined according to a specially constructed multifrequent signal. Signal construction involved redistributing the available signal power to specific harmonics in a chosen range of frequencies. To validate estimates of VO[2] kinetics derived from the multifrequent binary sequence (MFBS) WR forcing, comparisons were made with the data obtained from an established PRBS forcing. When comparing physiological data, it is necessary to consider the amount of variability between trials. Therefore, prior to assessing the agreement between data obtained from the MFBS and PRBS methods, this thesis sought to establish the degree of variability in estimates of VO[2] kinetics derived from PRBS exercise tests. The results presented in this thesis show estimates of the mean response time (MRT) of VO[2] derived from the MFBS method to be 46.8 (4.2) s (mean (standard deviation) seconds), compared with 45.2 (5.0) s for the PRBS method. This suggests that the two methods yield comparable determinations of VO[2] kinetics. Supporting evidence is provided by the limits of agreement. These indicate that the maximum difference likely to occur between the MRT obtained from the two methods (-6.5 to +9.6 s) is less than that expected due to variability in the MRT derived from PRBS forcings (-11.6 to +8.0 s). However, the limits also reveal the poor repeatability of VO[2] response data obtained from the PRBS used in the thesis. Consequently, the use of this data to assess the validity of t the MRT derived from MFBS forcings is not recommended. In addition to poor repeatability, the possibility exists that assessments of VO[2] kinetics derived from MFBS WR forcings will also depend on the distribution of power across the harmonic content of the sequence. Therefore, whilst MFBS WR forcings may be suited to the assessment of VO[2] kinetics in subjects with a reduced tolerance to exercise, there remain doubts concerning both the validity of the response data and applicability of the method. Until these issues have been resolved, care would need to be taken when using estimates of VO[2] kinetics derived from MFBS WR forcings to determine the functional state of the cardiorespiratory system.

Personal cooling garnents (peGs) are designed to relieve thermal stress in occupations that require the use of personal protective clothing (e.g. fire fighter, military personnel). The cooling source in peGs is usually delivered continuously, which over long periods requires a large battery source. Intermittent cooling has been found to be as effective as continuous cooling at maintaining thermal balance. Based on the observation that larger improvements in thermal perceptions are associated with rapid changes in skin temperature, it was hypothesised that intermittent cooling could also enhance thennal perceptions (i.e. temperature sensation and thennal comfort). The overall aim of the studies presented in this thesis was to test this hypothesis. In order to detect differences between intermittent and continuous cooling on thermal perceptions, it was important to use a reliable measurement tool to assess perceptual responses in conditions where a PCG would be utilised. The first study described in this thesis assessed the reliability of a graphic visual analogue scale (VAS) against a Likert scale (LS) for validity and reproducibility in the measurement of thennal perceptions in non-uniform, dynamic thermal environments. The study involved three identical conditions in which thermal perceptions were measured by both the V AS and LS in response to changes in the torso microclimate. During the condition, participants walked (Skm.hr-] , 2% incline) in a warm environment (3S0C, SO% relative humidity [RH]) and wore clothing (I.2 clo) that covered 88% of the body. The torso microclimate was manipulated by ventilating air of different temperatures and relative humidity through an air-perfused vest (APV). These thermal conditions were similar across all the studies presented in this thesis. The V AS were found to be slightly more reproducible for local thermal perceptions than the LS , and had greater validity during both stable and non-uniform, dynamic thermal environments. Therefore the use of the graphic VAS was adopted in all subsequent studies. To develop the intermittent cooling profiles that were assessed for their ability to enhance thermal perceptions, the second study involved ventilating different air temperatures (-15- 26°C) through the APV to determine what type of flu ctuations in skin temperatures are required to enhance thermal perceptions. The results suggested that the rate of change in mean skin temperature (f'sk) and torso skin temperatures (T sktorso) had a greater influence on thermal perceptions than absolute changes in Tsk and T sktorso. The results also confirmed the results from the first study, that increasing evaporative heat loss at the skin surface was the most effective method to manipulate the rate of change of skin temperatures, and consequently, thermal perceptions. To compare the capability of intermittent and continuous cooling profiles to enhance thermal perceptions, whilst maintaining thermal balance, the final study involved ventilating the APV with either fluctuating or continuous air velocities during both exercise and rest Three different intermittent cooling profiles were used; sinusoidal, sawtooth and step-change. Upon completion of the experiment, participants stated their preferred cooling profile. Based on the results it was concluded that intermittent cooling, which had 50% less air flow than continuous, maintained both thermal balance and thennal comfort when compared to continuous cooling. Out of the intennittent cooling profiles, the sinusoidal profile produced significantly cooler sensations and was 4111 participants' preferred choice. The results suggest that the presence of a significantly higher torso relative humidity (RH1orso) in the intennittent cooling profiles, compared to continuous profile, may have confounded their capability to enhance thennal perceptions over time. In addition, the cooling profi le that was perceived to the 'coolest' and/or the most ' stable' was generally the participants' preferred choice. This suggests that large fluctuations in skin temperature are not always perceived favourably. Based on the studies conducted as part of this thesis, it is concluded that in order to minimise high levels of RHtorso and provide smoother transitions in temperature sensation, an optimal cooling profile should consist of: 1) a sinusoidal pattern with a frequency greater tban 0.000139 Hz, 2) have a ratio of 2:1 ON/OFF periods, 3) OFF periods no longer tban 3 minutes, 4) highest flow rate not to exceed 255 L.min-], 5) provide a rate of change in f sk and t sklOISO of -{).29°C.min-1 and O. 78°C.min-], respectively, and 6) the incorporation of a drying agent into the design of an APV.

Many daily activities and sporting events require an individual to perform brief periods of maximal exercise (i.e. < 10s) interrupted by limited periods of recovery. In the first study an intermittent maximal exercise test was used to examine the decline in power output with successive exercise periods and identify the changes in the metabolic environment associated with such exercise. The exercise protocol consisted of ten 6s maximal sprints with 30s recovery between each sprint on a cycle ergometer. The results suggest that phosphocreatine (PCr) and anaerobic glycolysis provided the majority of the energy to sustain an average power output (MPO) of 870.1 ±159.2W in the first sprint. In the final sprint, however, no change in lactate concentration was apparent, yet the average power output was still 73% of that in the initial sprint. It was suggested that the energy was derived from PCr degradation and oxidative metabolism.