Good or Bad: Weight Training and Aerobic exercise on the same day?

Article: Mixing weight training and aerobics – by, Gretchen Reynolds – NYTimes.Com

(May 2012)

The article poses the question: Should we weight train and perform aerobic exercise in the same day?

Many fitness enthusiests, professional athletes, and coaches believe that weight training and performing aerobic exercise on the same day reduces the ability of muscles to strengthen and grow.

Alternatively, many other fitness enthusiests, professional athletes, and coaches believe weight training, performed on the same day as aerobic exercise, enhances the endurance training response. 

However, to date, there has been little science supporting or challenging the existence of muscle interference.

There were two groups of scientists involved in the research study: scientists from McMaster University in Ontario, Canada and scientists from the Karolinska Institute in Sweden.

Below is a table of their data:


McMaster University (Ontario, Canada) Karolinska Institute (Sweden)
VOLUNTEERS (NO WOMEN) Sedentary, middle-ages men that do not exercise much, if at all, over the course of the year Healthy and active young men, mostly college students, who regularly work out, but do not compete
EXERCISE PROTOCOLS 3 separate trials –  1.) Riding a stationary bike for 40 minutes at moderate pace; 2.) Another day, 8 strenuous sets of leg extension exercises; and 3.) 4 sets of leg extension exercises, then riding a stationary bike for 20 minutes. Begin by riding a stationary bike for 45 minutes using one leg (aerobic); 6 hours later, complete a series of strenuous leg extension exercises with both legs.
MUSCLE BIOPSIES Before and After each session Before and After each session

The professor of Kinesiology, Stuart Phillips, from McMaster University – who oversaw the Canadian study – hypothesized that they would see a greater response when the exercises were performed individually. 

More specifically, the Canadian scientists expected endurance training, on its own, to significantly affect portions of the muscle cell related to energy production, while resistance training would increase protein synthesis within the muscles, which is the first step to enlarging them.

Overall, the Scientists thought that combined training would dampen at least one of the molecular changes; physiologically, one of the responses would predominate and interfere with the other.

However, they were wrong.

Instead, after combined training, the men’s muscles displayed the same amount of change within both cellular pathways as after either type of exercise on its own, even though they had only completed ½ as much of each.

Dr. Phillips said there was no indication of interference.

The Swedish had similar results:  Their study showed little difference in the genetic and biomechanical responses within muscles whether men performed both aerobic and resistance training or aerobic training alone.


The scientists concluded that aerobic exercise can precede resistance exercise on the same day without compromising muscle building.  Also, if you prefer to weight train first, you will not affect your muscle building.

**Both studies looked only at immediate results.  However, Dr. Phillips believes that over the long term, the effects should be the same.


There is very controversial opinions among physical trainers about this topic, which is why the article caught my attention. 

In my opinion, it is important to combine both weight training and cardio (aerobic exercise) into ones workout regimen in order to see the best results, both physically and internally.

When I work out, I try to perform both my weight training and cardio on the same day, usually beginning with weight training (because my main focus is to lean out) and then finishing up with cardio.  The reason I perform my cardio last is so that I do not use up my energy resources during cardio, disallowing myself to give it my all during weight training.  I believe that cardio is cardio, and you will have the same affect performing cardio no matter what your energy levels are.






  1. I enjoy doing both on the same day.

  2. Pingback: Top Posts and Pages from 2012 – Jenna Carelli

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