What's the biggest debate in resistance-training? Machines vs. free-weights. Are free weights superior to machines, equal, or inferior? Let's break it down. Below you'll hear the augments for each stance. Here's what their teams look like:
Mantra: The body is the only machine you need!
Philosophy: Free weights kick ass; machines are for pussies.
Their Talking Points
Machines are non-functional
The machine selects your movement path so you don't develop as much efficiency, thus the gains in strength or size you make are less transferable to real life.
Machines don't improve the "stabilizers"
Because the movement path is fixed you don't need to depend on your own stability, nor do you use your body the best since you're usually seated or lying down.
Machines don't fit every body type equally
Machines aren't fully adjustable and the resistance curve might not fit you optimally. They don't work the same for all of us.
Free weights increase strength better
The central nervous system works harder with free weights because free-weight exercises demand more coordination, which is important for the body to develop. If you improve CNS efficiency, your strength potential and capacity to increase performance in other movements will go up.
Free-weights cause more muscle damage
If you create more muscle damage you'll stimulate more muscle growth.
These arguments have been around a long time. Some are legit; others just aren't accurate. For one thing, there's no such thing as stabilizers. Stabilizing is a muscle function, just like fixating and moving. Stabilizing means making a moving joint more stable while it's involved in movement.
A muscle can be a stabilizer in one exercise and a mover in a different exercise. For example, the lats and rhomboids will stabilize the shoulder joint in a bench press but be a prime mover in a row. Most muscles can be stabilizers or fixators (stabilizing a non-moving joint) in some exercises.
Mantra: Tension is tension!
Philosophy: Machines are safer and target muscles better.
Their Talking Points
Tension is tension
The muscles don't know if the resistance is coming from free weights, a machine, a pulley station, your body weight, a wheelbarrow, a bale of hay, etc. When a muscle does mechanical work against a resistance it will adapt and grow.
Machines provide more constant tension
A well-designed machine will change the resistance during the path, increasing it in the portion of the range of motion where you're stronger, thus making the muscles work hard for 100% of the rep. Free weight is deadweight, and up to two-thirds of the range of motion is done with the muscles not contracting fully (flyes for example).
Machines make it easier to target a muscle
One of the benefits of free weights is to involve more muscles in an exercise – for fixation, stabilization, and also as synergists. But this can also make machines superior if you want to better shift the focus to a single muscle.
You can more easily compensate with free weights
With a machine the path is pre-determined and can't change. While you can compensate a bit by changing body position, it's a lot less important than with free weights where you can change the bar path, movement, and body position to compensate.
Machines are less demanding on the nervous system
While stimulating the CNS is important for maximum strength and performance improvements, too much can limit your gains by creating CNS fatigue (dopamine depletion or adrenal receptor de-sensitization) or an overproduction of cortisol. If your goal is only to stimulate hypertrophy, creating more CNS fatigue to get the job done isn't always a good idea.
You can go to failure on machines
While going to failure isn't necessary for growth, it seems to be an effective stimulus for growth (study by Cameron and Mitchell).
Yes, you can go to failure on free-weight exercises. But when talking about multi-joint free-weight exercises that come with a higher neurological cost, going to failure (which also increases CNS stress) might have more drawbacks than benefits. Not to mention that it's safer to go to failure on machines and you're less likely to compensate with other muscles.
Both are right and both are wrong. The key is knowing which circumstances are best for machines and which are best for free weights.
When it comes to gaining muscle, it's all about triggering protein synthesis. That's undisputable. But it's not as simple as saying "X exercise = increased protein synthesis = muscle growth."
1. Muscle Fiber Fatigue
To quote Professor Zatsiorsky, "A muscle fiber that was recruited but not fatigued was not trained." This approach is supported by the work of Cameron and Mitchell (2012) that showed if you train to muscle failure (until you can't lift a weight anymore) the muscle gains are the same over an 8-week period whether you used 30% or 80% of your maximum.
Here we're talking about training to, or close to, failure. With each rep you're fatiguing more muscle fibers and your strength decreases (about 2-4% per rep). This forces your body to recruit more muscle fibers to continue moving the weight. Once you reach failure you've recruited and fatigued a large amount of your muscle fibers and have stimulated them to grow.
2. Muscle Damage
For decades, muscle damage was seen as the only way to stimulate growth. Damaging the muscle cells triggers the repair process, which is driven by the immune system and relies heavily on stem cells – they donate their material to repair the damaged muscle fibers and build them thicker.
Muscle damage is best accomplished by using fairly heavy weights (70-85%) for moderate reps (5-8, maybe up to 10 reps per set) on exercises where the target muscle will be stretched under load.
3. mTOR Activation
This triggers protein synthesis and initiates the muscle-building process. While every type of resistance training stimulates mTOR activation, two types have a greater impact – loading the eccentric or negative portion of the exercise and having a muscle under significant tension while it's stretched. So we're talking slow eccentrics (4-6 seconds) while contracting the muscles as hard as you can, and flexing the target muscle for 2 seconds in the stretched position.
4. Local Growth Factors and Lactate Release
The burn, or accumulating lactate (lactic acid), has long been associated with muscle growth by bodybuilders. And science has recently shown that they were right!
