Those poses might look benign, but anyone who has done one of these workouts knows they hurt like hell. Here’s why isometric exercise is one of the best ways to whip your body into shape.You can crush your cardio workout, go heavy in the weight room and flow through yoga class with ease. But then you sign up for a Pilates class or head to a barre studio, and the next thing you know you’re whimpering like a total newbie. Actually, that’s a pretty common experience. High-effort, low-impact workouts like barre and Pilates are a whole different beast than treadmill sessions or strength training, and even if you’re in good shape, these workouts are pretty much guaranteed to hurt. Why? The short answer: Your body forms a fitness baseline around whatever exercise you do most. “If you do a lot of weight training, for instance, your body adapts to a certain range of motion, certain rep range and even a preferred energy source to fuel the workout,” explains Cameron Yuen, a senior physical therapist at Bespoke Treatments in New York City. In other words, if you’re used to doing 10 reps on the leg press at the gym, your muscles will be in for a surprise when you confront them with 64 reps of pliés and relevés—small, controlled bending and elevating moves done in barre class (or at home) that fatigue the quads and calves in a less obvious, but equally serious, manner. “Most people’s bodies haven’t had to adapt to these demands before, so you will likely feel the burn much faster than you would with weight training,” Yuen says.
THE SCIENCE BEHIND THE PAIN
Let’s quickly recap how your muscles work. Your muscular system contains “motor units,” which consist of a motor nerve and muscle fibers that the nerve provides energy to. “You have a range of motor unit sizes, and different types of training result in different patterns of recruitments of these motor units,” Yuen explains. The two main sizes of muscle fibers are known as type 1 and type 2. When you do a workout like high-intensity interval training (HIIT), you’re working mainly type 2 muscle fibers, also known as the fast-twitch fibers, says Sylvia Roberts, a Pilates teacher on the fitness app Centr.com. “These muscles fatigue much more quickly than type 1, but are better in creating short bursts of power,” she says. In contrast, barre, Pilates and similar workouts place an emphasis on the type 1, or slow-twitch, muscle fibers. Type 1 fibers have a lower overall force output, but are highly resistant to fatigue. These workouts are often bodyweight-only or incorporate lighter amounts of resistance with zero rest periods. (HIIT workouts, on the other hand, involve more force and power but also involve more rest.) In Pilates or barre workouts, you’ll also find yourself contracting muscles from your core to your glutes for longer periods of time (called isometric holds), and putting them through difficult and unfamiliar ranges of motion, Yuen notes. These moves are where the benefits of these low-impact workouts can be found. They help you develop muscle endurance, have better control of your body and improve overall mobility and flexibility. If you haven’t taken one of these classes, the best gym equivalent might be holding a plank for 60 seconds or doing a two-minute wall sit. The exercises don’t involve much in the way of movement, but still burn like hell. These isometric holds are great for building strength without risking injury to your joints (since there is no jumping, running or pounding involved).
PUSHING THROUGH THE BURN
More times than not, the last few reps of a barre or Pilates exercise reduces your muscles to lumps of trembling flesh. That shaking is not just because they’re tired (though that’s part of it). “Sometimes, muscles shake because your body is essentially figuring out how much effort to devote to the task,” says Yuen. Translation: To avoid fatigue, your body will only use as many motor units as necessary. Because these activities aren’t ones you do as regularly as running or walking, your body isn’t sure how many motor units to activate. Shaking muscles are partly a response to your body turning on and off its motor units as it gauges the effort required to hold a contraction or pose. “In these cases, no need to dial it back,” Yuen says. “In fact, it’s better to keep going so that your body can figure out how much effort is needed.” To help your muscles push through the burn, proper hydration and concentration are key, says Roberts. Even more important, work on breathing slowly and deeply. “Proper breathing improves circulation, calms the body and assists in targeting the proper muscles,” Roberts says. Try to channel your breath towards an area that needs to be activated, released or relaxed. On the other hand, sometimes muscle tremors are purely the result of working your fibers to the point of exhaustion. “In this case, as some motor units get fatigued your body tries to switch to recruiting other ones,” Yuen says. You can tell that’s what is going on because your form will start to break down due to muscles that can no longer support your movements. At this point, switch to a different exercise that uses other muscle groups to give these fibers a chance to recover and repair any damage. The beauty of a barre or Pilates workout is that the stress your muscles experience is totally different than the efforts of a more traditional gym or CrossFit session. That’s beneficial in two ways: First, because the moves make you stronger. And second, because you can go back to your usual sweat sessions on other days of the week without worrying that you’re overtaxing your muscles and risking injury. You’ll get fitter, faster, and fine-tune your muscle control by adding these isometric exercises to your regular routine.