Visser, Bart3; Kofoed Nielsen, Pernille4; de Kraker, Heleen3; Smits, Miriam3; Jensen, Bente Rona6; Veeger, Dirkjan3; van Dieën, Jaap H.3
1 Section of Human Physiology, Department of Exercise and Sport Sciences, Faculty of Science, Københavns Universitet2 Department of Exercise and Sport Sciences, Faculty of Science, Københavns Universitet3 Faculty of Human Movement Sciences, Vrije Universiteit Amsterdam4 Afd. for Fysiologi, Arbejdsmiljøinstituttet5 Integrated Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, Københavns Universitet6 Integrated Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, Københavns Universitet
The object of the current study was to determine whether static contraction of proximal musculature has an effect on the blood flow more distally in the upper extremity. Static contractions of muscles in the neck shoulder region at three levels (relaxed, shoulders elevated and shoulders elevated loaded with 4.95 kg each) were combined with intermittent pinch forces at 0, 10 and 25% of the maximum voluntary contraction (MVC). Blood flow to the forearm was measured with Doppler ultrasound. Myoelectric activity of the forearm and neck-shoulder muscles was recorded to check for the workload levels. Across all levels of shoulder load, blood flow increased significantly with increasing pinch force (21% at 10% MVC and by 44% at 25% MVC). Blood flow was significantly affected by shoulder load, with the lowest blood flow at the highest shoulder load. Interactions of pinch force and shoulder load were not significant. The myoelectric activity of forearm muscles increased with increasing pinch force. The activation of the trapezius muscle decreased with increasing pinch force and increased with increasing shoulder load. The precise mechanisms accounting for the influence of shoulder load remains unclear. The results of this study indicate that shoulder load might influence blood flow to the forearm.