I studied ballet for years as a child then again as an adult in the city. I even searched for adult ballet classes in NJ, but could not find one. That’s how I ended up in ballroom dance.
Anyway, my reason for mentioning ballet is because I recently heard of some gymnasts doing ballet with the intent to help their gymnastics. Unfortunately, that is ineffective. With ballet, most leg positions, leaps, jumps, landings, and turns are done in a turn-out position. And the crown arm position is not a stable position for balance beam. With gymnastics, especially on balance beam and dismount landings the gymnast’s feet and legs must be in parallel, not turn-out. Parallel landings are more mechanically safe for the body, especially when the gymnast is landing with a force of 10-13 times her body weight. A ballet dancer might only land with twice her bodyweight. If the knee is not in line with the middle toes, severe damage to the knees can occur. Most knee pain is from the knee not being in line with the middle toes and hip upon landings or take-offs. More specifically, if a gymnast lands with her feet turned out on balance beam and her knees move forward due to momentum, she will cause damage, and may actually roll her ankle, fall, and get seriously injured.
Again, I love ballet, but not with the intent to compliment gymnastics. So when you are looking for cross training to help your gymnasts, try to align the movements with the sport you are trying to improve. Ballet, as wonderful as it is, does not do that.
I have seen the effects of it and also seen the knee pain after years of trying to perform gymnastics skills in turn-out, specifically landing, beam work, and rake-offs on roundoffs. Most gymnasts cannot detrain the turn-out easily to suit their gymnastics skills easily. So, from a sports-science point of view it is correct. And yes, sports science is what I do. I am a CSCS. The body will perform what it has been trained to do and in that case, it’s turn-out. And I studied ballet for about 7 years. Everything is turnout.Turning out in the compulsories is a mistake. It causes bad habits and potential damage to the patella tendon because the hip-knee-foot alignment on landings and take-offs. http://www.maximumtrainingsolutions.com/landing-mechanics-what-why-and-when/
Please keep in mind that ballet dancers land with a fraction of the force a gymnast lands. The more force on the landing, the more important it is to use proper mechanics. A ballet dancer lands with up to 2x their body-weight, that’s if they are getting 2-feet off the floor. A gymnast lands an average of 4x-13x times their body weight for tumbling, beam & bars dismounts, and vaults.I see the turn-out often and it is difficult to fix. And I see it with kids who take ballet as part of their gymnastics as well as those who take ballet before they enter the sport. It happens very often going into back handspring, lunging into roundoffs, and even stepping out of skills on beam.
I saw one gymnast today reach back, go into a bridge during her warm up with her feet turned out. The stress on the knees over time does become an issue. I agree with you that it is up to the coaches to try to correct it, but it is difficult to get a kid to adjust foot alignment. I have been hired by gyms to do stuff just like that in order to reduce injuries, knee pain, ankle pain, etc.
Some knee articles…
https://www.stopsportsinjuries.org/STOP/STOP/Prevent_Injuries/Knee_Injury_Prevention.aspx
https://www.medicalnewstoday.com/articles/321294.php
https://www.sportsinjuryclinic.net/sport-injuries/knee-pain
Hear more of Karen Goeller podcasts here, https://karengoeller.wordpress.com/karen-goeller-podcasts/