Lack of independent effect of type 2 diabetes beyond characteristic comorbidities and medications on small muscle mass exercising muscle blood flow and exercise tolerance

The aim of this study was to compare fatigability, contractile function, and blood flow to the knee extensor muscles after dynamic exercise in patients with type 2 diabetes mellitus (T2DM) and controls. The hypotheses were that patients with T2DM would demonstrate greater fatigability than controls, and greater fatigability would be associated with a lower exercise-induced increase in blood flow and greater impairments in contractile function. Patients with T2DM ( n = 15; 8 men; 62.4 ± 9.0 yr; 30.4 ± 7.7 kg/m2; 7,144 ± 3,294 steps/day) and 15 healthy control subjects (8 men, 58.4 ± 6.9 yr; 28.4 ± 4.6 kg/m2; 7,893 ± 2,323 steps/day) were matched for age, sex, body mass index, and physical activity. Fatigability was quantified as the reduction in knee extensor power during a 6-min dynamic exercise. Before and after exercise, vascular ultrasonography and electrical stimulation were used to assess skeletal muscle blood flow and contractile properties, respectively. Patients with T2DM had greater fatigability (30.0 ± 20.1% vs. 14.6 ± 19.0%, P < 0.001) and lower exercise-induced hyperemia (177 ± 90% vs. 194 ± 79%, P = 0.04) than controls but similar reductions in the electrically evoked twitch amplitude (37.6 ± 24.8% vs. 31.6 ± 30.1%, P = 0.98). Greater fatigability of the knee extensor muscles was associated with postexercise reductions in twitch amplitude ( r = 0.64, P = 0.001) and lesser exercise-induced hyperemia ( r = −0.56, P = 0.009). Patients with T2DM had greater lower-limb fatigability during dynamic exercise, which was associated with reduced contractile function and lower skeletal muscle blood flow. Thus, treatments focused on enhancing perfusion and reversing impairments in contractile function in patients with T2DM may offset lower-limb fatigability and aid in increasing exercise capacity. NEW & NOTEWORTHY Although prior studies compare patients with type 2 diabetes mellitus (T2DM) with lean controls, our study includes controls matched for age, body mass, and physical activity to more closely assess the effects of T2DM. Patients with T2DM demonstrated no impairment in macrovascular endothelial function, evidenced by similar flow-mediated dilation to controls. However, patients with T2DM had greater fatigability and reduced exercise-induced increase in blood flow (hyperemia) after a lower-limb dynamic fatiguing exercise compared with controls.

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Leg blood flow is impaired during small muscle mass exercise in patients with COPD

Journal of Applied Physiology ◽

10.1152/japplphysiol.00178.2017 ◽

2017 ◽

Vol 123 (3) ◽

pp. 624-631 ◽

Cited By ~ 6

Author(s):

U. W. Iepsen ◽

G. W. Munch ◽

M. Rugbjerg ◽

C. K. Ryrsø ◽

N. H. Secher ◽

...

Keyword(s):

