One of the biggest misconceptions about gaining strength and muscle is that you have to go to a gym and lift weights go get big. The reality is, you only need to put your body in some sort of resistance to build strength and size.
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Your body has no idea where the resistance is coming from - as long as the resistance is strong enough to cause your body to work for it.
Weights are a great way to put your body under stress, but bodyweight training, calisthenics, gymnastics and kettlebell workouts can be as effective, and in some aspects even better.
Most strength coaches and personal trainers agree that pull ups are one of the best exercises one can do for back development, size and strength. No other pulling exercise builds functional capability better than a basic pull up.
If a basic pull up is good, how about the other bodyweight exercises?
Below is a body built 90% with bodyweight training alone. Eero Westerberg utilizes some weights work in his routines but he primarily focuses on calisthenics, movement and bodyweight training.
Bodyweight Exercises Tend To Have Superior Neuromuscular Activity
Charles Poliquin, a world-renowned strength coach, brought up a neuromuscular activity (NMA) test where different exercises were tested for their neuromuscular activity.
The researches put strength exercises into 7 different levels depending on their neuromuscular activity:
Compound vs. Isolation muscular activation (neuromuscular activity - NMA)
Level 1 – Isolation exercise on variable resistance machine (i.e. Leg extension on cam type machine i.e. Cybex Leg Extension, DAVID Leg curl)
Level 2 – Complex exercise on variable resistance machine (i.e. Leg press on Nautilus machine, LifeFitness Incline Press Machine)
Level 3 – Isolation exercise with constant resistance machine (i.e. Scott pulley curls, Triceps pressdown on pulley machine.)
Level 4 – Complex exercise with constant resistance machine (i.e. Leg press on standard machine)
Level 5 – Isolation exercise with free weights (i.e. Scott barbell curls, lying flyes)
Level 6 – complex exercise with free weights (Snatch pulls, power cleans)
Level 7 – complex exercise with free weights (i.e. Power Snatch, dips on rings, rope climbing)
Some basic bodyweight exercises such as dips on rings and rope climbing hit the level 7 together with very demanding weightlifting exercises such as the power snatch.
Truth be told, dips on rings are still basic bodyweight work. Yet, they still hit the highest level for neuromuscular activity!
The neuromuscular activity of the advanced bodyweight moves such as the front lever or the muscle-up will be much greater, and as a result, they will produce the biggest neuromuscular impact.
In other words, nothing beats advanced bodyweight exercises and advanced weightlifting exercises for building raw strength.
Why does neuromuscular activity matter?
Strength by nature is mostly neuromuscular. It is not as much as about the size of the muscle, as it is about the neuromuscular efficiency in the central nervous system (CNS).
When it comes to natural bodybuilding and building strength without the use of external substances, strength is the king for building muscle.
If you have the ability to do i.e. biceps curls for 10 reps with 25kg (50lbs), the body's reaction to the stress will be greater than doing 10 reps with just 12.5kg (25lbs).
If you want to get big naturally and use only bodyweight training, you first have to get freaking strong.
Eero Westerberg has built his arms and biceps mostly with chin ups and other bodyweight exercises.
The strength from these moves translate very well to weights. Eero Westerberg is capable of bicep curling clean 30kg(60lbs) dumbbells like they are nothing.
The answer is time
How big you are going to get with bodyweight, calisthenics, gymnastic or movement training depends on how consistent you are with your training program.
It depends how far are you going to take your personal progress with bodyweight exercises. If you do regular push ups and never move past that point, your body will never experience the urge to grow bigger and stronger.
The answer is letting your body take the time to build muscle. It will take months and years, but if you stick with it, bodyweight training can be as effective for building muscle as weight training, but more effective for building movement capacity and overall strength.
The way to get big and strong with bodyweight training starts by correct programming, hard work and progressive overload.
Progressive overload will do the trick
Progressive overloading just means that you progressively increase the resistance of the exercise. With weights, progressive overloading is going from 20kg (40lbs) to 25kg (50lbs) and so on.
To find more about progressive overload, read this article:
With bodyweight exercises, you need to adjust the leverage of the exercise and make the exercise harder by other means than just adding weight.
A weighted vest can be used to make bodyweight and movement exercises harder but there are other ways to increase the difficulty as well.
Work hard and consistently and a body like this can be achievable naturally without the use of weights:

Choose your own path of physical fitness
Ultimately, it doesn't matter which path you take as long as the journey is fueled with hard work, consistency, and progressive overloading.
Use only bodyweight training and you will get big and strong.
Use only weights and you will get big and strong.
In the end, it is better not to limit yourself. Almost everyone is building a dogma with their way of training without seeing that other ways offer their exclusive benefits as well.
Weights have their place and are extremely effective tool to build strength and size. But so are calisthenics, gymnastics and movement training.
It all depends on your personal goals.
If you want to be the best UFC fighter in the world - you better incorporate bodyweight exercises and movement training into your workouts because they will provide the most bang for your buck for the sport you want to excel at.
Top MMA athletes such as Conor McGregor or GSP spend most of their strength training on movement skills, but at the same time they aren't afraid to use anything that is useful.
For functional strength, nothing beats gymnastic rings because they will provide an unstable environment where the only way for your body to cope with the stress, is to become strong enough to withstand it.
We want to provide you the best tools to choose the way of fitness you like the most. Whether you like bodyweight, movement, kettlebells or weights.
The choice is yours.