Barbara A. Hart

Plasma catecholamine response to acute psychological stress in humans : relation to aerobic fitness and exercise training

Existing cross-sectional studies on plasma catecholamine activity provide no support for the concept that a markedly high level of aerobic fitness modifies sympathoadrenal response to an acute psychological challenge in humans. In contrast, compromised sympathetic nervous system activity has been observed in individuals with low aerobic fitness and the relationship probably reflects a global deconditioning syndrome involving both psychological and physiological processes. The relationship between low levels of fitness and plasma norepinephrine may appear as a blunted or augmented response depending upon the nature of the task. Short-term (3-4 months) exercise training studies conducted with humans have not indicated a substantial adaptation in the relative plasma catecholamine change from a preexisting baseline during exposure to acute psychological stress. Exercise training can lower basal circulating plasma norepinephrine, resulting in lower absolute concentrations during an acute challenge, but the studies in this area lack consistency and the absolute change tends to be modest. There is no evidence that fitness or exercise training is significantly associated with plasma epinephrine activity during short-term psychological stress.

Sex Bias and the Validity of Believed Differences between Male and Female Interscholastic Athletic Coaches

Previous research indicates that young athletes as well as athletic administrators hold gender-role stereotypical beliefs about coaches that disfavor females. The validity of two such beliefs (lack of qualified female coaches and time constraints due to family responsibilities) was examined in a statewide survey of 256 female and 296 male interscholastic coaches and a nationwide survey of 2,719 male and 1,449 female interscholastic coaches. Statistical analyses (p less than .001) indicated that female coaches were (a) more qualified than their male counterparts with respect to coaching experience with female teams, professional training, and professional experience; (b) as qualified as male coaches with regard to intercollegiate playing experience; and (c) less qualified than male coaches with respect to high school playing experience and coaching experience with male teams. Findings also indicated that male rather than female coaches more often experienced time constraints due to family responsibilities.

Sympathetic nervous system and behavioral responses to stress following exercise training.

This study tests the hypothesis that a short-term (16 weeks) exercise program modifies sympathetic nervous system (SNS) and selected behavioral responses to acute psychological stress. Twenty-four previously sedentary middle-aged men with maximal aerobic capacity (VmaxO2) values less than 40 ml.kg-1.min-1 were assigned to experimental (n = 12) and control (n = 12) groups. All subjects performed a modified Stroop test (18 min) at pre- and postexercise training during which intravenous blood samples were drawn at three time intervals for plasma catecholamine (CA) determination. Motor performance was continuously recorded for assessment of premotor (PMT) and motor (MOT) components of reactions time. A set of anagrams were administered immediately following the modified Stroop to determine the level of cognitive fatigue induced. At both pre- and postexercise intervention, the total group (n = 24) manifested significant (p less than or equal to 0.05) elevations in state anxiety, heart rate, and plasma norepinephrine. No significant changes occurred over time on PMT or MOT. There were significantly (p less than or equal to 0.01) lengthened anagram performance scores poststress compared to nonstress values. The experimental group exercise trained 3 days/week for 16 weeks, resulting in a 20% increase in VO2max. However, there were no group differences on the CA or behavioral responses to the modified Stroop at pre- or postintervention. These findings do not support the hypothesis that short-term aerobic training significantly alters SNS activity or behavioral measures of central processing in middle-aged men exposed to an acute psychological challenge.

Grip responses to object load perturbations are stimulus and phase sensitive

Responses to load changes of a held object that challenge grasp stability are known to be adept and fast, but the responses to changes in load where grasp stability is not challenged are not well understood. In order to compare responses to these functionally opposite perturbations, the grasp response to increases and decreases in the load of a held object was examined. A pulling force used to create object load was abruptly altered so that it felt lighter (decreased load) or felt heavier (increased load). The perturbation occurred either during movement of the object (lift) or when the object was held steady (hold). Grip force modulation was earlier, larger, had a faster maximum rate and a smaller change in relative safety margin when load increased. Also, the grip force modulation was earlier, larger, had a faster maximum grip force rate and a smaller change in relative safety margin when the perturbation occurred during active lift. In the decreased loading condition, participants were not required to make a grip force adjustment to maintain grip. Interestingly, participants chose to make the adjustment (decreasing grasp force), albeit more slowly. During the lift phase, the nature of the task is more dynamic and the resulting additional mechanical stimulation may have lead to a facilitated response. The results point to the greater functional significance of increasing load for grip force modulation and the potential for greater sensory or motor facilitation during dynamic lifting.

Selected psychophysiological stress responses in men with high and low body fatness.

Previous research on catecholamine (CA) response to exercise has linked heightened adiposity to a hypostress syndrome. In the present study a cognitive/psychomotor stressor was employed to determine whether this association exists during less metabolically challenging tasks. Moreover, because stress is manifested in a multidimensional manner, measures of behavior and perceived distress were analyzed in addition to the physiological response. Men were selectively recruited for two body fatness groups (low, 12 +/- 4%, N = 9; high, 27 +/- 2%, N = 10) while being matched on age, lean weight, and peak absolute oxygen consumption. All men performed a modified Stroop task for 12 min to induce a psychophysiological stress response. Physiological changes included significant increases in heart rate, venous plasma norepinephrine, and epinephrine. Cognitive/psychomotor responses indicated no change in reaction time during the task but significant cognitive fatigue as indicated by post-task anagram performance. Perceived distress was suggested by elevated state anxiety. The high and low adiposity groups were similar on all measures of the psychophysiological stress response. These findings suggest that elevated adiposity is not characterized by a hypostress state during the relatively low metabolic challenge of a cognitive/psychomotor stressor.

Within-participant variation in landing kinetics: movement behavior trait or transient?

Variation across repeat performances ofa particular movement task by an individual is an inherent feature ofhuman motor behavior (Bates, DeVita,&Kinoshita, 1983; Newell and Corcos, 1993). This phenomenon is referred to as intraparticipant or within-participant variability (WPV) and is observed at multiple levels in movement processes (evidenced in muscular, kinetic, and kinematic measures) as well as in various behavioral outcome measures (e.g., speed and accuracy scores). Using a single score or the mean score from repeated tests to characterize some phenomenon is a common approach in science. However, WPV measures have been used in several domains to characterize and evaluate system functioning. Evaluating motor skill and motor skill learning has long incorporated such measures with the basic notion that less variation indicates better skill (Higgins, 1977; Latash, 1993; Lees & Bouracier, 1994). Heart rate variation is viewed as a symptom of healthy cardiac regulation and function that has been shown to respond positively (increases) with exercise (Seals & Chase, 1989). Also, variation in the temporal characteristics ofvarious cyclic behaviors (Ivry& Corcos, 1993) has been linked to specific neurological pathologies. Different explanations for the causes or sources of WPV have been given. For the human movement sci-