Chronic Obstructive Pulmonary Disease ◽

Blood Flow ◽

Muscle Mass ◽

Interstitial Fluid ◽

Muscle Blood Flow ◽

Knee Extensor ◽

Chronic Obstructive ◽

Obstructive Pulmonary Disease ◽

Endothelin 1 ◽

Small Muscle

Skeletal muscle blood flow is regulated to match the oxygen demand and dysregulation could contribute to exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). We measured leg hemodynamics and metabolites from vasoactive compounds in muscle interstitial fluid and plasma at rest, during one-legged knee-extensor exercise, and during arterial infusions of sodium nitroprusside (SNP) and acetylcholine (ACh), respectively. Ten patients with moderate to severe COPD and eight age- and sex-matched healthy controls were studied. During knee-extensor exercise (10 W), leg blood flow was lower in the patients compared with the controls (1.82 ± 0.11 vs. 2.36 ± 0.14 l/min, respectively; P < 0.05), which compromised leg oxygen delivery (372 ± 26 vs. 453 ± 32 ml O2/min, respectively; P < 0.05). At rest, plasma endothelin-1 (vasoconstrictor) was higher in the patients with COPD ( P < 0.05) and also tended to be higher during exercise ( P = 0.07), whereas the formation of interstitial prostacyclin (vasodilator) was only increased in the controls. There was no difference between groups in the nitrite/nitrate levels (vasodilator) in plasma or interstitial fluid during exercise. Moreover, patients and controls showed similar vasodilatory capacity in response to both endothelium-independent (SNP) and endothelium-dependent (ACh) stimulation. The results suggest that leg muscle blood flow is impaired during small muscle mass exercise in patients with COPD possibly due to impaired formation of prostacyclin and increased levels of endothelin-1. NEW & NOTEWORTHY This study demonstrates that chronic obstructive pulmonary disease (COPD) is associated with a reduced blood flow to skeletal muscle during small muscle mass exercise. In contrast to healthy individuals, interstitial prostacyclin levels did not increase during exercise and plasma endothelin-1 levels were higher in the patients with COPD.

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Aging attenuates vascular and metabolic plasticity but does not limit improvement in muscle Vo2 max

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.01070.2003 ◽

2004 ◽

Vol 286 (4) ◽

pp. H1565-H1572 ◽

Cited By ~ 43

Author(s):

L. Lawrenson ◽

J. Hoff ◽

R. S. Richardson

Keyword(s):

Blood Flow ◽

Exercise Training ◽

Muscle Mass ◽

Muscle Blood Flow ◽

Knee Extensor ◽

Quadriceps Muscle ◽

Whole Body ◽

Metabolic Adaptation ◽

Metabolic Plasticity ◽

Small Muscle

The interactions between exercise, vascular and metabolic plasticity, and aging have provided insight into the prevention and restoration of declining whole body and small muscle mass exercise performance known to occur with age. Metabolic and vascular adaptations to normoxic knee-extensor exercise training (1 h 3 times a week for 8 wk) were compared between six sedentary young (20 ± 1 yr) and six sedentary old (67 ± 2 yr) subjects. Arterial and venous blood samples, in conjunction with a thermodilution technique facilitated the measurement of quadriceps muscle blood flow and hematologic variables during incremental knee-extensor exercise. Pretraining, young and old subjects attained a similar maximal work rate (WRmax) (young = 27 ± 3, old = 24 ± 4 W) and similar maximal quadriceps O2 consumption (muscle V̇o2 max) (young = 0.52 ± 0.03, old = 0.42 ± 0.05 l/min), which increased equally in both groups posttraining (WRmax, young = 38 ± 1, old = 36 ± 4 W, Muscle V̇o2 max, young = 0.71 ± 0.1, old = 0.63 ± 0.1 l/min). Before training, muscle blood flow was ∼500 ml lower in the old compared with the young throughout incremental knee-extensor exercise. After 8 wk of knee-extensor exercise training, the young reduced muscle blood flow ∼700 ml/min, elevated arteriovenous O2 difference ∼1.3 ml/dl, and increased leg vascular resistance ∼17 mmHg·ml–1·min–1, whereas the old subjects revealed no training-induced changes in these variables. Together, these findings indicate that after 8 wk of small muscle mass exercise training, young and old subjects of equal initial metabolic capacity have a similar ability to increase quadriceps muscle WRmax and muscle V̇o2 max, despite an attenuated vascular and/or metabolic adaptation to submaximal exercise in the old.

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Vascular and metabolic response to isolated small muscle mass exercise: effect of age

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00135.2003 ◽

2003 ◽

Vol 285 (3) ◽

pp. H1023-H1031 ◽

Cited By ~ 123

Author(s):

L. Lawrenson ◽

J. G. Poole ◽

J. Kim ◽

C. Brown ◽

P. Patel ◽

...

