I've written at length about how I program the training sessions I coach for my younger kids. From utilizing Self-Organization principles to develop athleticism during warmups, to teaching a few speed skills and playing games that set kids up to utilize them, I've written long articles on how I implement some structure and reinforce it with play. This article won't be that lengthy.
The explanation of strength training for kids doesn't need to be long, because it's the thing I spend the least time doing formally. Especially when we are talking about young kids (9-12 years old), the following statement rings true:
Kids get stronger doing absolutely anything involving movement.
With this in mind, I spend roughly 10-15 minutes doing formal strength work with a little fun mixed in. This is roughly 5-10 minutes shorter than I spend on warming up or doing speed work and games, knowing that the kids have been building strength already just doing those things.
When it comes to teaching strength, however, I approach the combination of structure and fun a bit differently.
1. Structured Strength Training
This is the bulk of our strength training for the kids I coach. I spend more time doing structured stuff with them because they tend to really enjoy it, especially my younger kids because they feel they get more responsibility and are being treated as older. Now, 99% of the time kids will choose fun over structure, but they also enjoy feeling like one of the big kids. So for those 10 minutes or so, they're all in to "doing weights." This is also where clear communication and simplicity comes into play.
Every single day, I pick three structured exercises, and alternate the movement patterns each day. The first exercise is always a lower body movement, alternating each day between a hinge or a squat pattern. This could be a Kettlebell Deadlift one day, a Goblet Squat the next day, and then a KB Swing the day after that (I actually find Kettlebell Swings are a more effective way to teach the hinge pattern). I then pick an upper body movement, alternating between a push and a pull. I try to stick to bodyweight movements such as pushups and a bodyweight row, but sometimes this gets tricky due to the other groups using space within the facility. I do also alternate the plane of motion the kids move through for their pushes and pulls to best of space availability. Day one may be a Pushup ("Horizontal"), day two a Chinup hold ("Vertical"), day three a Bumper Plate Press ("Vertical"), and day four an Inverted Row ("Horizontal"). The third exercise is always a core move, focused primarily on anti-flexion/extension/rotation. This usually means a lot of hollow body holds, a suitcase carry (because most are too weak to perform a side plank), or a crawling variation.
The big key here for the structured strength training, is not to add a bunch of load or weight to a movement, but to reinforce the learning of movement patterns that will lay the foundation for training later down the road.
2. Strength Game, Challenge, or Stretch
If possible, I like to do a bit of game or challenge based play with the kids I train. This is often a game played on all fours, or something that requires coordination of the arms and legs. For example, "Bear Crawl Hockey" is a game utilizing a medball and some ground space. Athletes have to stay on all fours during the game for points to count, and it plays much like a game of field hockey or soccer. I might also play "King of the Monkeys" with them, which also introduces the concept of physical contact and being in another athlete's personal space.
Additionally, I may challenge them with a game or skill that requires the ability to maneuver their bodies through space and time. For example, weaving through a series of hoola hoops without hitting them. Or climbing all the way around a weight bench without hitting the ground. Simple things like this can truly help develop athleticism, and are often a kid's favorite.
Now, I do not always play a game at the end of the strength portion, as I try to spend more time doing that when we are working on speed and agility. Depending on how much spare time is left at the end of our structured strength training, I may also do some static stretching instead of a game.
While many debate the act of static stretching, I find it useful for two things: learning how to be uncomfortable and building buy-in. Most kids do not know how to adapt to being uncomfortable, which is a necessary skill for long term training. Athletes have to know how to push into discomfort (which is different than pain) as part of their training. Often times, training for certain adaptations can be brutal, and learning how to stick with something small like an uncomfortable stretching position can be useful in training.
I also use static stretching as form of buy-in from a kid's parents. In working with in a private facility, a kid's parents are ultimately footing the bill. If they don't believe in what you're doing, they won't pay for training anymore. And from experience, static stretching is something basically every parent seems to believe in as the biggest prevention of injury (I'm working on educating them on that). As far as the actual use of static stretching, I haven't found any negative effects of post-training stretching and therefore am fine with incorporating it with some spare time during a training session unless time does not allow.
Ultimately, I think kids do need a bit more structure when strength training. The weight room can be a dangerous place when not taken seriously, and a long term athletic development plan has to include preparing for further training as well.