Background:The Trier Social Stress Test (TSST) is a widely used laboratory protocol to study acute stress reactivity, a hallmark of which is a meaningful increase in saliva cortisol (>2.5 nmol/L) in most individuals, reflecting hypothalamic-pituitary-adrenal (HPA) axis activation. The Mannheim Multicomponent Stress Test (MMST) has potential as a low staff burden alternative to the TSST, with one study showing statistically significant increases in subjective stress, heart rate and saliva cortisol; however, uncertainty remains about the meaningfulness of these psychobiological responses. Objective:To assess whether the MMST is a viable alternative to the TSST. Methods:Using a between subjects design, 31 healthy adults were randomised to the standard TSST or the MMST using stratified block randomisation accounting for sex and trait anxiety. The standard TSST consisted of an anticipation phase, followed by a free speech and mental arithmetic task performed in front of a panel of trained actors. The MMST consisted of a computer based Paced Auditory Serial Addition Task (cognitive stressor) with additional motivational, emotional and acoustic stressors in the presence of one unresponsive observer. Results:Group × time interactions showed that the MMST induced smaller psychobiological responses compared with the TSST (mixed model ANCOVA, P < 0.05). Post-hoc analyses revealed that the MMST induced a significant yet smaller state anxiety response (score range 20-80, MMST: 47 ± 12 vs. TSST: 57 ± 9; P < 0.01, Cohens d = 0.9) and peak heart rate response (MMST: 98 ± 17 vs. TSST: 110 ± 21 bpm; P < 0.05, Cohens d = 0.6) compared with the TSST. Despite observing stereotypical neuroendocrine responses to the TSST, the MMST did not increase saliva α-amylase or cortisol (Δ saliva cortisol, 0.1 ± 1.1 vs. TSST: 10.3 ± 12.8 nmol/L; between group difference P < 0.01, Cohens d = 1.1). Moreover, meaningful increases in saliva cortisol (>2.5 nmol/L) were observed in 80% of participants after the TSST but in no participant after the MMST. Conclusion:The Mannheim Multicomponent Stress Test increased state anxiety and heart rate but not saliva cortisol. As such, the present results do not support the utility of the Mannheim Multicomponent Stress Test as a viable alternative to The Trier Social Stress Test.

Abstract Study Objectives Prospectively examine the association between sleep restriction, perceived sleep quality (PSQ) and upper respiratory tract infection (URTI). Methods In 1318 military recruits (68% males) self-reported sleep was assessed at the beginning and end of a 12-week training course. Sleep restriction was defined as an individualized reduction in sleep duration of ≥2 hours/night compared with civilian life. URTIs were retrieved from medical records. Results On commencing training, approximately half of recruits were sleep restricted (52%; 2.1 ± 1.6 h); despite the sleep debt, 58% of recruits with sleep restriction reported good PSQ. Regression adjusted for covariates showed that recruits commencing training with sleep restriction were more likely to suffer URTI during the course (OR = 2.93, 95% CI 1.29–6.69, p = .011). Moderation analysis showed this finding was driven by poor PSQ (B = −1.12, SE 0.50, p = .023), as no significant association between sleep restriction and URTI was observed in recruits reporting good PSQ, despite a similar magnitude of sleep restriction during training. Associations remained in the population completing training, accounting for loss to follow-up. Recruits reporting poor PSQ when healthy at the start and end of training were more susceptible to URTI (OR = 3.16, 95% CI 1.31–7.61, p = .010, vs good PSQ). Conclusion Good perceived sleep quality was associated with protection against the raised risk of respiratory infection during sleep restriction. Studies should determine whether improvements in sleep quality arising from behavioral sleep interventions translate to reduced respiratory infection during sleep restriction.

PURPOSE:To determine the relationship between vitamin D status and exercise performance in a large, prospective cohort study of young men and women across seasons (study 1). Then, in a randomized, placebo-controlled trial, to investigate the effects on exercise performance of achieving vitamin D sufficiency (serum 25(OH)D ≥ 50 nmol·L) by a unique comparison of safe, simulated-sunlight and oral vitamin D3 supplementation in wintertime (study 2). METHODS:In study 1, we determined 25(OH)D relationship with exercise performance in 967 military recruits. In study 2, 137 men received either placebo, simulated sunlight (1.3× standard erythemal dose in T-shirt and shorts, three times per week for 4 wk and then once per week for 8 wk) or oral vitamin D3 (1000 IU·d for 4 wk and then 400 IU·d for 8 wk). We measured serum 25(OH)D by high-pressure liquid chromatography tandem mass spectrometry and endurance, strength and power by 1.5-mile run, maximum dynamic lift and vertical jump, respectively. RESULTS:In study 1, only 9% of men and 36% of women were vitamin D sufficient during wintertime. After controlling for body composition, smoking, and season, 25(OH)D was positively associated with endurance performance (P ≤ 0.01, ΔR = 0.03-0.06, small f effect sizes): 1.5-mile run time was ~half a second faster for every 1 nmol·L increase in 25(OH)D. No significant effects on strength or power emerged (P > 0.05). In study 2, safe simulated sunlight and oral vitamin D3 supplementation were similarly effective in achieving vitamin D sufficiency in almost all (97%); however, this did not improve exercise performance (P > 0.05). CONCLUSIONS:Vitamin D status was associated with endurance performance but not strength or power in a prospective cohort study. Achieving vitamin D sufficiency via safe, simulated summer sunlight, or oral vitamin D3 supplementation did not improve exercise performance in a randomized-controlled trial.

The National Sleep Foundation recommends 7−9 hours of sleep per night for young adults. Habitually sleeping <6 hours per night has been shown to lower immunity and increase susceptibility to common cold following exposure to rhinovirus. However, no investigations have examined the importance of sleep duration on upper respiratory infection (URTI) and loss of training days in military recruits. PURPOSE: To identify if military recruits who typically sleep <6 hours per night during training suffer a greater incidence of URTI and, as a consequence, miss more training than recruits who meet sleep recommendations. METHODS: Participants included 651 British Army recruits aged 22 ± 3 years who completed 13 weeks of Phase 1 military training (67% males, 33% females). Recruits were members of 21 platoons (11 male, 10 female) who commenced training across the seasons (19% winter, 19% spring, 28% summer, and 33% autumn). At week 13, participants completed a questionnaire asking the normal time they went to sleep and awoke during training. Incidence of physician-diagnosed URTI and reduced or missed training days due to URTI were retrieved from medical records. RESULTS: Typical sleep duration during training was reported as 7.0 ± 0.8 hours per night with 5% of recruits reporting they normally slept <6 hours and 60% of recruits reporting 7-9 hours of sleep each night. In a logistic regression model, recruits who slept <6 hours per night were 4 times more likely to be diagnosed with URTI compared with recruits who slept 7−9 hours per night after controlling for sex, BMI, alcohol, smoking, and season of recruitment (OR 4.6; 95% CI, 1.7–12.8, P < 0.01). URTI’s diagnosed in recruits who slept <6 hours were spread across both sexes, 5 platoons and 3 seasons, showing sufficient heterogeneity. Overall, 49 recruits (8%) were diagnosed with at least one URTI, and 3 recruits (<1%) were diagnosed with two URTI’s. On average, each URTI resulted in 2.9 ± 1.5 reduced or missed training days. CONCLUSION: These findings show that military recruits who sleep <6 hours per night are more susceptible to URTI and miss more training due to URTI. Future studies should examine interventions to improve sleep hygiene in military training. Supported by MoD, UK.