Week one: HotPod Yoga
Getting out of bed early isn't easy in winter, but it's less painful when you're heading for a steamy, cocoonlike inflatable yoga pod. The theory is that 37°c heat (less intense than Bikram's 40.6°c) aids flexibility and the heat makes your heart work harder as you wind your way through a Vinyasa Flow session.
Mid-workout buzz? I like a dynamic routine and some classes delivered, but others were a bit too zen for my tastes. My one criticism is that the classes varied considerably from teacher to teacher.
All-day boost? Starting my day with yoga gave me a glow and I breezed my way through stressful meetings, but I'd say I felt relaxed rather than revived after the sessions.
Body benefits? I was much more flexible by day seven and some lingering muscle aches and pains from running had vanished. A week of gentle yoga didn't yield any huge toning or weight loss effects, but I felt positive, relaxed and much more comfortable in my body by Sunday.
Easy to stick to? Most definitely. The wonderful thing about yoga is that you can't really overdo it - your body will always feel better if you do a class, never worse.
Is it for you? If the thought of entering a cold, loud, shouty gym in January makes you want to curl up in the foetal position, HotPod yoga is seductive, soothing and surprisingly easy to stick to.
The details: Classes from £12; HotPods nationwide throughout the UK.
Week two: Flywheel
Reputedly the most hardcore indoor cycling workout you can do, this Manhattan-born regime involves 45 intense minutes of climbs (when you up the torque to pedal against resistance) and descents (when you up your RPM and pedal furiously), with some weight-work to tone arms.
Mid-workout buzz? Hell, yeah. Of all the workouts tested, Flywheel gave me the biggest endorphin rush. Expect to sweat buckets and be pushed hard, but the killer soundtrack and the heart-pumping high makes the time fly past.
All day boost? Yep, I felt on top of the world.
Body benefits? My skin was glowing, I had a spring in my step, and I swear my fitness levels improved - cycling around town on the Friday was a breeze compared to the weekend before.
Easy to stick to? The endorphin rush makes Flywheel scarily addictive, but ideally I'd combine regular Flywheel sessions with yoga and some core work, because if there's one downside to indoor cycle workouts, it's that they're a tad samey.
Is it for you? If you want to see fast results, Flywheel noticeably improves your fitness levels (and mood) in record time. I'm impressed.
The details: Class prices vary at Flywheel studios around the globe; Shoreditch House offers classes to members for £5
Week three: Barry's Bootcamp
Another US import, this cult workout has an army of celebrity fans, who swear by the signature hour-long regimes combining 30 minutes of interval cardio on a treadmill and 30 minutes of strength-training on the floor. Classes vary, teachers vary, so you never get bored. You get sore and tired, and then you get FIT.
Mid workout buzz? If anyone claimed to enjoy a Barry's workout, I'd call them a liar. Pre-class resembles the waiting room at an STD clinic, and mid-class, as you sprint from treadmill to bench and back again on the orders of a shouting Californian, all you want is for it to be over.
All day boost? But when it IS over, man, you feel good.
Body benefits? Most def. Because it combines interval cardio with resistance work and core exercises it was easily the most well-rounded regime of my month, and I swear my legs, arms and abs felt firmer by Sunday.
Easy to stick to? It's famously addictive, mainly because of the results - commit to three sessions a week and you'll look and feel very different in a month.
Is it for you? If motivation is an issue, I'd highly recommend Barry's - you'll see fast results, you'll be won over by the infectiously upbeat instructors, and you'll get seriously hooked on the Chocolate Peanut Butter protein shakes on offer after class. As your technique and fitness improves, the results will only get better, so there's no danger of plateauing and getting bored.
The details: Locations globally; UK locations in Euston and Shoreditch; UK classes from £20.
Week Four: Barrcore Online
A ballet-inspired fusion of cardio pilates and yoga, but there's nothing zen about this regime.
Your legs and abs will shake and you'll ache in places you never knew you had muscles BUT you can expect a whittled waist and toned bum as a result. There are various studios across London, but I'm testing the online workout videos.
Mid workout buzz? Yes - the videos are clear, instructors are upbeat, and you really feel like you're getting exercise bang for your buck - or as good a workout as you can give your abs in a 30-minute class.
All day boost? It's not quite the endorphin high you'll get from seriously intense interval cardio work (as at Barry's and Flywheel) but Barrecore leaves you feeling limber, light and like you're using your body the way it's meant to be used.
Body benefits? I'm totally sold on Barrecore - the online classes combine interval training with strengthening postures for a much more well-rounded workout than traditional Pilates and yoga workouts.
Easy to stick to? Yes. I loved the fact that I could do the online classes at home over Christmas, but if you mixed the online subscription with weekly studio sessions you'd really be onto a winner.
Is it for you? If you love the ethos of yoga and pilates but feel like you want to up your fitness and see more tangible results, Barrecore is your new best friend. AND you can do it from home.
The details: A Barrecore online subscription costs £25 per month; studio classes start at £22. Classes at various London locations.
There's nothing like a brand new workout kit to get you motivated...