Entin P L, Robertshaw D, Rawson R E
Department of Physiology, New York State College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA.
J Appl Physiol (1985). 1999 Nov;87(5):1887-93. doi: 10.1152/jappl.1999.87.5.1887.
During galloping, many animals display 1:1 coupling of breaths and strides. Locomotor respiratory coupling (LRC) may limit respiratory evaporative heat loss (REHL) by constraining respiratory frequency (f). Five sheep were exercised twice each, according to a five-step protocol: 5 min at the walk, 5 min at the trot (trot1), 10 min at the gallop, 5 min at the trot (trot2), and 5 min at the walk. Rectal temperature (T(re)), stride frequency, f, REHL, and arterial CO(2) tension and pH were measured at each step. Tidal volume (VT) was calculated. LRC was observed only during galloping. The coupling ratio remained at 1:1 while VT increased continuously during galloping, causing REHL to increase from 2.9 +/- 0.2 (SE) W/kg at the end of trot1 to a peak of 5.3 +/- 0.3 W/kg. T(re) rose from 39.0 +/- 0.1 degrees C preexercise to 40.2 +/- 0.2 degrees C at the end of galloping. At the gallop-trot2 transition, VT fell and f rose, despite a continued rise in T(re). Arterial CO(2) tension fell from 36.5 +/- 1.1 Torr preexercise to 31.8 +/- 1.4 Torr by the end of trot1 and then further to 21.5 +/- 1.2 Torr by the end of galloping, resulting in alkalosis. In conclusion, LRC did not prevent increases in REHL in sheep because VT increased. The increased VT caused hypocapnia and presumably elevated the cost of breathing.
在飞奔过程中，许多动物表现出呼吸与步伐的1:1耦合。运动性呼吸耦合（LRC）可能通过限制呼吸频率（f）来限制呼吸蒸发散热（REHL）。五只绵羊按照五步方案各进行两次运动：步行5分钟、小跑5分钟（小跑1）、飞奔10分钟、小跑5分钟（小跑2）、步行5分钟。在每个步骤测量直肠温度（T(re)）、步频、f、REHL、动脉血二氧化碳分压和pH值。计算潮气量（VT）。仅在飞奔过程中观察到LRC。耦合比保持在1:1，而在飞奔过程中VT持续增加，导致REHL从小跑1结束时的2.9±0.2（SE）W/kg增加到峰值5.3±0.3 W/kg。T(re)从运动前的39.0±0.1℃升至飞奔结束时的40.2±0.2℃。在从飞奔到小跑2的过渡阶段，尽管T(re)持续上升，但VT下降且f上升。动脉血二氧化碳分压从运动前的36.5±1.1 Torr降至小跑1结束时的31.8±1.4 Torr，然后在飞奔结束时进一步降至21.5±1.2 Torr，导致碱中毒。总之，LRC并未阻止绵羊的REHL增加，因为VT增加。VT增加导致低碳酸血症，可能还增加了呼吸成本。
