Forearm blood flow responses to fatiguing isometric contractions in women and men

• Published in: American journal of physiology. Heart and circulatory physiology 2007-07, Vol.293 (1), p.H805-H812
• Main Authors: Thompson, Benjamin C, Fadia, Tanvi, Pincivero, Danny M, Scheuermann, Barry W
• Format: Article
• Language: English
• Subjects: Adult; Blood Flow Velocity - physiology; Blood pressure; Exercise; Exercise Test; Exercise Tolerance - physiology; Fatigue; Female; Forearm - blood supply; Forearm - physiology; Gender differences; Humans; Isometric Contraction - physiology; Male; Muscle Fatigue - physiology; Muscle, Skeletal - blood supply; Muscle, Skeletal - physiology; Muscular system; Sex Factors; Studies
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.01136.2006

1 Cardiopulmonary and Metabolism Research Laboratory and 2 Human Performance and Fatigue Laboratory, Department of Kinesiology, University of Toledo, Toledo, Ohio Submitted 16 October 2006 ; accepted in final form 25 April 2007 Previous studies suggest that women experience less vascular occlusion than men when generating the same relative contractile force. This study examined forearm blood flow (FBF) in women and men during isometric handgrip exercise requiring the same relative force. Thirty-eight subjects [20 women and 18 men, 22.8 ± 0.6 yrs old (means ± SE)] performed low- and moderate-force handgrip exercise on two occasions. Subjects performed five maximum voluntary contractions (MVC) before exercise to determine 20% and 50% MVC target forces. Time to task failure (TTF) was determined when the subject could not maintain force within 5% of the target force. Mean blood velocity was measured in the brachial artery with the use of Doppler ultrasonography. Arterial diameter was measured at rest and used to calculate absolute FBF (FBFa; ml/min) and relative FBF (FBFr; ml·min –1 ·100 ml –1 ). Women generated less ( P < 0.05) absolute maximal force (208 ± 10 N) than men (357 ± 17 N). The TTF was longer ( P < 0.05) at 20% MVC for women (349 ± 32 s) than for men (230 ± 23 s), but no difference between the sexes was observed at 50% MVC (women: 69 ± 5 s; men: 71 ± 8 s). FBFa and FBFr increased ( P < 0.05) from rest to TTF in both women and men during 20% and 50% MVC trials. FBFr was greater in women than in men at 30% TTF during 50% MVC. At exercise durations 60% of TTF, FBFa was lower ( P < 0.05) in women than in men during handgrip at 20% MVC. Despite the longer exercise duration for women at the lower contraction intensity, FBFr was similar between the sexes, suggesting that muscle perfusion is matched to the exercising muscle mass independent of sex. muscle fatigue; electromyography; muscle contraction; endurance Address for reprint requests and other correspondence: B. W. Scheuermann, Cardiopulmonary and Metabolism Research Laboratory, Dept. of Kinesiology, Health & Human Services Bldg., Univ. of Toledo, Toledo, OH 43606 (e-mail: barry.scheuermann{at}utoledo.edu )