AbstractThe work described in this thesis was conducted to assess the contribution psychological skills training (PST) including goal-setting, relaxation strategies,
mental imagery and positive self-talk, can make to the capability to suppress or tolerate the physiological responses to thermally stressful environments. PST, a
technique originally developed in sport psychology studies, was specifically tailored to aid individuals in adverse conditions, thereby providing some insight in to the contribution psychological factors can make to survival. This approach was designed to provide some idea of the contribution the will to survive may make in hazardous and threatening circumstances. We hypothesised that psychological training could significantly alter the responses elicited by thermal stimuli. The assumption was that psychological skills that have proven to be efficacious under psychological and physiological stress in challenging sporting environments, could also prove influential in more hazardous thermal environments.
Study I examined the influence of mental imagery on the vasomotor responses to thermoneutral (26-28'C), cool (12.5'C) and warm (40'C) air in twelve healthy male subjects. We assessed whether hot and cold mental images could alter peripheral vasomotor tone and thermal perception in these environments. This study was conducted to quantify the influence of a psychological skill whilst at rest and in an environment with few external stimuli. Comparisons between control and mental imagery periods (hot and cold), both before and after mental imagery training, suggested that a single psychological skill has a limited capacity to alter the largely involuntary vasomotor responses to thermoneutral, cool, and warm air as only transient and insignificant effects were observed. There is also only a limited impact of this type of mental practice on thermal perception in a thermoneutral (26-28'C) environment. The null hypothesis was therefore accepted.
The subsequent study (study 2) examined the impact of a package of
psychological skills on the responses that are recognised as being under greater
voluntary control at rest, but have been thought to be involuntary following acute cold-water stimulation, namely breath-holding. This study involved 32 healthy male subjects completing two immersions into cold-water (I VC), an activity that significantly reduces maximal breath-hold time and that can be a precursor to drowning following accidental immersion. On immersion the subjects were required to breath-hold for as long as possible. Following an initial breath-hold immersion subjects were ranked in order of lowest to highest breath-hold time (BHwater,), and allocated to either a control group (CG: BRm, r time mean [s. d]; n= 16: 24.01 [6.72] sec) or a psychological intervention group (PIG: n= 16: 24.66 [14.60] sec). Over the 7-day period between immersions the CG continued normal daily activity whereas the PIG completed five 1-hour PST sessions comprising goal-setting, relaxation strategies, mental imagery and positive self-talk; the final session provided a summary of the first 4 skills. Subjects then completed a second breath-hold immersion during which the PIG recorded a significantly longer breath-hold time after psychological intervention compared to the CG (BHwater4: 4.25 [31.63] sec; CG: 21.34 [16.3 1 ]; P=0.026). PST conferred an almost 80% improvement in BHwater suggesting psychological factors may significantly influence the respiratory responses to cold-water immersion providing the first indication of the influence of mental 'will' in such conditions.
Study 3 examined the impact of PST on maximal BHwater following coldhabituation, thus assessing the extent to which habituation to cold water includes a conscious psychological component. Twenty healthy, non-habituated male subjects completed an initial immersion into cold-water (I2°C whilst breath-holding (BHwater) and were subsequently matched and allocated to one of two groups, a habituation only group (HAB, n= 10: BHwater22.00 [10.33] sec) and a habituation plus PST group (H-PST, n= 10: 22.38 [10.65]sec). In the interim period (7-10 days) between breath-hold immersions all subjects completed 5 free breathing immersions into cold-water (12'C). In addition, the H-PST group completed the same PST intervention as used in study 2, aimed at consciously increasing maximal BHwater time on immersion. After their respective interventions all subjects completed a second breath-hold immersion. Results showed that the habituation regimen significantly reduced the cardiorespiratory responses to immersion in both groups by a similar magnitude. Significant changes took place in both groups by the 4th habituation immersion. Statisicial analysis showed no significant differences between groups in BHwater (P = 0.299) indicating PST did not have a significant and additive effect upon the ability to breath-hold on immersion after habituation (HAB, n= 10:BHwater 36.31 [23.88] sec; H-PST, n= 10: 49.25 [30.87]).
Study 4 examined the influence of a PST package on the voluntarybehavioural responses to prolonged thermal stress whilst exercising (30'C for 90minutes). Eighteen subjects completed a total of 3 exercise trials in the heat in whichthey were required to run as far as possible on a treadmill until exhaustion occurred,or the allotted time expired. Following trial 2 subjects were matched and allocated toeither a CG or PIG based on the variability in run performance shown between trial Iand 2. The groups alos did not significantly differ based on maximal oxygen uptake,or sum of skinfold (s. o. s) measurement but were not matched on these criteria. As with study 2, the CG continued normal daily activity between trials 2 and 3 whereas the PIG completed a version of the previously used PST package tailored to help them cope with the unpleasant sensations associated with elevated deep body temperature and prolonged exercise in the heat. Inter-trial variability was 1.70 [2.82]% between trial I and 2 in the CG versus 0.98% [5.28] in the PIG. Between trial 2 and 3 the CG improved by 2.74% [4.03] whereas the PIG ran 6.88% [5.82] further in trial 3. In percentage terms, the PIG ran significantly further in trial 3. The mechanism underpinning the change in performance in the PIG was not statistically linked to any of the physiological variables measured. Overall, the findings suggest PST may also influence the capacity to tolerate the unpleasant physiological responses to exercise in the heat, but were less influential than in the cold.
The possible mechanisms underpinning the changes that take place with PSTare considered. It is concluded that psychological skills training significantlyinfluenced the physiological responses over which there is greatest voluntary controlThe present work demonstrates the potential role psychological factors may play in surviving certain conditions and scenarios which involve the choice to tolerate or suppress the evoked responses to thermal stimuli or, to succumb to the environmental conditions. The distinction between individuals in making this choice may be a product of mental will and provides the first evidence that the will to survive may have some genuine foundation between being a victim or a survivor following accidental exposure.
|Date of Award
|Richard Thelwell (Supervisor) & Mike Tipton (Supervisor)