Serum potassium during exercise in Hereford calves: influence of physical conditioning.
We determined how rapidly serum potassium concentration ([K+]) increased, its magnitude, and how quickly it decreased during and after a 3.5-min exercise bout at maximal speed capability in eight Hereford steers, before and after physical conditioning. Serum [K+] values rose rapidly after the start of exercise and declined rapidly to within 7% of preexercise values 5 min after exercise ceased. Before physical conditioning, serum [K+] increased from an average of 4.19 meq/l at rest to 6.71 meq/l at the highest treadmill speed the animals could sustain (1.8-2.4 m/s at a 3 degrees incline). After physical conditioning, the serum [K+] increase at comparable treadmill speeds was approximately 5% lower than before conditioning (average of 6.37 meq/l); however, the animals could now exercise from 0.6 to 0.8 m/s faster than before conditioning, and their maximal serum [K+] rose to an average of 7.47 meq/l, a 10% increase over preconditioned maximal values. We conclude that higher speeds and accompanying increases in serum [K+] attained by conditioned animals may place them at greater risk of cardiotoxicity than before conditioning.
Fosha-Dolezal
S R
SR
Department of Anatomy and Physiology, College of Veterinary Medicine, Kansas State University, Manhattan 66506.
Fedde
M R
MR
D000818:Animals; D002417:Cattle / Q000097:blood* / Q000502:physiology; D002418:Cattle Diseases / Q000209:etiology; D004594:Electrophysiology; D006321:Heart / Q000502:physiology; D006323:Heart Arrest / Q000209:etiology / Q000662:veterinary; D006339:Heart Rate; D008297:Male; D009132:Muscles / Q000502:physiology; D009474:Neurons / Q000502:physiology; D010805:Physical Conditioning, Animal; D005082:Physical Exertion; D011188:Potassium / Q000097:blood*; D014693:Ventricular Fibrillation / Q000209:etiology / Q000662:veterinary
D011188:Potassium