What it is: Alpha is a full-body workout that emphasizes what Life Time Fitness calls "functional fitness." The exercises — from walking lunges to jumping rope — are designed to train your muscles to perform better at everyday movements. According to trainer Abby Thayer, it's a one-stop fitness regime.

"Alpha includes everything," she said, "power, strength, endurance, agility, mobility and speed."

The draw? The challenging class changes dramatically from day to day. And, Thayer said, "Your body needs change." While the 60-minute session always includes weight and cardio training, the specific exercises and the focus change daily. The mantra of the class is that while you're working out with a group, you're competing only with yourself.

Where it's held: Alpha workouts have their own gyms. The Alpha gym at New Hope Life Time Fitness is a big (7,000-square-foot), open room outfitted with lots of equipment — from jump ropes to climbing ropes, rings and weights, as well as a line of cardio equipment, including treadmills and versa climbers, skillmills and stationary bikes.

Trial run: The morning class I joined was a small but welcoming group. (Groups are limited to 20, with one instructor for every 10 people.) The whiteboard listed the day's workout: a weightlifting segment that included walking lunges with dumbbells, push ups and side planks; the cardio segment ("Metcon" in Life Time speak) included jumping rope, kettlebell swings, burpees and rope climbing.

The regimen had a nice build and logical sequencing. The warm-ups led smoothly into the weightlifting, which was divided into doable-but-demanding sets. Cardio can be a challenge for me, so I was thrilled with the approach: Go all out and do what you can in 15 minutes. I'll admit I didn't make it all the way through the 300 turns on the jump rope, 100 kettle bell swings, 30 burpees, five rope climbs and a repeat of the 300 jump ropes. Still, I did what I could, and felt pretty darn good about it.

What I liked: As a middle-aged gym rat, I was familiar with most of the exercises, but I appreciated that Thayer gave me pointers on how to improve my form. She also helped me tackle new tasks and gave me alternative exercises so I wouldn't injure my bum knee. Or my bum shoulder. Or my … wait, don't get me started.

Who it's for: Any group-class junkie who's up for a challenge in a supportive setting.

Who it's not for: The instructors are clearly skilled at offering pointers and offering alternative exercises. Still, this class may not be for confirmed couch potatoes. Some experience in a gym would be a plus.

Where: Alpha is offered at 15 of the 23 Life Time Fitness locations in Minnesota. Go to lifetimefitness.com for more info.

Cost: $199 a month for three classes a week, $249 a month for unlimited classes, with a Life Time Fitness membership. (Cost includes an active metabolic test.)

The payoff: "I've seen changes in my body that I've never seen before," said 26-year-old Aisha Baker of Minnetonka.