A strength training session in which you burn, say, 300 calories burns more calories than a cardio session where you burn 300 calories on the treadmill. Impossible? No it's not. At least, if you take into account the raised calorie burning after training.
Yes, we're talking about elevated post-exercise oxygen consumption, or EPOC: the phenomenon whereby your body burns more oxygen, and therefore also more calories, after a training session. Sports scientists only started studying this effect in the nineties, but the results of their research indicate that, for people who want to control their weight, strength training is a good alternative to endurance and cardio training.
In 2005 researchers at Shippensburg University in the US published the results of a human study in the European Journal of Applied Physiology. For this they had got eight women, average age 31, to undergo two training sessions. On one occasion the women did weight training [CT]. They did three sets of leg-presses, knee-extensions, leg-curls, biceps-curls, triceps-extensions and bench presses with 65 percent of the weight at which they could just manage one rep. Between each set the women rested for 30 seconds, and after each exercise for two minutes.
On the other occasion the women ran on a treadmill. The researchers increased the intensity slightly every three minutes until the women were running at 85 percent of their maximal heart rate [TM]. The women stopped running when they had burned as many calories as they had done during the strength training session.
During the first hour after each training session the researchers measured how much oxygen [and therefore calories] the women burned. In the figure below you see that in the first hour after both training sessions the women's oxygen expenditure was higher than before the training session. In the first half hour, oxygen expenditure was significantly higher after the CT training than after the TM training.
The graph above shows the respiratory exchange ration [RER]. This is the ratio between inhaled and exhaled oxygen. The lower the RER, the more calories you burn from fat and the fewer from carbs. So the women derived most of the energy for their EPOC after the strength training session from fat.
The researchers suspect that strength training uses relatively large amounts of energy that does not come directly from combustion processes, and which are therefore not visible if you just measure oxygen use during a training session. Restoration of the unnoticed energy reserves only shows up, in terms of oxygen expenditure, after the training session.
Eur J Appl Physiol. 2005 Aug;94(5-6):500-4.