Abstract 

Background: Running is a sport for everyone. The sport continues to grow in popularity, probably due to its accessibility and many health benefits such as stress reduction and increased maximal oxygen consumption. During high-intensity exercise, lactate is generated from anaerobic metabolism, in regions with high glucose levels or where glycolysis is active. One way to measure a runner's endurance is the amount of lactate in the blood. The relationship between lactate accumulation (LA) and perceived exertion (RPE) with added carbohydrates during shorter durations of running is uncertain. However, extra carbohydrates seem to be beneficial because they can delay fatigue and time to exhaustion. 

Aim: This study aimed to investigate whether glucose ingested before treadmill running had an impact on LA and the rate of RPE in exercise runners. It was also investigated whether LA is associated with RPE according to the BORG scale. 

Methods: In this study with a crossover design, 15 healthy runners, two women and 13 men, were included. The participants ran at least 10 kilometers during one exercise session per week. The intervention consisted of 4 or 5 speed-increasing intervals lasting 4 minutes per interval. LA and RPE were measured continuously during the intervals. In the first intervention, participants fasted for 90 minutes before the measurement. In the second intervention, a glucose amount of 1g/kg body weight was also ingested before the measurement. Paired t-tests were used to statistically analyze the influence of glucose on LA and RPE. Spearman's correlation coefficient was used to analyze the relationship between LA and RPE (r-value). Two graphs were generated to illustrate the correlation between the LA values from the first and the second intervention and similarly for the correlation between the RPE values. 

Results: As expected, LA increased with each increasing interval, reflecting the trend in RPE, which also consistently increased during the measurement. At the time of LA, the interpolated speed (km/h) during the first intervention without added glucose (14.5) was higher than the second intervention with added glucose (13.6). A fair correlation (-0.475) was found between LA and RPE for the second interval where LA increased as RPE decreased. 

Conclusion: In this study, glucose showed no significant differences for LA or RPE. However, we found that glucose strengthened the association between LA and RPE, which means that glucose does not have an effect on LA or RPE during speed-increasing running intervals.