Is it best to mix aerobics and weight training on the same day?

It is advisable to do weight training and aerobic exercise on the same day? This is a common, and controversial, question among physically active individuals. Many believe that aerobic exercise practiced on the same day as weight training reduces the capacity of muscle cells to hypertrophy (grow). On the other hand, others claim that weight training performed on the same day as aerobic exercise will decrease the benefits of the aerobic activity.

To provide more scientific background to the debate and try to answer the question, two studies were carried out—one at McMaster University in Canada, and another at the Karolinska Institute in Sweden—and the results were recently released.

In the Swedish study, published in the March issue of Medicine & Science in Sports & Exercise, volunteers first rode a stationary bicycle for 45 minutes using only one leg; an action that provided the aerobic component of the experiment. Six hours later, they performed with both legs a series of strenuous leg extension exercises, so that each participant had one leg subjected to combined exercise (aerobic + weight training) the same day, while the other leg experienced only aerobic exercise. The scientists performed muscle biopsies before and after each exercise session.

In the Canadian study, published last month in The Journal of Applied Physiology, the volunteers performed three separate workouts. In the first, the subjects rode an ergometric bicycle for 40 minutes at a moderate pace. The next day, the same volunteers performed eight sets of relatively strenuous leg extension exercises. In the final session, both types of exercises were preformed on the same day: four sets of leg extensions and then bike riding for 20 minutes. As in the Swedish study, scientists performed muscle biopsies before and after each session.

In the Swedish study the study volunteers were otherwise active and healthy young men. In the Canadian study, the subjects were sedentary middle-aged men.

According to Professor Stuart Pillips, who oversaw the Canadian study, the hypothesis was that there would be a greater response when the exercises were done individually,  on separate days. They expected the aerobic exercise would significantly affect the production of mitochondria (structures within cells responsible for energy production) in the muscle cells, whereas the weight training would stimulate protein synthesis in muscles, the first step for their growth.

For the combined training Canadian scientists hypothesized that at least one of these changes would be reduced, and one response would predominate and interfere with the other. However, it did not. Instead, after the combined training, the muscles showed the same amount of cellular changes observed as when exercise was carried out on separate days. So, surprisingly, there was no interference.

The Swedish researchers reached a similar result. The study showed little difference in genetic and biomechanical responses within the muscles of the volunteers who underwent cardiovascular and weight training. In other words, the scientists concluded that aerobic exercise may precede weight training on the same day without compromising muscle development. And while the studies were conducted only in men, the researchers believe that the results would be similar in women.

Now that you know you can do both types of exercises on the same day, make a workout routine that is most convenient for you, mixing aerobic and weight training as you wish.  A good start of the week to everyone!

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