Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, PC210
Resistance exercise training improves microvascular blood volume in response to feeding.
B. Phillips1, J. P. Williams2,1, K. Smith1, P. J. Atherton1, K. A. Sjoberg3, K. Varadhan1, B. Kiens3, E. A. Richter3, M. J. Rennie1
1. School of Graduate Entry Medicine and Health, University of Nottingham, Derby, United Kingdom. 2. Anaesthetic Department, Southern Derbyshire Acute Hospitals NHS Trust, Derby, United Kingdom. 3. Department of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark.
Insulin and nutrient delivery to the muscle microvasculature are rate limiting for insulin action, and possibly anabolic responses to nutrients. Both muscle contraction and feeding [insulin] can increase total blood flow and microvascular blood volume (MBV) in skeletal muscle (1). Since exercise is associated with improvements in metabolic function (i.e., insulin sensitivity) we hypothesised that resistance exercise training (RET) would sensitize the muscle microvasculature to feeding. In preliminary studies we recruited 6 healthy male subjects (58.8±9.8 y, BMI; 26.9±1.0 kg.m2) 3 of whom underwent 20 weeks of supervised whole body RET with the remainder acting as untrained (UT) controls. Leg blood flow (LBF) was measured using Doppler Ultrasound and MBV by contrast enhanced ultrasound (CEUS). Measures were made: (i) in the postabsorptive, rested state, where subjects had fasted for 12 h and remained in a supine position for 50 min, and (ii) in the fed state (Glamin: prime; 34 mg.kg-1, continuous dose; 102 mg.kg.hr-1 and 20% dextrose infused at a rate to maintain blood glucose between 7-7.5 mmol.l-1). Under both postabsorptive and fed conditions, LBF was measured over 40 min before an infusion of DefinityTM perflutren microbubbles (1.5 ml in 18.5 ml 0.9% saline, 1.2 ml.min-1 (2). After 9 min to allow attainment of steady state bubble concentration, microbubbles were destroyed by high energy ultrasound and refilling of the microvascular space (representing MBV) was imaged during 4 consecutive 45 s recordings and data was analysed using Q-lab software. LBF is reported in l.min-1 whereas MBV is percentage change in acoustic intensity (AI) area under the curve (AUC); data was analysed using an unpaired t-test and reported as means±SE. There was no effect of RET on postabsorptive LBF (UT: 0.48±0.04, RET: 0.38±0.01 l.min-1) or on fed state LBF (UT: 0.55±0.09, RET: 0.41±0.07 l.min-1) which did not increase after feeding in either group (UT: +11.58±8.52. RET: +7.56±16.63%). In contrast, MBV was significantly greater in response to feeding only in the RET group (UT: +7.8±11.4%, RET: +68.9±17.7%, P<0.05). We conclude that RET improves MBV responses to feeding even in the absence of significant changes in LBF. Improvements in MBV after RET may underlie beneficial metabolic adaptation to exercise, such as improved insulin sensitivity and anabolic responses to nutrients.
Where applicable, experiments conform with Society ethical requirements