To test the hypothesis that the dependence of the pressor response on muscle length is caused by changes in perfusion, we compared the cardiovascular responses to static contraction at short and long muscle lengths during free perfusion with those during circulatory arrest. Five males performed 2-min static knee extension exercise at 30% of maximal voluntary torque at each of two muscle lengths at a knee angle of 40° (short) and 90° (long). The subjects performed two trials – a free perfusion trial and a circulatory arrest trial. For circulatory arrest, an occlusion cuff placed around the proximal portion of the thigh was inflated to 250 mmHg 2 min before exercise. Mean arterial pressure (MAP), minute ventilation (VE), and the muscle oxygenation index in the vastus lateralis muscle were measured using near-infrared spectroscopy. In the free perfusion trial, MAP and VE were significantly greater during contractions at 90° than at 40° (p < 0.05). The muscle oxygenation index was significantly lower during contractions at 90° than at 40° (p < 0.05). Circulatory arrest diminished these differences. These results suggest that the relationship between muscle length and the pressor response can be explained by changes in perfusion, which are related to muscle length.
Mean Arterial Pressure Maximal Voluntary Contraction Pressor Response Knee Extensor Oxygenation Index
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
This is a preview of subscription content, log in to check access
The authors gratefully acknowledge Dr. Taku Wakahara for invaluable technical support with the ultrasonic apparatus.
Mitchell JH, Payne FC, Saltin B, Schibye B. (1980) The role of muscle mass in the cardiovascular response to static contractions. J Physiol 309: 45–54.PubMedGoogle Scholar
Bevegard S, Freyschuss U, Strandell T. (1966) Circulatory adaptation to arm and leg exercise in supine and sitting position. J Appl Physiol 21: 37–46.PubMedGoogle Scholar
Fisher JP, White MJ. (2004) Muscle afferent contributions to the cardiovascular response to isometric exercise. Exp Physiol 89: 639–646.PubMedCrossRefGoogle Scholar
Ng AV, Agre JC, Hanson P, Harrington MS, Nagle FJ. (1994) Influence of muscle length and force on endurance and pressor responses to isometric exercise. J Appl Physiol 76: 2561–2569.PubMedGoogle Scholar
Miura H, McCully K, Nioka S, Chance B. (2004) Relationship between muscle architectural features and oxygenation status determined by near infrared device. Eur J Appl Physiol 91: 273–.278.PubMedCrossRefGoogle Scholar
Williamson JW, Fadel PJ Mitchell JH. (2006). New insights into central cardiovascular control during exercise in humans: a central command update. Exp Physiol 91: 51–58.PubMedCrossRefGoogle Scholar
Williamson JW, Olesen HL, Pott F, Mitchell JH, Secher NH. (1996) Central command increases cardiac output during static exercise in humans. Acta Physiol Scand 156: 429–434.PubMedCrossRefGoogle Scholar
Mitchell, JH, Kaufman MP, Iwamoto GA. (1983) The exercise pressor reflex: its cardiovascular effects, afferent mechanisms, and central pathways. Annu Rev Physiol 45: 229–242.PubMedCrossRefGoogle Scholar