Exercise Training Augments Regional Bone and Marrow Blood Flow during Exercise

Abstract

Introduction The principal nutrient artery to the femur demonstrates an increase in nitric oxide mediated vasodilation in rats after treadmill exercise training. The present study sought to determine whether exercise training improves hindlimb bone and marrow blood flow distribution at rest and during exercise. Methods Six-eight month old male Sprague-Dawley rats were exercise trained (ET) with treadmill walking at 15 m/min up a 15° incline for 60 min/d over a 10–12 wk period. Sedentary (SED) control animals were acclimated to treadmill exercise for 5 min/d during the week preceding the blood flow measurements. Blood flow to nine distinct regions of the femur, tibia, and fibula were determined at rest and during low-intensity exercise (15 m/min walking, 0° incline) using the reference sample microsphere method. Results The results demonstrate an augmentation of exercise hyperemia above that observed in SED rats during exercise in only one region of bone, the femoral diaphysis of ET rats. However, while exercise hyperemia occurred in 3 of the 9 hindlimb bone regions measured in SED rats, exercise hyperemia occurred in 7 of 9 regions in ET rats. Conclusion These data indicate an increase in generalized hindlimb bone and marrow blood flow during physical activity following a period of exercise training. Elevations in regional bone and marrow blood flow after training may augment medullary pressure and bone interstitial fluid flow, thus benefiting bone integrity.

Mechanical, hormonal and metabolic influences on blood vessels, blood flow and bone

“…Mean arterial pressure did not differ between the young sedentary and exercise-trained animals at rest and during exercise (Stabley et al 2014). Only blood flow to the femoral diaphysis in the exercised-trained rats was significantly higher than the sedentary group (Stabley et al 2014). In other words, the sedentary animals were able to augment regional bone blood flow during acute exercise to similar degrees as the exercise-trained rodents (Stabley et al 2014).…”

“…The ilium was the only bone to experience declines in blood flow with exercise and, overall, these data suggest that vasoconstriction occurred in the bone vasculature (Gross et al 1979). In contrast, blood flow to various hind limb bones and bone regions was augmented with 5 minutes of treadmill exercise in sedentary young and old rats (Dominguez et al 2010) and in young sedentary and exercise-trained rats (Stabley et al 2014) vs. resting conditions. Mean arterial pressure did not differ between the young sedentary and exercise-trained animals at rest and during exercise (Stabley et al 2014).…”

“…In contrast, blood flow to various hind limb bones and bone regions was augmented with 5 minutes of treadmill exercise in sedentary young and old rats (Dominguez et al 2010) and in young sedentary and exercise-trained rats (Stabley et al 2014) vs. resting conditions. Mean arterial pressure did not differ between the young sedentary and exercise-trained animals at rest and during exercise (Stabley et al 2014). Only blood flow to the femoral diaphysis in the exercised-trained rats was significantly higher than the sedentary group (Stabley et al 2014).…”

“…Thus, augmented femoral bone blood flow elicited by daily bouts of treadmill exercise served to enhance vasodilator function and presumably caused alterations in bone interstitial fluid flow and pressure as well (Dominguez et al 2010). Additionally, when comparing hind limb bone blood flow between rest and an acute bout of treadmill exercise (5 min) in sedentary and exercise-trained (10–12 weeks of treadmill exercise) rats, exercise hyperemia occurred in 33% and 78% of the examined bone regions in the sedentary and exercised-trained animals, respectively (Stabley et al 2014). The authors concluded that exercise-training delivers blood to more regions of bone as opposed to enhancing blood flow capacity (Stabley et al 2014).…”

“…It would be beneficial to ascertain whether intermittent PTH administration serves to deliver blood flow to more regions of bone tissue as reported following long-term (18 months) treatment in humans (Moore et al 2010) and subsequent to chronic (10–12 weeks) exercise training in rats (Stabley et al 2014). Additionally, data indicate independent actions of PTH on bone blood vessels and bone, whereby the effects may occur more rapidly in the vasculature.…”