How to calculate calorie expenditure during strength training

During cardio training, a consistently elevated heart rate allows you to easily calculate the calories burned. With strength training, everything is more complicated, since they alternate periods of work and rest between approaches.

When you perform a set of any exercise, your heart rate increases, and when you rest, it decreases. But even at this time, you spend more calories than at rest, due to the oxygen debt – excess O₂ consumption after intense work.

Moreover, you will continue to spend more energy after you leave the gym, until the body returns to a calm state. All this complicates the calculations, so the only way to say exactly how much you spend is with a gas analyzer – a special mask that is put on your face during training, then the amount of oxygen consumed is determined and calories are counted.

At the same time, based on research data, we can roughly imagine how much energy strength training spends.

How Many Calories Does Strength Training Burn

In one study, scientists tested how many calories men and women would burn during strength training. Participants performed eight strength exercises, each with one set of 15 repetitions. The weight of the weights was chosen so that a person could perform the exercise exactly 15 times.

The scientists calculated the energy expenditure and found that men spent an average of 5.6 kcal per minute during training, and women – 3.4 kcal per minute. This is not surprising, given that the average weight of women was 62 kg, and men – 90 kg, and the latter had significantly more muscle mass.

In another experiment, for a full workout of 10 exercises, each of which was performed in three sets of 10 times and resting for a minute, women spent about 155 kcal. And then an additional 31 kcal during recovery due to oxygen debt. The workout lasted 45 minutes, so we can conclude that they again spent about 3.4 kcal per minute. The average age of the women was 29 years old, the average weight was 59 kg.

During strength training, women spend about 3.4 kcal per minute, and men – about 5-6 kcal per minute.

It does not really matter whether you work with heavy weights for a small number of repetitions or choose lighter equipment and do 10-15 repetitions with them. At least if you perform the exercises until your muscles are significantly fatigued.

In one study, scientists decided to calculate how much energy is spent on strength training with different intensities. Young trained men performed classic strength exercises: bench press, squats, pull-ups on the block and others, and scientists used a gas analyzer to find out how many calories they spent.

The study authors tested three training modes:

1. Low intensity — 2 sets of 15 reps with 60% of the one-repetition maximum. That is, from the weight with which you can do the exercise only once.
2. Medium intensity — 3 sets of 10 reps with 75% of 1RM.
3. High intensity — 6 sets of 5 reps with 90% of 1RM.

In all modes, the men rested for 2 minutes between sets.

As a result, it turned out that high-intensity strength training helped the participants burn about 610 kcal, medium — 360 kcal, and low — 283 kcal. But this difference arose solely due to the duration of the workouts. Low-intensity exercises took only 44 minutes, medium — 61 minutes, and high — 116 minutes.

It turns out that during low-intensity strength training, men spent about 6.4 kcal/min, with medium intensity – 5.9 kcal/min, and with high intensity – 5.2 kcal/min. A greater number of repetitions with a small weight turned out to be more energy-consuming than short approaches with heavy weights. Although if people had been training for the same amount of time, the difference in energy expenditure would still be small – only about 50 kcal.

On the other hand, in this study, scientists did not evaluate oxygen debt. There is reason to believe that after heavy strength exercises, people consume more oxygen and spend more calories at rest than after training with medium intensity. However, all this has not been studied well enough.

How to calculate how many calories you burned during strength training

You can roughly calculate the number of calories burned by multiplying the time of your workout by the approximate energy expenditure for women and men – 3.4 kcal / min and 5.6 kcal / min, respectively.

But here it is necessary to take into account that the studies where these figures were obtained were young people with a small percentage of fat. Men and women with a different body composition may spend less energy.

Energy expenditure during training can vary depending on the following factors.

1. Rest time between sets. In studies, people rested between sets and repetitions for a fixed 60-120 seconds. If you talk for a long time with other exercisers or forget yourself, scrolling through the feed on a social network, much fewer calories may be burned during training. And vice versa: if you reduce the amount of rest, energy expenditure will increase.
2. Body composition. Since muscles consume energy, and fat serves as its source, body composition directly affects calorie expenditure. The more muscles a person has, the more energy they spend both at rest and during exercise.
3. Fitness level. The longer you do an activity, the fewer calories you spend on it. This happens because when learning new skills, the body strains much more than necessary. Over time, the body gets used to the movement and finds the most effective way to perform it, so energy costs are reduced.

Of course, it is difficult to predict exactly how many calories you need to subtract or add if, for example, you rest for 5 minutes instead of 2. Or have a high percentage of fat mass and very little muscle. All that remains is to focus on the general values ​​and keep in mind that your energy costs may be slightly more or less than stated.

We tried entering the data of men from a study with three strength training modes and got values ​​that weren’t even close to those stated in the experiment results. According to the calculators, a man weighing 83 kg should spend 186-192 kcal in 44 minutes of average strength training, and if the training was hard – 373-383 kcal. In the study, men spent an average of 283 kcal. Thus, the calculators are off by about 100 kcal in either direction.

But with women, this tool works more or less accurately. If you check the data from the experiments above, the calculator is off by only 10 kcal.