Does Bulk Oxygen Delivery During Forearm Exercise Predict Heavy Intensity Exercise Time To Task Failure?

Abstract

The primary role of the cardiovascular system during exercise is to deliver oxygen in proportion to the demands of the active muscle. It is well known that acute alterations in oxygen delivery within an individual alter exercise performance. However, it is not known whether differences in oxygen delivery between subjects predict differences in exercise performance. PURPOSE: To determine whether bulk oxygen delivery to the exercising limb predicts differences in time to task failure (TTF) during heavy intensity submaximal exercise in healthy individuals. METHODS: Eight recreationally active (261.57 ± 19.35 mets) healthy males (24.25 ± 8 yrs) performed rhythmic isometric handgrip contractions (30 kg - 1 s: 2 s contraction/relaxation duty cycle) until failure. Failure was defined as the inability to generate 30 kg force on three consecutive forearm contractions. Oxygen delivery to the exercising forearm was calculated based on arterial oxygen content (oxygen saturation via pulse oximeter and [hemoglobin] via venous blood sample) and continuously measured brachial artery blood flow (BABF; Doppler and Echo ultrasound) during rest and throughout exercise. RESULTS: Neither bulk oxygen delivery to the forearm nor BABF predicted any of the difference in TTF between subjects (oxygen delivery n = 6, r2 = 0.00001, P > 0.05; BABF n = 8, r2 = 0.01, P > 0.05). CONCLUSIONS: Preliminary evidence suggests that bulk blood flow and oxygen delivery to the exercising limb is not an indicator of time to task failure during high intensity forearm exercise in healthy, recreationally active individuals. This work was funded by the Natural Science and Engineering Research Council (NSERC) of Canada, Canada Foundation for Innovation and Ontario Innovation Trust Grants to M. Tschakovsky.