If endothelial dysfunction is an integral component of the pathogenesis of vascular disease, as currently believed, this study supports the value of an exercise program in the management of type 2 diabetes.

Non-technical summary This is the first study, to our knowledge, to use cardiac MRI before and after intensive and closely supervised resistance and endurance exercise training in humans. There is a long held belief that these different forms of training induce 'concentric' and 'eccentric' adaptation of the heart, but this concept is based on echocardiographic assessments and cross-sectional comparison of different types of elite athletes. Our findings, using highly sensitive MRI methodology, suggest that concept may need to be reconsidered. This study is of fundamental importance to the understanding of the impact of exercise on human cardiac morphology and physiology.Abstract The principle that 'concentric' cardiac hypertrophy occurs in response to strength training, whilst 'eccentric' hypertrophy results from endurance exercise has been a fundamental tenet of exercise science. This notion is largely based on cross-sectional comparisons of athletes using echocardiography. In this study, young (27.4 ± 1.1 years) untrained subjects were randomly assigned to supervised, intensive, endurance (END, n = 10) or resistance (RES, n = 13) exercise and cardiac MRI scans and myocardial speckle tracking echocardiography were performed at baseline, after 6 months of training and after a subsequent 6 weeks of detraining. Aerobic fitness increased significantly in END (3.5 to 3.8 l min −1 , P < 0.05) but was unchanged in RES. Muscular strength significantly improved compared to baseline in both RES and END ( = 53.0 ± 1.1 versus 36.4 ± 4.5 kg, both P < 0.001) as did lean body mass (2.3 ± 0.4 kg, P < 0.001 versus 1.4 ± 0.6 kg P < 0.05). MRI derived left ventricular (LV) mass increased significantly following END (112.5 ± 7.3 to 121.8 ± 6.6 g, P < 0.01) but not RES, whilst training increased end-diastolic volume ( LVEDV, END: +9.0 ± 5.0 versus RES +3.1 ± 3.6 ml, P = 0.05). Interventricular wall thickness significantly increased with training in END (1.06 ± 0.0 to 1.14 ± 0.06, P < 0.05) but not RES. Longitudinal strain and strain rates did not change following exercise training. Detraining reduced aerobic fitness, LV mass and wall thickness in END (P < 0.05), whereas LVEDV remained elevated. This study is the first to use MRI to compare LV adaptation in response to intensive supervised endurance and resistance training. Our findings provide some support for the 'Morganroth hypothesis' , as it pertains to LV remodelling in response to endurance training, but cast some doubt over the proposal that remodelling occurs in response to resistance training.

Exercise training of a muscle group improves local vascular function in subjects with chronic heart failure (CHF). We studied forearm resistance vessel function in 12 patients with CHF in response to an 8-wk exercise program, which specifically excluded forearm exercise, using a crossover design. Forearm blood flow (FBF) was measured using strain-gauge plethysmography. Responses to three dose levels of intra-arterial acetylcholine were significantly augmented after exercise training when analyzed in terms of absolute flows (7.0 +/- 1.8 to 10.9 +/- 2.1 ml x 100 ml(-1) x min(-1) for the highest dose, P < 0.05 by ANOVA), forearm vascular resistance (21.5 +/- 5.0 to 15.3 +/- 3.9 ml x 100 ml forearm(-1) x min(-1), P < 0.01), or FBF ratios (P < 0.01, ANOVA). FBF ratio responses to sodium nitroprusside were also significantly increased after training (P < 0.05, ANOVA). Reactive hyperemic flow significantly increased in both upper limbs after training (27.9 +/- 2.7 to 33.5 +/- 3.1 ml x 100 ml(-1) x min(-1), infused limb; P < 0.05 by paired t-test). Exercise training improves endothelium-dependent and -independent vascular function and peak vasodilator capacity in patients with CHF. These effects on the vasculature are generalized, as they were evident in a vascular bed not directly involved in the exercise stimulus.

Pyke K, Green DJ, Weisbrod C, Best M, Dembo L, O'Driscoll G, Tschakovsky ME. Nitric oxide is not obligatory for radial artery flowmediated dilation following release of 5 or 10 min distal occlusion. Am J Physiol Heart Circ Physiol 298: H119 -H126, 2010. First published October 30, 2009 doi:10.1152/ajpheart.00571.2009.-This study investigated the nitric oxide (NO) dependence of radial artery (RA) flowmediated dilation (FMD) in response to three different reactive hyperemia (RH) shear stimulus profiles. Ten healthy males underwent the following three RH trials: 1) 5 min occlusion (5 trial), 2) 10 min occlusion (10 trial), and 3) 10 min occlusion with cuff reinflation at 30 s (10 -30 trial). Trials were performed during saline infusion and repeated during N G -monomethyl-L-arginine (L-NMMA) infusion in the brachial artery. RA blood flow velocity was measured with Doppler ultrasound, and B-mode RA images were analyzed using automated edge detection software. Shear rate estimation of shear stress was calculated as the blood flow velocity/vessel diameter. L-NMMA decreased baseline vascular conductance by 35%. L-NMMA infusion did not affect the peak shear rate stimulus (P ϭ 0.681) or the area under the curve (AUC) of shear rate to peak FMD (P ϭ 0.088). The AUC was significantly larger in the 10 trial vs. the 10 -30 or 5 trial (P Ͻ 0.001). Although percent FMD (%change in diameter) in the 10 trial was larger than that in the 5 trial (P ϭ 0.035), there was no significant difference in %FMD between the saline and L-NMMA conditions in any trial: 5 trial, 5.62 Ϯ 1.48 vs. 5.63 Ϯ 1.27%; 10 trial, 9.07 Ϯ 1.16 vs. 11.22 Ϯ 2.21%; 10 -30 trial, 6.52 Ϯ 1.43 vs. 7.98 Ϯ 1.51% for saline and L-NMMA, respectively (P ϭ 0.158). We conclude the following: 1) RH following 10 min of occlusion results in an enhanced stimulus and %FMD compared with 5 min of occlusion. 2) When the occlusion cuff is reinflated 30 s postrelease of a 10 min occlusion, it does not result in an enhanced %FMD compared with that which results from RH following 5 min of occlusion.3) The lack of effect of L-NMMA on FMD suggests that NO may not be obligatory for radial artery FMD in response to either 5 or 10 min of occlusion in healthy volunteers. nitric oxide; endothelium; shear stress IN HEALTHY ARTERIES, an increase in blood flow (and shear stress) results in endothelial-dependent flow-mediated dilation (FMD) (29,32,41). FMD can therefore serve as an index of endothelial function and provide insight regarding vascular health (42). Originally published by Celermajer et al. (8), the test most commonly performed in humans increases shear stress in conduit arteries (e.g., the brachial, radial, femoral, or popliteal) via reactive hyperemia following the release of temporary limb ischemia (8). A "standard" technique has emerged that stipulates a 5-min cuff occlusion duration, a cuff position distal to the site of conduit artery diameter measurement, and the absence of exercise performed during occlusion (31). The primary reason for these constraints is the desire to cre...

These results suggest that moderate intensity circuit training designed to minimize the involvement of the arms improves functional capacity, body composition, and strength in healthy, middle-aged subjects without significantly influencing upper limb vascular function. This finding contrasts with previous studies in subjects with type 2 diabetes and heart failure that employed an identical training program.