Related Experiment Videos
Failure of caffeine to affect substrate utilization during prolonged running
Insights
Caffeine ingestion in well-trained marathoners elevated free fatty acids but did not alter substrate utilization during treadmill running. Perceived exertion decreased with both caffeinated and decaffeinated coffee compared to a control.
Area of Science:
- Exercise Physiology
- Nutritional Biochemistry
Background:
- Caffeine is a widely used ergogenic aid in endurance sports.
- Its effects on substrate metabolism and performance in highly trained athletes require further investigation.
Purpose of the Study:
- To investigate the impact of caffeine on substrate utilization and perceived exertion during submaximal treadmill running in elite male marathoners.
- To determine if caffeine alters key metabolic markers and physiological responses in trained endurance athletes.
Main Methods:
- Nine sub-3-hour male marathoners completed three 45-minute treadmill runs at 75% VO2max.
- Participants consumed decaffeinated coffee or decaffeinated coffee with 400mg caffeine in a randomized, double-blind, crossover design.
- Blood samples (free fatty acids, triglycerides, glucose, lactic acid) and respiratory measures (VO2, VCO2, R, VE) were analyzed.
Main Results:
- Caffeine ingestion significantly increased plasma free fatty acids and lactic acid concentration prior to exercise.
- No significant differences were observed in oxygen consumption (VO2), carbon dioxide production (VCO2), or respiratory exchange ratio (R) between conditions.
- Perceived exertion was significantly lower in both caffeine and decaffeinated conditions compared to the control run.
Conclusions:
- While caffeine elevates pre-exercise free fatty acids, it does not appear to alter substrate utilization during submaximal running in well-trained marathoners.
- Caffeine and decaffeinated coffee may reduce perceived exertion during prolonged exercise in this population.
Abstract:
Nine sub-3-h male marathoners performed three 45-min monitored treadmill runs at approximately 75% of VO2max during a 2-wk period. The men were assigned in a random, double-blind fashion following the control run to receive either 350 ml of decaffeinated coffee or 350 ml of decaffeinated coffee with 400 mg of caffeine added 1 h before the second run with crossover to the other beverage for the third run. Venous blood was analyzed for free fatty acids, triglycerides, glucose, and lactic acid before beverage consumption and before and after each run. Oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory exchange ratio (R), ventilation (VE), and perceived exertion were measured at 15, 30, and 45 min of each run. Of the blood parameters, free fatty acid and lactic acid concentration increased following caffeine ingestion. There was no difference in VO2, VCO2, or R between the three runs. Perceived exertion showed a significant decrease (P less than 0.05) at each time point in caffeine added and decaffeinated compared to control. Triglycerides, glucose, and lactic acid increased similarly in all three runs. In these well-trained marathoners, although plasma free fatty acids were elevated significantly prior to exercise after caffeine ingestion, there was no indirect evidence of altered substrate utilization during subsequent treadmill running.