Is the blood flow response to a single contraction determined by work performed?

Nine healthy volunteers performed a series of single handgrip isometric contractions to test the hypothesis that the blood flow response to a contraction is determined solely by the tension-time index (isometric analog of work). Contractions were performed in duplicate at 15, 30, and 60% of maximal voluntary contraction (MVC) at durations of 0.5, 1, and 2 s. Forearm blood flow (FBF) was measured beat by beat by using Doppler ultrasound. Peak FBF responded in a graded fashion to graded increases in peak tension with contraction time held constant (35, 56, and 90 ml/min for 15, 30, and 60% MVC for 1 s, respectively). When tension was kept constant, peak FBF responded in a graded fashion to graded increases in duration (77, 90, and 97 ml/min for 60% MVC for 0.5, 1, and 2 s). With a constant tension-time index, peak FBF responded in a graded fashion to graded increases in peak tension (48, 56, and 77 ml/min for 15% MVC/2 s, 30% MVC/1 s, and 60% MVC/0.5 s). Similar trends were also observed for total postcontraction hyperemia. Blood flow increased regardless of whether the change in tension-time index was accomplished by an increase in tension or duration of contraction. However, with a constant tension-time index, the change in blood flow was related to the peak tension developed. Our results suggest that the blood flow response to a single muscle contraction is not determined solely by the work performed (tension-time index) but also by the number of muscle fibers recruited.

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Effects of acetylcholine and nitric oxide on forearm blood flow at rest and after a single muscle contraction

Journal of Applied Physiology ◽

10.1152/jappl.1998.85.6.2249 ◽

1998 ◽

Vol 85 (6) ◽

pp. 2249-2254 ◽

Cited By ~ 68

Author(s):

R. W. Brock ◽

M. E. Tschakovsky ◽

J. K. Shoemaker ◽

J. R. Halliwill ◽

M. J. Joyner ◽

...

Keyword(s):

Nitric Oxide ◽

Blood Flow ◽

Muscle Contraction ◽

Forearm Blood Flow ◽

Mechanical Effect ◽

Voluntary Contraction ◽

Single Muscle ◽

Cuff Inflation ◽

S Period ◽

Echo Doppler Ultrasound

We tested the hypothesis that ACh or nitric oxide (NO) might be involved in the vasodilation that accompanies a single contraction of the forearm. Eight adults (3 women and 5 men) completed single 1-s-duration contractions of the forearm to raise and lower a weight equivalent to ∼20% maximal voluntary contraction through a distance of 5 cm. In a second protocol, each subject had a cuff, placed completely about the forearm, inflated to 120 mmHg for a 1-s period, then released as a simulation of the mechanical effect of muscle contraction. Three conditions were studied, always in this order: 1) control, with intra-arterial infusion of saline; 2) after muscarinic blockade with atropine; and 3) after NO synthase inhibition with N G-monomethyl-l-arginine (l-NMMA) plus atropine. Forearm blood flow (FBF), measured by combined pulsed and echo Doppler ultrasound, was reduced at rest with l-NMMA-atropine compared with the other two conditions. After the single contraction, there were no effects of atropine, butl-NMMA reduced the peak FBF and the total postcontraction hyperemia. After the single cuff inflation, atropine had no effects, whereasl-NMMA caused changes similar to those seen after contraction, reducing the peak FBF and the total hyperemia. The observation thatl-NMMA reduced FBF in response to both cuff inflation and a brief contraction indicates that NO from the vascular endothelium might modulate the basal level of vascular tone and the mechanical component of the hyperemia with exercise. It is unlikely that ACh and NO from the endothelium are involved in the dilator response to a single muscle contraction.

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250 DIMINISHED FOREARM BLOOD FLOW RESPONSE TO BEHAVIORAL CHALLENGE IN ENDURANCED TRAINED ATHLETES

Medicine & Science in Sports & Exercise ◽

10.1249/00005768-199305001-00252 ◽

1993 ◽

Vol 25 (Supplement) ◽

pp. S46

Author(s):

R. P. Claytor ◽

M. J Turner ◽

T. W. Journell ◽

J. T. Lightfoot

Keyword(s):

Blood Flow ◽

Forearm Blood Flow ◽

Blood Flow Response ◽

Flow Response

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734 FOREARM BLOOD FLOW RESPONSE TO A STEP INCREASE IN COMBINED FOREARM AND LEG EXERCISE

Medicine & Science in Sports & Exercise ◽

10.1249/00005768-199405001-00736 ◽

1994 ◽

Vol 26 (Supplement) ◽

pp. S131

Author(s):

M. E. Tschakovsky ◽

R. L. Hughson

Keyword(s):

Blood Flow ◽

Forearm Blood Flow ◽

Blood Flow Response ◽

Flow Response ◽

Leg Exercise

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Blood flow response to muscle contractions is more closely related to metabolic rate than contractile work

Journal of Applied Physiology ◽

10.1152/japplphysiol.00400.2004 ◽

2005 ◽

Vol 98 (6) ◽

pp. 2096-2100 ◽

Cited By ~ 25

Author(s):

Jason J. Hamann ◽

Heidi A. Kluess ◽

John B. Buckwalter ◽

Philip S. Clifford

Keyword(s):

Blood Flow ◽

Steady State ◽

Short Duration ◽

Muscle Activation ◽

Muscle Metabolism ◽

Metabolic Cost ◽

Blood Flow Response ◽

Flow Response ◽

Long Duration ◽

Tension Time

The magnitude of the blood flow response to exercise has been linked to both the contractile work performed and the metabolic cost of the activity. Under certain conditions, contractile work and metabolic cost may be dissociated. This study examined the blood flow response to trains of contractions when contraction duration was manipulated under conditions of similar tension-time indexes (isometric analog of work). Previous investigations have shown that trains of short-duration contractions have a greater ATP utilization, which may result from an augmented ion transport required for muscle activation and relaxation. On the basis of these findings, we hypothesized that the blood flow response would be greater to a train of short-duration contractions than a train of long-duration contractions. Canine gastrocnemius-plantaris muscle ( n = 8) was isolated, and blood flow assessed with an ultrasound flow probe placed around the popliteal artery. The sciatic nerve was stimulated to produce two contraction protocols that resulted in similar contraction-to-rest ratios: short duration: 0.25 s/0.75 s vs. long duration: 1 s /3 s. In accord with the design of the experiment, the tension-time indexes were identical for the two contraction protocols (short: 18.6 ± 1.0 vs. long: 18.6 ± 1.0 kN·s). Steady-state oxygen consumption was greater in the short-duration contractions (17.2 ± 0.9 ml·100 g−1·min−1) than in the long-duration contractions (11.7 ± 0.7 ml·100 g−1·min−1). Similarly, the steady-state blood flow was greater in contractions of short duration (125 ± 7 ml/min) compared with long-duration contractions (92 ± 7 ml/min). Contractions of short duration resulted in significantly higher oxygen consumptions and blood flows compared with contractions of long duration despite the same total contractile work. The blood flow response to muscle contraction appears to be more closely associated with muscle metabolism than contractile work performed.

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