Ponganis P J, Kooyman G L, Winter L M, Starke L N
Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla 92093-0204, USA.
J Comp Physiol B. 1997 Jan;167(1):9-16. doi: 10.1007/s003600050042.
California sea lions, Zalophus californianus, were trained to elicit maximum voluntary breath holds during stationary underwater targeting, submerged swimming, and trained diving. Lowest heart rate during rest periods was 57 bpm. The heart rate profiles in all three protocols were dominated by a bradycardia of 20-50 bpm, and demonstrated that otariid diving heart rates were at or below resting heart rate. Venous blood samples were collected after submerged swimming periods of 1-3 min. Plasma lactate began to increase only after 2.3-min submersions. This rise in lactate and our inability to train sea lions to dive or swim submerged for periods longer than 3 min lead us to conclude that an aerobic limit had been reached. Due to the similarity of heart rate responses and swimming velocities recorded during submerged swimming and trained diving, this 2.3-min limit should approximate the aerobic dive limit in these 40-kg sea lions. Total body O2 stores, based on measurements of blood and muscle O2 stores in these animals, and prior lung O2 store analyses, were 37-43 ml O2 kg-1. The aerobic dive limit, calculated with these O2 stores and prior measurements of at-sea metabolic rates of sea lions, is 1.8-2 min, similar to that measured by the change in post-submersion lactate concentration.
加利福尼亚海狮（Zalophus californianus）接受训练，以便在静止水下定位、水下游泳和训练潜水时实现最大自主屏气。休息期间的最低心率为57次/分钟。在所有三种实验方案中，心率曲线均以20 - 50次/分钟的心动过缓为主，这表明海狗科动物的潜水心率处于或低于静息心率。在1 - 3分钟的水下游泳期后采集静脉血样。血浆乳酸仅在潜水2.3分钟后才开始增加。乳酸的这种升高以及我们无法训练海狮潜水或水下游泳超过3分钟，使我们得出结论，即已达到有氧极限。由于在水下游泳和训练潜水期间记录的心率反应和游泳速度相似，这个2.3分钟的极限应接近这些40千克海狮的有氧潜水极限。根据对这些动物血液和肌肉氧气储备的测量以及先前对肺氧气储备的分析，全身氧气储备为37 - 43毫升氧气/千克。用这些氧气储备和先前对海狮海上代谢率的测量计算出的有氧潜水极限为1.8 - 2分钟，与通过潜水后乳酸浓度变化测量的结果相似。
