Can training with just weight machines make you stronger?

Whomever has been a member of a gym in the past 15 years, will have noticed how slowly but surely, machines have taken a back seat and more and more space is given to 3-dimensional weight equipment, like suspension (TRX-)trainers, gym balls, kettle bells and even fun stuff that were formerly totally unheard of like pole dances and climbing walls.
A very popular trend is the development of Cross-Fit in which both strength and endurance is equally valued and in which Olympic weightlifting exercises are also incorporated.
As someone who has dabbled both in Olympic and power lifting as well as endurance cycling, I've been very happy about this development even though I keep using machines myself too. Recently, Christian Finn, a coach who specialized in rehab training, pointed out how machines have a more important role than most of us realize. It's well worth sharing it in our blog, too.

Machines can increase your functional strength... really!

• functional carryover
• muscular development
• recovering from an injury

Functional Carryover

We’ll start with the idea that the strength you build with machines like the leg press, leg extension, or leg curl doesn’t transfer to anything you do outside the gym. That is, you don’t run faster, jump higher, or improve your endurance.

The argument goes something like this:
“There’s no sport or activity that involves sitting down and pushing a weight away from you, or sitting down and straightening your legs with a weight pushing down on your shins.”

This should be easy to test, and indeed many studies over the years have used machine-based training routines to enhance athletic performance.
For example, in this 2011 study of elite cyclists, Danish researchers found that a combination of strength training and cycling improved performance during a 45-minute time trial to a greater extent than cycling alone. This was purely a machine-based routine: leg extension, leg press, leg curl, and calf raise.
Without any help from the squat, lunge, or deadlift, the cyclists somehow improved their endurance by an impressive 8 percent in 16 weeks.

In a 2017 study, Spanish researchers trained a group of pro handball players with two different types of leg press: the conventional 45-degree leg press and one that uses a flywheel. Both produced improvements in a variety of performance measures, including 20-meter sprint time and vertical jump height.

Were these training programs ideal for the elite competitive athletes who used them in the studies? Certainly not. I don’t think anyone reading this would write machine-only programs, if all options were on the table.

The key point, though, is one all fitness pros should understand: An exercise doesn’t have to be identical to an activity for the strength it builds to improve performance.

Muscular Development

Basic physiology tells us that bigger muscles are typically stronger muscles. While the ratio isn’t exactly one to one, we know that if your client increases the size of his thigh muscles, he’ll almost certainly have stronger legs as a result.

The squat is often described as the best overall exercise for lower-body muscle mass. But let’s consider the comparative benefits of the leg press.

Obviously, there’s less reliance on technique with the leg press, which makes it an easier alternative for clients who are new to strength training.

But for many clients, lower back strength will be the biggest limiting factor during the squat. Their form will break down before the legs have gotten a sufficient training stimulus. That’s rarely a factor with the leg press; you can use higher volume and heavier loads with less risk of injury.

“Less risk” doesn’t mean “no risk.” As Stuart McGill, PhD, notes in Low Back Disorders, allowing a client’s pelvis to come off the back support causes the lumbar spine to flex under load, potentially putting her at risk for a disc herniation.

To mitigate the risk, McGill recommends pressing with one leg at a time to ensure the pelvis stays in contact with the pad—which brings me to another potential advantage to using the machine: Your client can isolate each leg without balance being a limiting factor, as it might be with free-weight exercises like the split squat, lunge, or step-up.

Another important point: The quadriceps, as you know, is a group of four muscles. No exercise works all of them to the same degree.

That’s where the much-maligned leg extension comes in handy. It’s most effective for stimulating the rectus femoris, the dual-function muscle that acts as both a knee extensor and hip flexor.

While the squat produces high levels of muscle activation in the vastus lateralis and vastus medialis, the leg extension typically produces higher levels of rectus femoris activity.

In a 12-week program using the leg extension exclusively, the rectus femoris grew much faster than the other three muscles in the quads.

For the hamstrings, a combination of free-weight and machine exercises delivers better results than either one alone.

A 2015 study in the Journal of Strength and Conditioning Research showed that the lying leg curl and stiff-legged deadlift produced similar activation of the upper hamstrings. However, the leg curl led to greater activation of the lower lateral and medial parts or the muscle.

Here’s how study author Brad Schoenfeld describes the results:

“The differences in activation of the lower hamstrings was stark, with the leg curl showing greater lower lateral hamstrings activity of approximately 170 percent and lower medial hamstrings activity of approximately 65 percent compared to the stiff-legged deadlift.”

Of course, none of your clients come to you with the goal of increasing the girth of their lower hamstrings. And even if someone wanted to, you’re still limited by both genetics and the difficulty of isolating specific areas of individual muscles, relative to other parts.

So your best bet for overall development is to use a variety of exercises to ensure you work all sections of the targeted muscles. Since machines are better at training some of those areas, you’d want to include them in the program.

Injury Recovery

Final thoughts

Let’s review what we just learned about the outcomes associated with machine exercises:

• increased speed and vertical jump height
• increased muscle mass in specific parts of muscles that are hard to develop with free-weight exercises
• accelerated recovery and reduced pain in knee joints

All of those are clearly “functional” outcomes. That is, they produce positive changes in areas your clients want to improve. And that’s without mentioning increased strength, which makes life in general easier to navigate.

So why are machine exercises so often described as nonfunctional?

source: Weight Machines Build Functional Strength. Seriously.