Lactate itself can trigger muscle growth (Oishi et al. 2015, Nalbandian and Takeda 2016). It increases stem cell activity, increases follistatin and decreases myostatin which leads to muscle growth. A correlation between lactate and MGF (IGF-1) release in muscle has also been found. These local growth factors will directly stimulate protein synthesis in the muscle. These are maximized with a fairly long time under tension (40-70 seconds per set) and, in the case of local growth factors accumulation, keeping the target muscle under constant tension.
Out of all of these pathways for growth, free weights have a clear advantage ONLY in the muscle damage pathway, and it's only slightly superior in the mTOR pathway.
Local growth factors and lactate release tend to be better suited to machines because of the more constant loading/tension, and muscle fatigue is also better suited to machines because of the lower neurological cost.
Here's a recap table:
Effectiveness for Hypertrophy
Let's look at the pathways for muscle growth and you'll see how they apply to free weights and machines:
When the muscle fibers are stretched while they're producing force, muscle damage can occur.
And here's a fun fact: The more uneven the force production is divided over the involved muscle fibers, the more muscle damage will occur. When the force is unevenly divided over the involved muscle fibers some of these fibers will stretch faster than others. This creates a shearing action that causes more muscle damage than simply lowering a weight. That's why you get sore when you do a new exercise, but stop being sore after you've done it often.
At first the intramuscular coordination (how well the muscle fibers work together) is inefficient, the muscle fibers aren't as coordinated, and the load isn't divided equally. This leads to more muscle damage. The more you practice an exercise, the better the intramuscular coordination becomes and the less damage occurs. The second thing that causes the most damage is when a muscle is under load in the stretched position.
So what makes free weights superior in this pathway? These lifts aren't as controlled and it takes longer to become neurologically efficient and have great intramuscular coordination. That's because the path isn't fixed. With machines you become efficient much more easily and quickly reduce how much damage the exercise is creating.
Machines are superior to free weights in this pathway. Why? Three things...
- Going to failure (to accumulate as much fatigue as possible) increases the neurological demand of an exercise. As such, going to failure on exercises with a lower neurological demand is less traumatizing on the nervous system. Isolation exercises on machines or pulleys, isolation exercises with free weights, and multi-joint exercises on machine or pulleys are the best options when going to failure.
- Going to failure on machine exercises is safer, especially when we're talking about multi-joint exercises. There's also less chance of a technical breakdown.
- On machine exercises there will be less compensation than with free weights. The more fatigue you accumulate in a set (or the heavier the weight is) the more you'll tend to compensate with muscles other than the one you're targeting.
Local growth factors (like IGF-1) can be released directly inside the trained muscle when performing mechanical work. It's accentuated when a muscle is deprived of oxygen (which is why occlusion training is effective) and when lactate/hydrogen ions accumulate inside a muscle. In both cases we have two elements that need to be present for that to happen:
- Stopping or greatly reducing blood flow to the muscle (and out of the muscle). When blood can't come in, oxygen can't come in. When blood can't exit a muscle, lactate stays trapped and accumulates inside the muscle. Occlusion (using a pressure cuff to stop blood flow) does that, but so does keeping a muscle under constant tension – flexing the muscle as hard as possible every inch of every rep.
- Being under load for 40-70 seconds. This is required to be in the "lactate" zone and for the oxygen deprivation to have an effect.
To maximize GF release, machines or pulleys are a better choice because it's easier to keep a muscle under load because of the nature of the exercise and the more constant tension provided. Free weight isolation exercises can also work, but you need to actively try to contract the target muscle as hard as possible to compensate for the reduction in loading at certain points in the range of motion.
For the two other pathways for growth (mTOR and lactate accumulation) we don't see significant differences in free weights, pulleys, and machines. To maximize mTOR activation, you need to emphasize the eccentric phase of the movement (lowering slowly while flexing the muscle hard) and the stretched position where you must maintain tension. Example:
There might be a slight advantage with free weights with mTOR activation because free weights are often better at overloading the muscles in the "stretched" position.
As for building-up lactate, sets lasting 40-70 seconds under load is best, which can be done equally well with pretty much any exercise, although form might break down more easily on exercises like a squat or deadlift.
Free weights (multi-joint versions) are best when...
- Your main goal is overall strength.
- You want to focus on muscle damage which is best done with fairly heavy weights (70-85%) and moderate reps (5-10 reps/set) using exercises where you can put the target muscle in a stretched position.
- You want to do more with fewer exercises.
Machines/pulleys are best when...
- You're trying to focus on one muscle you have hard time feeling with free weights.
- You want to stimulate growth using the growth-factors method.
- You want to use the muscle fatigue/failure approach.
Free weights and machines are equal when...
- You want to maximize mTOR (slow eccentric, pause in the stretched position) or lactate accumulation (40-70 seconds under load per set). Any tool can be used efficiently, but you must be aware of changes in technique when using longer sets.
It's all about selecting the best tool for the specific job you want to do. Going "no machine" or "no free weights" is about as smart as going "no carbs" or "no fat." Sure, it can work for a while, but it makes the process more complex, less fun, and ultimately less productive in the long run.