Leg Muscle Metabolism in Trained and Untrained Men

To elucidate the effects of sucrose or caffeine ingestion on metabolic responses to prolonged exercise and on performance of a finishing spurt after the prolonged exercise, seven male physical education students performed four sets of 30 min running (62%-67% VO2 max) followed by progressive exhaustive running on a treadmill. Before each set, they took 350 ml solution containing either sucrose 23.8 g (97.5 kcal), caffeine 200 mg, or a placebo. The duration of the exhaustive running after sucrose, caffeine, or placebo ingestion was not significantly different. Exhaustion would possibly be attained not by depletion of muscle glycogen but by a decrease in the capacity of muscle cells to produce high tension for anaerobic metabolism. Total energy and energy from carbohydrate combusted during four sets of running were estimated at 1255 kcal and 810 kcal in the sucrose trial, 1271 kcal and 624 kcal in the caffeine trial, and 1248 kcal and 649 kcal in the placebo trial. Judging from the figures above, glycogen sparing during prolonged running seemed to be attained by sucrose ingestion but not by caffeine ingestion. The latter finding would be caused by lower intensity and a larger amount of ingested caffeine. In conclusion, performance of progressive exhaustive running following endurance running for 2 h could not be improved either by sucrose or caffeine ingestion. Glycogen sparing in the muscle, however, was suggested by sucrose ingestion but not by caffeine ingestion.

Section: Discussionmentioning

confidence: 91%

Effects of Sucrose or Caffeine Ingestion on Running Performance and Biochemical Responses to Endurance Running

Sasaki¹,

Takaoka²,

Ishiko³

1987

“…Based on the data of the present study, it is tempting to speculate that the reduced blood lactate concentration in trained subjects as opposed to untrained subjects working at the same relative work rate is, in part, the result of an increased fat oxidation. It has been demonstrated that at the same percent of VO2max a greater percentage of fat is oxidized by well-trained as compared to untrained subjects (5). Using a one-legged experimental protocol similar to that of Saltin's et al (21), Henriksson (9) found that metabolism of fat was more pronounced in an endurance-trained leg when compared to its contralateral control during the same relative submaximal exercise.…”

Section: Discussionmentioning

confidence: 99%

Alteration in the Lactate Threshold with Changes in Substrate Availability*

Ivy¹,

Costill²,

Handel³

et al. 1981

The lactate threshold (LT) was studied (N=9) during ergometer cycling under control (C), high blood glucose (G), and high blood free fatty acid (F) conditions. During the G trial blood lactate (HLa) was greater than C at all work loads (P less than 0.05) Adjusted blood HLa values (HLa - pre-exercise value = delta HLa), however, were essentially the same for the C and G trials. Determination of the LT disclosed that there was no difference between the two treatments (C = 53.9 +/- 2.6% VO2 max; G=52.7 +/- 3.1% VO2max). Elevation of blood FFA levels, however, reduced both the HLa and deltaHLa at all work loads from 150-250 W (P less than 0.05) although VO2 was the same as C. In addition, a significant increase in the LT (F = 59.8 +/- 2.6% VO2max) was found for the F treatment. These data suggest that (1) the LT can be altered by substrate availability and (2) that muscle tissue anoxia may not be solely responsible for lactate production during submaximal work.

“…Of particular interest were the low initial glycogen levels in these athletes prior to the SM exercise (Table 4). Typical resting glycogen values for able-bodied athletes average approximately 120-140 mmol kg-1 wet tissue weight (7,14). Although antecedent diet was not controlled, the relatively low values reported for these athletes may indicate more dependence on glycogen stores for the specific act of basic wheelchair ambulation than for walking, particularly considering the inefficiency of wheelchair mobilization (4).…”

Section: Discussionmentioning

confidence: 99%

Glycogen Utilization in Wheelchair-Dependent Athletes*

Skrinar¹,

Evans²,

Ornstein³

et al. 1982

Seven wheelchair-dependent endurance athletes (5 males, 2 females, mean age = 27 years, mean VO2 max = 2.01 1/min) consented to maximal and submaximal (SM) testing on a wheelchair ergometer for the purpose of determining aerobic capacity, plasma substrate concentration, and muscle glycogen utilization during prolonged exercise. Results from an initial graded maximal test were used to determine exercise intensity levels during a subsequent 1-h submaximal endurance ride on the wheelchair ergometer (60%-70% VO2 max). Muscle biopsy samples (N = 5) were taken from the M. deltoideus (anterior head) before and after the submaximal exercise. Hematocrit (Hct), hemoglobin (Hb), glycerol (G), glucose (Glu), and free fatty acids (FFA) measured from venous blood taken before, midway, and at completion of the SM test demonstrated changes in plasma volume and substrate level similar to those of other athletes observed while running on a treadmill or exercising on a cycle ergometer. Type I fibers were characteristically depleted of glycogen, as measured by PAS stain, as a result of the SM endurance ride. Pre-exercise glycogen values were similar among subjects (means = 92.46 mmol X kg-1 +/- SEM 1.8) while muscle glycogen utilization varied from 17.4 to 46.6 mmol X kg-1. These findings indicate that physiologic response patterns of the upper arm muscles of trained wheelchair athletes during acute endurance exercise correspond to those observed in the leg muscles of able-bodied endurance athletes.