Sex,stress, and health: Does stress predict health symptoms differently for the two sexes?

Objectives: Previous studies have been inconsistent with regard to the extent to which stress perception, rather than stressor exposure, predicts negative health symptoms. Because sex differences have been observed in all three of these variables, in this study the possibility that sex differences also exist in the relationships between them is investigated. Methods: Self‐report inventories of perceived stress, stressor exposure, and negative health symptoms were given to 107 young‐adult participants (65 females, 42 males). Results: Sex differences were observed in the associations among perceived stress, stressor exposure, and negative health symptom rates. Specifically, while higher perceived stress and higher stressor exposure rates independently predicted higher negative health symptoms rates in females, only higher stressor exposure rates independently predicted higher negative health symptoms in males. Indeed, unexpectedly, after controlling for exposure to stressors there was a trend towards higher perceived stress predicting lower negative health symptoms in males. Conclusions: While exposure to stress was a significant negative predictor of health for both sexes, perception of stress was predictive only for females. One implication of this finding is that different psychological models are needed to predict health symptoms in the two sexes. Copyright © 2005 John Wiley & Sons, Ltd.     

Effects of exercise on muscle activation and metabolism in multiple sclerosis

We investigated the role of metabolism in muscle fatigue during voluntary exercise in persons with mild multiple sclerosis (MS). Six MS and 8 healthy control subjects performed intermittent, progressive, isometric contractions of the ankle dorsiflexors, during which we measured maximum voluntary force (MVC), inorganic phosphate (Pi), phosphocreatine (PCr), and pH. During exercise. MVC fell sooner in MS, but by the end of exercise the relative decrease in MVC was similar in both groups. In contrast, at the end of exercise Pi/PCr increased to 1.86 ± 0.22 in controls but to only 0.66 ± 0.04 in MS (P < 0.01); likewise, pH was 6.75±0.04 in controls and unchanged (7.06 ± 0.04) in MS (P <0.01). The smaller metabolic change at the same relative exercise intensity suggests a failure of muscle activation that is present even in mild MS. Neurophsyiologic measures of activation indicated some central activation failure and no neuromuscular junction impairment in MS, and suggested that activation failure beyond the muscle membrane(excitation–contraction coupling) may be important in MS. We conclude that metabolic factors do not play a significant role in the development of muscle fatigue during voluntary exercise in mild MS. © 1994 John Wiley & Sons, Inc.