Engineering topics

Kruk, B.

Publications and source records attributed to Kruk, B..

4 records

NASA NTRS2000

Body Temperatures During Exercise in Deconditioned Dogs: Effect of NACL and Glucose Infusion

Infusion of glucose (Glu) into normal exercising dogs attenuates the rise in rectal temperature (Delta-Tre) when compared with delta-Tre during FFA infusion or no infusion. Rates of rise and delta-=Tre levels are higher during exercise after confinement. Therefore, the purpose of this study was to determine if Glu infusion would attenuate the exercise-induced excess hyperthermia after deconditioning. Rectal and quadricep femoris muscle temperatures (Tmu) were measured in 7 male, mongrel dogs dogs (19.6 +/- SD 3.0 kg) during 90 minutes of treadmill exercise (3.1 +/-SD 0.2 W/kg) with infusion (30ml/min/kg) of 40% Glu or 0.9% NaCL before BC) and after confinement (AC) in cages (40 x 110 x 80 cm) for 8 wk. Mean (+/-SE body wt. were 19.6 +/- 1.1 kg BC and 19.5 +/- 1.1kg AC, exercise VO2 were not different (40.0 - 42.0 mi/min/kg-1). With NaCl AC, NaCl BC, GluAC, and GluBC: Delta-Tre were, 1.8, 1.4, 1.3 and 0.9C respectively; and Delta-Tmu were 2.3, 1.9, 1.6, and 1.4C. respectively (P<0.05 from GluBC). Compared with NaCl infusion, attenuated both Delta-Tre and Delta-Tmu BC and AC, respectively. Compared with GluBC, GluAC attenuated Delta-Tmu but not Delta-Tre. Thus. with similar heat production, the mechanism for attenuation at bad body temperature with Glu infusion must affect avenues of heat dissipation.

Greenleaf, J. E.↗

NASA NTRS1995

Glucose Infusion into Exercising Dogs after Confinement: Rectal and Active Muscle Temperatures

Intravenous glucose infusion into ambulatory dogs results in attenuation of exercise-induced increase of both rectal and thigh muscle temperatures. That glucose (Glu) infusion attenuates excessive increase in body temperature from restricted activity during confinement deconditioning. Intravenous glucose infusion attenuates the rise in exercise core temperature in deconditioned dogs by a yet undefined mechanism.

Greenleaf, J. E.↗

NASA NTRS1985

Exercise hyperthermia as a factor limiting physical performance - Temperature effect on muscle metabolism

The effect of trunk cooling on the muscle contents of ATP, ADP, AMP, creatine phosphate (CrP), and creatine, as well as of glycogen, some glycolytic intermediates, pyruvate, and lactate were assessed in 11 fasted dogs exercised at 20 C on treadmill to exhaustion. Without cooling, dogs were able to run 57 min, and their rectal (Tre) and muscle (Tm) temperatures increased to 41.8 and 43.0 C, respectively. Cooling with ice packs prolonged the ability to run by 45 percent, and resulted in lower Tre (by 1.1 C) and Tm (by 1.2 C). Depletion of muscle content of total high-energy phosphates (ATP + CrP) and glycogen, and increases in contents of AMP, pyruvate, and lactate were lower in cooled dogs than in non-cooled dogs. The muscle content of lactiate correlated positively with TM. These results indicate that hypothermia accelerates glycolysis, and shifts the equilibrium between high- and low-energy phosphates in favor of the latter. The adverse effect of hypothermia on muscle metabolism may be relevant to the limitation of endurance.

Kozlowski, S.↗

NASA NTRS1985

Hypothalamic, rectal, and muscle temperatures in exercising dogs - Effect of cooling

An experimental investigation of the mechanisms of performance prolongation during exercise is presented. Measurements were obtained of the rectal, muscle, and hypothalamic temperature of dogs during treadmill exercise at an ambient temperature of 22 + or - 1 C, with and without cooling by use of ice packs. In comparison with exercise without cooling, exercise with cooling was found to: (1) increase exercise duration from 90 + or - 14 to 145 + or - 15 min; (2) attenuate increases in hypothalamic, rectal and muscle temperature; (3) decrease respiratory and heart rates; and (4) lower blood lactic acid content. It is shown that although significant differences were found between the brain, core, and muscle temperatures during exercise with and without cooling, an inverse relation was observed between muscle temperature and the total duration of exercise. It is suggested that sustained muscle hyperthermia may have contributed to the limitation of working ability in exercise with and without cooling.

Kruk, B.↗