KettleFIT on-demand classes are designed to do with one kettlebell, but it's great to have options and if you have a matching pair, there's usually at least one opportunity per class to use "doubles" for extra credit.
You'll get a great cardio and strength workout in one by doing a fairly high number of repetitions of the exercises, so if you only have one kettlebell you'll want to choose a "medium" weight that you can work with for several minutes without needing to set it down.
A really simple rule of thumb is you should be able to strict press it overhead 20 times (with one arm) in under a minute. If you're struggling for those last few reps it might be a bit heavy, and likewise if you can do far more than 20, it's probably too light - but please, better to err on the light side when choosing your weight.
How many kettlebells do I need for KettleSPORT?
KettleSPORT training cycles are written for best case scenario: having pairs of kettlebells ranging from 50% to 120% of your "medium" weight (the weight you're training to complete your five or ten minute sets of jerk, snatch, or long cycle with, without stopping).
The programs indicate what weights and what pace to perform the exercises with. Just use the closest weights you have available. It's okay to double up if you need to... just add or subtract reps to the suggested reps per minute based on the weight of the kettlebells you have available. Plus/minus 1 rep per minute per 1 kg, i.e. if you have weights 2 kg lighter than what the program calls for, add 2 reps per minutes to your pace.
Prior to designing our own, we've always preferred steel competition grade kettlebells. We love these because they're all the same size regardless of weight, so you'll hone your technique much more quickly rather than needing to change it every time you pick up a heavier or lighter kettlebell. PS better technique = better results.
However, a nice powder coat cast iron kettlebell is more common, less expensive, and although not as comfortable, gets the job done.
We recommend avoiding plastic or vinyl coated kettlebells.
If we had to choose only two kettlebells, we'd pick a matching pair of "medium" weight kettlebells over a variety of individual weights, but it depends a bit on what your personal fitness goals are. If your #1 goal is to build muscle, you may opt for one medium and one heavy instead.
(A really simple rule of thumb to pick a "medium" weight is you should be able to strict press it overhead 20 times (with one arm) in under a minute. If you're struggling for those last few reps it might be a bit heavy, and likewise if you can do far more than 20, it's probably too light - but please, better to err on the light side when choosing your weight).
Doesn't that hurt your back?
Pro Kettlebell techniques and classes produce strong & lean full-body glory while keeping you safe.
Don't fall for risky widespread practices many personal trainers unfortunately have been taught.
These pro techniques & methods - used by world champion athletes who can't afford injury - enable people dealing with a wide range of physical limitations to protect their backs and joints and get a fantastic strength and conditioning workout at the same time.