Frisbee J C, Murrant C L, Wilson B A, Barclay J K
Department of Human Biology and Nutritional Sciences, University of Guelph, Ontario, Canada.
Med Sci Sports Exerc. 1999 Sep;31(9):1293-8. doi: 10.1097/00005768-199909000-00010.
The effects of an acute polycythemia on muscle fatigue development were investigated in the self-perfused canine gastrocnemius in situ.
Following isolation of the gastrocnemius, dogs (N = 5) were made polycythemic through a bolus injection of packed erythrocytes (hematocrit (Hct) = 90-92%) to raise systemic Hct to 63.5 +/- 0.5%. Subsequently, the gastrocnemius was stimulated, through the sciatic nerve, to perform 20 min of isotonic tetanic contractions (60 x min(-1), 200 ms, 50Hz). Control (normocythemic) animals (N = 5) underwent an identical contraction regimen.
Although blood flow to the gastrocnemius was not different at any time, oxygen delivery was significantly increased during polycythemia (peak = 33.7 +/- 2.2 mL x 100 g(-1) x min-1) over control (peak = 25.1 +/- 2.1 mL x 100 g(-1)x min(-1)) at all times during contraction. Oxygen uptake by the gastrocnemius, although consistently increased, was not significantly different between the normocythemic and polycythemic conditions at any time. The rate of fatigue was significantly decreased over the first 6 min of contraction in polycythemic animals (3.5 +/- 0.6% x min(-1)) when compared with controls (5.8 +/- 0.7% x min(-1)). Subsequent fatigue development was not different between groups. As a result of the early rate differences in fatigue, however, the work production in polycythemic animals was significantly greater than in normocythemic dogs for the duration of the contraction period.
We conclude that during high metabolic rate isotonic tetanic contractions, muscle fatigue development is diminished by polycythemia, but the ergogenic effect appears to be transient.
在自体灌注的犬原位腓肠肌中研究急性红细胞增多症对肌肉疲劳发展的影响。
分离腓肠肌后，通过大剂量注射浓缩红细胞（血细胞比容（Hct）= 90 - 92%）使犬（N = 5）发生红细胞增多症，以将全身Hct提高至63.5±0.5%。随后，通过坐骨神经刺激腓肠肌进行20分钟的等张强直收缩（60次/分钟，200毫秒，50赫兹）。对照（正常血细胞比容）动物（N = 5）接受相同的收缩方案。
尽管在任何时候腓肠肌的血流量都没有差异，但在收缩过程中的所有时间，红细胞增多症期间的氧输送量均显著高于对照（峰值 = 33.7±2.2毫升×100克⁻¹×分钟⁻¹）（对照峰值 = 25.1±2.1毫升×100克⁻¹×分钟⁻¹）。腓肠肌的氧摄取量虽然持续增加，但在正常血细胞比容和红细胞增多症状态下的任何时候均无显著差异。与对照（5.8±0.7%×分钟⁻¹）相比，红细胞增多症动物在收缩的前6分钟疲劳率显著降低（3.5±0.6%×分钟⁻¹）。随后各组之间的疲劳发展没有差异。然而，由于疲劳早期速率的差异，在收缩期持续时间内，红细胞增多症动物的做功量显著大于正常血细胞比容的犬。
我们得出结论，在高代谢率的等张强直收缩过程中，红细胞增多症可减轻肌肉疲劳的发展，但这种促力作用似乎是短暂的。
