Recovery of microvascular PO2 during the exercise off-transient in muscles of different fiber type. |
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Authors: | Paul McDonough Brad J Behnke Timothy I Musch David C Poole |
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Institution: | Department of Anatomy, Kansas State University, Manhattan 66506-5802, USA. paul.mcdonough@utsouthwestern.edu |
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Abstract: | The speed with which muscle energetic status recovers after exercise is dependent on oxidative capacity and vascular O(2) pressures. Because vascular control differs between muscles composed of fast- vs. slow-twitch fibers, we explored the possibility that microvascular O(2) pressure (Pmv(O(2)); proportional to the O(2) delivery-to-O(2) uptake ratio) would differ during recovery in fast-twitch peroneal (Per: 86% type II) compared with slow-twitch soleus (Sol: 84% type I). Specifically, we hypothesized that, in Per, Pmv(O(2)) would be reduced immediately after contractions and would recover more slowly during the off-transient from contractions compared with Sol. The Per and Sol muscles of six female Sprague-Dawley rats (weight = approximately 220 g) were studied after the cessation of electrical stimulation (120 s; 1 Hz) to compare the recovery profiles of Pmv(O(2)). As hypothesized, Pmv(O(2)) was lower throughout recovery in Per compared with Sol (end contraction: 13.4 +/- 2.2 vs. 20.2 +/- 0.9 Torr; end recovery: 24.0 +/- 2.4 vs. 27.4 +/- 1.2 Torr, Per vs. Sol; P
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