Abstract-Work stress has repeatedly been associated with an increased risk for cardiovascular disease. This study tested whether this relationship could be explained by exaggerated cardiovascular reactivity to work or impaired recovery in leisure time. Vagal tone was assessed as a possible determinant of these work stress effects. Participants included 109 male white-collar workers (age, 47.2Ϯ5.3) who were monitored on 2 workdays and 1 nonworkday for ambulatory blood pressure, heart rate, and heart rate variability. Chronic work stress was defined according to Siegrist's model as (1) high imbalance, a combination of high effort and low reward at work, or (2) high overcommitment, an exhaustive work-related coping style indexing the inability to unwind. All findings were adjusted for possible differences in posture and physical activity between the work stress groups. High imbalance was associated with a higher heart rate during work and directly after work, a higher systolic blood pressure during work and leisure time, and a lower 24-hour vagal tone on all 3 measurement days. Overcommitment was not associated with an unfavorable ambulatory profile. Logistic regression analysis revealed that heart rate [odds ratio 1-SD increase 1.95 (95% CI, 1.02 to 3.77)] and vagal tone [odds ratio 1-SD decrease 2.67 (95% CI, 1.24 to 5.75)] were independently associated with incident mild hypertension. Surprisingly, the values during sleep were more predictive for mild hypertension than the values during work. The results from the present study suggest that the detrimental effects of work stress are partly mediated by increased heart rate reactivity to a stressful workday, an increase in systolic blood pressure level, and lower vagal tone.

Impedance cardiography was introduced over 20 years ago as a noninvasive and unobtrusive technique for measuring systolic time intervals and cardiac output. Although our understanding of the physiological events reflected in the impedance cardiogram has become more refined, the technique's theoretical basis remains somewhat controversial and acceptance of its validity has relied heavily upon empirical validation. Largely as a consequence of this status, there have been inadequate grounds on which to develop sound methodological standardization. Currently, the methodological approaches that have been most frequently adopted may be viewed as representing the standard. The various aspects of impedance methodology are discussed, and alternative approaches described, with the objective of providing an informed basis for choosing among these methodological alternatives. It is recommended that studies utilizing impedance cardiography should be reported with clear and detailed methodological description. This should help clarify the extent to which methodological differences may underlie any discrepant research observations, as well as facilitate the emergence of improved methodological standards.

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A growing amount of evidence indicates that free radicals play an important role as mediators of skeletal muscle damage and inflammation after strenuous exercise. It has been postulated that the generation of oxygen free radicals is increased during exercise as a result of increases in mitochondrial oxygen consumption and electron transport flux, inducing lipid peroxidation. The literature suggests that dietary antioxidants are able to detoxify the peroxides produced during exercise, which could otherwise result in lipid peroxidation, and that they are capable of scavenging peroxyl radicals and therefore may prevent muscle damage. Endogenous antioxidant enzymes also play a protective role in the process of lipid peroxidation. The studies reviewed (rodent and human) show significant increases of malondialdehyde (a product of lipid peroxidation) after exercise to exhaustion, and also favourable changes in plasma antioxidant levels and in antioxidant enzyme activity. In trained individuals and trained rats, the antioxidant enzyme activity increases markedly. In this way, the increased oxidative stress induced by exercise is compromised by increased antioxidant activity, preventing lipid peroxidation. Human studies have shown that dietary supplementation with antioxidant vitamins has favourable effects on lipid peroxidation after exercise. Although several points of discussion still exist, the question whether antioxidant vitamins and antioxidant enzymes play a protective role in exercise-induced muscle damage can be answered affirmatively. The human studies reviewed indicate that antioxidant vitamin supplementation can be recommended to individuals performing regular heavy exercise. Moreover, trained individuals have an advantage compared with untrained individuals, as training results in increased activity of several major antioxidant enzymes and overall antioxidant status. However, future studies are needed in order to be able to give more specific information and recommendations on this topic.