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The Science Behind Building Strength

We live in the time of instant gratification. With technology giving us instant entertainment at our fingertips, package delivery in two days, and even groceries at our door step in an hour, it seems we do not have to wait for anything. Unfortunately, our bodies have not caught up with the trend of instant results. As a physical therapist, I am constantly reminding patients to, well, be PATIENT. This is especially true when it comes to seeing gains in muscle strength. If strength gains are not instant, how long does it take to build strength?

The answer to this question depends largely on why the muscle is weak and how weak the muscle actually is. Muscle strength is defined as the amount of force a muscle can generate with a single effort (1). There are several factors that may influence muscle strength, including your age, gender, muscle composition, your nervous system’s ability to fire your muscles, and most importantly, knowing how to properly strengthen your muscles.

Where do I start

It all comes down to whether the muscle is truly weak in the first place. You might have been told before by your physical therapist that your glutes or rotator cuff muscles are weak, but what we are really saying is that they appear weak. When a muscle appears weak, it has trouble activating. This might be because it has actually weakened (maybe due to surgery), but sometimes a muscle can’t activate because it doesn’t know how! The apparent weakness in a muscle can be due to poor motor control (how well it listens and responds to what your brain tells it to do) or poor understanding of what the muscle is meant to do.

Once a strength training program begins, the initial changes in muscle strength are due to changes in the way your brain connects with your muscles. We call this change neural adaptation (3). During the first weeks of strength training, your brain responds to training by recruiting more muscle fibers, or motor units, with each muscle contraction. This means you have more muscle fibers working in your favor to help you squat, lunge, or plank. These changes can be seen as quickly as one to two weeks of proper muscle activation.

When Will You See Results?

After six to eight weeks of training, if you’ve challenged your muscles sufficiently, your muscle fibers will actually start to increase in size. This further boosts muscle strength as the muscle cross-sectional area enlarges or “hypertrophies.” This is when you start to see the first signs of muscle enlargement and the much hoped for ripples when you flex your biceps.

How Much Weight and How Often Do I Need to Strength Train to See Results?

Resistance training should be performed two to three days a week for optimal gains. To see results in six to eight weeks, you need to be consistent with your strength training workouts. Our muscles build strength by breaking down and repairing themselves. Therefore, the weight should be heavy enough to cause the muscle to break down, but you also need to give that muscle enough time to repair itself. So if you are thinking that working the same muscle every day can help you get stronger, faster, think again. Stressing the same muscle with heavy weight multiples days in a row will only cause the muscle to break down, not rebuild.

How much weight is too much? When beginning, you should start with sets of ten. Repeat the exercise ten times, take a short (thirty to sixty second break) and repeat for three sets. The exercise should feel challenging, yet attainable. Once you can perform three sets of ten with ease, it is time to increase weights (3).

In short, don’t get frustrated if you don’t see your muscles changing right away. It takes time for our muscles to strengthen. With a consistent and challenging weight training program, you will see gains. Gains in muscle strength aren’t just for good looks either. Strong muscles will protect you from injury, improve your mobility, and make simple tasks, such as stairs or picking up your kids, easy.


1. Guide to Physical Therapist Practice. http://guidetoptpractice.apta.org/content/1/SEC20.extract
2. Neural Adaptations and Strength Training. Bridge Athletic, 2017. http://blog.bridgeathletic.com/neural-adaptations-and-strength-training
3. Exercise Physiology: Theory and Application to Fitness and Performance. Powers and Howley. 2009



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