The present work describes that under increasing physical load the voice fundamental frequency (voice pitch) remains on a given level as long as the physical load is well tolerated by the subject, whereas heart rate and blood pressure continuously increase during increasing physical load. This voice pitch level was compared to voice pitch levels under mental load. Using a word recognition system, 11 well trained, young male subjects had to solve 2 moderate mental load tasks. Before, during and after each task, there were structured relaxation phases. The physical load protocol was a standard bicycle stress test. In each protocol phase the subjects had to count from 1 to 10 in order to provide a standardized speech sample. Heart rate and blood pressure were recorded in all phases. Voice frequency was at average 106 +/- 5.2 Hz in the relaxation phases ('rest level') and was increased under mental load (115.9 +/- 5.7 Hz, Pillais-P = 0.037). During physical stress testing, voice pitch remained unchanged ('tolerated load level') between 100 and 200 W (117.4 +/- 4.8 Hz) and increased shortly before physical exhaustion ('exhaustion level', 275-350 W, 142.9 +/- 5.6 Hz, Pillais-P = 0.007). In contrast, heart rate and blood pressure increased continuously with the physical load. Three voice pitch levels could be verified also individually for each subject. For the practical monitoring of emotional stress the individual anchor frequencies for these levels must be assessed. These data indicate that the relationship between both types of load and voice pitch is non-linear with multiple plateaus and transition functions between them.

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It is well known that there is a relationship between the voice the human emotional status. Previous studies have demonstrated that changes of fundamental frequency ( f(0)), in particular, have a significant relationship with emotional load. The aim of the present study was to investigate how f(0) changes in response to an unknown emotionally stressful task under real-life conditions. A further question was whether repetitions of this task lead to an adaptation of f(0), indicating a lower emotional load. The participants of this study included 26 healthy males. f(0) and heart rate ( f(c)) were recorded for baseline testing (BLT) under relaxed laboratory conditions. Then the participants were asked to negotiate a natural obstacle by way of sliding down a rope hanging from a handlebar without any safety provisions, thus being exposed to the danger of a fall from a height of up to 12 m into shallow water (guerrilla slide I, GSI). The task was repeated after 30 min (GSII) and after 3 days of physical strain (GSIII). Immediately before starting the task the participants were asked to give a standardised speech sample, during which f(c) was recorded. The mode value of f(0) ( f(0,mode)) of the speech samples was used for further analysis. The mean (SD) value of f(0,mode) at BLT was 114.9 (14.8) Hz; this increased to 138.8 (19.6) Hz at GSI ( P<0.000), decreased to 135.9 (19.6) Hz at GSII and to 130.0 (21.5) Hz at GSIII ( P=0.012). The increase in f(c) was significantly different from BLT to GSI ( P<0.000). The repetitions of the task did not produce significant changes in f(c). It was shown that f(0,mode) is a sensitive parameter to describe changes in emotional load, at least in response to short-term psychoemotional stress, and seems to throw light upon the amount of adaptation caused by increased experience.

This research examined the impact of psychological and physical demands on a group of elite soldiers (N = 9) before, during and after training exercises involving routine and unrehearse tasks. Based on the psychological concept of toughening, we expected soldier responses to unrehearsed demands to be les resilient than to routine training demands. As hypothesized soldiers rated their perceptions of physical and psychologica demands higher during the unrehearsed training phase of the study. It was also hypothesized that soldiers would recover more from physical demands than from psychological de mands after the training exercise. Although a trend in the data marginally supported this hypothesis, a note of caution is warranted because of the small sample size. Limitations and implications of the study are discussed, with particular emphasis on the dual importance of psychological and physical training in preparing soldiers for mission demands.