Building Muscle: Results in Less Than Six Weeks?

One of the most frustrating aspects of weight training is it time to see results. Muscles grow when they’re challenged by progressively greater amounts of resistance over time and are forced to adapt by becoming larger. Resistance-trained muscles not only become more defined, they become stronger too. Most fitness experts will tell you it takes 6 to 8 weeks of heavy resistance training to see a change in muscle size, but a new study challenges that assumption. According to this study, muscle growth may occur as early as 3 weeks after starting a strength training program.

Muscle Growth and Strength Training: Does It Happen Sooner Than We Think?

In a study published in the European Journal of Physiology, researchers put twenty-five previously sedentary men through a challenging 2-month resistance training program. The men strength trained 3 days a week during the 2 month period. Their training regimen consisted of three sets of bench press, leg extension and leg press to failure with 2 minutes of rest between sets.

The researchers followed the men’s progress by measuring the cross-sectional area of their thigh muscles on a weekly basis using CT scanning. You would expect this method of measuring thigh circumference to be more accurate than using a tape measure. Using CT scanning, they found a slight increase in thigh circumference in these men at the end of the first week. It’s not unusual for muscles to increase slightly in size due to fluid retention early in strength training. That’s why your muscles look a little more defined when you first start strength training.

What’s more surprising is their thigh cross-sectional area continued to increase each week that it was measured. Further increases in size after the third week of training aren’t so easily explained by muscle swelling and are more likely to be due to true muscle hypertrophy or enlargement. Based on these results, the researchers in this study believe muscle enlargement may begin as early as the third week of training. That’s good news if like immediate gratification.

Other studies also support the idea that muscle growth occurs early in the course of strength training. To get muscle hypertrophy, new muscle satellite stem cells need to be activated and protein synthesis has to be ramped up. According to research published in the Journal of Applied Physiology, muscle stem cells start to increase as early as 4 days after a strength training session, and protein synthesis goes up within 5 hours after a workout.

Strength Gains Occur Early Too

When you first start strength training, you’ll find that you’re stronger after only a few workouts, but this increase in strength isn’t due to an increase in muscle size. It’s due to neural adaptions. Muscle fibers are organized into motor units. Each motor unit contains multiple muscle fibers and a nerve cell. When more motor units are activated and when they’re able to work better together as a unit, it increases the amount you can lift. Neural adaptations that make this possible early in a strength training workout before there’s evidence of muscle hypertrophy. So, you become stronger before your muscles change in size. That’s why you can lift more weight early in a training program even though your muscles don’t look larger.

The Bottom Line?

It takes time to build muscle, but muscles may increase in size as early as 3 weeks after starting a strength-training routine. You’ll also be stronger since neural adaptations take place after only a few workouts that increase the amount of weight you can lift. Keep lifting. You may be getting benefits faster than you think.



Eur. J. Appl. Physiol. 2011 Nov; 111(11): 2785-90.
Journal of Applied Physiology January 2007 vol. 102 no. 1 368-373.