Samuel J. E. Lucas

Physiological responses to a five-day adventure race: Continuous blood glucose, hemodynamics and metabolites the 2012 GODZone field-study

Background/Objective Adventure racing is an ultra-endurance activity that imposes a unique multifaceted stress on the human body. The purpose of this field study was to examine the physiological responses to a 5-day adventure race. Methods Eight competitors, two teams (1 female each) in the 2012 GODZone adventure race volunteered. Competitors trekked, cycled and paddled ∼326 km in ∼116 hours. Continuous glucose was measured the day before and throughout. Body mass, urinary solutes, and blood pressure and heart rate during resting, standing, and repeated squat-stand conditions, were assessed pre and post. Results Despite no changes in mean blood glucose levels, there was increased glycemic variability (Standard deviation glucose; Pre: 0.5 ± 0.1 vs Race: 1.0 ± 0.2 mmol/L, p = 0.02) and periods of hypoglycemia (i.e., Min glucose Pre: 4.1 ± 0.3 vs Race: 3.6 ± 0.5 mmol/L, p = 0.05) during the race. After the race, the blood pressure during resting, standing and squat-stand conditions was significantly lower, by 14 ± 14 mmHg, 16 ± 15 mmHg and 18 ± 15 mmHg (all p < 0.05), respectively, with no change in heart rate. During five-days of adventure racing there is increased glycemic variability and more frequent periods of low blood glucose levels. Additionally, following the race pronounced hypotension is observed in competitors. Conclusion We observed more frequent glucose fluctuations, lower glucose levels and significant perturbations in blood pressure control. Further research is warranted to examine the long-term impact of adventure racing on metabolic and cardiovascular function.

Hot-water immersion increases popliteal artery shear stress in Peripheral Arterial Disease

Exercise improves peripheral vascular function in healthy and diseased populations; this is partly attributed to the exposure of the endothelium to transient, repetitive increases in blood flow and antegrade shear stress [1]. Traditional exercise poses significant barriers for patients with Peripheral Arterial Disease (PAD), as the condition manifests as debilitating walking-induced muscle pain (claudication) caused by obstruction to blood flow. PAD patients represent a large cohort who might therefore benefit from an alternative approach to exercise. Local limb heating in young, healthy adults has been shown to induce blood flow patterns indicative of promoting beneficial adaptations in peripheral arteries [2-4]. Additionally, preliminary evidence exists demonstrating sauna therapy improves symptoms and clinical indices in PAD [5]. The aim of this study was to investigate the acute vascular and cardiovascular responses to heat by lower limb hot-water immersion in patients with PAD and in healthy, elderly controls.