Keyword(s):

Blood Flow ◽

Muscle Mass ◽

Vascular Resistance ◽

Metabolic Response ◽

Muscle Blood Flow ◽

Knee Extensor ◽

Quadriceps Muscle ◽

Vasodilatory Response ◽

Small Muscle ◽

Effect Of Age

To determine the effect of age on quadriceps muscle blood flow (QMBF), leg vascular resistance (LVR), and maximum oxygen uptake (QV̇O2 max), a thermal dilution technique was used in conjunction with arterial and venous femoral blood sampling in six sedentary young (19.8 ± 1.3 yr) and six sedentary old (66.5 ± 2.1 yr) males during incremental knee extensor exercise (KE). Young and old attained a similar maximal KE work rate (WRmax) (young: 25.2 ± 2.1 and old: 24.1 ± 4 W) and QV̇O2 max (young: 0.52 ± 0.03 and old: 0.42 ± 0.05 l/min). QMBF during KE was lower in old subjects by ∼500 ml/min across all work rates, with old subjects demonstrating a significantly lower QMBF/W (old: 174 ± 20 and young: 239 ± 46 ml · min–1 · W–1). Although the vasodilatory response to incremental KE was ∼142% greater in the old (young: 0.0019 and old: 0.0046 mmHg · min · ml–1 · W–1), consistently elevated leg vascular resistance (LVR) in the old, ∼80% higher LVR in the old at 50% WR and ∼40% higher LVR in the old at WRmax (young: 44.1 ± 3.6 and old: 31.0 ± 1.7 mmHg · min · ml–1), dictated that during incremental KE the LVR of the old subjects was never less than that of the young subjects. Pulse pressures, indicative of arterial vessel compliance, were ∼36% higher in the old subjects across all work rates. In conclusion, well-matched sedentary young and old subjects with similar quadriceps muscle mass achieved a similar WRmax and QV̇O2 max during incremental KE. The old subjects, despite a reduced QMBF, had a greater vasodilatory response to incremental KE. Given that small muscle mass exercise, such as KE, utilizes only a fraction of maximal cardiac output, peripheral mechanisms such as consistently elevated leg vascular resistance and greater pulse pressures appear to be responsible for reduced blood flow persisting throughout graded KE in the old subjects.

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Postexercise Hemodynamics in Patients With Type 2 Diabetes: Effect of Exercise Intensity and Duration

Journal of Clinical Exercise Physiology ◽

10.31189/2165-6193-6.1.1 ◽

2017 ◽

Vol 6 (1) ◽

pp. 1-8

Author(s):

Thomas K. Pellinger ◽

Catherine B. Pearce ◽

Grant H. Simmons ◽

Jack L. Snitzer

Keyword(s):

Blood Pressure ◽

Type 2 Diabetes ◽

Blood Flow ◽

Systolic Blood Pressure ◽

Vascular Function ◽

Muscle Blood Flow ◽

Vascular Conductance ◽

Femoral Blood Flow ◽

Femoral Blood

Background: For individuals with type 2 diabetes (T2D), the hemodynamic response to regular exercise is critical for regulating blood glucose, protecting vascular function, and reducing cardiovascular disease risk, but the hemodynamic responses to differing doses of acute exercise in T2D are unclear. We aimed to compare postexercise (PE) hemodynamics in patients with T2D in response to 4 doses of dynamic exercise. Methods: Eight subjects with well-controlled T2D (42–64 years old.; hemoglobin A1c: 6.6% ± 0.9%) participated in 4 study days, during which they exercised on a cycle ergometer at 4 different combinations of exercise duration and intensity: 30 min at 40% V˙O2peak (30@40), 30 min at 60% V˙O2peak (30@60), 60 min at 40% V˙O2peak (60@40), and 60 min at 60% V˙O2peak (60@60). Heart rate, arterial pressure, and femoral blood flow (Doppler ultrasound) were measured pre-exercise and every 15 min through 120 min PE. Femoral vascular conductance was calculated as flow/pressure. Results: Compared with pre-exercise baseline, femoral blood flow and femoral vascular conductance were higher through at least 105 min of recovery in all conditions (all P < .05), except for the 30@40 trial. Compared with the pre-exercise measures, systolic blood pressure was lower through at least 75 min of recovery in all conditions (all P < .05), except for the 30@40 trial. Conclusion: These results suggest that exercise must be at least moderate in intensity or prolonged in duration (>30 min) to promote sustained PE elevations in skeletal muscle blood flow and reductions in systolic blood pressure in patients with T2D.

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