Introduction-Physical inactivity, high screen time, and short sleep are targets of public health initiatives for children. However, few data exist on how many U.S. children meet guidelines for these behaviors-data vital to inform which need greater targeting. This study describes national prevalence estimates of U.S. children who meet physical activity, screen time, and sleep guidelines alone or in combination across each childhood year.Methods-This analysis (completed in 2019) used cross-sectional data from the 2016-2017 National Survey of Children's Health, a nationally representative sample of U.S. children. Child physical activity (days/week with ≥60 minutes), recreational screen time (hours/day of TV viewing and electronic device use), and sleep duration (hours/day) were assessed via parental report. Guidelines recommend ≥60 minutes/day of physical activity, ≤2 hours/day of screen time, and 9-12 hours/day of sleep for ages 6-12 years (8-10 hours for ages 13-17 years).Results-Only 8.8% (95% CI=8.2%, 9.5%) of U.S. children meet all three guidelines combined. Most attain the sleep guideline (86.0%, 95% CI=85.2%, 86.7%), but a lower proportion meet physical activity (23.0%, 95% CI=22.1%, 23.9%) or screen time (32.9%, 95% CI=31.9%, 33.8%) guidelines. A substantial age effect was identified, with prevalence of meeting each distinct guideline, and all three, declining with age (p<0.001).Conclusion-Few U.S. children meet all three movement guidelines; with prevalence rates of children meeting guidelines declining with age. Although many meet sleep guidelines, few meet physical activity or screen time guidelines. Initiatives targeting physical activity and screen time, particularly for adolescents, should be pursued.

. Nitric oxide concentration increases in the cutaneous interstitial space during heat stress in humans. J Appl Physiol 94: 1971Physiol 94: -1977Physiol 94: , 2003 10.1152/japplphysiol.00826. 2002To examine the role of nitric oxide (NO) in cutaneous active vasodilation, we measured the NO concentration from skin before and during whole body heat stress in nine healthy subjects. A forearm site was instrumented with a NO-selective, amperometric electrode and an adjacent intradermal microdialysis probe. Skin blood flow (SkBF) was monitored by laser-Doppler flowmetry (LDF). NO concentrations and LDF were measured in normothermia and heat stress. After heat stress, a solution of ACh was perfused through the microdialysis probe to pharmacologically generate NO and verify the electrode's function. During whole body warming, both SkBF and NO concentrations began to increase at the same internal temperature. Both SkBF and NO concentrations increased during heat stress (402 Ϯ 76% change from LDF baseline, P Ͻ 0.05; 22 Ϯ 5% change from NO baseline, P Ͻ 0.05). During a second baseline condition after heat stress, ACh perfusion led to increases in both SkBF and NO concentrations (496 Ϯ 119% change from LDF baseline, P Ͻ 0.05; 16 Ϯ 10% change from NO baseline, P Ͻ 0.05). We conclude that NO does increase in skin during heat stress in humans, attendant to active vasodilation. This result suggests that NO has a role beyond that of a permissive factor in the process; rather, NO may well be an effector of cutaneous vasodilation during heat stress. skin blood flow; vasodilation; amperometric electrode; thermoregulation THE HUMAN CUTANEOUS CIRCULATION is a major effector of thermoregulatory homeostasis. During periods of whole body heat stress, this circulation undergoes a profound reflex vasodilation to deliver blood, and hence heat, to the body's surface for removal to the environment. During periods of cold stress, the cutaneous blood vessels are intensely vasoconstricted to reduce loss of heat from the body to the environment. These reflex changes in skin blood flow (SkBF) occur in response to changes in internal temperature and skin temperature (T sk ) and are mediated by two branches of the sympathetic nervous system: an active vasodilator system and an active vasoconstrictor system (17).The mechanisms by which the active vasodilator system causes increases in SkBF during heat stress have been the subject of numerous investigations since the system was first described over 70 years ago (18). A number of these studies demonstrated that muscarinic-receptor blockade with atropine could slightly delay (10, 17, 19, 22) and attenuate (17, 19) the reflex increase in SkBF during heat stress. This finding of partial reductions in the active vasodilator response despite complete muscarinic-receptor blockade established a role for cholinergic nerves in the process of active vasodilation, but it left open to question the exact nature of this involvement. In 1995, our laboratory showed that thermoregulatory active vasodilation involve...

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