Study note • PMID 9624641
Pre-exercise carbohydrate ingestion: effect of the glycemic index on endurance exercise performance.
Worth trying if it fits your goal and context.
ELI5
In plain language
This study aimed to examine the effect of glycemic index of pre-exercise carbohydrate (CHO) ingestion on exercise metabolism and performance. (controlled study; trained participants).
The abstract doesn’t indicate a clear change in Time-trial performance under the tested conditions. Treat this as a signal, not a guarantee; confirm methods and context in the full paper.
Takeaways
What the abstract suggests
- • Study question: This study aimed to examine the effect of glycemic index of pre-exercise carbohydrate (CHO) ingestion on exercise metabolism and performance.
- • The abstract doesn’t indicate a clear change in Time-trial performance under the tested conditions.
- • Population: trained participants.
- • Protocol cues (title/abstract): 45 min • 50 min • 30 min • 10 min • 67% VO2max.
Protocol
Protocol (as reported)
- • Intervention/exposure: carbohydrate, carb (vs placebo).
- • Dose/time/duration cues in abstract/title: 45 min • 50 min • 30 min • 10 min • 67% VO2max.
- • Outcomes: Time to exhaustion, Time-trial performance, Fat oxidation.
- • Replication note: abstracts often omit adherence and timing; confirm details before changing training or supplementation.
Fit
Who it helps, and who should skip it
Who it helps
- • Athletes similar to the study population (trained participants) working on fueling.
- • Athletes who can measure Time to exhaustion, Time-trial performance, Fat oxidation with a repeatable workout or time-trial effort.
Who should skip
- • If you have symptoms or conditions that make the intervention risky, get professional guidance.
- • If you’re near race day and can’t safely test, defer the experiment.
Methods
What the study actually did
- • Design: controlled study (placebo-controlled).
- • Population: trained participants.
- • Comparator: placebo.
- • Outcomes measured: Time to exhaustion, Time-trial performance, Fat oxidation.
- • Protocol cues mentioned: 45 min • 50 min • 30 min • 10 min • 67% VO2max.
- • Source: PubMed PMID 9624641 (1998) — Medicine and science in sports and exercise.
Results excerpt
What the abstract reports
“Plasma glucose concentrations were higher (P < 0.01) after ingestion in HGI compared with LGI and CON (7.53 +/- 0.64 vs 5.55 +/- 0.21 and 4.65 +/- 0.14 mmol.L-1 for HGI, LGI, and CON, respectively, 30 min postprandial; mean +/- SE) but declined…”
Note: excerpts are short; for full context, read the paper.
Limits
Limitations & bias
- • Abstract-only summaries can miss critical details (population, protocol, adherence, and context).
- • Single studies often don’t generalize to your event, history, and training load; treat results as a starting point.
- • If your context differs (elite vs recreational; cycling vs running), adjust expectations and be conservative.
- • This is performance information, not medical advice.
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Practical performance outcome used in many studies: closer to racing than lab-only metrics.