Research letter Exercise training prior to night shift work improves physical work capacity and arterial stiffness Christine Scha ¨fer 1 , Barbara Mayr 1 , Edith E Mu ¨ ller 1 , Christoph Augner 2 , Juliane Hannemann 3 , Rainer H Bo ¨ ger 3 , Martin Scho ¨ nfelder 1,4 and Josef Niebauer 1 Shift work is an independent risk factor for metabolic and cardiovascular diseases (CVDs). Notably, shift workers have a 40% increased risk of suffering CVD in contrast to non-shift workers 1 and the risk increases by 7.1% every five years of night shift duty. 2 Mechanisms linking shift work with increased CVD morbidity and mortality are not fully understood but a tendency toward an unhealthy lifestyle with subse- quently deteriorating cardiovascular risk factors has been identified. As a consequence endothelial dysfunc- tion develops, which in the long term leads to a loss of elasticity of the arterial wall, that is, arterial stiffening. 3 Regular aerobic exercise has repeatedly been shown to improve endothelial and vascular function. 4–7 Recent studies have shown that already in young adults phys- ical work capacity is connected with arterial stiffness 8 and may have long-term protective influences on the development of CVD. 9 So it is important to promote or to maintain regular exercise activities at any age. Further, exercise serves as a non-photic synchronizer of circadian rhythmicity. 10 Therefore, the study aimed to investigate whether timed aerobic exercise prior to night shift work improves the cardiovascular risk pro- file and arterial stiffness in healthy individuals. The study was performed in accordance with the Declaration of Helsinki and its current amendments, and was approved by the Ethical Committee of the Hamburg State Chamber, Germany and by the Ethical Committee of the State of Salzburg, Austria. The trial is registered at ClinicalTrials.gov (NCT01767181) and was part of the EU funded multi- centre trial EuRhythDia under the Framework 7 call. To test the influence of exercise, repeated-measures analysis of variance (three times – before exercise, after exercise (12 weeks) and after a wash-out-phase (24 weeks), with a fixed factor of group) was conducted. In the case of significance, a paired sample t-test, a Friedman test or a Wilcoxon-signed rank test for post hoc analysis was applied. For dependent samples, t-test or a Wilcoxon-signed rank test was conducted to test group differences. p-values of < 0.05 were regarded as statistically significant. All analyses were performed using IBM SPSS Statistics Version 21.0.0.1. Healthy night shift workers (N ¼ 64, 20.1% male, 36.7  12.2 years) were randomized into a training group (three months’ timed and supervised physical exercise, n ¼ 52) and a control group (recommendations only, n ¼ 12). The training group performed 35 min of high-intensity interval training (HIIT) on cycle ergometers within 2 h prior to each night shift for 12 consecutive weeks. HIIT was based on the first erg- ometer test of each participant and started with an initial warm-up for 5 min at 60–65% of maximum heart rate (HR max ), following four bouts of 4 min intervals at 85– 95% HR max, with 3 min active recovery at 65–75% HR max . Cool-down was performed for 5 min at 60– 65% HR max . Workload was gradually adapted during the intervention according to the participant’s HR. After 12 weeks a ‘wash-out’ of 12 weeks followed with- out any intervention. Control group participants were urged to maintain their current lifestyle throughout the entire study and thus not to modify their exercise, life- style and eating behaviours. All participants underwent assessment of anthropometric measures, lipid profile, 1 University Institute of Sports Medicine, Prevention and Rehabilitation and Research Institute of Molecular Medicine and Rehabilitation, Paracelsus Medical University, Salzburg, Austria 2 Institute for Human Resources Research in Health Care, University Clinics of the Paracelsus Medical University, Salzburg, Austria 3 Department of Clinical Pharmacology and Toxicology, University Medical Centre Hamburg-Eppendorf, Hamburg, Germany 4 Department of Sport and Health Sciences, Exercise Biology, Technical University of Munich, Germany Corresponding author: Josef Niebauer, University Institute of Sports Medicine, Prevention and Rehabilitation, Paracelsus Medical University Salzburg, Lindhofstr. 20, 5020 Salzburg, Austria. Email: j.niebauer@salk.at European Journal of Preventive Cardiology 0(00) 1–3 ! The European Society of Cardiology 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/2047487319848196 journals.sagepub.com/home/ejpc