Thermoregulatory and metabolic responses to jogging prior to and during pregnancy.

CLAPP, JAMES F. III; WESLEY, MARY; SLEAMAKER, ROBERT H.
Medicine & Science in Sports & Exercise: April 1987
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CLAPP, III, J. F., M. WESLEY, and R. H. SLEAMAKER. Thermal and metabolic responses to jogging prior to and during pregnancy. Med. Sci. Sports Exerc, Vol. 19, No. 2, pp. 124-130, 1987. Ten joggers were serially studied prior to and during pregnancy at their individual training intensity levels to estimate their thermal and metabolic response to exercise in the field. Prior to conception, a 20-min run at 74% of [latin capital V with dot above]O2max (range = 62 to 90%) increased the respiratory exchange ratio to 0.90 +/- 0.01 (range = 0.87 to 0.96) with a rise in whole blood glucose (5.19 +/- 0.14 to 6.63 +/- 0.23 mM [middle dot] l-1), lactate (0.61 +/- 0.06 to 2.62 +/- 0.74 mM [middle dot] l-1), and rectal temperature (37.5 +/-0.1 to 39.0 +/- 0.1[degrees]C). Despite a spontaneous decrease in exercise intensity to 57 +/- 5% of [latin capital V with dot above]O2max (range = 34 to 79%) at 20 and to 47 +/-2% of [latin capital V with dot above]O2max (range = 36 to 59%) at 32 wk gestation, the rise in respiratory exchange ratio with exercise was maintained at 0.92 +/- 0.02 (range = 0.88 to 0.97) and 0.93 +/- 0.01 (range = 0.88 to 0.97), respectively, suggesting a shift to the left in the relationship between exercise intensity and fractional carbohydrate utilization by muscle during exercise in pregnancy. The concomitant changes in whole blood glucose before and after exercise at 20 (4.46 +/- 0.16 to 4.45 +/- 0.08 mM [middle dot] l-1) and 32 (5.30 +/- 0.19 to 4.55 +/- 0.15 mM [middle dot] l-1) wk further strengthen this view. Post-exercise, whole blood lactate levels at 20 (0.53 +/- 0.06 to 1.59 +/- 0.30 mM [middle dot] l-1) and 32 (0.77 +/- 0.07 to 0.89 +/- 0.11 mM [middle dot] l-1) wk were lower than those observed prior to pregnancy. The magnitude and pattern of the thermoregulatory response was altered with advancing gestation. As a whole, the data suggest that multiple aspects of the physiological response to antigravitational endurance exercise are altered with advancing gestation.

(C)1987The American College of Sports Medicine