Pilates is a form of resistance training. Your muscles contract against external resistance in every Pilates session, whether that resistance comes from your own body weight on a mat, spring tension on a reformer, or gravity working against your limbs in unstable positions. The NHS officially lists Pilates as a muscle-strengthening activity that counts toward weekly exercise guidelines.
That said, there’s a meaningful gap between “qualifies as resistance training” and “replaces a full strength training program.” Where Pilates falls on that spectrum depends on the format you’re doing, how hard you push it, and what your goals actually are.
Why Pilates Meets the Definition
Resistance training is any exercise where muscles contract against an external force to progressively improve strength, power, or endurance. That force can come from free weights, machines, bands, water, or body weight. Pilates checks this box clearly. Mat Pilates uses body weight and gravity as resistance. Reformer Pilates adds spring-loaded resistance that you can dial up or down, with specific tension ranges depending on the spring color and manufacturer.
On a typical reformer, springs range from about 1 to 30 kilograms of resistance depending on how far the carriage travels. A heavy spring on an Align-Pilates reformer, for example, provides between 5 and 30 kg of force. Lighter springs drop to 1 to 7 kg. This isn’t trivial, but it’s also not comparable to loading a barbell with 60 or 100 kg for squats. The resistance exists on a different scale, and it’s applied differently, often through longer ranges of motion with sustained time under tension.
Mat Pilates vs. Reformer Pilates
These two formats create resistance through different mechanisms, and the distinction matters if you’re evaluating Pilates as your primary strength work.
Mat Pilates relies entirely on body weight. You’re working against gravity in positions that challenge stability, and the difficulty increases as you change leverage or slow down movements. Think of a plank hold progressing to a single-leg plank: same body weight, harder because of the position. This is effective for building core endurance and control, but it has a natural ceiling. Once you can manage your own body weight in a given position, the only way forward is adjusting the angle or tempo.
Reformer Pilates introduces adjustable spring tension, straps, and a sliding carriage that lets you load movements in ways mat work can’t. You can increase resistance by adding heavier springs, changing your body’s position relative to the machine, or extending the range of motion. This gives reformer work a longer progression path and more options for genuinely challenging your muscles.
How Pilates Applies Progressive Overload
Progressive overload, the principle of gradually increasing the demand on your muscles over time, is what separates effective resistance training from movement that just maintains what you have. Traditional weightlifting does this simply: add more weight to the bar. Pilates takes a less obvious but still valid approach.
On a reformer, you can progress through five variables: spring resistance, leverage (your body’s position relative to the machine), tempo (slower movements mean more time under tension), range of motion, and control demands (reducing stability to make muscles work harder). A beginner doing footwork on two heavy springs will eventually move to single-leg variations, slower tempos, or more challenging body angles.
The limitation is practical. Spring resistance has a ceiling that traditional weights don’t. Once you’ve maxed out the heaviest springs on a reformer at the most challenging leverage, you’ve reached the upper limit of what that equipment can provide. For someone whose goal is building significant muscle mass or maximal strength, this ceiling arrives relatively quickly, especially for large muscle groups like the glutes and quadriceps.
Energy Expenditure Compared to Weightlifting
A typical Pilates session averages around 3.7 METs (a standard measure of exercise intensity where 1 MET equals resting). That places it in the light-to-moderate intensity range. For context, the 2024 Compendium of Physical Activities categorizes traditional mat Pilates at just 1.8 METs and general Pilates at 2.8 METs, though actual measured values in studies tend to run higher, particularly when rest intervals are kept short.
Sessions with rest periods under 60 seconds reached about 3.4 METs on average, while those with longer breaks dropped to around 2.0 METs. One study measuring equipment-based Pilates recorded 9.2 METs, though that appears to be an outlier among the available research. Conventional resistance training with weights typically falls in the 3.5 to 6.0 MET range depending on intensity, so Pilates generally sits at the lower end of the effort spectrum for muscle-strengthening activities.
This doesn’t mean Pilates is “easy.” The metabolic cost reflects total energy output, not how challenging a movement feels in the moment. A slow, controlled single-leg reformer exercise can be brutally difficult for the muscles involved while still registering as moderate on a whole-body energy scale.
What Pilates Does Well
Pilates excels at building core endurance, improving spinal mobility, and developing the kind of muscular control that translates to better posture and movement quality. The emphasis on slow, precise movements with constant tension creates a training stimulus that’s particularly effective for deep stabilizing muscles that traditional weightlifting often misses. For people recovering from injury, dealing with back pain, or returning to exercise after a long break, Pilates provides meaningful resistance in a controlled, low-impact environment.
There’s also modest evidence for bone health benefits. A meta-analysis in PLOS ONE found that Pilates produced a small but statistically significant improvement in bone mineral density in pre-post comparisons, particularly among postmenopausal women. The effect was larger for Pilates than for yoga, though neither produced dramatic results compared to higher-impact or heavier resistance training.
Where Pilates Falls Short as Strength Training
If your goal is maximizing muscle size, developing peak strength, or building the kind of force output needed for sports performance, Pilates alone won’t get you there. The resistance levels are too low for the large muscle groups that respond to heavy loading, and the progressive overload options, while real, plateau faster than with free weights or machines.
Most Pilates classes also emphasize high repetitions with lighter resistance, which builds muscular endurance more than maximal strength. There’s nothing wrong with that, it’s a legitimate fitness quality, but it’s a different adaptation than what heavier resistance training produces. Someone who needs to build significant leg or upper body strength will hit the limits of what Pilates can provide faster than someone focused on core stability and movement quality.
Using Pilates as Part of a Resistance Training Program
For many people, the most practical approach is treating Pilates as one component of a broader resistance training routine rather than the whole thing. Two sessions of heavier strength work per week paired with one or two Pilates sessions gives you the benefits of both: the heavy loading that drives muscle and bone adaptation alongside the controlled, precision-focused work that improves stability and movement quality.
If Pilates is the only resistance training you’re willing to do, it still counts. You’ll build real strength, particularly in your core and smaller stabilizing muscles, and you’ll meet the minimum guidelines for muscle-strengthening activity. Reformer Pilates with progressively heavier springs will take you further than mat work alone. Just know that the ceiling exists, and if your goals eventually outgrow it, adding heavier external resistance is the logical next step.