Details

Autor(en) / Beteiligte

• Laaksonen, Marko S.
• Björklund, Glenn
• Heinonen, Ilkka
• Kemppainen, Jukka
• Knuuti, Juhani
• Kyröläinen, Heikki
• Kalliokoski, Kari K.

Titel

Perfusion heterogeneity does not explain excess muscle oxygen uptake during variable intensity exercise

Ist Teil von

• Clinical physiology and functional imaging, 2010-07, Vol.30 (4), p.241-249

Ort / Verlag

Oxford, UK: Blackwell Publishing Ltd

Erscheinungsjahr

2010

Quelle

Wiley Online Library - AutoHoldings Journals

Beschreibungen/Notizen

• Summary The association between muscle oxygen uptake (VO2) and perfusion or perfusion heterogeneity (relative dispersion, RD) was studied in eight healthy male subjects during intermittent isometric (1 s on, 2 s off) one‐legged knee‐extension exercise at variable intensities using positron emission tomography and a‐v blood sampling. Resistance during the first 6 min of exercise was 50% of maximal isometric voluntary contraction force (MVC) (HI‐1), followed by 6 min at 10% MVC (LOW) and finishing with 6 min at 50% MVC (HI‐2). Muscle perfusion and O2 delivery during HI‐1 (26 ± 5 and 5·4 ± 1·0 ml 100 g−1 min−1) and HI‐2 (28 ± 4 and 5·8 ± 0·7 ml 100 g−1 min−1) were similar, but both were higher (P<0·01) than during LOW (15 ± 3 and 3·0 ± 0·6 ml 100 g−1 min−1). Muscle VO2 was also higher during both HI workloads (HI‐1 3·3 ± 0·4 and HI‐2 4·1 ± 0·6 ml 100 g−1 min−1) than LOW (1·4 ± 0·4 ml 100 g−1 min−1; P<0·01) and 25% higher during HI‐2 than HI‐1 (P<0·05). O2 extraction was higher during HI workloads (HI‐1 62 ± 7 and HI‐2 70 ± 7%) than LOW (45 ± 8%; P<0·01). O2 extraction tended to be higher (P = 0·08) during HI‐2 when compared to HI‐1. Perfusion was less heterogeneous (P<0·05) during HI workloads when compared to LOW with no difference between HI workloads. Thus, during one‐legged knee‐extension exercise at variable intensities, skeletal muscle perfusion and O2 delivery are unchanged between high‐intensity workloads, whereas muscle VO2 is increased during the second high‐intensity workload. Perfusion heterogeneity cannot explain this discrepancy between O2 delivery and uptake. We propose that the excess muscle VO2 during the second high‐intensity workload is derived from working muscle cells.