Walk in? No way. You’ll have to book in advance to try Boston’s most popular fitness classes.

back bay yoga

Photograph courtesy
of back bay yoga

Black-Light Yoga, at Back Bay Yoga
Downward dog meets electronica during this sweaty flow, which is more about tougher positions than achieving Zen. The best part? The black lights provide anonymity so you won’t feel self-conscious about your moves—or lack thereof.
$130 for a 10-class card, 364 Boylston St., Boston, 617-375-9642,

Whipped, at Equinox Franklin Street
Apropos to how you’ll feel when class is over, Whipped incorporates a kitchen sink of equipment (battle ropes, kettlebells, medicine balls) into a hard-core 60-minute class. Though the room fits 44, people are often turned away at peak times.
Membership prices vary, 225 Franklin St., Boston, 617-426-2140,

Tone, at Btone Fitness Back Bay
Pilates fans will love the Megaformer—Lagree Fitness Method’s take on the reformer machine—which is designed to give you an intense strength-training session in just 45 minutes.
starts at $125 for five classes, 30 Newbury St., Boston, 617-578-8663,

Core Fusion, at Exhale Spa Back Bay and Battery Wharf
The Core Fusion classes here (barre, cardio, and more) use weights, balls, bands, isometrics, and body weight as resistance for a full-body workout. Each Exhale location offers more than 10 classes a day to meet demand.
$230 for 10 classes, 28 Arlington St., Boston, 617-532-7000; 2 Battery Wharf, Boston, 617-603-3100;

Reboot Ride, at Recycle Studio
The sessions at these high-end cycling-only studios feature weighted bars and pumped-up playlists to give the upper body a workout. They’ll put your regular spin class to shame.
$192 for 10 rides, 9 Newbury St., Boston; 643A Tremont St., Boston;