The article notes that all subjects had at least one year of experience with resistance training, though none had any extensive experience with kettlebell or barbell training specifically.

Considering that only about 29% of Adults 18-44 yrs. old (pg. 217) met the recommended levels of muscle-strengthening activity in 2011, this is still a “special population”. Furthermore, the average age was around 22, which means the results of this study can’t really be generalized across populations (duh!).

From the article:

For the back squat exercise, subjects began in an upright position with the barbell resting on the upper back and shoulders. While maintaining a flat back, subjects then slowly flexed the hips and knees, continuing downward until the hamstrings were parallel to the ground. Once the downward motion was completed, subjects extended the hips and knees to return to the initial position. The researcher visually assessed the degree of knee flexion, and verbal feedback was provided to the subjects.

The initial load was subjectively estimated by the researcher, and from such estimates, heavier weights were added until the maximum load was achieved in no more than 4 attempts. In case the movement was not fully completed, the previous load was considered representative of the subject’s maximum strength.

Again, maximum Power (Force x Velocity) is usually developed under loads <30% 1RM, which is probably why they chose to use vertical jump as a measurement as well. Nonetheless, the power clean is still a good measure of power because it requires a very specific rate of force development, i.e. you can’t do a “slow” power clean…

From the full article:

For the power clean, the lift was started with the weight bar on the platform. Subjects approached the bar and, with their hips and knees flexed, grasped the bar with a pronated grip, torso at approximately a 45 angle in relation to the floor. From that position, they raised the bar by forcefully extending their hips and knees. After the bar passed the knees, there was a slight rebending of the knees, followed by a second rapid extension of the hips and knees. Once the hips and knees were fully extended and the shoulders shrugged, the elbows were flexed to pull the body under the bar. Simultaneously, the hips and knees were flexed to a quarter squat position. After catching the barbell at the shoulders, the subjects then stood up by extending the hips and knees to a fully erect position.

The researcher estimated the initial load subjectively, and from that, heavier weights were added until the maximum load was achieved in no more than 4 attempts. In case the movement was not fully performed to completion, the load previous to the failure was considered representative of the maximum strength.

The vertical jump is widely used to test power development. Furthermore, the relationship between lifting weights and increasing vertical jump ability is fairly well established (see 5th citation).

Specifically, they tested a countermovement jump with arm movements in this study, as opposed to something like the one-step test, or no-arms test. Procedure:

Subjects performed 3 countermovement vertical jumps with arm swings with 30-second rest between jumps. The best of 3 trials was used to represent vertical jump ability.

Participants trained with a 16kg kettlebell from DDK.

Goblet squats are akin to barbell front squats, in which the load (center of gravity) is placed more directly over the base of support (our feet) on your deltoids. “Back” squats are just the typical squat that most people think of, i.e. the load is placed behind the neck, on your trapezius muscle.

Goblet squats:

Front squat:

Back squat:

Again, pretty much the same thing, except the speed component is emphasized during the kettlebell swings, and the high pull is now a full power clean. The only difference there is that the power clean includes a “finished” position, while high pull is sort of open-ended, making the power clean more difficult with respect to technique.

http://youtu.be/0QCUdVKyhE8?t=14s

They chose very similar movements here so that they could rightly compare the different performance gains that each movement may have produced.

Kettlebell swings are performed by swinging the kettlebell – two-handed – between the legs, allowing a full hip hinge, and then swinging it back up to shoulder level.

High pulls are a bit different since they are done with a barbell in this context, but it’s basically the same muscle groups activating.

http://youtu.be/gncr0Xg1QWU?t=26s

3 sets of 6 repetitions.

This set/rep scheme fits with the accepted scheme for maximizing strength gains, somewhere between 2-5 sets and less than 6 reps.

Periodization is a type of program design which includes preplanned, systematic variations in training specificity, intensity, and volume organized in periods or cycles within an overall program.

Linear periodization is the most basic variation in program design, and is most suitable for novice athletes. It’s characterized by a consistent decrease in volume, with a simultaneous increase in intensity, leading up to some designated point.

It differs from the undulating periodization model, which is more suitable for advanced athletes.