How to Build Muscle: The Science Behind Muscle Growth

building muscle

How to Build Muscle | Muscle-Building Nutrition | Muscle-Building Supplements | Hypertrophy Training | Strength Training | Chest Workouts | Back Workouts | Arm Workouts | Shoulder Workouts | Leg Workouts

The desire to look and feel better is typically what motivates many people to join a gym or start working out. And muscle building plays a key role in transforming your physique. Muscle building increases lean muscle mass by growing muscle cells and fibers. While cardio workouts provide overall health and cardiovascular benefits, focused strength training is what carves out your body for a tighter, more toned look.

But first, it’s important to take a look at how to build muscle. In this guide, we’ll cover why building muscle is so important, its science, and the fundamental principles that can help you achieve it.

Benefits of Building Muscle

Building muscle provides more benefits than just making you look better and feel stronger. It’s a healthy goal for all adults to maintain and build muscle mass, not just people trying to emphasize their physique. Adults start losing muscle mass at age 30, and research suggests that physically inactive people lose 3-5 percent of their lean muscle mass every ten years. To prevent this loss, muscles need to be stressed through regular strength training.

Incorporating strength and resistance training into your workouts can help:

  • Manage weight by increasing lean muscle mass, which burns more calories
  • Increase bone density and promote strong bones
  • Protect joints from injury and decrease the risks of falls as you age
  • Reduce symptoms of some chronic conditions, such as heart disease, depression, and diabetes

How Long Does it Take to Build Muscle?

You might be wondering—just how long does it take to build muscle? It’s difficult to say how long it takes a person to build muscle as every individual is different. Factors such as genetics, gender, age, hormones, diet, and exercise routine can all play a role in the timeline for gaining muscle.

In general, you’ll likely start to build muscle before physically seeing the results of your hard work. Building muscle with consistent workouts and nutrition typically takes several months and happens over a long period of time. But those new to lifting can experience a phenomenon called "newbie gains". This means beginner lifters can build muscle faster than experienced lifters because their bodies are shocked by this new form of training.

If you fall into that beginner-lifter category, the maximum amount of muscle you can gain in one month is around one to four pounds. This is typically enough for most people to start seeing some definition.

Your workout frequency and duration also greatly affect how long it takes to build muscle. Consistency is key, especially for strength training. If you’re just trying to up your physical fitness, you should aim to strength train twice a week. These sessions can take as little as 20-30 minutes and still be effective. During strength training sessions, aim for 8-10 exercises targeting major muscle groups. Perform 8-12 repetitions of each exercise and 2-3 sets of repetitions.

If you have bigger goals for building muscle, aim to train at least three to four days a week. It sounds kind of obvious, but regularly training your muscles is the best way to build muscle. So, if you want to see definition sooner rather than later, develop a consistent lifting routine.

No gym equipment is needed to start, as body weight alone helps build strength and muscle. Over time, you can add additional weights or more complex movements. Body weight exercises include movements such as push-ups, planks, lunges, and squats without holding additional weights. Free weights, weight machines, medicine balls, and resistance bands are additional tools to build muscle.

Science: How to Build Muscle

When you’re trying to build muscle, there are three important scientific concepts to keep in mind: mechanical tension, muscle damage, and metabolic stress.

Mechanical Tension

Mechanical tension may be the most critical factor for muscle growth. For your muscles to experience mechanical tension, you have to perform resistance training of some kind. For example, performing a bicep curl with a dumbbell or barbell causes tension in the bicep muscles. Don’t be afraid to push yourself. In fact, when it comes to muscle building, pushing yourself when it comes to weight is the best way to see results. By using a weight that feels challenging, you’ll set yourself up for optimal mechanical tension, and thus, muscle growth.

Muscle Damage

Strength training, such as weight lifting, causes trauma to your muscles. Cells in your muscle fibers repair the damage caused by the strength training, and the muscle fibers increase in size. This process makes the muscle bigger over time as the size of muscle fibers continues to increase. Resistance training also helps your body release growth hormones naturally, which helps turn free amino acids into proteins that increase muscle size.

Metabolic Stress

During a strength workout, fatigue in muscles leads to a build-up of metabolites (leftovers from the chemical reactions that happen when your muscles use energy), such as lactate and hydrogen ions. These metabolites cause the release of hormones and other byproducts that cause muscles to grow. Different types of training like low-intensity resistance training and high-intensity interval training can maximize metabolic stress during workouts.


