Prolonged, uninterrupted sitting negatively impacts markers of peripheral vascular health, particularly, vasodilatory function of leg arteries. Whether sitting can similarly impact measures of central vascular health, as well as overall leg vasoreactivity (i.e., vaso-dilatory and vasoconstrictor function) remains unknown. To address this, measurements were made in relatively healthy participants (i.e., free of overt disease; n = 20, age = 26 § 7; body mass index = 30 § 7 kg/m2; 7 female) pre, during and post 3 hours of uninterrupted sitting. Measures of central vascular health included arterial wave reflection (augmentation index and Reflection Magnitude-RM%) and aortic vascular stiffness (aortic pulse wavevelocity). Local vasoreactivity of the distal, posterior tibialartery was measured using flow-mediated dilation-FMD, coupled with low-flow mediated constriction, and microvascular function was assessed through the total hyperemic blood velocity (area-under-curve) response during FMD. After sitting, there was a significant increase in aortic pulse wave velocity (pre sit = 5.7 § 0.3 vs post sit = 6.1 § 0.3 m/s; p=0.009, d = 0.36), whereas, augmentation index decreased (pre sit=13 § 3 vs post sit=3 § 1%; p < 0.001, d = 0.71). Albeit a moderate effect for decrease, RM % was not significantly altered during sitting (p = 0.13, d = 0.3). Vasodilatory (i.e., FMD pre sit = 0.5 § 0.04 vs post sit =0.3 § 0.04 mm; p = 0.014, d = 0.29) and micro vascular function (i.e., Microvascular area-under-curve: pre sit = 2,196 § 333 vs1, 157 §172 AU; p = 0.003, d = 0.31) decreased, but vasoconstrictor function (low-flow mediated constriction; p = 0.85, d = 0.005) was unaffected by sitting. In conclusion, these data demonstrate that a prolonged bout of uninterrupted sitting negatively impacts markers of peripheral and central vascular health in relatively healthy adults.

Advances in spinal cord injury-based research in the last 50 years have resulted in significant improvements to therapy options. However, the efficacy of such research could be further enhanced if threats to internal and external validity were addressed. To provide perspective, a sample topic was identified: the effects of acute and chronic exercise on clinical and sub-clinical markers of cardiovascular health. The intention was not a systematic review, nor a critique of exercise-based research, but rather a means to generate further discussion. Thirty-one articles were identified, and four common issues were found relating to: (1) sampling; (2) study design; (3) control group; and (4) clinical inference. These concerns were largely attributed to insufficient resources, and challenges associated with recruiting individuals with spinal cord injury. Overcoming these challenges will be difficult, but some opportunities include: (1) implementing multi-center trials; (2) sampling from subject groups appropriate to the research question; (3) including an appropriate control group; and (4) clearly defining clinical inference. These opportunities are not always feasible, and some easier to implement than others. However, addressing these concerns may assist in progressing spinal cord injury-based research, thereby helping to ensure steady advancement of therapy options for persons with spinal cord injury.

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