To determine whether pre-exercise muscle glycogen levels influence the ergogenic benefits derived from carbohydrate (CHO) feedings during exercise, eight experienced cyclists completed four, 1680 kJ isokinetic cycling trials as quickly as possible. Trials were conducted under the following pre-exercise muscle glycogen (vastus lateralis) and feeding conditions: 1) high glycogen (180.2 ± 9.7 mmol•kg ww-1) with carbohydrate feedings during exercise (HGCHO trial), 2) high glycogen (170.2 ± 10.4 mmol•kg ww-1) with placebo feedings during exercise (HG-PLA trial), 3) low glycogen (99.8 ± 6.0 mmol•kg ww-1) with carbohydrate feedings during exercise (LG-CHO trial), and 4) low glycogen (109.7 ± 5.3 mmol-kg ww-1) with placebo feedings during exercise (LG-PLA trial). The placebo feedings contained no CHO. The CHO feedings provided 116 ± 6 g CHO•trial-1 and prevented the fall in serum glucose that occurred during both placebo trials. Performance times for the HG-CHO, HGPLA, LG-CHO, and LG-PLA trials averaged 117.18 ± 1.44, 118.67 ± 1.84, 121.18 ± 1.88 (P<0.05 vs. HG-CHO), and 122.91 ± 2.46 (P<0.05 vs. HG-CHO, HG-PLA) min, respectively. There were no between trial differences in relative V02 (75 ± 2 % of V02 max) or self-selected pace (8.42 ± 0.14 min-120 kJ-1) during the initial 1200 kJ of exercise. During the remaining 480 kJ, pace was similar under the HG-CHO, HG-PLA, and LG-CHO conditions (8.59 ± 0.14 min-1 20 kJ-1) but was significantly slower over the final 240 kJ of the LG-PLA trial (9.67 ± 0.43 min. 120 kJ-1). In conclusion, when pre-exercise muscle glycogen levels were low, CHO feedings enabled subjects to maintain their optimal pace throughout the exercise bout, but when pre-exercise glycogen levels were elevated, CHO feedings provided no ergogenic benefit. / Human Performance Laboratory
| Identifer | oai:union.ndltd.org:BSU/oai:cardinalscholar.bsu.edu:handle/181942 |
| Date | January 1992 |
| Creators | Widrick, Jeffrey J. |
| Contributors | Costill, David L. |
| Source Sets | Ball State University |
| Detected Language | English |
| Format | vii, 84 leaves : ill. ; 28 cm. |
| Source | Virtual Press |
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