After an intensive workout the body expends extra energy. Researchers suspect that because of this, strength training can help in maintaining a healthy weight, and they are studying ways of increasing the ‘after burn’. One such method is to consume caffeine before pumping iron, as sports scientists at California State University discovered.
After a demanding workout muscle cells need to recover. They need to replenish their creatine phosphate and glycogen reserves and restore their buffers. We’re not even talking about the recovery of damaged muscle proteins, but this process costs energy too. Researchers measure this increased energy expenditure by measuring oxygen consumption; when the latter is higher, it is called elevated post-exercise oxygen consumption, or EPOC for short.
As far back as 1989 researchers showed that caffeine [structural formula shown below] raised the EPOC of untrained women after a cardio training session. [Eur J Appl Physiol Occup Physiol. 1989; 59(1-2): 48-54.] [Eur J Appl Physiol Occup Physiol. 1992; 65(5): 459-63.]
But does this also happen after a strength training session? And in men who are experienced strength trainers? To answer this question the researchers devised an experiment in which 14 experienced strength athletes aged between 18 and 34 took part.
The test subjects completed the training schedule shown below twice. On one occasion they took a placebo before training and on the other occasion they took 6 mg caffeine per kg bodyweight. For two days before the experiment started the subjects abstained from all foods and beverages containing caffeine.
The caffeine supplement increased the intensity of the training, as you can see in the table below. The mild stimulant raised the post-training energy expenditure by 15 percent, and also reduced the RER. That means that the body was deriving less energy from carbohydrates and more from fat.
When they took the supplement the test subjects burned 24 calories more. That’s not a huge amount, in the researchers’ opinion. But of course everyone is entitled to his (or her) own opinion.
Effect of acute caffeine ingestion on EPOC after intense resistance training.
This study investigated the effect of acute caffeine (CAF) intake on postexercise oxygen consumption (EPOC) after intense resistance training.
Fourteen strength-trained men (mean ± SD age and mass =23.1 ± 4.2 yr and 83.4 ± 13.2 kg, respectively) who were caffeine users initially completed one-repetition maximum testing (1-RM) of four exercises: bench press, leg press, lat row, and shoulder press. On each of two days separated by one week, they completed four sets of each exercise to fatigue at 70-80% 1-RM, which was preceded by ingestion of CAF (6 mg/kg) or placebo. Pre-exercise, indirect calorimetry was used to assess energy expenditure for 35 min; this was repeated for 75 min postexercise while subjects remained seated in a quiet lab. Two-way analysis of variance with repeated measures was used to examine differences in gas exchange variables across time and treatment.
Results revealed that EPOC was significantly higher (P<0.05) with CAF (26.7 ± 4.1 L) compared to placebo (22.8 ± 3.8 L). With CAF ingestion, oxygen uptake was significantly higher (P<0.05) from 10 min pre-exercise to 70 min postexercise. Respiratory exchange ratio was significantly different (P<0.05) with CAF versus placebo. Caffeine intake increased total energy expenditure by 15% (P<0.05), but the additional calories burned was minimal (+27 kcal).
Caffeine ingestion in individuals regularly completing rigorous resistance training significantly increases EPOC and energy expenditure pre-and post-exercise, yet the magnitude of this effect is relatively small.
PMID: 21297558 [PubMed – indexed for MEDLINE]