Muscle blood flow during exercise
This is an excerpt from Advanced Neuromuscular Exercise Physiology-2nd Edition by Phillip Gardiner.
During exercise, blood flow increases in working muscle as a function of workload, and the relationship is quite linear (Saltin et al. 1998). Muscle perfusion during exercise for a sedentary individual is about 250 mL/min in 100 g of tissue, and it can rise to 400 mL/min in trained athletes (Saltin et al. 1998; Saltin 2007). Mechanical and biochemical mechanisms cause this increased muscle blood flow. However, the blood available for exercising muscles is not limitless—exercising at a high intensity with 15 kg of muscle (about 50% of the total muscle mass of a 75 kg man) can exceed the heart’s capacity to supply blood (figure 3.1; Calbet et al. 2004). Athletes such as cross-country skiers, who use their arms and legs at relatively high intensities for prolonged durations, experience this limit in blood availability. Therefore, there must be in place mechanisms that increase blood flow when there is metabolic demand, as well as mechanisms that cause active muscles to undergo some level of vasoconstriction during exercise (Rowell 1997). During high blood flow, sympathetically mediated vasoconstriction is necessary to maintain peripheral resistance in order to maintain blood pressure (Saltin 2007). When metabolic rates and blood flow demands are high, such as when the arms and legs are working simultaneously, noradrenaline spillover from the legs helps to counteract the strong local vasodilator signals and helps to maintain central pressure.
This section discusses the general physiological mechanisms that maintain blood pressure when muscle demands for oxygen delivery are high and the local mechanisms that match blood flow to metabolic demand. There are many proposed mechanisms controlling exercise blood flow, with perhaps a significant degree of redundancy, so that finding the role played by individual mechanisms has not been possible to date.
Can Muscle Massage After Exercise Accelerate Recovery?
Muscle blood flow can be increased in resting muscles by muscle compression, which evokes a rapid vasodilator response. Therefore, if accumulation of substances in exercising muscle, such as lactate and hydrogen ion, is assumed to contribute to fatigue, is it not reasonable to assume that massage of the muscle immediately following exercise maintains elevated blood flow and thus accelerates the removal of such substances and thus facilitates recovery? This is the question that Dr. Michael Tschakovsky and colleagues at Queen’s University at Kingston, Ontario, addressed experimentally (Wiltshire et al. 2010). Subjects maintained a handgrip task at 40% of MVC for 2 min, after which they had passive rest, or performed 10 min of rhythmic forearm contractions at 10% of MVC, or were treated to forearm massage (effleurage and petrissage). The researchers found that massage substantially reduced forearm blood flow and removal of lactate, primarily due to the suppression of flow during the massage strokes. There was also a reduction in flow with active recovery, although in this situation some of the lactate was removed and metabolized by the working muscle fibers. On the basis of these results, the researchers recommended that sport massage be avoided in situations of acute bouts of repeated exercise.More Excerpts From Advanced Neuromuscular Exercise Physiology 2nd Edition
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