Principles: How to Gain Muscle

Hypertrophy Training

Hypertrophy training involves doing more sets and repetitions of movements, then resting between sets. For example, you could do 6-12 repetitions in a set, rest for 60-90 seconds, then do another set of 6-12 repetitions, rest for 60-90 seconds, and do one more set. At this point, the muscles start to fatigue which should help with hypertrophy.

Use a weight that allows you to complete all repetitions but still feels challenging at the end of a set. By the end of your set, you shouldn’t feel like you can perform 1 more rep. If you do, then either increase your weight or reps until you do get to that point.

Intensity Techniques

To increase intensity in a workout, consider these techniques:

  • Use heavier weights and decrease the number of repetitions performed.
  • Decrease rest time in between sets.
  • Increase the time under tension by slowing down the movement or pausing for a few seconds while the muscle is contracted.

Major Muscle Groups

To build muscle most effectively:

  • Focus your strength training sessions on the major muscle groups.
  • Rotate sections of the body that you strength train.
  • Allow at least one day of recovery between workouts focusing on a particular muscle group. For example, you could train your upper body and abdominal muscles one day, then train your legs the next day.

Your major muscle groups include:

Upper body


  • Abdominal muscles
  • Lower back


  • Gluteal muscles (buttocks)
  • Quadriceps
  • Calf muscles
  • Hamstrings


Nutrition is critical to building muscle. Even if you follow all the other principles to gain muscle, you won’t build muscle effectively if you aren’t eating enough of the right types and combinations of foods.


  • Timing of meals and snacks: Meal and snack times need to be strategic to gain muscle. Eat a carbohydrate and protein-rich snack before strength training, such as half of peanut butter and jelly on whole-wheat bread. After a workout, refuel with carbohydrate and protein-rich snacks, such as 1 cup of 2% Greek yogurt with berries and granola. Eat frequently throughout the day to ensure a steady supply of fuel and amino acids for your muscles.
  • Calories: It’s essential to consume enough calories when trying to build muscle. If calorie intake is too low, protein is converted into glucose and used for energy instead of muscle repair and growth. Caloric needs depend on various factors, including age, body size, gender, and activity level.
  • Protein: Protein is essential for muscle healing after workouts and the growth of muscles. However, your body can only use about 30 grams of protein at a time, so it’s best to eat adequate amounts of protein and balanced meals and snacks. Spread protein throughout the day, and include a good source of protein at all meals and snacks. An adult needs about 0.7-0.8 grams of protein per pound of body weight to gain muscle mass, which is about 110-120 grams per day for a person who weighs 150 pounds.
  • Carbohydrates: Carbs are essential for growth because they fuel your muscles. Healthy sources of carbohydrates, like whole grains, fruits, and starchy vegetables, should be included in the diet to ensure adequate energy for workouts, and to refuel muscles between workouts.
  • Fat: Rather than strictly limiting fats, focus on incorporating healthy fats. Healthy fats include foods such as avocado, olive oil, chia seeds, oily fish, and nuts.

Our Top Tips for Building Muscle

  • Consider working with a licensed professional trainer if you need help learning proper form and technique. Trainers can guide you if you aren’t sure where to start with a strength training regimen or need help choosing which exercises to combine in a workout.
  • Consider working with a dietitian if you need help with the diet portion of muscle building. A registered dietitian can help make a meal plan and suggest foods that would work for your goals and help you grow muscle.
  • Get plenty of rest. Make sure to sleep 7-9 hours every night, and allow up to 48 hours between workouts for muscle tissues to recover from the previous exercise. Recovery time is essential for muscle growth.
  • Strength train two times per week minimum, and up to five to six times per week if you have bigger goals.
  • Rotate muscle groups to allow muscles to recover between workout sessions.
  • Try to train with free weights for the majority of your workout, such as dumbbells, barbells (long bars with weights added), or kettlebells, instead of using machines. Machines increase fitness, but workouts with free weights engage more muscles in each movement.
  • Increase to heavier weights when the weights start to feel too easy. Muscle tissues grow when they are challenged.
  • Try compound movements that work multiple muscles at once. Squats and bench press are good examples of this.
  • Consider joining a group fitness class that incorporates strength training at a gym if you need external accountability and motivation.

Get Support

Learning how to build muscle requires some understanding of the principles and science behind strength training. As always, check with a physician before starting a new workout regimen, especially if you have a known health condition. Consider including additional support from fitness experts and nutritionists to better understand the best way for your body to build muscle.

How to Build Muscle | Muscle-Building Nutrition | Muscle-Building Supplements | Hypertrophy Training | Strength Training | Chest Workouts | Back Workouts | Arm Workouts | Shoulder Workouts | Leg Workouts

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