No Polyesters for kids under 10. Nylons or Multis only. Somewhere around the ages of 12 to 14 maybe introduce a Poly/Syn. hybrid. The later the better if you can afford it. If they start breaking strings weekly its hard to not go with the Poly to save on stringing costs as they get older.
Multi's only. Keep them from getting injured. I'd even go as far as trying some cheaper gut strings ( NOT that Gaucho stuff) IF they aren't string breakers. It may last them longer with keeping the tension consistent longer. I have my daughters racquet strung with gut and it seems to last her longer than the others. She isn't a 10 year old in Champs level though. Just a thought.
My advice for anyone concerned about arm health is to go easy on the tension. There are an awful lot of racquets, particularly the ones with dense string patterns, that string up much tighter within their given tension ranges than you would expect. In other words, the recommended tension range needs to be taken with a grain of salt. Most people don't want to accept this.
Case in point. A 12 yr old who plays a Radical MP strung with X-1 Biphase at 57 lbs. At 57 lbs, the string bed is like a rock. I don't care how soft the string is. It's like a rock. Now this young player is being yelled at to hit deep and yelled at to hit with topspin and frankly it's only a matter of time before his arm falls off for trying. The only way he can hit deep with that set up is to hit flat. Let me ask you all this: Given the current state of the game, is there any future in hitting flat?
I think you're oversimplifying a bit. The kid's arm won't fall off because the X-1 will stretch and lose some tension after break in. If he goes lower because he's worried about it feeling "like a rock" at first as you say, then he might find it difficult to control after the strings settle in.
My recommendation is to know what type of machine is being used by the stringer before you decide on tension. If it's electric/drop weight, compensate 2-3 lbs. less, should work out just fine.
We're talking about 10 year olds here. Half of them don't even know what string is, they won't be able to tell the difference in a couple of Lbs. I would say syn. gut @ 50 maybe high 40s
We're talking about 10 year olds here. Half of them don't even know what string is, they won't be able to tell the difference in a couple of Lbs. I would say syn. gut @ 50 maybe high 40s